--- /srv/rebuilderd/tmp/rebuilderdVDaAZ6/inputs/erlang-doc_27.3.4.3+dfsg-1_all.deb
+++ /srv/rebuilderd/tmp/rebuilderdVDaAZ6/out/erlang-doc_27.3.4.3+dfsg-1_all.deb
├── file list
│ @@ -1,3 +1,3 @@
│  -rw-r--r--   0        0        0        4 2025-09-15 15:42:37.000000 debian-binary
│ --rw-r--r--   0        0        0    39772 2025-09-15 15:42:37.000000 control.tar.xz
│ --rw-r--r--   0        0        0 16799364 2025-09-15 15:42:37.000000 data.tar.xz
│ +-rw-r--r--   0        0        0    39764 2025-09-15 15:42:37.000000 control.tar.xz
│ +-rw-r--r--   0        0        0 16798896 2025-09-15 15:42:37.000000 data.tar.xz
├── control.tar.xz
│ ├── control.tar
│ │ ├── ./md5sums
│ │ │ ├── ./md5sums
│ │ │ │┄ Files differ
│ │ │ ├── line order
│ │ │ │ @@ -129,15 +129,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/doc/system/dist/search_data-3853893B.js
│ │ │ │ +usr/share/doc/erlang-doc/html/doc/system/dist/search_data-DBFDB6FD.js
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/dist/sidebar_items-4A143270.js
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/distributed.html
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/distributed_applications.html
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/documentation.html
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/drivers.html
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/eff_guide_functions.html
│ │ │ │  usr/share/doc/erlang-doc/html/doc/system/eff_guide_processes.html
│ │ │ │ @@ -443,15 +443,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/search_data-7019F81A.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/search_data-F51EF764.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/sidebar_items-14E9F638.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/engine_keys.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/engine_load.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/fips.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/licenses.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/new_api.html
│ │ │ │ @@ -608,15 +608,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/search_data-76AA0443.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/search_data-24CC7BE0.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/dist/sidebar_items-4C553487.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/doc_storage.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/edoc.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/edoc_cmd.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/edoc_doclet.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/edoc_doclet_chunks.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/edoc-1.3.2/doc/html/edoc_doclet_markdown.html
│ │ │ │ @@ -673,15 +673,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/search_data-D82831C4.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/search_data-1F14090C.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/dist/sidebar_items-8A5CCEF3.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/ei.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/ei_connect.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/ei_global.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/ei_users_guide.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/erl_call_cmd.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/erl_interface-5.5.2/doc/html/erl_interface.epub
│ │ │ │ @@ -781,15 +781,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/search_data-FF6A1601.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/search_data-D71AAFA6.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/dist/sidebar_items-B6B07F6E.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/ftp.epub
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/ftp.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/ftp_client.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/introduction.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ftp-1.2.3/doc/html/notes.html
│ │ │ │ @@ -1300,15 +1300,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/search_data-C5321E03.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/search_data-8726EDEC.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/dist/sidebar_items-DF937488.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/notes.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/reltool.epub
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/reltool.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/reltool_examples.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/reltool-1.0.1/doc/html/reltool_intro.html
│ │ │ │ @@ -1370,15 +1370,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/search_data-E8F08406.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/search_data-F5F44AEB.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/dist/sidebar_items-EAF2F83F.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/error_logging.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/notes.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/rb.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/rel.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/sasl-4.2.2/doc/html/release_handler.html
│ │ │ │ @@ -1500,15 +1500,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/search_data-E0401131.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/search_data-AAB6B0F2.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/dist/sidebar_items-F32BF3C6.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/hardening.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/introduction.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/notes.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/search.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssh-5.2.11.3/doc/html/ssh.epub
│ │ │ │ @@ -1542,15 +1542,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/search_data-880670C6.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/search_data-06452E63.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/dist/sidebar_items-BCF27D9A.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/notes.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/search.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/ssl.epub
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/ssl.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/ssl-11.2.12.2/doc/html/ssl_app.html
│ │ │ │ @@ -1719,15 +1719,15 @@
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/remixicon-NKANDIL5.woff2
│ │ │ │ -usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/search_data-7B342769.js
│ │ │ │ +usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/search_data-BA5DB564.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/dist/sidebar_items-3CBBBF05.js
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/getting_started.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/index.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/introduction.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/notes.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/search.html
│ │ │ │  usr/share/doc/erlang-doc/html/lib/tftp-1.2.2/doc/html/tftp.epub
├── data.tar.xz
│ ├── data.tar
│ │ ├── file list
│ │ │ @@ -137,15 +137,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)      292 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/ssh.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      293 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/ssl.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      294 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/stdlib.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)      300 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/syntax_tools.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     2286 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5648 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/404.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   654614 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/Erlang System Documentation.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   654631 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/Erlang System Documentation.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)    53542 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/applications.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    97489 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/appup_cookbook.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7982 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/ballpoint-pen.svg
│ │ │  -rw-r--r--   0 root         (0) root         (0)     2284 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/dist1.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5214 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/dist2.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5007 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/assets/dist3.gif
│ │ │ @@ -181,15 +181,15 @@
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│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5472 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5368 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1956 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/remixicon-NKANDIL5.woff2
│ │ │ --rw-r--r--   0 root         (0) root         (0)  1016759 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/search_data-3853893B.js
│ │ │ +-rw-r--r--   0 root         (0) root         (0)  1016759 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/search_data-DBFDB6FD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    32130 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/dist/sidebar_items-4A143270.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    30039 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/distributed.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20667 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/distributed_applications.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    52930 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/documentation.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15036 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/drivers.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    26945 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/eff_guide_functions.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    52169 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/doc/system/eff_guide_processes.html
│ │ │ @@ -351,15 +351,15 @@
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1060 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6010 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/404.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6692 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/api-reference.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)    96856 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)    96859 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   140490 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1_getting_started.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9328 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1_introduction.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7454 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1_overview.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    78800 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1_spec.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    35477 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/asn1ct.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     1340 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/asn1-5.3.4.2/doc/html/assets/exclusive_Win_But.gif
│ │ │ @@ -397,15 +397,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10672 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/api-reference.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     4963 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/assets/config.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10726 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/assets/html_logs.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/assets/logo.png
│ │ │  -rw-r--r--   0 root         (0) root         (0)     9561 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/assets/tc_execution.gif
│ │ │  -rw-r--r--   0 root         (0) root         (0)    21795 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/basics_chapter.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   399357 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/common_test.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   399355 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/common_test.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)     7502 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/common_test_app.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    59626 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/config_file_chapter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    25541 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/cover_chapter.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   182818 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/ct.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12310 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/ct_cover.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    30032 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/ct_ftp.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    77362 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/common_test-1.27.7/doc/html/ct_hooks.html
│ │ │ @@ -466,15 +466,15 @@
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/assets/logo.png
│ │ │  -rw-r--r--   0 root         (0) root         (0)    24226 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/beam_ssa.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)   450809 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/cerl.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28701 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/cerl_clauses.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    28995 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/cerl_trees.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    84370 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/compile.html
│ │ │ --rw-r--r--   0 root         (0) root         (0)   181853 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/compiler.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   181850 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/compiler.epub
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20933 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/handlebars.runtime-CFQAK6SD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33580 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/handlebars.templates-K7URE6B4.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70589 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/html-55NP3CS6.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67213 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/html-erlang-WGRVP7UZ.css
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17732 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/inconsolata-latin-400-normal-OXLHDACS.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17976 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/compiler-8.6.1.2/doc/html/dist/inconsolata-latin-700-normal-S55P5GAG.woff2
│ │ │ @@ -500,15 +500,15 @@
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/
│ │ │  -rw-r--r--   0 root         (0) root         (0)      992 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/.build
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6016 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/404.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    35139 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/algorithm_details.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)     6670 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/api-reference.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/assets/
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5837 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/assets/logo.png
│ │ │ --rw-r--r--   0 root         (0) root         (0)   127041 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/crypto.epub
│ │ │ +-rw-r--r--   0 root         (0) root         (0)   127046 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/crypto.epub
│ │ │  -rw-r--r--   0 root         (0) root         (0)   294963 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/crypto.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    10018 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/crypto_app.html
│ │ │  drwxr-xr-x   0 root         (0) root         (0)        0 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/
│ │ │  -rw-r--r--   0 root         (0) root         (0)    20933 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/handlebars.runtime-CFQAK6SD.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    33580 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/handlebars.templates-K7URE6B4.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    70589 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/html-55NP3CS6.js
│ │ │  -rw-r--r--   0 root         (0) root         (0)    67213 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/html-erlang-WGRVP7UZ.css
│ │ │ @@ -521,15 +521,15 @@
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23236 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23580 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)    23040 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  -rw-r--r--   0 root         (0) root         (0)     5624 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/crypto-5.5.3/doc/html/dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
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│ │ │  -rw-r--r--   0 root         (0) root         (0)    54017 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wx.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    19452 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wxAcceleratorEntry.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    15130 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wxAcceleratorTable.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    12373 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wxActivateEvent.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    19127 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wxArtProvider.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    17639 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wxAuiDockArt.html
│ │ │  -rw-r--r--   0 root         (0) root         (0)    63043 2025-09-15 15:42:37.000000 ./usr/share/doc/erlang-doc/html/lib/wx-2.4.3/doc/html/wxAuiManager.html
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/.build
│ │ │ @@ -37,15 +37,15 @@
│ │ │  dist/lato-latin-300-normal-YUMVEFOL.woff2
│ │ │  dist/lato-latin-400-normal-W7754I4D.woff2
│ │ │  dist/lato-latin-700-normal-2XVSBPG4.woff2
│ │ │  dist/lato-latin-ext-300-normal-VPGGJKJL.woff2
│ │ │  dist/lato-latin-ext-400-normal-N27NCBWW.woff2
│ │ │  dist/lato-latin-ext-700-normal-Q2L5DVMW.woff2
│ │ │  dist/remixicon-NKANDIL5.woff2
│ │ │ -dist/search_data-3853893B.js
│ │ │ +dist/search_data-DBFDB6FD.js
│ │ │  dist/sidebar_items-4A143270.js
│ │ │  distributed.html
│ │ │  distributed_applications.html
│ │ │  documentation.html
│ │ │  drivers.html
│ │ │  eff_guide_functions.html
│ │ │  eff_guide_processes.html
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/Erlang System Documentation.epub
│ │ │ ├── zipinfo {}
│ │ │ │ @@ -1,93 +1,93 @@
│ │ │ │ -Zip file size: 654614 bytes, number of entries: 91
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│ │ │ │ -?rw-r--r--  6.1 unx    21209 bx defN 25-Sep-15 16:39 OEBPS/eff_guide_functions.xhtml
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│ │ │ │ -?rw-r--r--  6.1 unx    24284 bx defN 25-Sep-15 16:39 OEBPS/distributed.xhtml
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│ │ │ │ -?rw-r--r--  6.1 unx    35510 bx defN 25-Sep-15 16:39 OEBPS/c_port.xhtml
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│ │ │ │ -?rw-r--r--  6.1 unx     5837 bx defN 25-Sep-15 16:39 OEBPS/assets/logo.png
│ │ │ │ -?rw-r--r--  6.1 unx     5837 bx defN 25-Sep-15 16:39 OEBPS/assets/erlang-logo.png
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│ │ │ │ -?rw-r--r--  6.1 unx     2939 bx stor 25-Sep-15 16:39 OEBPS/assets/dist4.gif
│ │ │ │ -?rw-r--r--  6.1 unx     5007 bx stor 25-Sep-15 16:39 OEBPS/assets/dist3.gif
│ │ │ │ -?rw-r--r--  6.1 unx     5214 bx stor 25-Sep-15 16:39 OEBPS/assets/dist2.gif
│ │ │ │ -?rw-r--r--  6.1 unx     2284 bx stor 25-Sep-15 16:39 OEBPS/assets/dist1.gif
│ │ │ │ -?rw-r--r--  6.1 unx     7982 bx stor 25-Sep-15 16:39 OEBPS/assets/ballpoint-pen.svg
│ │ │ │ -?rw-r--r--  6.1 unx    91721 bx defN 25-Sep-15 16:39 OEBPS/appup_cookbook.xhtml
│ │ │ │ -?rw-r--r--  6.1 unx    47722 bx defN 25-Sep-15 16:39 OEBPS/applications.xhtml
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│ │ │ │ -?rw-r--r--  6.1 unx      162 bx defN 25-Sep-15 16:39 META-INF/com.apple.ibooks.display-options.xml
│ │ │ │ -91 files, 3077736 bytes uncompressed, 638682 bytes compressed:  79.3%
│ │ │ │ +Zip file size: 654631 bytes, number of entries: 91
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│ │ │ │ +?rw-r--r--  6.1 unx     2166 bx defN 25-Oct-04 11:40 OEBPS/tutorial.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx      764 bx defN 25-Oct-04 11:40 OEBPS/title.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    12466 bx defN 25-Oct-04 11:40 OEBPS/system_principles.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     7346 bx defN 25-Oct-04 11:40 OEBPS/system_limits.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    63476 bx defN 25-Oct-04 11:40 OEBPS/sup_princ.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   253918 bx defN 25-Oct-04 11:40 OEBPS/statem.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   111264 bx defN 25-Oct-04 11:40 OEBPS/spec_proc.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   249951 bx defN 25-Oct-04 11:40 OEBPS/seq_prog.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    70943 bx defN 25-Oct-04 11:40 OEBPS/robustness.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx     4596 bx defN 25-Oct-04 11:40 OEBPS/reference_manual.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    19455 bx defN 25-Oct-04 11:40 OEBPS/ref_man_records.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    14454 bx defN 25-Oct-04 11:40 OEBPS/ref_man_functions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    49542 bx defN 25-Oct-04 11:40 OEBPS/records_macros.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    15206 bx defN 25-Oct-04 11:40 OEBPS/profiling.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx     8959 bx defN 25-Oct-04 11:40 OEBPS/otp-patch-apply.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     9082 bx defN 25-Oct-04 11:40 OEBPS/opaques.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx     5477 bx defN 25-Oct-04 11:40 OEBPS/memory.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    39594 bx defN 25-Oct-04 11:40 OEBPS/macros.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    31439 bx defN 25-Oct-04 11:40 OEBPS/listhandling.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    42996 bx defN 25-Oct-04 11:40 OEBPS/list_comprehensions.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    55516 bx defN 25-Oct-04 11:40 OEBPS/install.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    28229 bx defN 25-Oct-04 11:40 OEBPS/install-win32.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    35715 bx defN 25-Oct-04 11:40 OEBPS/install-cross.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    31341 bx defN 25-Oct-04 11:40 OEBPS/gen_server_concepts.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   118675 bx defN 25-Oct-04 11:40 OEBPS/funs.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     8453 bx defN 25-Oct-04 11:40 OEBPS/features.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx     2365 bx defN 25-Oct-04 11:40 OEBPS/example.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    26747 bx defN 25-Oct-04 11:40 OEBPS/events.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    13609 bx defN 25-Oct-04 11:40 OEBPS/error_logging.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    42501 bx defN 25-Oct-04 11:40 OEBPS/erl_interface.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    18220 bx defN 25-Oct-04 11:40 OEBPS/embedded.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    21209 bx defN 25-Oct-04 11:40 OEBPS/eff_guide_functions.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     9338 bx defN 25-Oct-04 11:40 OEBPS/drivers.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    47180 bx defN 25-Oct-04 11:40 OEBPS/documentation.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx    24284 bx defN 25-Oct-04 11:40 OEBPS/distributed.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    14562 bx defN 25-Oct-04 11:40 OEBPS/dist/epub-erlang-ESPT6BQV.css
│ │ │ │ +?rw-r--r--  6.1 unx      499 bx defN 25-Oct-04 11:40 OEBPS/dist/epub-LSJCIYTM.js
│ │ │ │ +?rw-r--r--  6.1 unx    36780 bx defN 25-Oct-04 11:40 OEBPS/design_principles.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    15003 bx defN 25-Oct-04 11:40 OEBPS/debugging.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    71771 bx defN 25-Oct-04 11:40 OEBPS/data_types.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx   115067 bx defN 25-Oct-04 11:40 OEBPS/create_target.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx   129900 bx defN 25-Oct-04 11:40 OEBPS/conc_prog.xhtml
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│ │ │ │ +?rw-r--r--  6.1 unx     5177 bx defN 25-Oct-04 11:40 OEBPS/character_set.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    40707 bx defN 25-Oct-04 11:40 OEBPS/c_portdriver.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    35510 bx defN 25-Oct-04 11:40 OEBPS/c_port.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    34819 bx defN 25-Oct-04 11:40 OEBPS/bit_syntax.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    53327 bx defN 25-Oct-04 11:40 OEBPS/binaryhandling.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     7606 bx defN 25-Oct-04 11:40 OEBPS/benchmarking.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx     5837 bx defN 25-Oct-04 11:40 OEBPS/assets/logo.png
│ │ │ │ +?rw-r--r--  6.1 unx     5837 bx defN 25-Oct-04 11:40 OEBPS/assets/erlang-logo.png
│ │ │ │ +?rw-r--r--  6.1 unx     7044 bx stor 25-Oct-04 11:40 OEBPS/assets/dist5.gif
│ │ │ │ +?rw-r--r--  6.1 unx     2939 bx stor 25-Oct-04 11:40 OEBPS/assets/dist4.gif
│ │ │ │ +?rw-r--r--  6.1 unx     5007 bx stor 25-Oct-04 11:40 OEBPS/assets/dist3.gif
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│ │ │ │ +?rw-r--r--  6.1 unx    91721 bx defN 25-Oct-04 11:40 OEBPS/appup_cookbook.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx    47722 bx defN 25-Oct-04 11:40 OEBPS/applications.xhtml
│ │ │ │ +?rw-r--r--  6.1 unx      252 bx defN 25-Oct-04 11:40 META-INF/container.xml
│ │ │ │ +?rw-r--r--  6.1 unx      162 bx defN 25-Oct-04 11:40 META-INF/com.apple.ibooks.display-options.xml
│ │ │ │ +91 files, 3077736 bytes uncompressed, 638699 bytes compressed:  79.3%
│ │ │ ├── zipdetails --redact --walk --utc {}
│ │ │ │ @@ -1,29 +1,29 @@
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│ │ │ │ -0002F   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
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│ │ │ │ +0002F   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ @@ -31,30 +31,30 @@
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│ │ │ │ -00060 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
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│ │ │ │  #          Zero length filename
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│ │ │ │ @@ -62,30 +62,30 @@
│ │ │ │  
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│ │ │ │  01DC1 PAYLOAD
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│ │ │ │ -04BAF PAYLOAD
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│ │ │ │ -072B8 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
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│ │ │ │ -0817E Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
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│ │ │ │ -08192 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ -08B4F Uncompressed Size     0000F7F4 (63476)
│ │ │ │ -08B53 Filename Length       0015 (21)
│ │ │ │ -08B55 Extra Length          001C (28)
│ │ │ │ -08B57 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8B57: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -08B6C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -08B6E   Length              0009 (9)
│ │ │ │ -08B70   Flags               03 (3) 'Modification Access'
│ │ │ │ -08B71   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -08B75   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -08B79 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -08B7B   Length              000B (11)
│ │ │ │ -08B7D   Version             01 (1)
│ │ │ │ -08B7E   UID Size            04 (4)
│ │ │ │ -08B7F   UID                 00000000 (0)
│ │ │ │ -08B83   GID Size            04 (4)
│ │ │ │ -08B84   GID                 00000000 (0)
│ │ │ │ -08B88 PAYLOAD
│ │ │ │ -
│ │ │ │ -0C409 LOCAL HEADER #11      04034B50 (67324752)
│ │ │ │ -0C40D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -0C40E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -0C40F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -0C411 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -0C413 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -0C417 CRC                   BCC7BD76 (3167206774)
│ │ │ │ -0C41B Compressed Size       0000AAE2 (43746)
│ │ │ │ -0C41F Uncompressed Size     0003DFDE (253918)
│ │ │ │ -0C423 Filename Length       0012 (18)
│ │ │ │ -0C425 Extra Length          001C (28)
│ │ │ │ -0C427 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0xC427: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -0C439 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -0C43B   Length              0009 (9)
│ │ │ │ -0C43D   Flags               03 (3) 'Modification Access'
│ │ │ │ -0C43E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -0C442   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -0C446 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -0C448   Length              000B (11)
│ │ │ │ -0C44A   Version             01 (1)
│ │ │ │ -0C44B   UID Size            04 (4)
│ │ │ │ -0C44C   UID                 00000000 (0)
│ │ │ │ -0C450   GID Size            04 (4)
│ │ │ │ -0C451   GID                 00000000 (0)
│ │ │ │ -0C455 PAYLOAD
│ │ │ │ -
│ │ │ │ -16F37 LOCAL HEADER #12      04034B50 (67324752)
│ │ │ │ -16F3B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -16F3C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -16F3D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -16F3F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -16F41 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -16F45 CRC                   04CE9FF5 (80650229)
│ │ │ │ -16F49 Compressed Size       00003B19 (15129)
│ │ │ │ -16F4D Uncompressed Size     0001B2A0 (111264)
│ │ │ │ -16F51 Filename Length       0015 (21)
│ │ │ │ -16F53 Extra Length          001C (28)
│ │ │ │ -16F55 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x16F55: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -16F6A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -16F6C   Length              0009 (9)
│ │ │ │ -16F6E   Flags               03 (3) 'Modification Access'
│ │ │ │ -16F6F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -16F73   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -16F77 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -16F79   Length              000B (11)
│ │ │ │ -16F7B   Version             01 (1)
│ │ │ │ -16F7C   UID Size            04 (4)
│ │ │ │ -16F7D   UID                 00000000 (0)
│ │ │ │ -16F81   GID Size            04 (4)
│ │ │ │ -16F82   GID                 00000000 (0)
│ │ │ │ -16F86 PAYLOAD
│ │ │ │ -
│ │ │ │ -1AA9F LOCAL HEADER #13      04034B50 (67324752)
│ │ │ │ -1AAA3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -1AAA4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -1AAA5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -1AAA7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -1AAA9 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -1AAAD CRC                   0952F615 (156431893)
│ │ │ │ -1AAB1 Compressed Size       0000908F (37007)
│ │ │ │ -1AAB5 Uncompressed Size     0003D05F (249951)
│ │ │ │ -1AAB9 Filename Length       0014 (20)
│ │ │ │ -1AABB Extra Length          001C (28)
│ │ │ │ -1AABD Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x1AABD: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -1AAD1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -1AAD3   Length              0009 (9)
│ │ │ │ -1AAD5   Flags               03 (3) 'Modification Access'
│ │ │ │ -1AAD6   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -1AADA   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -1AADE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -1AAE0   Length              000B (11)
│ │ │ │ -1AAE2   Version             01 (1)
│ │ │ │ -1AAE3   UID Size            04 (4)
│ │ │ │ -1AAE4   UID                 00000000 (0)
│ │ │ │ -1AAE8   GID Size            04 (4)
│ │ │ │ -1AAE9   GID                 00000000 (0)
│ │ │ │ -1AAED PAYLOAD
│ │ │ │ -
│ │ │ │ -23B7C LOCAL HEADER #14      04034B50 (67324752)
│ │ │ │ -23B80 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -23B81 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -23B82 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -23B84 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -23B86 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -23B8A CRC                   8221D9E1 (2183256545)
│ │ │ │ -23B8E Compressed Size       00002A63 (10851)
│ │ │ │ -23B92 Uncompressed Size     0001151F (70943)
│ │ │ │ -23B96 Filename Length       0016 (22)
│ │ │ │ -23B98 Extra Length          001C (28)
│ │ │ │ -23B9A Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x23B9A: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -23BB0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -23BB2   Length              0009 (9)
│ │ │ │ -23BB4   Flags               03 (3) 'Modification Access'
│ │ │ │ -23BB5   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -23BB9   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -23BBD Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -23BBF   Length              000B (11)
│ │ │ │ -23BC1   Version             01 (1)
│ │ │ │ -23BC2   UID Size            04 (4)
│ │ │ │ -23BC3   UID                 00000000 (0)
│ │ │ │ -23BC7   GID Size            04 (4)
│ │ │ │ -23BC8   GID                 00000000 (0)
│ │ │ │ -23BCC PAYLOAD
│ │ │ │ -
│ │ │ │ -2662F LOCAL HEADER #15      04034B50 (67324752)
│ │ │ │ -26633 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -26634 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -26635 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -26637 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -26639 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2663D CRC                   AD2220D4 (2904694996)
│ │ │ │ -26641 Compressed Size       000014DA (5338)
│ │ │ │ -26645 Uncompressed Size     00005176 (20854)
│ │ │ │ -26649 Filename Length       001D (29)
│ │ │ │ -2664B Extra Length          001C (28)
│ │ │ │ -2664D Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2664D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2666A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2666C   Length              0009 (9)
│ │ │ │ -2666E   Flags               03 (3) 'Modification Access'
│ │ │ │ -2666F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -26673   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -26677 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -26679   Length              000B (11)
│ │ │ │ -2667B   Version             01 (1)
│ │ │ │ -2667C   UID Size            04 (4)
│ │ │ │ -2667D   UID                 00000000 (0)
│ │ │ │ -26681   GID Size            04 (4)
│ │ │ │ -26682   GID                 00000000 (0)
│ │ │ │ -26686 PAYLOAD
│ │ │ │ -
│ │ │ │ -27B60 LOCAL HEADER #16      04034B50 (67324752)
│ │ │ │ -27B64 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -27B65 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -27B66 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -27B68 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -27B6A Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -27B6E CRC                   DF988056 (3751313494)
│ │ │ │ -27B72 Compressed Size       000037FC (14332)
│ │ │ │ -27B76 Uncompressed Size     0000E9F0 (59888)
│ │ │ │ -27B7A Filename Length       001C (28)
│ │ │ │ -27B7C Extra Length          001C (28)
│ │ │ │ -27B7E Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x27B7E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -27B9A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -27B9C   Length              0009 (9)
│ │ │ │ -27B9E   Flags               03 (3) 'Modification Access'
│ │ │ │ -27B9F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -27BA3   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -27BA7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -27BA9   Length              000B (11)
│ │ │ │ -27BAB   Version             01 (1)
│ │ │ │ -27BAC   UID Size            04 (4)
│ │ │ │ -27BAD   UID                 00000000 (0)
│ │ │ │ -27BB1   GID Size            04 (4)
│ │ │ │ -27BB2   GID                 00000000 (0)
│ │ │ │ -27BB6 PAYLOAD
│ │ │ │ -
│ │ │ │ -2B3B2 LOCAL HEADER #17      04034B50 (67324752)
│ │ │ │ -2B3B6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -2B3B7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -2B3B8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -2B3BA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -2B3BC Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2B3C0 CRC                   76141A43 (1981028931)
│ │ │ │ -2B3C4 Compressed Size       000006A0 (1696)
│ │ │ │ -2B3C8 Uncompressed Size     000011F4 (4596)
│ │ │ │ -2B3CC Filename Length       001C (28)
│ │ │ │ -2B3CE Extra Length          001C (28)
│ │ │ │ -2B3D0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2B3D0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2B3EC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2B3EE   Length              0009 (9)
│ │ │ │ -2B3F0   Flags               03 (3) 'Modification Access'
│ │ │ │ -2B3F1   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2B3F5   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2B3F9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -2B3FB   Length              000B (11)
│ │ │ │ -2B3FD   Version             01 (1)
│ │ │ │ -2B3FE   UID Size            04 (4)
│ │ │ │ -2B3FF   UID                 00000000 (0)
│ │ │ │ -2B403   GID Size            04 (4)
│ │ │ │ -2B404   GID                 00000000 (0)
│ │ │ │ -2B408 PAYLOAD
│ │ │ │ -
│ │ │ │ -2BAA8 LOCAL HEADER #18      04034B50 (67324752)
│ │ │ │ -2BAAC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -2BAAD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -2BAAE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -2BAB0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -2BAB2 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2BAB6 CRC                   EB30CBDF (3945843679)
│ │ │ │ -2BABA Compressed Size       0000107B (4219)
│ │ │ │ -2BABE Uncompressed Size     00004BFF (19455)
│ │ │ │ -2BAC2 Filename Length       001B (27)
│ │ │ │ -2BAC4 Extra Length          001C (28)
│ │ │ │ -2BAC6 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2BAC6: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2BAE1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2BAE3   Length              0009 (9)
│ │ │ │ -2BAE5   Flags               03 (3) 'Modification Access'
│ │ │ │ -2BAE6   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2BAEA   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2BAEE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -2BAF0   Length              000B (11)
│ │ │ │ -2BAF2   Version             01 (1)
│ │ │ │ -2BAF3   UID Size            04 (4)
│ │ │ │ -2BAF4   UID                 00000000 (0)
│ │ │ │ -2BAF8   GID Size            04 (4)
│ │ │ │ -2BAF9   GID                 00000000 (0)
│ │ │ │ -2BAFD PAYLOAD
│ │ │ │ -
│ │ │ │ -2CB78 LOCAL HEADER #19      04034B50 (67324752)
│ │ │ │ -2CB7C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -2CB7D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -2CB7E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -2CB80 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -2CB82 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2CB86 CRC                   0931FA1A (154270234)
│ │ │ │ -2CB8A Compressed Size       000033AB (13227)
│ │ │ │ -2CB8E Uncompressed Size     0000BC94 (48276)
│ │ │ │ -2CB92 Filename Length       001D (29)
│ │ │ │ -2CB94 Extra Length          001C (28)
│ │ │ │ -2CB96 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2CB96: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2CBB3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2CBB5   Length              0009 (9)
│ │ │ │ -2CBB7   Flags               03 (3) 'Modification Access'
│ │ │ │ -2CBB8   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2CBBC   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2CBC0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -2CBC2   Length              000B (11)
│ │ │ │ -2CBC4   Version             01 (1)
│ │ │ │ -2CBC5   UID Size            04 (4)
│ │ │ │ -2CBC6   UID                 00000000 (0)
│ │ │ │ -2CBCA   GID Size            04 (4)
│ │ │ │ -2CBCB   GID                 00000000 (0)
│ │ │ │ -2CBCF PAYLOAD
│ │ │ │ -
│ │ │ │ -2FF7A LOCAL HEADER #20      04034B50 (67324752)
│ │ │ │ -2FF7E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -2FF7F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -2FF80 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -2FF82 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -2FF84 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2FF88 CRC                   C8CACC1B (3368733723)
│ │ │ │ -2FF8C Compressed Size       00000D69 (3433)
│ │ │ │ -2FF90 Uncompressed Size     00003876 (14454)
│ │ │ │ -2FF94 Filename Length       001D (29)
│ │ │ │ -2FF96 Extra Length          001C (28)
│ │ │ │ -2FF98 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x2FF98: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -2FFB5 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -2FFB7   Length              0009 (9)
│ │ │ │ -2FFB9   Flags               03 (3) 'Modification Access'
│ │ │ │ -2FFBA   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2FFBE   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -2FFC2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -2FFC4   Length              000B (11)
│ │ │ │ -2FFC6   Version             01 (1)
│ │ │ │ -2FFC7   UID Size            04 (4)
│ │ │ │ -2FFC8   UID                 00000000 (0)
│ │ │ │ -2FFCC   GID Size            04 (4)
│ │ │ │ -2FFCD   GID                 00000000 (0)
│ │ │ │ -2FFD1 PAYLOAD
│ │ │ │ -
│ │ │ │ -30D3A LOCAL HEADER #21      04034B50 (67324752)
│ │ │ │ -30D3E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -30D3F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -30D40 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -30D42 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -30D44 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -30D48 CRC                   9D87D38D (2642924429)
│ │ │ │ -30D4C Compressed Size       00001C6C (7276)
│ │ │ │ -30D50 Uncompressed Size     0000C186 (49542)
│ │ │ │ -30D54 Filename Length       001A (26)
│ │ │ │ -30D56 Extra Length          001C (28)
│ │ │ │ -30D58 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x30D58: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -30D72 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -30D74   Length              0009 (9)
│ │ │ │ -30D76   Flags               03 (3) 'Modification Access'
│ │ │ │ -30D77   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -30D7B   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -30D7F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -30D81   Length              000B (11)
│ │ │ │ -30D83   Version             01 (1)
│ │ │ │ -30D84   UID Size            04 (4)
│ │ │ │ -30D85   UID                 00000000 (0)
│ │ │ │ -30D89   GID Size            04 (4)
│ │ │ │ -30D8A   GID                 00000000 (0)
│ │ │ │ -30D8E PAYLOAD
│ │ │ │ -
│ │ │ │ -329FA LOCAL HEADER #22      04034B50 (67324752)
│ │ │ │ -329FE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -329FF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -32A00 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -32A02 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -32A04 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -32A08 CRC                   D63ABE1D (3594173981)
│ │ │ │ -32A0C Compressed Size       000003A3 (931)
│ │ │ │ -32A10 Uncompressed Size     0000088E (2190)
│ │ │ │ -32A14 Filename Length       0012 (18)
│ │ │ │ -32A16 Extra Length          001C (28)
│ │ │ │ -32A18 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x32A18: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -32A2A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -32A2C   Length              0009 (9)
│ │ │ │ -32A2E   Flags               03 (3) 'Modification Access'
│ │ │ │ -32A2F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -32A33   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -32A37 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -32A39   Length              000B (11)
│ │ │ │ -32A3B   Version             01 (1)
│ │ │ │ -32A3C   UID Size            04 (4)
│ │ │ │ -32A3D   UID                 00000000 (0)
│ │ │ │ -32A41   GID Size            04 (4)
│ │ │ │ -32A42   GID                 00000000 (0)
│ │ │ │ -32A46 PAYLOAD
│ │ │ │ -
│ │ │ │ -32DE9 LOCAL HEADER #23      04034B50 (67324752)
│ │ │ │ -32DED Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -32DEE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -32DEF General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -32DF1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -32DF3 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -32DF7 CRC                   67B17E06 (1739685382)
│ │ │ │ -32DFB Compressed Size       000001D4 (468)
│ │ │ │ -32DFF Uncompressed Size     00000311 (785)
│ │ │ │ -32E03 Filename Length       0020 (32)
│ │ │ │ -32E05 Extra Length          001C (28)
│ │ │ │ -32E07 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x32E07: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -32E27 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -32E29   Length              0009 (9)
│ │ │ │ -32E2B   Flags               03 (3) 'Modification Access'
│ │ │ │ -32E2C   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -32E30   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -32E34 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -32E36   Length              000B (11)
│ │ │ │ -32E38   Version             01 (1)
│ │ │ │ -32E39   UID Size            04 (4)
│ │ │ │ -32E3A   UID                 00000000 (0)
│ │ │ │ -32E3E   GID Size            04 (4)
│ │ │ │ -32E3F   GID                 00000000 (0)
│ │ │ │ -32E43 PAYLOAD
│ │ │ │ -
│ │ │ │ -33017 LOCAL HEADER #24      04034B50 (67324752)
│ │ │ │ -3301B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3301C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3301D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3301F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -33021 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -33025 CRC                   B3D894D1 (3017315537)
│ │ │ │ -33029 Compressed Size       000017AE (6062)
│ │ │ │ -3302D Uncompressed Size     00009CD3 (40147)
│ │ │ │ -33031 Filename Length       001B (27)
│ │ │ │ -33033 Extra Length          001C (28)
│ │ │ │ -33035 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x33035: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -33050 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -33052   Length              0009 (9)
│ │ │ │ -33054   Flags               03 (3) 'Modification Access'
│ │ │ │ -33055   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -33059   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3305D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3305F   Length              000B (11)
│ │ │ │ -33061   Version             01 (1)
│ │ │ │ -33062   UID Size            04 (4)
│ │ │ │ -33063   UID                 00000000 (0)
│ │ │ │ -33067   GID Size            04 (4)
│ │ │ │ -33068   GID                 00000000 (0)
│ │ │ │ -3306C PAYLOAD
│ │ │ │ -
│ │ │ │ -3481A LOCAL HEADER #25      04034B50 (67324752)
│ │ │ │ -3481E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3481F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -34820 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -34822 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -34824 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -34828 CRC                   26417E48 (641826376)
│ │ │ │ -3482C Compressed Size       00001371 (4977)
│ │ │ │ -34830 Uncompressed Size     00003B66 (15206)
│ │ │ │ -34834 Filename Length       0015 (21)
│ │ │ │ -34836 Extra Length          001C (28)
│ │ │ │ -34838 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x34838: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3484D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3484F   Length              0009 (9)
│ │ │ │ -34851   Flags               03 (3) 'Modification Access'
│ │ │ │ -34852   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -34856   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3485A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3485C   Length              000B (11)
│ │ │ │ -3485E   Version             01 (1)
│ │ │ │ -3485F   UID Size            04 (4)
│ │ │ │ -34860   UID                 00000000 (0)
│ │ │ │ -34864   GID Size            04 (4)
│ │ │ │ -34865   GID                 00000000 (0)
│ │ │ │ -34869 PAYLOAD
│ │ │ │ -
│ │ │ │ -35BDA LOCAL HEADER #26      04034B50 (67324752)
│ │ │ │ -35BDE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -35BDF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -35BE0 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -35BE2 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -35BE4 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -35BE8 CRC                   8884496A (2290370922)
│ │ │ │ -35BEC Compressed Size       00000AD1 (2769)
│ │ │ │ -35BF0 Uncompressed Size     00002135 (8501)
│ │ │ │ -35BF4 Filename Length       0011 (17)
│ │ │ │ -35BF6 Extra Length          001C (28)
│ │ │ │ -35BF8 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x35BF8: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -35C09 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -35C0B   Length              0009 (9)
│ │ │ │ -35C0D   Flags               03 (3) 'Modification Access'
│ │ │ │ -35C0E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -35C12   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -35C16 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -35C18   Length              000B (11)
│ │ │ │ -35C1A   Version             01 (1)
│ │ │ │ -35C1B   UID Size            04 (4)
│ │ │ │ -35C1C   UID                 00000000 (0)
│ │ │ │ -35C20   GID Size            04 (4)
│ │ │ │ -35C21   GID                 00000000 (0)
│ │ │ │ -35C25 PAYLOAD
│ │ │ │ -
│ │ │ │ -366F6 LOCAL HEADER #27      04034B50 (67324752)
│ │ │ │ -366FA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -366FB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -366FC General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -366FE Compression Method    0008 (8) 'Deflated'
│ │ │ │ -36700 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -36704 CRC                   DB40B17A (3678450042)
│ │ │ │ -36708 Compressed Size       000003FE (1022)
│ │ │ │ -3670C Uncompressed Size     00000E99 (3737)
│ │ │ │ -36710 Filename Length       0014 (20)
│ │ │ │ -36712 Extra Length          001C (28)
│ │ │ │ -36714 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x36714: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -36728 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3672A   Length              0009 (9)
│ │ │ │ -3672C   Flags               03 (3) 'Modification Access'
│ │ │ │ -3672D   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -36731   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -36735 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -36737   Length              000B (11)
│ │ │ │ -36739   Version             01 (1)
│ │ │ │ -3673A   UID Size            04 (4)
│ │ │ │ -3673B   UID                 00000000 (0)
│ │ │ │ -3673F   GID Size            04 (4)
│ │ │ │ -36740   GID                 00000000 (0)
│ │ │ │ -36744 PAYLOAD
│ │ │ │ -
│ │ │ │ -36B42 LOCAL HEADER #28      04034B50 (67324752)
│ │ │ │ -36B46 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -36B47 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -36B48 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -36B4A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -36B4C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -36B50 CRC                   6E954352 (1855275858)
│ │ │ │ -36B54 Compressed Size       00001262 (4706)
│ │ │ │ -36B58 Uncompressed Size     00003469 (13417)
│ │ │ │ -36B5C Filename Length       0014 (20)
│ │ │ │ -36B5E Extra Length          001C (28)
│ │ │ │ -36B60 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x36B60: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -36B74 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -36B76   Length              0009 (9)
│ │ │ │ -36B78   Flags               03 (3) 'Modification Access'
│ │ │ │ -36B79   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -36B7D   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -36B81 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -36B83   Length              000B (11)
│ │ │ │ -36B85   Version             01 (1)
│ │ │ │ -36B86   UID Size            04 (4)
│ │ │ │ -36B87   UID                 00000000 (0)
│ │ │ │ -36B8B   GID Size            04 (4)
│ │ │ │ -36B8C   GID                 00000000 (0)
│ │ │ │ -36B90 PAYLOAD
│ │ │ │ -
│ │ │ │ -37DF2 LOCAL HEADER #29      04034B50 (67324752)
│ │ │ │ -37DF6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -37DF7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -37DF8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -37DFA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -37DFC Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -37E00 CRC                   DB1D4E7B (3676130939)
│ │ │ │ -37E04 Compressed Size       00000ACF (2767)
│ │ │ │ -37E08 Uncompressed Size     000022FF (8959)
│ │ │ │ -37E0C Filename Length       001B (27)
│ │ │ │ -37E0E Extra Length          001C (28)
│ │ │ │ -37E10 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x37E10: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -37E2B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -37E2D   Length              0009 (9)
│ │ │ │ -37E2F   Flags               03 (3) 'Modification Access'
│ │ │ │ -37E30   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -37E34   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -37E38 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -37E3A   Length              000B (11)
│ │ │ │ -37E3C   Version             01 (1)
│ │ │ │ -37E3D   UID Size            04 (4)
│ │ │ │ -37E3E   UID                 00000000 (0)
│ │ │ │ -37E42   GID Size            04 (4)
│ │ │ │ -37E43   GID                 00000000 (0)
│ │ │ │ -37E47 PAYLOAD
│ │ │ │ -
│ │ │ │ -38916 LOCAL HEADER #30      04034B50 (67324752)
│ │ │ │ -3891A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3891B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3891C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3891E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -38920 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -38924 CRC                   B74B6217 (3075170839)
│ │ │ │ -38928 Compressed Size       00000A8E (2702)
│ │ │ │ -3892C Uncompressed Size     0000237A (9082)
│ │ │ │ -38930 Filename Length       0013 (19)
│ │ │ │ -38932 Extra Length          001C (28)
│ │ │ │ -38934 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x38934: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -38947 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -38949   Length              0009 (9)
│ │ │ │ -3894B   Flags               03 (3) 'Modification Access'
│ │ │ │ -3894C   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -38950   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -38954 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -38956   Length              000B (11)
│ │ │ │ -38958   Version             01 (1)
│ │ │ │ -38959   UID Size            04 (4)
│ │ │ │ -3895A   UID                 00000000 (0)
│ │ │ │ -3895E   GID Size            04 (4)
│ │ │ │ -3895F   GID                 00000000 (0)
│ │ │ │ -38963 PAYLOAD
│ │ │ │ -
│ │ │ │ -393F1 LOCAL HEADER #31      04034B50 (67324752)
│ │ │ │ -393F5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -393F6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -393F7 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -393F9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -393FB Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -393FF CRC                   33B87EA3 (867729059)
│ │ │ │ -39403 Compressed Size       00000F48 (3912)
│ │ │ │ -39407 Uncompressed Size     000036F1 (14065)
│ │ │ │ -3940B Filename Length       000F (15)
│ │ │ │ -3940D Extra Length          001C (28)
│ │ │ │ -3940F Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3940F: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3941E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -39420   Length              0009 (9)
│ │ │ │ -39422   Flags               03 (3) 'Modification Access'
│ │ │ │ -39423   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -39427   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3942B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3942D   Length              000B (11)
│ │ │ │ -3942F   Version             01 (1)
│ │ │ │ -39430   UID Size            04 (4)
│ │ │ │ -39431   UID                 00000000 (0)
│ │ │ │ -39435   GID Size            04 (4)
│ │ │ │ -39436   GID                 00000000 (0)
│ │ │ │ -3943A PAYLOAD
│ │ │ │ -
│ │ │ │ -3A382 LOCAL HEADER #32      04034B50 (67324752)
│ │ │ │ -3A386 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3A387 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3A388 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3A38A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3A38C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3A390 CRC                   7FB04E29 (2142260777)
│ │ │ │ -3A394 Compressed Size       0000066A (1642)
│ │ │ │ -3A398 Uncompressed Size     000018DF (6367)
│ │ │ │ -3A39C Filename Length       000F (15)
│ │ │ │ -3A39E Extra Length          001C (28)
│ │ │ │ -3A3A0 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3A3A0: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3A3AF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3A3B1   Length              0009 (9)
│ │ │ │ -3A3B3   Flags               03 (3) 'Modification Access'
│ │ │ │ -3A3B4   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3A3B8   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3A3BC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3A3BE   Length              000B (11)
│ │ │ │ -3A3C0   Version             01 (1)
│ │ │ │ -3A3C1   UID Size            04 (4)
│ │ │ │ -3A3C2   UID                 00000000 (0)
│ │ │ │ -3A3C6   GID Size            04 (4)
│ │ │ │ -3A3C7   GID                 00000000 (0)
│ │ │ │ -3A3CB PAYLOAD
│ │ │ │ -
│ │ │ │ -3AA35 LOCAL HEADER #33      04034B50 (67324752)
│ │ │ │ -3AA39 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3AA3A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3AA3B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3AA3D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3AA3F Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3AA43 CRC                   5FF08021 (1609596961)
│ │ │ │ -3AA47 Compressed Size       00001A4A (6730)
│ │ │ │ -3AA4B Uncompressed Size     000064F2 (25842)
│ │ │ │ -3AA4F Filename Length       0013 (19)
│ │ │ │ -3AA51 Extra Length          001C (28)
│ │ │ │ -3AA53 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3AA53: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3AA66 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3AA68   Length              0009 (9)
│ │ │ │ -3AA6A   Flags               03 (3) 'Modification Access'
│ │ │ │ -3AA6B   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3AA6F   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3AA73 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3AA75   Length              000B (11)
│ │ │ │ -3AA77   Version             01 (1)
│ │ │ │ -3AA78   UID Size            04 (4)
│ │ │ │ -3AA79   UID                 00000000 (0)
│ │ │ │ -3AA7D   GID Size            04 (4)
│ │ │ │ -3AA7E   GID                 00000000 (0)
│ │ │ │ -3AA82 PAYLOAD
│ │ │ │ -
│ │ │ │ -3C4CC LOCAL HEADER #34      04034B50 (67324752)
│ │ │ │ -3C4D0 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3C4D1 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3C4D2 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3C4D4 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3C4D6 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3C4DA CRC                   B885C195 (3095773589)
│ │ │ │ -3C4DE Compressed Size       000009A5 (2469)
│ │ │ │ -3C4E2 Uncompressed Size     00001B64 (7012)
│ │ │ │ -3C4E6 Filename Length       0010 (16)
│ │ │ │ -3C4E8 Extra Length          001C (28)
│ │ │ │ -3C4EA Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3C4EA: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3C4FA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3C4FC   Length              0009 (9)
│ │ │ │ -3C4FE   Flags               03 (3) 'Modification Access'
│ │ │ │ -3C4FF   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3C503   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3C507 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3C509   Length              000B (11)
│ │ │ │ -3C50B   Version             01 (1)
│ │ │ │ -3C50C   UID Size            04 (4)
│ │ │ │ -3C50D   UID                 00000000 (0)
│ │ │ │ -3C511   GID Size            04 (4)
│ │ │ │ -3C512   GID                 00000000 (0)
│ │ │ │ -3C516 PAYLOAD
│ │ │ │ -
│ │ │ │ -3CEBB LOCAL HEADER #35      04034B50 (67324752)
│ │ │ │ -3CEBF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3CEC0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3CEC1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3CEC3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3CEC5 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3CEC9 CRC                   297E5B60 (696146784)
│ │ │ │ -3CECD Compressed Size       000006B7 (1719)
│ │ │ │ -3CED1 Uncompressed Size     00001565 (5477)
│ │ │ │ -3CED5 Filename Length       0012 (18)
│ │ │ │ -3CED7 Extra Length          001C (28)
│ │ │ │ -3CED9 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3CED9: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3CEEB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3CEED   Length              0009 (9)
│ │ │ │ -3CEEF   Flags               03 (3) 'Modification Access'
│ │ │ │ -3CEF0   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3CEF4   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3CEF8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3CEFA   Length              000B (11)
│ │ │ │ -3CEFC   Version             01 (1)
│ │ │ │ -3CEFD   UID Size            04 (4)
│ │ │ │ -3CEFE   UID                 00000000 (0)
│ │ │ │ -3CF02   GID Size            04 (4)
│ │ │ │ -3CF03   GID                 00000000 (0)
│ │ │ │ -3CF07 PAYLOAD
│ │ │ │ -
│ │ │ │ -3D5BE LOCAL HEADER #36      04034B50 (67324752)
│ │ │ │ -3D5C2 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -3D5C3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -3D5C4 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -3D5C6 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -3D5C8 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3D5CC CRC                   963999A8 (2520357288)
│ │ │ │ -3D5D0 Compressed Size       00002A16 (10774)
│ │ │ │ -3D5D4 Uncompressed Size     0000B1C5 (45509)
│ │ │ │ -3D5D8 Filename Length       0010 (16)
│ │ │ │ -3D5DA Extra Length          001C (28)
│ │ │ │ -3D5DC Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x3D5DC: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -3D5EC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -3D5EE   Length              0009 (9)
│ │ │ │ -3D5F0   Flags               03 (3) 'Modification Access'
│ │ │ │ -3D5F1   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3D5F5   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -3D5F9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -3D5FB   Length              000B (11)
│ │ │ │ -3D5FD   Version             01 (1)
│ │ │ │ -3D5FE   UID Size            04 (4)
│ │ │ │ -3D5FF   UID                 00000000 (0)
│ │ │ │ -3D603   GID Size            04 (4)
│ │ │ │ -3D604   GID                 00000000 (0)
│ │ │ │ -3D608 PAYLOAD
│ │ │ │ -
│ │ │ │ -4001E LOCAL HEADER #37      04034B50 (67324752)
│ │ │ │ -40022 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -40023 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -40024 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -40026 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -40028 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4002C CRC                   412FC61A (1093649946)
│ │ │ │ -40030 Compressed Size       00001E8C (7820)
│ │ │ │ -40034 Uncompressed Size     00009AAA (39594)
│ │ │ │ -40038 Filename Length       0012 (18)
│ │ │ │ -4003A Extra Length          001C (28)
│ │ │ │ -4003C Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4003C: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4004E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -40050   Length              0009 (9)
│ │ │ │ -40052   Flags               03 (3) 'Modification Access'
│ │ │ │ -40053   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -40057   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4005B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4005D   Length              000B (11)
│ │ │ │ -4005F   Version             01 (1)
│ │ │ │ -40060   UID Size            04 (4)
│ │ │ │ -40061   UID                 00000000 (0)
│ │ │ │ -40065   GID Size            04 (4)
│ │ │ │ -40066   GID                 00000000 (0)
│ │ │ │ -4006A PAYLOAD
│ │ │ │ -
│ │ │ │ -41EF6 LOCAL HEADER #38      04034B50 (67324752)
│ │ │ │ -41EFA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -41EFB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -41EFC General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -41EFE Compression Method    0008 (8) 'Deflated'
│ │ │ │ -41F00 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -41F04 CRC                   889828DF (2291673311)
│ │ │ │ -41F08 Compressed Size       00001479 (5241)
│ │ │ │ -41F0C Uncompressed Size     00007ACF (31439)
│ │ │ │ -41F10 Filename Length       0018 (24)
│ │ │ │ -41F12 Extra Length          001C (28)
│ │ │ │ -41F14 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x41F14: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -41F2C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -41F2E   Length              0009 (9)
│ │ │ │ -41F30   Flags               03 (3) 'Modification Access'
│ │ │ │ -41F31   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -41F35   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -41F39 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -41F3B   Length              000B (11)
│ │ │ │ -41F3D   Version             01 (1)
│ │ │ │ -41F3E   UID Size            04 (4)
│ │ │ │ -41F3F   UID                 00000000 (0)
│ │ │ │ -41F43   GID Size            04 (4)
│ │ │ │ -41F44   GID                 00000000 (0)
│ │ │ │ -41F48 PAYLOAD
│ │ │ │ -
│ │ │ │ -433C1 LOCAL HEADER #39      04034B50 (67324752)
│ │ │ │ -433C5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -433C6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -433C7 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -433C9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -433CB Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -433CF CRC                   2812718D (672297357)
│ │ │ │ -433D3 Compressed Size       000018D3 (6355)
│ │ │ │ -433D7 Uncompressed Size     0000A7F4 (42996)
│ │ │ │ -433DB Filename Length       001F (31)
│ │ │ │ -433DD Extra Length          001C (28)
│ │ │ │ -433DF Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x433DF: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -433FE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -43400   Length              0009 (9)
│ │ │ │ -43402   Flags               03 (3) 'Modification Access'
│ │ │ │ -43403   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -43407   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4340B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4340D   Length              000B (11)
│ │ │ │ -4340F   Version             01 (1)
│ │ │ │ -43410   UID Size            04 (4)
│ │ │ │ -43411   UID                 00000000 (0)
│ │ │ │ -43415   GID Size            04 (4)
│ │ │ │ -43416   GID                 00000000 (0)
│ │ │ │ -4341A PAYLOAD
│ │ │ │ -
│ │ │ │ -44CED LOCAL HEADER #40      04034B50 (67324752)
│ │ │ │ -44CF1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -44CF2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -44CF3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -44CF5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -44CF7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -44CFB CRC                   705BC16B (1885061483)
│ │ │ │ -44CFF Compressed Size       000003F7 (1015)
│ │ │ │ -44D03 Uncompressed Size     000008A3 (2211)
│ │ │ │ -44D07 Filename Length       001E (30)
│ │ │ │ -44D09 Extra Length          001C (28)
│ │ │ │ -44D0B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x44D0B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -44D29 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -44D2B   Length              0009 (9)
│ │ │ │ -44D2D   Flags               03 (3) 'Modification Access'
│ │ │ │ -44D2E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -44D32   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -44D36 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -44D38   Length              000B (11)
│ │ │ │ -44D3A   Version             01 (1)
│ │ │ │ -44D3B   UID Size            04 (4)
│ │ │ │ -44D3C   UID                 00000000 (0)
│ │ │ │ -44D40   GID Size            04 (4)
│ │ │ │ -44D41   GID                 00000000 (0)
│ │ │ │ -44D45 PAYLOAD
│ │ │ │ -
│ │ │ │ -4513C LOCAL HEADER #41      04034B50 (67324752)
│ │ │ │ -45140 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -45141 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -45142 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -45144 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -45146 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4514A CRC                   BAFC6D2D (3137105197)
│ │ │ │ -4514E Compressed Size       00004293 (17043)
│ │ │ │ -45152 Uncompressed Size     0000D8DC (55516)
│ │ │ │ -45156 Filename Length       0013 (19)
│ │ │ │ -45158 Extra Length          001C (28)
│ │ │ │ -4515A Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4515A: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4516D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4516F   Length              0009 (9)
│ │ │ │ -45171   Flags               03 (3) 'Modification Access'
│ │ │ │ -45172   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -45176   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4517A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4517C   Length              000B (11)
│ │ │ │ -4517E   Version             01 (1)
│ │ │ │ -4517F   UID Size            04 (4)
│ │ │ │ -45180   UID                 00000000 (0)
│ │ │ │ -45184   GID Size            04 (4)
│ │ │ │ -45185   GID                 00000000 (0)
│ │ │ │ -45189 PAYLOAD
│ │ │ │ -
│ │ │ │ -4941C LOCAL HEADER #42      04034B50 (67324752)
│ │ │ │ -49420 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -49421 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -49422 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -49424 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -49426 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4942A CRC                   49C65647 (1237734983)
│ │ │ │ -4942E Compressed Size       000026C3 (9923)
│ │ │ │ -49432 Uncompressed Size     00006E45 (28229)
│ │ │ │ -49436 Filename Length       0019 (25)
│ │ │ │ -49438 Extra Length          001C (28)
│ │ │ │ -4943A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4943A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -49453 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -49455   Length              0009 (9)
│ │ │ │ -49457   Flags               03 (3) 'Modification Access'
│ │ │ │ -49458   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4945C   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -49460 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -49462   Length              000B (11)
│ │ │ │ -49464   Version             01 (1)
│ │ │ │ -49465   UID Size            04 (4)
│ │ │ │ -49466   UID                 00000000 (0)
│ │ │ │ -4946A   GID Size            04 (4)
│ │ │ │ -4946B   GID                 00000000 (0)
│ │ │ │ -4946F PAYLOAD
│ │ │ │ -
│ │ │ │ -4BB32 LOCAL HEADER #43      04034B50 (67324752)
│ │ │ │ -4BB36 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4BB37 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4BB38 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4BB3A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4BB3C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4BB40 CRC                   063987F6 (104433654)
│ │ │ │ -4BB44 Compressed Size       0000273A (10042)
│ │ │ │ -4BB48 Uncompressed Size     00008B83 (35715)
│ │ │ │ -4BB4C Filename Length       0019 (25)
│ │ │ │ -4BB4E Extra Length          001C (28)
│ │ │ │ -4BB50 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4BB50: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4BB69 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4BB6B   Length              0009 (9)
│ │ │ │ -4BB6D   Flags               03 (3) 'Modification Access'
│ │ │ │ -4BB6E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4BB72   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4BB76 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4BB78   Length              000B (11)
│ │ │ │ -4BB7A   Version             01 (1)
│ │ │ │ -4BB7B   UID Size            04 (4)
│ │ │ │ -4BB7C   UID                 00000000 (0)
│ │ │ │ -4BB80   GID Size            04 (4)
│ │ │ │ -4BB81   GID                 00000000 (0)
│ │ │ │ -4BB85 PAYLOAD
│ │ │ │ -
│ │ │ │ -4E2BF LOCAL HEADER #44      04034B50 (67324752)
│ │ │ │ -4E2C3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4E2C4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4E2C5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4E2C7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4E2C9 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4E2CD CRC                   F2DA5952 (4074395986)
│ │ │ │ -4E2D1 Compressed Size       00000CEE (3310)
│ │ │ │ -4E2D5 Uncompressed Size     0000517A (20858)
│ │ │ │ -4E2D9 Filename Length       0021 (33)
│ │ │ │ -4E2DB Extra Length          001C (28)
│ │ │ │ -4E2DD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4E2DD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4E2FE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4E300   Length              0009 (9)
│ │ │ │ -4E302   Flags               03 (3) 'Modification Access'
│ │ │ │ -4E303   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4E307   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4E30B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4E30D   Length              000B (11)
│ │ │ │ -4E30F   Version             01 (1)
│ │ │ │ -4E310   UID Size            04 (4)
│ │ │ │ -4E311   UID                 00000000 (0)
│ │ │ │ -4E315   GID Size            04 (4)
│ │ │ │ -4E316   GID                 00000000 (0)
│ │ │ │ -4E31A PAYLOAD
│ │ │ │ -
│ │ │ │ -4F008 LOCAL HEADER #45      04034B50 (67324752)
│ │ │ │ -4F00C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4F00D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4F00E General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4F010 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4F012 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4F016 CRC                   8C66FDEA (2355559914)
│ │ │ │ -4F01A Compressed Size       00000468 (1128)
│ │ │ │ -4F01E Uncompressed Size     00000931 (2353)
│ │ │ │ -4F022 Filename Length       001B (27)
│ │ │ │ -4F024 Extra Length          001C (28)
│ │ │ │ -4F026 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4F026: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4F041 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4F043   Length              0009 (9)
│ │ │ │ -4F045   Flags               03 (3) 'Modification Access'
│ │ │ │ -4F046   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4F04A   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4F04E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4F050   Length              000B (11)
│ │ │ │ -4F052   Version             01 (1)
│ │ │ │ -4F053   UID Size            04 (4)
│ │ │ │ -4F054   UID                 00000000 (0)
│ │ │ │ -4F058   GID Size            04 (4)
│ │ │ │ -4F059   GID                 00000000 (0)
│ │ │ │ -4F05D PAYLOAD
│ │ │ │ -
│ │ │ │ -4F4C5 LOCAL HEADER #46      04034B50 (67324752)
│ │ │ │ -4F4C9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -4F4CA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -4F4CB General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -4F4CD Compression Method    0008 (8) 'Deflated'
│ │ │ │ -4F4CF Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4F4D3 CRC                   FC713245 (4235276869)
│ │ │ │ -4F4D7 Compressed Size       000016F4 (5876)
│ │ │ │ -4F4DB Uncompressed Size     00007A6D (31341)
│ │ │ │ -4F4DF Filename Length       001F (31)
│ │ │ │ -4F4E1 Extra Length          001C (28)
│ │ │ │ -4F4E3 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x4F4E3: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -4F502 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -4F504   Length              0009 (9)
│ │ │ │ -4F506   Flags               03 (3) 'Modification Access'
│ │ │ │ -4F507   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4F50B   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -4F50F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -4F511   Length              000B (11)
│ │ │ │ -4F513   Version             01 (1)
│ │ │ │ -4F514   UID Size            04 (4)
│ │ │ │ -4F515   UID                 00000000 (0)
│ │ │ │ -4F519   GID Size            04 (4)
│ │ │ │ -4F51A   GID                 00000000 (0)
│ │ │ │ -4F51E PAYLOAD
│ │ │ │ -
│ │ │ │ -50C12 LOCAL HEADER #47      04034B50 (67324752)
│ │ │ │ -50C16 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -50C17 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -50C18 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -50C1A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -50C1C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -50C20 CRC                   6703890F (1728284943)
│ │ │ │ -50C24 Compressed Size       00004177 (16759)
│ │ │ │ -50C28 Uncompressed Size     0001CF93 (118675)
│ │ │ │ -50C2C Filename Length       0010 (16)
│ │ │ │ -50C2E Extra Length          001C (28)
│ │ │ │ -50C30 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x50C30: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -50C40 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -50C42   Length              0009 (9)
│ │ │ │ -50C44   Flags               03 (3) 'Modification Access'
│ │ │ │ -50C45   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -50C49   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -50C4D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -50C4F   Length              000B (11)
│ │ │ │ -50C51   Version             01 (1)
│ │ │ │ -50C52   UID Size            04 (4)
│ │ │ │ -50C53   UID                 00000000 (0)
│ │ │ │ -50C57   GID Size            04 (4)
│ │ │ │ -50C58   GID                 00000000 (0)
│ │ │ │ -50C5C PAYLOAD
│ │ │ │ -
│ │ │ │ -54DD3 LOCAL HEADER #48      04034B50 (67324752)
│ │ │ │ -54DD7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -54DD8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -54DD9 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -54DDB Compression Method    0008 (8) 'Deflated'
│ │ │ │ -54DDD Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -54DE1 CRC                   7903D415 (2030294037)
│ │ │ │ -54DE5 Compressed Size       00000A94 (2708)
│ │ │ │ -54DE9 Uncompressed Size     00002105 (8453)
│ │ │ │ -54DED Filename Length       0014 (20)
│ │ │ │ -54DEF Extra Length          001C (28)
│ │ │ │ -54DF1 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x54DF1: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -54E05 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -54E07   Length              0009 (9)
│ │ │ │ -54E09   Flags               03 (3) 'Modification Access'
│ │ │ │ -54E0A   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -54E0E   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -54E12 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -54E14   Length              000B (11)
│ │ │ │ -54E16   Version             01 (1)
│ │ │ │ -54E17   UID Size            04 (4)
│ │ │ │ -54E18   UID                 00000000 (0)
│ │ │ │ -54E1C   GID Size            04 (4)
│ │ │ │ -54E1D   GID                 00000000 (0)
│ │ │ │ -54E21 PAYLOAD
│ │ │ │ -
│ │ │ │ -558B5 LOCAL HEADER #49      04034B50 (67324752)
│ │ │ │ -558B9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -558BA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -558BB General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -558BD Compression Method    0008 (8) 'Deflated'
│ │ │ │ -558BF Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -558C3 CRC                   1D304539 (489702713)
│ │ │ │ -558C7 Compressed Size       0000AC97 (44183)
│ │ │ │ -558CB Uncompressed Size     0003E418 (255000)
│ │ │ │ -558CF Filename Length       0017 (23)
│ │ │ │ -558D1 Extra Length          001C (28)
│ │ │ │ -558D3 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x558D3: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -558EA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -558EC   Length              0009 (9)
│ │ │ │ -558EE   Flags               03 (3) 'Modification Access'
│ │ │ │ -558EF   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -558F3   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -558F7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -558F9   Length              000B (11)
│ │ │ │ -558FB   Version             01 (1)
│ │ │ │ -558FC   UID Size            04 (4)
│ │ │ │ -558FD   UID                 00000000 (0)
│ │ │ │ -55901   GID Size            04 (4)
│ │ │ │ -55902   GID                 00000000 (0)
│ │ │ │ -55906 PAYLOAD
│ │ │ │ -
│ │ │ │ -6059D LOCAL HEADER #50      04034B50 (67324752)
│ │ │ │ -605A1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -605A2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -605A3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -605A5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -605A7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -605AB CRC                   73C7E563 (1942480227)
│ │ │ │ -605AF Compressed Size       00000400 (1024)
│ │ │ │ -605B3 Uncompressed Size     0000093D (2365)
│ │ │ │ -605B7 Filename Length       0013 (19)
│ │ │ │ -605B9 Extra Length          001C (28)
│ │ │ │ -605BB Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x605BB: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -605CE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -605D0   Length              0009 (9)
│ │ │ │ -605D2   Flags               03 (3) 'Modification Access'
│ │ │ │ -605D3   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -605D7   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -605DB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -605DD   Length              000B (11)
│ │ │ │ -605DF   Version             01 (1)
│ │ │ │ -605E0   UID Size            04 (4)
│ │ │ │ -605E1   UID                 00000000 (0)
│ │ │ │ -605E5   GID Size            04 (4)
│ │ │ │ -605E6   GID                 00000000 (0)
│ │ │ │ -605EA PAYLOAD
│ │ │ │ -
│ │ │ │ -609EA LOCAL HEADER #51      04034B50 (67324752)
│ │ │ │ -609EE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -609EF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -609F0 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -609F2 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -609F4 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -609F8 CRC                   7EF400B8 (2129920184)
│ │ │ │ -609FC Compressed Size       000014E5 (5349)
│ │ │ │ -60A00 Uncompressed Size     0000687B (26747)
│ │ │ │ -60A04 Filename Length       0012 (18)
│ │ │ │ -60A06 Extra Length          001C (28)
│ │ │ │ -60A08 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x60A08: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -60A1A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -60A1C   Length              0009 (9)
│ │ │ │ -60A1E   Flags               03 (3) 'Modification Access'
│ │ │ │ -60A1F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -60A23   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -60A27 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -60A29   Length              000B (11)
│ │ │ │ -60A2B   Version             01 (1)
│ │ │ │ -60A2C   UID Size            04 (4)
│ │ │ │ -60A2D   UID                 00000000 (0)
│ │ │ │ -60A31   GID Size            04 (4)
│ │ │ │ -60A32   GID                 00000000 (0)
│ │ │ │ -60A36 PAYLOAD
│ │ │ │ -
│ │ │ │ -61F1B LOCAL HEADER #52      04034B50 (67324752)
│ │ │ │ -61F1F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -61F20 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -61F21 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -61F23 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -61F25 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -61F29 CRC                   693EF524 (1765733668)
│ │ │ │ -61F2D Compressed Size       000011EB (4587)
│ │ │ │ -61F31 Uncompressed Size     000040F5 (16629)
│ │ │ │ -61F35 Filename Length       0012 (18)
│ │ │ │ -61F37 Extra Length          001C (28)
│ │ │ │ -61F39 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x61F39: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -61F4B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -61F4D   Length              0009 (9)
│ │ │ │ -61F4F   Flags               03 (3) 'Modification Access'
│ │ │ │ -61F50   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -61F54   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -61F58 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -61F5A   Length              000B (11)
│ │ │ │ -61F5C   Version             01 (1)
│ │ │ │ -61F5D   UID Size            04 (4)
│ │ │ │ -61F5E   UID                 00000000 (0)
│ │ │ │ -61F62   GID Size            04 (4)
│ │ │ │ -61F63   GID                 00000000 (0)
│ │ │ │ -61F67 PAYLOAD
│ │ │ │ -
│ │ │ │ -63152 LOCAL HEADER #53      04034B50 (67324752)
│ │ │ │ -63156 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -63157 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -63158 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6315A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6315C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -63160 CRC                   23CF3462 (600781922)
│ │ │ │ -63164 Compressed Size       000009DA (2522)
│ │ │ │ -63168 Uncompressed Size     00003529 (13609)
│ │ │ │ -6316C Filename Length       0019 (25)
│ │ │ │ -6316E Extra Length          001C (28)
│ │ │ │ -63170 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x63170: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -63189 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6318B   Length              0009 (9)
│ │ │ │ -6318D   Flags               03 (3) 'Modification Access'
│ │ │ │ -6318E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -63192   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -63196 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -63198   Length              000B (11)
│ │ │ │ -6319A   Version             01 (1)
│ │ │ │ -6319B   UID Size            04 (4)
│ │ │ │ -6319C   UID                 00000000 (0)
│ │ │ │ -631A0   GID Size            04 (4)
│ │ │ │ -631A1   GID                 00000000 (0)
│ │ │ │ -631A5 PAYLOAD
│ │ │ │ -
│ │ │ │ -63B7F LOCAL HEADER #54      04034B50 (67324752)
│ │ │ │ -63B83 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -63B84 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -63B85 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -63B87 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -63B89 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -63B8D CRC                   3E165161 (1041650017)
│ │ │ │ -63B91 Compressed Size       000018B0 (6320)
│ │ │ │ -63B95 Uncompressed Size     0000A605 (42501)
│ │ │ │ -63B99 Filename Length       0019 (25)
│ │ │ │ -63B9B Extra Length          001C (28)
│ │ │ │ -63B9D Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x63B9D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -63BB6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -63BB8   Length              0009 (9)
│ │ │ │ -63BBA   Flags               03 (3) 'Modification Access'
│ │ │ │ -63BBB   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -63BBF   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -63BC3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -63BC5   Length              000B (11)
│ │ │ │ -63BC7   Version             01 (1)
│ │ │ │ -63BC8   UID Size            04 (4)
│ │ │ │ -63BC9   UID                 00000000 (0)
│ │ │ │ -63BCD   GID Size            04 (4)
│ │ │ │ -63BCE   GID                 00000000 (0)
│ │ │ │ -63BD2 PAYLOAD
│ │ │ │ -
│ │ │ │ -65482 LOCAL HEADER #55      04034B50 (67324752)
│ │ │ │ -65486 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -65487 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -65488 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6548A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6548C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -65490 CRC                   80854D35 (2156219701)
│ │ │ │ -65494 Compressed Size       0000177D (6013)
│ │ │ │ -65498 Uncompressed Size     0000472C (18220)
│ │ │ │ -6549C Filename Length       0014 (20)
│ │ │ │ -6549E Extra Length          001C (28)
│ │ │ │ -654A0 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x654A0: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -654B4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -654B6   Length              0009 (9)
│ │ │ │ -654B8   Flags               03 (3) 'Modification Access'
│ │ │ │ -654B9   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -654BD   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -654C1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -654C3   Length              000B (11)
│ │ │ │ -654C5   Version             01 (1)
│ │ │ │ -654C6   UID Size            04 (4)
│ │ │ │ -654C7   UID                 00000000 (0)
│ │ │ │ -654CB   GID Size            04 (4)
│ │ │ │ -654CC   GID                 00000000 (0)
│ │ │ │ -654D0 PAYLOAD
│ │ │ │ -
│ │ │ │ -66C4D LOCAL HEADER #56      04034B50 (67324752)
│ │ │ │ -66C51 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -66C52 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -66C53 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -66C55 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -66C57 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -66C5B CRC                   8CE827B6 (2364024758)
│ │ │ │ -66C5F Compressed Size       0000040A (1034)
│ │ │ │ -66C63 Uncompressed Size     00000825 (2085)
│ │ │ │ -66C67 Filename Length       001C (28)
│ │ │ │ -66C69 Extra Length          001C (28)
│ │ │ │ -66C6B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x66C6B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -66C87 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -66C89   Length              0009 (9)
│ │ │ │ -66C8B   Flags               03 (3) 'Modification Access'
│ │ │ │ -66C8C   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -66C90   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -66C94 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -66C96   Length              000B (11)
│ │ │ │ -66C98   Version             01 (1)
│ │ │ │ -66C99   UID Size            04 (4)
│ │ │ │ -66C9A   UID                 00000000 (0)
│ │ │ │ -66C9E   GID Size            04 (4)
│ │ │ │ -66C9F   GID                 00000000 (0)
│ │ │ │ -66CA3 PAYLOAD
│ │ │ │ -
│ │ │ │ -670AD LOCAL HEADER #57      04034B50 (67324752)
│ │ │ │ -670B1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -670B2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -670B3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -670B5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -670B7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -670BB CRC                   060C597A (101472634)
│ │ │ │ -670BF Compressed Size       00002480 (9344)
│ │ │ │ -670C3 Uncompressed Size     0000B56F (46447)
│ │ │ │ -670C7 Filename Length       001F (31)
│ │ │ │ -670C9 Extra Length          001C (28)
│ │ │ │ -670CB Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x670CB: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -670EA Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -670EC   Length              0009 (9)
│ │ │ │ -670EE   Flags               03 (3) 'Modification Access'
│ │ │ │ -670EF   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -670F3   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -670F7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -670F9   Length              000B (11)
│ │ │ │ -670FB   Version             01 (1)
│ │ │ │ -670FC   UID Size            04 (4)
│ │ │ │ -670FD   UID                 00000000 (0)
│ │ │ │ -67101   GID Size            04 (4)
│ │ │ │ -67102   GID                 00000000 (0)
│ │ │ │ -67106 PAYLOAD
│ │ │ │ -
│ │ │ │ -69586 LOCAL HEADER #58      04034B50 (67324752)
│ │ │ │ -6958A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6958B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6958C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6958E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -69590 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -69594 CRC                   F8304094 (4163911828)
│ │ │ │ -69598 Compressed Size       00000E78 (3704)
│ │ │ │ -6959C Uncompressed Size     000052D9 (21209)
│ │ │ │ -695A0 Filename Length       001F (31)
│ │ │ │ -695A2 Extra Length          001C (28)
│ │ │ │ -695A4 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x695A4: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -695C3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -695C5   Length              0009 (9)
│ │ │ │ -695C7   Flags               03 (3) 'Modification Access'
│ │ │ │ -695C8   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -695CC   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -695D0 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -695D2   Length              000B (11)
│ │ │ │ -695D4   Version             01 (1)
│ │ │ │ -695D5   UID Size            04 (4)
│ │ │ │ -695D6   UID                 00000000 (0)
│ │ │ │ -695DA   GID Size            04 (4)
│ │ │ │ -695DB   GID                 00000000 (0)
│ │ │ │ -695DF PAYLOAD
│ │ │ │ -
│ │ │ │ -6A457 LOCAL HEADER #59      04034B50 (67324752)
│ │ │ │ -6A45B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6A45C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6A45D General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6A45F Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6A461 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6A465 CRC                   B30F51A1 (3004125601)
│ │ │ │ -6A469 Compressed Size       00000A44 (2628)
│ │ │ │ -6A46D Uncompressed Size     0000247A (9338)
│ │ │ │ -6A471 Filename Length       0013 (19)
│ │ │ │ -6A473 Extra Length          001C (28)
│ │ │ │ -6A475 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6A475: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6A488 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6A48A   Length              0009 (9)
│ │ │ │ -6A48C   Flags               03 (3) 'Modification Access'
│ │ │ │ -6A48D   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6A491   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6A495 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6A497   Length              000B (11)
│ │ │ │ -6A499   Version             01 (1)
│ │ │ │ -6A49A   UID Size            04 (4)
│ │ │ │ -6A49B   UID                 00000000 (0)
│ │ │ │ -6A49F   GID Size            04 (4)
│ │ │ │ -6A4A0   GID                 00000000 (0)
│ │ │ │ -6A4A4 PAYLOAD
│ │ │ │ -
│ │ │ │ -6AEE8 LOCAL HEADER #60      04034B50 (67324752)
│ │ │ │ -6AEEC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6AEED Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6AEEE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6AEF0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6AEF2 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6AEF6 CRC                   1E73B85F (510900319)
│ │ │ │ -6AEFA Compressed Size       00002487 (9351)
│ │ │ │ -6AEFE Uncompressed Size     0000B84C (47180)
│ │ │ │ -6AF02 Filename Length       0019 (25)
│ │ │ │ -6AF04 Extra Length          001C (28)
│ │ │ │ -6AF06 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6AF06: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6AF1F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6AF21   Length              0009 (9)
│ │ │ │ -6AF23   Flags               03 (3) 'Modification Access'
│ │ │ │ -6AF24   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6AF28   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6AF2C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6AF2E   Length              000B (11)
│ │ │ │ -6AF30   Version             01 (1)
│ │ │ │ -6AF31   UID Size            04 (4)
│ │ │ │ -6AF32   UID                 00000000 (0)
│ │ │ │ -6AF36   GID Size            04 (4)
│ │ │ │ -6AF37   GID                 00000000 (0)
│ │ │ │ -6AF3B PAYLOAD
│ │ │ │ -
│ │ │ │ -6D3C2 LOCAL HEADER #61      04034B50 (67324752)
│ │ │ │ -6D3C6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6D3C7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6D3C8 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6D3CA Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6D3CC Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6D3D0 CRC                   685E5016 (1751011350)
│ │ │ │ -6D3D4 Compressed Size       00000EF9 (3833)
│ │ │ │ -6D3D8 Uncompressed Size     00003A2C (14892)
│ │ │ │ -6D3DC Filename Length       0024 (36)
│ │ │ │ -6D3DE Extra Length          001C (28)
│ │ │ │ -6D3E0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6D3E0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6D404 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6D406   Length              0009 (9)
│ │ │ │ -6D408   Flags               03 (3) 'Modification Access'
│ │ │ │ -6D409   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6D40D   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6D411 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6D413   Length              000B (11)
│ │ │ │ -6D415   Version             01 (1)
│ │ │ │ -6D416   UID Size            04 (4)
│ │ │ │ -6D417   UID                 00000000 (0)
│ │ │ │ -6D41B   GID Size            04 (4)
│ │ │ │ -6D41C   GID                 00000000 (0)
│ │ │ │ -6D420 PAYLOAD
│ │ │ │ -
│ │ │ │ -6E319 LOCAL HEADER #62      04034B50 (67324752)
│ │ │ │ -6E31D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6E31E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6E31F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6E321 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6E323 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6E327 CRC                   25BAB0D7 (632991959)
│ │ │ │ -6E32B Compressed Size       00001AC2 (6850)
│ │ │ │ -6E32F Uncompressed Size     00005EDC (24284)
│ │ │ │ -6E333 Filename Length       0017 (23)
│ │ │ │ -6E335 Extra Length          001C (28)
│ │ │ │ -6E337 Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6E337: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6E34E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6E350   Length              0009 (9)
│ │ │ │ -6E352   Flags               03 (3) 'Modification Access'
│ │ │ │ -6E353   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6E357   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6E35B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6E35D   Length              000B (11)
│ │ │ │ -6E35F   Version             01 (1)
│ │ │ │ -6E360   UID Size            04 (4)
│ │ │ │ -6E361   UID                 00000000 (0)
│ │ │ │ -6E365   GID Size            04 (4)
│ │ │ │ -6E366   GID                 00000000 (0)
│ │ │ │ -6E36A PAYLOAD
│ │ │ │ -
│ │ │ │ -6FE2C LOCAL HEADER #63      04034B50 (67324752)
│ │ │ │ -6FE30 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -6FE31 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -6FE32 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -6FE34 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -6FE36 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6FE3A CRC                   11E32AF1 (300100337)
│ │ │ │ -6FE3E Compressed Size       00000ED3 (3795)
│ │ │ │ -6FE42 Uncompressed Size     000038E2 (14562)
│ │ │ │ -6FE46 Filename Length       0023 (35)
│ │ │ │ -6FE48 Extra Length          001C (28)
│ │ │ │ -6FE4A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x6FE4A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -6FE6D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -6FE6F   Length              0009 (9)
│ │ │ │ -6FE71   Flags               03 (3) 'Modification Access'
│ │ │ │ -6FE72   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6FE76   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -6FE7A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -6FE7C   Length              000B (11)
│ │ │ │ -6FE7E   Version             01 (1)
│ │ │ │ -6FE7F   UID Size            04 (4)
│ │ │ │ -6FE80   UID                 00000000 (0)
│ │ │ │ -6FE84   GID Size            04 (4)
│ │ │ │ -6FE85   GID                 00000000 (0)
│ │ │ │ -6FE89 PAYLOAD
│ │ │ │ -
│ │ │ │ -70D5C LOCAL HEADER #64      04034B50 (67324752)
│ │ │ │ -70D60 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -70D61 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -70D62 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -70D64 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -70D66 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -70D6A CRC                   2DB7929F (767005343)
│ │ │ │ -70D6E Compressed Size       00000113 (275)
│ │ │ │ -70D72 Uncompressed Size     000001F3 (499)
│ │ │ │ -70D76 Filename Length       001B (27)
│ │ │ │ -70D78 Extra Length          001C (28)
│ │ │ │ -70D7A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x70D7A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -70D95 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -70D97   Length              0009 (9)
│ │ │ │ -70D99   Flags               03 (3) 'Modification Access'
│ │ │ │ -70D9A   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -70D9E   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -70DA2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -70DA4   Length              000B (11)
│ │ │ │ -70DA6   Version             01 (1)
│ │ │ │ -70DA7   UID Size            04 (4)
│ │ │ │ -70DA8   UID                 00000000 (0)
│ │ │ │ -70DAC   GID Size            04 (4)
│ │ │ │ -70DAD   GID                 00000000 (0)
│ │ │ │ -70DB1 PAYLOAD
│ │ │ │ -
│ │ │ │ -70EC4 LOCAL HEADER #65      04034B50 (67324752)
│ │ │ │ -70EC8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -70EC9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -70ECA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -70ECC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -70ECE Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -70ED2 CRC                   AA7430BF (2859741375)
│ │ │ │ -70ED6 Compressed Size       00001890 (6288)
│ │ │ │ -70EDA Uncompressed Size     00008FAC (36780)
│ │ │ │ -70EDE Filename Length       001D (29)
│ │ │ │ -70EE0 Extra Length          001C (28)
│ │ │ │ -70EE2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x70EE2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -70EFF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -70F01   Length              0009 (9)
│ │ │ │ -70F03   Flags               03 (3) 'Modification Access'
│ │ │ │ -70F04   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -70F08   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -70F0C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -70F0E   Length              000B (11)
│ │ │ │ -70F10   Version             01 (1)
│ │ │ │ -70F11   UID Size            04 (4)
│ │ │ │ -70F12   UID                 00000000 (0)
│ │ │ │ -70F16   GID Size            04 (4)
│ │ │ │ -70F17   GID                 00000000 (0)
│ │ │ │ -70F1B PAYLOAD
│ │ │ │ -
│ │ │ │ -727AB LOCAL HEADER #66      04034B50 (67324752)
│ │ │ │ -727AF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -727B0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -727B1 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -727B3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -727B5 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -727B9 CRC                   5F656D2A (1600482602)
│ │ │ │ -727BD Compressed Size       0000164C (5708)
│ │ │ │ -727C1 Uncompressed Size     00003A9B (15003)
│ │ │ │ -727C5 Filename Length       0015 (21)
│ │ │ │ -727C7 Extra Length          001C (28)
│ │ │ │ -727C9 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x727C9: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -727DE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -727E0   Length              0009 (9)
│ │ │ │ -727E2   Flags               03 (3) 'Modification Access'
│ │ │ │ -727E3   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -727E7   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -727EB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -727ED   Length              000B (11)
│ │ │ │ -727EF   Version             01 (1)
│ │ │ │ -727F0   UID Size            04 (4)
│ │ │ │ -727F1   UID                 00000000 (0)
│ │ │ │ -727F5   GID Size            04 (4)
│ │ │ │ -727F6   GID                 00000000 (0)
│ │ │ │ -727FA PAYLOAD
│ │ │ │ -
│ │ │ │ -73E46 LOCAL HEADER #67      04034B50 (67324752)
│ │ │ │ -73E4A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -73E4B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -73E4C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -73E4E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -73E50 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -73E54 CRC                   DBD9148D (3688436877)
│ │ │ │ -73E58 Compressed Size       00003B4F (15183)
│ │ │ │ -73E5C Uncompressed Size     0001185B (71771)
│ │ │ │ -73E60 Filename Length       0016 (22)
│ │ │ │ -73E62 Extra Length          001C (28)
│ │ │ │ -73E64 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x73E64: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -73E7A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -73E7C   Length              0009 (9)
│ │ │ │ -73E7E   Flags               03 (3) 'Modification Access'
│ │ │ │ -73E7F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -73E83   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -73E87 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -73E89   Length              000B (11)
│ │ │ │ -73E8B   Version             01 (1)
│ │ │ │ -73E8C   UID Size            04 (4)
│ │ │ │ -73E8D   UID                 00000000 (0)
│ │ │ │ -73E91   GID Size            04 (4)
│ │ │ │ -73E92   GID                 00000000 (0)
│ │ │ │ -73E96 PAYLOAD
│ │ │ │ -
│ │ │ │ -779E5 LOCAL HEADER #68      04034B50 (67324752)
│ │ │ │ -779E9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -779EA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -779EB General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -779ED Compression Method    0008 (8) 'Deflated'
│ │ │ │ -779EF Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -779F3 CRC                   C7B6EF21 (3350654753)
│ │ │ │ -779F7 Compressed Size       00003E88 (16008)
│ │ │ │ -779FB Uncompressed Size     0001C17B (115067)
│ │ │ │ -779FF Filename Length       0019 (25)
│ │ │ │ -77A01 Extra Length          001C (28)
│ │ │ │ -77A03 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x77A03: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -77A1C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -77A1E   Length              0009 (9)
│ │ │ │ -77A20   Flags               03 (3) 'Modification Access'
│ │ │ │ -77A21   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -77A25   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -77A29 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -77A2B   Length              000B (11)
│ │ │ │ -77A2D   Version             01 (1)
│ │ │ │ -77A2E   UID Size            04 (4)
│ │ │ │ -77A2F   UID                 00000000 (0)
│ │ │ │ -77A33   GID Size            04 (4)
│ │ │ │ -77A34   GID                 00000000 (0)
│ │ │ │ -77A38 PAYLOAD
│ │ │ │ -
│ │ │ │ -7B8C0 LOCAL HEADER #69      04034B50 (67324752)
│ │ │ │ -7B8C4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7B8C5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7B8C6 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7B8C8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7B8CA Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -7B8CE CRC                   59E53244 (1508192836)
│ │ │ │ -7B8D2 Compressed Size       00000835 (2101)
│ │ │ │ -7B8D6 Uncompressed Size     00003383 (13187)
│ │ │ │ -7B8DA Filename Length       0011 (17)
│ │ │ │ -7B8DC Extra Length          001C (28)
│ │ │ │ -7B8DE Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7B8DE: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7B8EF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7B8F1   Length              0009 (9)
│ │ │ │ -7B8F3   Flags               03 (3) 'Modification Access'
│ │ │ │ -7B8F4   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -7B8F8   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -7B8FC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7B8FE   Length              000B (11)
│ │ │ │ -7B900   Version             01 (1)
│ │ │ │ -7B901   UID Size            04 (4)
│ │ │ │ -7B902   UID                 00000000 (0)
│ │ │ │ -7B906   GID Size            04 (4)
│ │ │ │ -7B907   GID                 00000000 (0)
│ │ │ │ -7B90B PAYLOAD
│ │ │ │ -
│ │ │ │ -7C140 LOCAL HEADER #70      04034B50 (67324752)
│ │ │ │ -7C144 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -7C145 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -7C146 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -7C148 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -7C14A Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -7C14E CRC                   D1DF86DD (3521087197)
│ │ │ │ -7C152 Compressed Size       00005184 (20868)
│ │ │ │ -7C156 Uncompressed Size     0001FB6C (129900)
│ │ │ │ -7C15A Filename Length       0015 (21)
│ │ │ │ -7C15C Extra Length          001C (28)
│ │ │ │ -7C15E Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x7C15E: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -7C173 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -7C175   Length              0009 (9)
│ │ │ │ -7C177   Flags               03 (3) 'Modification Access'
│ │ │ │ -7C178   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -7C17C   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -7C180 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -7C182   Length              000B (11)
│ │ │ │ -7C184   Version             01 (1)
│ │ │ │ -7C185   UID Size            04 (4)
│ │ │ │ -7C186   UID                 00000000 (0)
│ │ │ │ -7C18A   GID Size            04 (4)
│ │ │ │ -7C18B   GID                 00000000 (0)
│ │ │ │ -7C18F PAYLOAD
│ │ │ │ -
│ │ │ │ -81313 LOCAL HEADER #71      04034B50 (67324752)
│ │ │ │ -81317 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -81318 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -81319 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8131B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8131D Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -81321 CRC                   419D467F (1100826239)
│ │ │ │ -81325 Compressed Size       00001B0A (6922)
│ │ │ │ -81329 Uncompressed Size     000081CF (33231)
│ │ │ │ -8132D Filename Length       0019 (25)
│ │ │ │ -8132F Extra Length          001C (28)
│ │ │ │ -81331 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x81331: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8134A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8134C   Length              0009 (9)
│ │ │ │ -8134E   Flags               03 (3) 'Modification Access'
│ │ │ │ -8134F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -81353   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -81357 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -81359   Length              000B (11)
│ │ │ │ -8135B   Version             01 (1)
│ │ │ │ -8135C   UID Size            04 (4)
│ │ │ │ -8135D   UID                 00000000 (0)
│ │ │ │ -81361   GID Size            04 (4)
│ │ │ │ -81362   GID                 00000000 (0)
│ │ │ │ -81366 PAYLOAD
│ │ │ │ -
│ │ │ │ -82E70 LOCAL HEADER #72      04034B50 (67324752)
│ │ │ │ -82E74 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -82E75 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -82E76 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -82E78 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -82E7A Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -82E7E CRC                   49C11139 (1237389625)
│ │ │ │ -82E82 Compressed Size       00000D97 (3479)
│ │ │ │ -82E86 Uncompressed Size     00002E9F (11935)
│ │ │ │ -82E8A Filename Length       0018 (24)
│ │ │ │ -82E8C Extra Length          001C (28)
│ │ │ │ -82E8E Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x82E8E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -82EA6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -82EA8   Length              0009 (9)
│ │ │ │ -82EAA   Flags               03 (3) 'Modification Access'
│ │ │ │ -82EAB   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -82EAF   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -82EB3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -82EB5   Length              000B (11)
│ │ │ │ -82EB7   Version             01 (1)
│ │ │ │ -82EB8   UID Size            04 (4)
│ │ │ │ -82EB9   UID                 00000000 (0)
│ │ │ │ -82EBD   GID Size            04 (4)
│ │ │ │ -82EBE   GID                 00000000 (0)
│ │ │ │ -82EC2 PAYLOAD
│ │ │ │ -
│ │ │ │ -83C59 LOCAL HEADER #73      04034B50 (67324752)
│ │ │ │ -83C5D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -83C5E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -83C5F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -83C61 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -83C63 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -83C67 CRC                   0350D61E (55629342)
│ │ │ │ -83C6B Compressed Size       000001E0 (480)
│ │ │ │ -83C6F Uncompressed Size     00000323 (803)
│ │ │ │ -83C73 Filename Length       0011 (17)
│ │ │ │ -83C75 Extra Length          001C (28)
│ │ │ │ -83C77 Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x83C77: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -83C88 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -83C8A   Length              0009 (9)
│ │ │ │ -83C8C   Flags               03 (3) 'Modification Access'
│ │ │ │ -83C8D   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -83C91   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -83C95 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -83C97   Length              000B (11)
│ │ │ │ -83C99   Version             01 (1)
│ │ │ │ -83C9A   UID Size            04 (4)
│ │ │ │ -83C9B   UID                 00000000 (0)
│ │ │ │ -83C9F   GID Size            04 (4)
│ │ │ │ -83CA0   GID                 00000000 (0)
│ │ │ │ -83CA4 PAYLOAD
│ │ │ │ -
│ │ │ │ -83E84 LOCAL HEADER #74      04034B50 (67324752)
│ │ │ │ -83E88 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -83E89 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -83E8A General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -83E8C Compression Method    0008 (8) 'Deflated'
│ │ │ │ -83E8E Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -83E92 CRC                   3FD13568 (1070675304)
│ │ │ │ -83E96 Compressed Size       000006C2 (1730)
│ │ │ │ -83E9A Uncompressed Size     00001439 (5177)
│ │ │ │ -83E9E Filename Length       0019 (25)
│ │ │ │ -83EA0 Extra Length          001C (28)
│ │ │ │ -83EA2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x83EA2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -83EBB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -83EBD   Length              0009 (9)
│ │ │ │ -83EBF   Flags               03 (3) 'Modification Access'
│ │ │ │ -83EC0   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -83EC4   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -83EC8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -83ECA   Length              000B (11)
│ │ │ │ -83ECC   Version             01 (1)
│ │ │ │ -83ECD   UID Size            04 (4)
│ │ │ │ -83ECE   UID                 00000000 (0)
│ │ │ │ -83ED2   GID Size            04 (4)
│ │ │ │ -83ED3   GID                 00000000 (0)
│ │ │ │ -83ED7 PAYLOAD
│ │ │ │ -
│ │ │ │ -84599 LOCAL HEADER #75      04034B50 (67324752)
│ │ │ │ -8459D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8459E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8459F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -845A1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -845A3 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -845A7 CRC                   89473D13 (2303147283)
│ │ │ │ -845AB Compressed Size       00001B8B (7051)
│ │ │ │ -845AF Uncompressed Size     00009F03 (40707)
│ │ │ │ -845B3 Filename Length       0018 (24)
│ │ │ │ -845B5 Extra Length          001C (28)
│ │ │ │ -845B7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x845B7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -845CF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -845D1   Length              0009 (9)
│ │ │ │ -845D3   Flags               03 (3) 'Modification Access'
│ │ │ │ -845D4   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -845D8   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -845DC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -845DE   Length              000B (11)
│ │ │ │ -845E0   Version             01 (1)
│ │ │ │ -845E1   UID Size            04 (4)
│ │ │ │ -845E2   UID                 00000000 (0)
│ │ │ │ -845E6   GID Size            04 (4)
│ │ │ │ -845E7   GID                 00000000 (0)
│ │ │ │ -845EB PAYLOAD
│ │ │ │ -
│ │ │ │ -86176 LOCAL HEADER #76      04034B50 (67324752)
│ │ │ │ -8617A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8617B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8617C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8617E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -86180 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -86184 CRC                   D941FB49 (3644980041)
│ │ │ │ -86188 Compressed Size       000016FB (5883)
│ │ │ │ -8618C Uncompressed Size     00008AB6 (35510)
│ │ │ │ -86190 Filename Length       0012 (18)
│ │ │ │ -86192 Extra Length          001C (28)
│ │ │ │ -86194 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x86194: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -861A6 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -861A8   Length              0009 (9)
│ │ │ │ -861AA   Flags               03 (3) 'Modification Access'
│ │ │ │ -861AB   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -861AF   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -861B3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -861B5   Length              000B (11)
│ │ │ │ -861B7   Version             01 (1)
│ │ │ │ -861B8   UID Size            04 (4)
│ │ │ │ -861B9   UID                 00000000 (0)
│ │ │ │ -861BD   GID Size            04 (4)
│ │ │ │ -861BE   GID                 00000000 (0)
│ │ │ │ -861C2 PAYLOAD
│ │ │ │ -
│ │ │ │ -878BD LOCAL HEADER #77      04034B50 (67324752)
│ │ │ │ -878C1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -878C2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -878C3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -878C5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -878C7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -878CB CRC                   F5B21857 (4122089559)
│ │ │ │ -878CF Compressed Size       00001E15 (7701)
│ │ │ │ -878D3 Uncompressed Size     00008803 (34819)
│ │ │ │ -878D7 Filename Length       0016 (22)
│ │ │ │ -878D9 Extra Length          001C (28)
│ │ │ │ -878DB Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x878DB: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -878F1 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -878F3   Length              0009 (9)
│ │ │ │ -878F5   Flags               03 (3) 'Modification Access'
│ │ │ │ -878F6   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -878FA   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -878FE Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -87900   Length              000B (11)
│ │ │ │ -87902   Version             01 (1)
│ │ │ │ -87903   UID Size            04 (4)
│ │ │ │ -87904   UID                 00000000 (0)
│ │ │ │ -87908   GID Size            04 (4)
│ │ │ │ -87909   GID                 00000000 (0)
│ │ │ │ -8790D PAYLOAD
│ │ │ │ -
│ │ │ │ -89722 LOCAL HEADER #78      04034B50 (67324752)
│ │ │ │ -89726 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -89727 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -89728 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8972A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8972C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -89730 CRC                   B502BD51 (3036855633)
│ │ │ │ -89734 Compressed Size       000029A6 (10662)
│ │ │ │ -89738 Uncompressed Size     0000D04F (53327)
│ │ │ │ -8973C Filename Length       001A (26)
│ │ │ │ -8973E Extra Length          001C (28)
│ │ │ │ -89740 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x89740: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8975A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8975C   Length              0009 (9)
│ │ │ │ -8975E   Flags               03 (3) 'Modification Access'
│ │ │ │ -8975F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -89763   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -89767 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -89769   Length              000B (11)
│ │ │ │ -8976B   Version             01 (1)
│ │ │ │ -8976C   UID Size            04 (4)
│ │ │ │ -8976D   UID                 00000000 (0)
│ │ │ │ -89771   GID Size            04 (4)
│ │ │ │ -89772   GID                 00000000 (0)
│ │ │ │ -89776 PAYLOAD
│ │ │ │ -
│ │ │ │ -8C11C LOCAL HEADER #79      04034B50 (67324752)
│ │ │ │ -8C120 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8C121 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8C122 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8C124 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8C126 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8C12A CRC                   82C57F0D (2193981197)
│ │ │ │ -8C12E Compressed Size       000009AC (2476)
│ │ │ │ -8C132 Uncompressed Size     00001DB6 (7606)
│ │ │ │ -8C136 Filename Length       0018 (24)
│ │ │ │ -8C138 Extra Length          001C (28)
│ │ │ │ -8C13A Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8C13A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8C152 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8C154   Length              0009 (9)
│ │ │ │ -8C156   Flags               03 (3) 'Modification Access'
│ │ │ │ -8C157   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8C15B   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8C15F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -8C161   Length              000B (11)
│ │ │ │ -8C163   Version             01 (1)
│ │ │ │ -8C164   UID Size            04 (4)
│ │ │ │ -8C165   UID                 00000000 (0)
│ │ │ │ -8C169   GID Size            04 (4)
│ │ │ │ -8C16A   GID                 00000000 (0)
│ │ │ │ -8C16E PAYLOAD
│ │ │ │ -
│ │ │ │ -8CB1A LOCAL HEADER #80      04034B50 (67324752)
│ │ │ │ -8CB1E Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8CB1F Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8CB20 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8CB22 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8CB24 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8CB28 CRC                   F5E2129F (4125233823)
│ │ │ │ -8CB2C Compressed Size       000016BC (5820)
│ │ │ │ -8CB30 Uncompressed Size     000016CD (5837)
│ │ │ │ -8CB34 Filename Length       0015 (21)
│ │ │ │ -8CB36 Extra Length          001C (28)
│ │ │ │ -8CB38 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8CB38: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8CB4D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8CB4F   Length              0009 (9)
│ │ │ │ -8CB51   Flags               03 (3) 'Modification Access'
│ │ │ │ -8CB52   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8CB56   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8CB5A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -8CB5C   Length              000B (11)
│ │ │ │ -8CB5E   Version             01 (1)
│ │ │ │ -8CB5F   UID Size            04 (4)
│ │ │ │ -8CB60   UID                 00000000 (0)
│ │ │ │ -8CB64   GID Size            04 (4)
│ │ │ │ -8CB65   GID                 00000000 (0)
│ │ │ │ -8CB69 PAYLOAD
│ │ │ │ -
│ │ │ │ -8E225 LOCAL HEADER #81      04034B50 (67324752)
│ │ │ │ -8E229 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -8E22A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8E22B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -8E22D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -8E22F Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8E233 CRC                   F5E2129F (4125233823)
│ │ │ │ -8E237 Compressed Size       000016BC (5820)
│ │ │ │ -8E23B Uncompressed Size     000016CD (5837)
│ │ │ │ -8E23F Filename Length       001C (28)
│ │ │ │ -8E241 Extra Length          001C (28)
│ │ │ │ -8E243 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8E243: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8E25F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8E261   Length              0009 (9)
│ │ │ │ -8E263   Flags               03 (3) 'Modification Access'
│ │ │ │ -8E264   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8E268   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8E26C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -8E26E   Length              000B (11)
│ │ │ │ -8E270   Version             01 (1)
│ │ │ │ -8E271   UID Size            04 (4)
│ │ │ │ -8E272   UID                 00000000 (0)
│ │ │ │ -8E276   GID Size            04 (4)
│ │ │ │ -8E277   GID                 00000000 (0)
│ │ │ │ -8E27B PAYLOAD
│ │ │ │ -
│ │ │ │ -8F937 LOCAL HEADER #82      04034B50 (67324752)
│ │ │ │ -8F93B Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -8F93C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -8F93D General Purpose Flag  0000 (0)
│ │ │ │ -8F93F Compression Method    0000 (0) 'Stored'
│ │ │ │ -8F941 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8F945 CRC                   FC95F24B (4237685323)
│ │ │ │ -8F949 Compressed Size       00001B84 (7044)
│ │ │ │ -8F94D Uncompressed Size     00001B84 (7044)
│ │ │ │ -8F951 Filename Length       0016 (22)
│ │ │ │ -8F953 Extra Length          001C (28)
│ │ │ │ -8F955 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x8F955: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -8F96B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -8F96D   Length              0009 (9)
│ │ │ │ -8F96F   Flags               03 (3) 'Modification Access'
│ │ │ │ -8F970   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8F974   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -8F978 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -8F97A   Length              000B (11)
│ │ │ │ -8F97C   Version             01 (1)
│ │ │ │ -8F97D   UID Size            04 (4)
│ │ │ │ -8F97E   UID                 00000000 (0)
│ │ │ │ -8F982   GID Size            04 (4)
│ │ │ │ -8F983   GID                 00000000 (0)
│ │ │ │ -8F987 PAYLOAD
│ │ │ │ -
│ │ │ │ -9150B LOCAL HEADER #83      04034B50 (67324752)
│ │ │ │ -9150F Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -91510 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -91511 General Purpose Flag  0000 (0)
│ │ │ │ -91513 Compression Method    0000 (0) 'Stored'
│ │ │ │ -91515 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -91519 CRC                   D0D71F86 (3503759238)
│ │ │ │ -9151D Compressed Size       00000B7B (2939)
│ │ │ │ -91521 Uncompressed Size     00000B7B (2939)
│ │ │ │ -91525 Filename Length       0016 (22)
│ │ │ │ -91527 Extra Length          001C (28)
│ │ │ │ -91529 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x91529: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9153F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -91541   Length              0009 (9)
│ │ │ │ -91543   Flags               03 (3) 'Modification Access'
│ │ │ │ -91544   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -91548   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9154C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9154E   Length              000B (11)
│ │ │ │ -91550   Version             01 (1)
│ │ │ │ -91551   UID Size            04 (4)
│ │ │ │ -91552   UID                 00000000 (0)
│ │ │ │ -91556   GID Size            04 (4)
│ │ │ │ -91557   GID                 00000000 (0)
│ │ │ │ -9155B PAYLOAD
│ │ │ │ -
│ │ │ │ -920D6 LOCAL HEADER #84      04034B50 (67324752)
│ │ │ │ -920DA Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -920DB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -920DC General Purpose Flag  0000 (0)
│ │ │ │ -920DE Compression Method    0000 (0) 'Stored'
│ │ │ │ -920E0 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -920E4 CRC                   FFF9C4D2 (4294558930)
│ │ │ │ -920E8 Compressed Size       0000138F (5007)
│ │ │ │ -920EC Uncompressed Size     0000138F (5007)
│ │ │ │ -920F0 Filename Length       0016 (22)
│ │ │ │ -920F2 Extra Length          001C (28)
│ │ │ │ -920F4 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x920F4: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9210A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9210C   Length              0009 (9)
│ │ │ │ -9210E   Flags               03 (3) 'Modification Access'
│ │ │ │ -9210F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -92113   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -92117 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -92119   Length              000B (11)
│ │ │ │ -9211B   Version             01 (1)
│ │ │ │ -9211C   UID Size            04 (4)
│ │ │ │ -9211D   UID                 00000000 (0)
│ │ │ │ -92121   GID Size            04 (4)
│ │ │ │ -92122   GID                 00000000 (0)
│ │ │ │ -92126 PAYLOAD
│ │ │ │ -
│ │ │ │ -934B5 LOCAL HEADER #85      04034B50 (67324752)
│ │ │ │ -934B9 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -934BA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -934BB General Purpose Flag  0000 (0)
│ │ │ │ -934BD Compression Method    0000 (0) 'Stored'
│ │ │ │ -934BF Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -934C3 CRC                   A1037E8E (2701360782)
│ │ │ │ -934C7 Compressed Size       0000145E (5214)
│ │ │ │ -934CB Uncompressed Size     0000145E (5214)
│ │ │ │ -934CF Filename Length       0016 (22)
│ │ │ │ -934D1 Extra Length          001C (28)
│ │ │ │ -934D3 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x934D3: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -934E9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -934EB   Length              0009 (9)
│ │ │ │ -934ED   Flags               03 (3) 'Modification Access'
│ │ │ │ -934EE   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -934F2   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -934F6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -934F8   Length              000B (11)
│ │ │ │ -934FA   Version             01 (1)
│ │ │ │ -934FB   UID Size            04 (4)
│ │ │ │ -934FC   UID                 00000000 (0)
│ │ │ │ -93500   GID Size            04 (4)
│ │ │ │ -93501   GID                 00000000 (0)
│ │ │ │ -93505 PAYLOAD
│ │ │ │ -
│ │ │ │ -94963 LOCAL HEADER #86      04034B50 (67324752)
│ │ │ │ -94967 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -94968 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -94969 General Purpose Flag  0000 (0)
│ │ │ │ -9496B Compression Method    0000 (0) 'Stored'
│ │ │ │ -9496D Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -94971 CRC                   5E9E64F1 (1587438833)
│ │ │ │ -94975 Compressed Size       000008EC (2284)
│ │ │ │ -94979 Uncompressed Size     000008EC (2284)
│ │ │ │ -9497D Filename Length       0016 (22)
│ │ │ │ -9497F Extra Length          001C (28)
│ │ │ │ -94981 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x94981: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -94997 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -94999   Length              0009 (9)
│ │ │ │ -9499B   Flags               03 (3) 'Modification Access'
│ │ │ │ -9499C   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -949A0   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -949A4 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -949A6   Length              000B (11)
│ │ │ │ -949A8   Version             01 (1)
│ │ │ │ -949A9   UID Size            04 (4)
│ │ │ │ -949AA   UID                 00000000 (0)
│ │ │ │ -949AE   GID Size            04 (4)
│ │ │ │ -949AF   GID                 00000000 (0)
│ │ │ │ -949B3 PAYLOAD
│ │ │ │ -
│ │ │ │ -9529F LOCAL HEADER #87      04034B50 (67324752)
│ │ │ │ -952A3 Extract Zip Spec      0A (10) '1.0'
│ │ │ │ -952A4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -952A5 General Purpose Flag  0000 (0)
│ │ │ │ -952A7 Compression Method    0000 (0) 'Stored'
│ │ │ │ -952A9 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -952AD CRC                   42E340AB (1122189483)
│ │ │ │ -952B1 Compressed Size       00001F2E (7982)
│ │ │ │ -952B5 Uncompressed Size     00001F2E (7982)
│ │ │ │ -952B9 Filename Length       001E (30)
│ │ │ │ -952BB Extra Length          001C (28)
│ │ │ │ -952BD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x952BD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -952DB Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -952DD   Length              0009 (9)
│ │ │ │ -952DF   Flags               03 (3) 'Modification Access'
│ │ │ │ -952E0   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -952E4   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -952E8 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -952EA   Length              000B (11)
│ │ │ │ -952EC   Version             01 (1)
│ │ │ │ -952ED   UID Size            04 (4)
│ │ │ │ -952EE   UID                 00000000 (0)
│ │ │ │ -952F2   GID Size            04 (4)
│ │ │ │ -952F3   GID                 00000000 (0)
│ │ │ │ -952F7 PAYLOAD
│ │ │ │ -
│ │ │ │ -97225 LOCAL HEADER #88      04034B50 (67324752)
│ │ │ │ -97229 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9722A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9722B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9722D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9722F Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -97233 CRC                   AB590681 (2874738305)
│ │ │ │ -97237 Compressed Size       00003D6A (15722)
│ │ │ │ -9723B Uncompressed Size     00016649 (91721)
│ │ │ │ -9723F Filename Length       001A (26)
│ │ │ │ -97241 Extra Length          001C (28)
│ │ │ │ -97243 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x97243: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9725D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9725F   Length              0009 (9)
│ │ │ │ -97261   Flags               03 (3) 'Modification Access'
│ │ │ │ -97262   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -97266   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9726A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9726C   Length              000B (11)
│ │ │ │ -9726E   Version             01 (1)
│ │ │ │ -9726F   UID Size            04 (4)
│ │ │ │ -97270   UID                 00000000 (0)
│ │ │ │ -97274   GID Size            04 (4)
│ │ │ │ -97275   GID                 00000000 (0)
│ │ │ │ -97279 PAYLOAD
│ │ │ │ -
│ │ │ │ -9AFE3 LOCAL HEADER #89      04034B50 (67324752)
│ │ │ │ -9AFE7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9AFE8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9AFE9 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9AFEB Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9AFED Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9AFF1 CRC                   4A57375D (1247229789)
│ │ │ │ -9AFF5 Compressed Size       000029BA (10682)
│ │ │ │ -9AFF9 Uncompressed Size     0000BA6A (47722)
│ │ │ │ -9AFFD Filename Length       0018 (24)
│ │ │ │ -9AFFF Extra Length          001C (28)
│ │ │ │ -9B001 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9B001: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9B019 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9B01B   Length              0009 (9)
│ │ │ │ -9B01D   Flags               03 (3) 'Modification Access'
│ │ │ │ -9B01E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9B022   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9B026 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9B028   Length              000B (11)
│ │ │ │ -9B02A   Version             01 (1)
│ │ │ │ -9B02B   UID Size            04 (4)
│ │ │ │ -9B02C   UID                 00000000 (0)
│ │ │ │ -9B030   GID Size            04 (4)
│ │ │ │ -9B031   GID                 00000000 (0)
│ │ │ │ -9B035 PAYLOAD
│ │ │ │ -
│ │ │ │ -9D9EF LOCAL HEADER #90      04034B50 (67324752)
│ │ │ │ -9D9F3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9D9F4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9D9F5 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9D9F7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9D9F9 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9D9FD CRC                   DCB3B516 (3702764822)
│ │ │ │ -9DA01 Compressed Size       000000AE (174)
│ │ │ │ -9DA05 Uncompressed Size     000000FC (252)
│ │ │ │ -9DA09 Filename Length       0016 (22)
│ │ │ │ -9DA0B Extra Length          001C (28)
│ │ │ │ -9DA0D Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9DA0D: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9DA23 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9DA25   Length              0009 (9)
│ │ │ │ -9DA27   Flags               03 (3) 'Modification Access'
│ │ │ │ -9DA28   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9DA2C   Access Time         68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9DA30 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9DA32   Length              000B (11)
│ │ │ │ -9DA34   Version             01 (1)
│ │ │ │ -9DA35   UID Size            04 (4)
│ │ │ │ -9DA36   UID                 00000000 (0)
│ │ │ │ -9DA3A   GID Size            04 (4)
│ │ │ │ -9DA3B   GID                 00000000 (0)
│ │ │ │ -9DA3F PAYLOAD               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
│ │ │ │ +04B62 LOCAL HEADER #5       04034B50 (67324752)
│ │ │ │ +04B66 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +04B67 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +04B68 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +04B6A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +04B6C Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +04B70 CRC                   A25ED8D1 (2724124881)
│ │ │ │ +04B74 Compressed Size       000003F0 (1008)
│ │ │ │ +04B78 Uncompressed Size     00000876 (2166)
│ │ │ │ +04B7C Filename Length       0014 (20)
│ │ │ │ +04B7E Extra Length          001C (28)
│ │ │ │ +04B80 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4B80: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +04B94 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +04B96   Length              0009 (9)
│ │ │ │ +04B98   Flags               03 (3) 'Modification Access'
│ │ │ │ +04B99   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +04B9D   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +04BA1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +04BA3   Length              000B (11)
│ │ │ │ +04BA5   Version             01 (1)
│ │ │ │ +04BA6   UID Size            04 (4)
│ │ │ │ +04BA7   UID                 00000000 (0)
│ │ │ │ +04BAB   GID Size            04 (4)
│ │ │ │ +04BAC   GID                 00000000 (0)
│ │ │ │ +04BB0 PAYLOAD
│ │ │ │ +
│ │ │ │ +04FA0 LOCAL HEADER #6       04034B50 (67324752)
│ │ │ │ +04FA4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +04FA5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +04FA6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +04FA8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +04FAA Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +04FAE CRC                   9809A48F (2550768783)
│ │ │ │ +04FB2 Compressed Size       000001AE (430)
│ │ │ │ +04FB6 Uncompressed Size     000002FC (764)
│ │ │ │ +04FBA Filename Length       0011 (17)
│ │ │ │ +04FBC Extra Length          001C (28)
│ │ │ │ +04FBE Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4FBE: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +04FCF Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +04FD1   Length              0009 (9)
│ │ │ │ +04FD3   Flags               03 (3) 'Modification Access'
│ │ │ │ +04FD4   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +04FD8   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +04FDC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +04FDE   Length              000B (11)
│ │ │ │ +04FE0   Version             01 (1)
│ │ │ │ +04FE1   UID Size            04 (4)
│ │ │ │ +04FE2   UID                 00000000 (0)
│ │ │ │ +04FE6   GID Size            04 (4)
│ │ │ │ +04FE7   GID                 00000000 (0)
│ │ │ │ +04FEB PAYLOAD
│ │ │ │ +
│ │ │ │ +05199 LOCAL HEADER #7       04034B50 (67324752)
│ │ │ │ +0519D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +0519E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +0519F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +051A1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +051A3 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +051A7 CRC                   420A745F (1107981407)
│ │ │ │ +051AB Compressed Size       000020C9 (8393)
│ │ │ │ +051AF Uncompressed Size     0000B4B0 (46256)
│ │ │ │ +051B3 Filename Length       001B (27)
│ │ │ │ +051B5 Extra Length          001C (28)
│ │ │ │ +051B7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x51B7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +051D2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +051D4   Length              0009 (9)
│ │ │ │ +051D6   Flags               03 (3) 'Modification Access'
│ │ │ │ +051D7   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +051DB   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +051DF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +051E1   Length              000B (11)
│ │ │ │ +051E3   Version             01 (1)
│ │ │ │ +051E4   UID Size            04 (4)
│ │ │ │ +051E5   UID                 00000000 (0)
│ │ │ │ +051E9   GID Size            04 (4)
│ │ │ │ +051EA   GID                 00000000 (0)
│ │ │ │ +051EE PAYLOAD
│ │ │ │ +
│ │ │ │ +072B7 LOCAL HEADER #8       04034B50 (67324752)
│ │ │ │ +072BB Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +072BC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +072BD General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +072BF Compression Method    0008 (8) 'Deflated'
│ │ │ │ +072C1 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +072C5 CRC                   219043B3 (563102643)
│ │ │ │ +072C9 Compressed Size       00000E6F (3695)
│ │ │ │ +072CD Uncompressed Size     000030B2 (12466)
│ │ │ │ +072D1 Filename Length       001D (29)
│ │ │ │ +072D3 Extra Length          001C (28)
│ │ │ │ +072D5 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x72D5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +072F2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +072F4   Length              0009 (9)
│ │ │ │ +072F6   Flags               03 (3) 'Modification Access'
│ │ │ │ +072F7   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +072FB   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +072FF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +07301   Length              000B (11)
│ │ │ │ +07303   Version             01 (1)
│ │ │ │ +07304   UID Size            04 (4)
│ │ │ │ +07305   UID                 00000000 (0)
│ │ │ │ +07309   GID Size            04 (4)
│ │ │ │ +0730A   GID                 00000000 (0)
│ │ │ │ +0730E PAYLOAD
│ │ │ │ +
│ │ │ │ +0817D LOCAL HEADER #9       04034B50 (67324752)
│ │ │ │ +08181 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +08182 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +08183 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +08185 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +08187 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +0818B CRC                   FEA15075 (4271984757)
│ │ │ │ +0818F Compressed Size       00000972 (2418)
│ │ │ │ +08193 Uncompressed Size     00001CB2 (7346)
│ │ │ │ +08197 Filename Length       0019 (25)
│ │ │ │ +08199 Extra Length          001C (28)
│ │ │ │ +0819B Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x819B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +081B4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +081B6   Length              0009 (9)
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│ │ │ │ +081B9   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +081BD   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +081C1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +081C3   Length              000B (11)
│ │ │ │ +081C5   Version             01 (1)
│ │ │ │ +081C6   UID Size            04 (4)
│ │ │ │ +081C7   UID                 00000000 (0)
│ │ │ │ +081CB   GID Size            04 (4)
│ │ │ │ +081CC   GID                 00000000 (0)
│ │ │ │ +081D0 PAYLOAD
│ │ │ │ +
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│ │ │ │ +08B46 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +08B47 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +08B48 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +08B4A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +08B4C Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +08B50 CRC                   FDEE69AB (4260260267)
│ │ │ │ +08B54 Compressed Size       0000387B (14459)
│ │ │ │ +08B58 Uncompressed Size     0000F7F4 (63476)
│ │ │ │ +08B5C Filename Length       0015 (21)
│ │ │ │ +08B5E Extra Length          001C (28)
│ │ │ │ +08B60 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x8B60: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +08B75 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +08B77   Length              0009 (9)
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│ │ │ │ +08B7A   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +08B7E   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +08B82 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +08B84   Length              000B (11)
│ │ │ │ +08B86   Version             01 (1)
│ │ │ │ +08B87   UID Size            04 (4)
│ │ │ │ +08B88   UID                 00000000 (0)
│ │ │ │ +08B8C   GID Size            04 (4)
│ │ │ │ +08B8D   GID                 00000000 (0)
│ │ │ │ +08B91 PAYLOAD
│ │ │ │ +
│ │ │ │ +0C40C LOCAL HEADER #11      04034B50 (67324752)
│ │ │ │ +0C410 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +0C411 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +0C412 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +0C414 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +0C416 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +0C41A CRC                   39632DCF (962801103)
│ │ │ │ +0C41E Compressed Size       0000AAE7 (43751)
│ │ │ │ +0C422 Uncompressed Size     0003DFDE (253918)
│ │ │ │ +0C426 Filename Length       0012 (18)
│ │ │ │ +0C428 Extra Length          001C (28)
│ │ │ │ +0C42A Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0xC42A: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +0C43C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +0C43E   Length              0009 (9)
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│ │ │ │ +0C441   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +0C445   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +0C449 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +0C44B   Length              000B (11)
│ │ │ │ +0C44D   Version             01 (1)
│ │ │ │ +0C44E   UID Size            04 (4)
│ │ │ │ +0C44F   UID                 00000000 (0)
│ │ │ │ +0C453   GID Size            04 (4)
│ │ │ │ +0C454   GID                 00000000 (0)
│ │ │ │ +0C458 PAYLOAD
│ │ │ │ +
│ │ │ │ +16F3F LOCAL HEADER #12      04034B50 (67324752)
│ │ │ │ +16F43 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +16F44 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +16F45 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +16F47 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +16F49 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +16F4D CRC                   5DC3E4ED (1573119213)
│ │ │ │ +16F51 Compressed Size       00003B24 (15140)
│ │ │ │ +16F55 Uncompressed Size     0001B2A0 (111264)
│ │ │ │ +16F59 Filename Length       0015 (21)
│ │ │ │ +16F5B Extra Length          001C (28)
│ │ │ │ +16F5D Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x16F5D: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +16F72 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +16F77   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +16F7B   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +16F7F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +16F81   Length              000B (11)
│ │ │ │ +16F83   Version             01 (1)
│ │ │ │ +16F84   UID Size            04 (4)
│ │ │ │ +16F85   UID                 00000000 (0)
│ │ │ │ +16F89   GID Size            04 (4)
│ │ │ │ +16F8A   GID                 00000000 (0)
│ │ │ │ +16F8E PAYLOAD
│ │ │ │ +
│ │ │ │ +1AAB2 LOCAL HEADER #13      04034B50 (67324752)
│ │ │ │ +1AAB6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +1AAB7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +1AAB8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +1AABC Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +1AAC0 CRC                   A61975B2 (2786686386)
│ │ │ │ +1AAC4 Compressed Size       00009089 (37001)
│ │ │ │ +1AAC8 Uncompressed Size     0003D05F (249951)
│ │ │ │ +1AACC Filename Length       0014 (20)
│ │ │ │ +1AACE Extra Length          001C (28)
│ │ │ │ +1AAD0 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x1AAD0: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +1AAE4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +1AAE9   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +1AAED   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +1AAF1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +1AAF3   Length              000B (11)
│ │ │ │ +1AAF5   Version             01 (1)
│ │ │ │ +1AAF6   UID Size            04 (4)
│ │ │ │ +1AAF7   UID                 00000000 (0)
│ │ │ │ +1AAFB   GID Size            04 (4)
│ │ │ │ +1AAFC   GID                 00000000 (0)
│ │ │ │ +1AB00 PAYLOAD
│ │ │ │ +
│ │ │ │ +23B89 LOCAL HEADER #14      04034B50 (67324752)
│ │ │ │ +23B8D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +23B8E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +23B8F General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +23B91 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +23B93 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +23B97 CRC                   FA5A550E (4200224014)
│ │ │ │ +23B9B Compressed Size       00002A65 (10853)
│ │ │ │ +23B9F Uncompressed Size     0001151F (70943)
│ │ │ │ +23BA3 Filename Length       0016 (22)
│ │ │ │ +23BA5 Extra Length          001C (28)
│ │ │ │ +23BA7 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x23BA7: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +23BBD Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +23BBF   Length              0009 (9)
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│ │ │ │ +23BC2   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +23BC6   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +23BCA Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +23BCC   Length              000B (11)
│ │ │ │ +23BCE   Version             01 (1)
│ │ │ │ +23BCF   UID Size            04 (4)
│ │ │ │ +23BD0   UID                 00000000 (0)
│ │ │ │ +23BD4   GID Size            04 (4)
│ │ │ │ +23BD5   GID                 00000000 (0)
│ │ │ │ +23BD9 PAYLOAD
│ │ │ │ +
│ │ │ │ +2663E LOCAL HEADER #15      04034B50 (67324752)
│ │ │ │ +26642 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +26643 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +26644 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +26646 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +26648 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +2664C CRC                   98DE7C3B (2564717627)
│ │ │ │ +26650 Compressed Size       000014DA (5338)
│ │ │ │ +26654 Uncompressed Size     00005176 (20854)
│ │ │ │ +26658 Filename Length       001D (29)
│ │ │ │ +2665A Extra Length          001C (28)
│ │ │ │ +2665C Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x2665C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +26679 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +2667E   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +26682   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +26686 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +26688   Length              000B (11)
│ │ │ │ +2668A   Version             01 (1)
│ │ │ │ +2668B   UID Size            04 (4)
│ │ │ │ +2668C   UID                 00000000 (0)
│ │ │ │ +26690   GID Size            04 (4)
│ │ │ │ +26691   GID                 00000000 (0)
│ │ │ │ +26695 PAYLOAD
│ │ │ │ +
│ │ │ │ +27B6F LOCAL HEADER #16      04034B50 (67324752)
│ │ │ │ +27B73 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +27B74 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +27B75 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +27B77 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +27B79 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +27B7D CRC                   BFE8A81B (3219695643)
│ │ │ │ +27B81 Compressed Size       000037FA (14330)
│ │ │ │ +27B85 Uncompressed Size     0000E9F0 (59888)
│ │ │ │ +27B89 Filename Length       001C (28)
│ │ │ │ +27B8B Extra Length          001C (28)
│ │ │ │ +27B8D Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x27B8D: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +27BA9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +27BAB   Length              0009 (9)
│ │ │ │ +27BAD   Flags               03 (3) 'Modification Access'
│ │ │ │ +27BAE   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +27BB2   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +27BB6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +27BB8   Length              000B (11)
│ │ │ │ +27BBA   Version             01 (1)
│ │ │ │ +27BBB   UID Size            04 (4)
│ │ │ │ +27BBC   UID                 00000000 (0)
│ │ │ │ +27BC0   GID Size            04 (4)
│ │ │ │ +27BC1   GID                 00000000 (0)
│ │ │ │ +27BC5 PAYLOAD
│ │ │ │ +
│ │ │ │ +2B3BF LOCAL HEADER #17      04034B50 (67324752)
│ │ │ │ +2B3C3 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +2B3C4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +2B3C5 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +2B3C7 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +2B3C9 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +2B3CD CRC                   76141A43 (1981028931)
│ │ │ │ +2B3D1 Compressed Size       000006A0 (1696)
│ │ │ │ +2B3D5 Uncompressed Size     000011F4 (4596)
│ │ │ │ +2B3D9 Filename Length       001C (28)
│ │ │ │ +2B3DB Extra Length          001C (28)
│ │ │ │ +2B3DD Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x2B3DD: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +2B3F9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +2B3FB   Length              0009 (9)
│ │ │ │ +2B3FD   Flags               03 (3) 'Modification Access'
│ │ │ │ +2B3FE   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +2B402   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +2B406 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +2B408   Length              000B (11)
│ │ │ │ +2B40A   Version             01 (1)
│ │ │ │ +2B40B   UID Size            04 (4)
│ │ │ │ +2B40C   UID                 00000000 (0)
│ │ │ │ +2B410   GID Size            04 (4)
│ │ │ │ +2B411   GID                 00000000 (0)
│ │ │ │ +2B415 PAYLOAD
│ │ │ │ +
│ │ │ │ +2BAB5 LOCAL HEADER #18      04034B50 (67324752)
│ │ │ │ +2BAB9 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +2BABA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +2BABB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +2BABD Compression Method    0008 (8) 'Deflated'
│ │ │ │ +2BABF Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +2BAC3 CRC                   2586B243 (629584451)
│ │ │ │ +2BAC7 Compressed Size       00001081 (4225)
│ │ │ │ +2BACB Uncompressed Size     00004BFF (19455)
│ │ │ │ +2BACF Filename Length       001B (27)
│ │ │ │ +2BAD1 Extra Length          001C (28)
│ │ │ │ +2BAD3 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x2BAD3: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +2BAEE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +2BAF0   Length              0009 (9)
│ │ │ │ +2BAF2   Flags               03 (3) 'Modification Access'
│ │ │ │ +2BAF3   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +2BAF7   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +2BAFB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +2BAFD   Length              000B (11)
│ │ │ │ +2BAFF   Version             01 (1)
│ │ │ │ +2BB00   UID Size            04 (4)
│ │ │ │ +2BB01   UID                 00000000 (0)
│ │ │ │ +2BB05   GID Size            04 (4)
│ │ │ │ +2BB06   GID                 00000000 (0)
│ │ │ │ +2BB0A PAYLOAD
│ │ │ │ +
│ │ │ │ +2CB8B LOCAL HEADER #19      04034B50 (67324752)
│ │ │ │ +2CB8F Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +2CB90 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +2CB91 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +2CB93 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +2CB95 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +2CB99 CRC                   B55F93AA (3042939818)
│ │ │ │ +2CB9D Compressed Size       000033AB (13227)
│ │ │ │ +2CBA1 Uncompressed Size     0000BC94 (48276)
│ │ │ │ +2CBA5 Filename Length       001D (29)
│ │ │ │ +2CBA7 Extra Length          001C (28)
│ │ │ │ +2CBA9 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +37E01 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +38925 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +393FC Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +39411 Filename Length       000F (15)
│ │ │ │ +39413 Extra Length          001C (28)
│ │ │ │ +39415 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x39415: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +3942D   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +39440 PAYLOAD
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│ │ │ │ +3A38C Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +3A38D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3A38E General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +3A392 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +3A396 CRC                   7FB04E29 (2142260777)
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│ │ │ │ +3A39E Uncompressed Size     000018DF (6367)
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│ │ │ │ +3A3A6 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x3A3A6: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +3A3BE   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +3A3D1 PAYLOAD
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│ │ │ │ +3AA40 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3AA41 General Purpose Flag  0000 (0)
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│ │ │ │ +3AA45 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +3AA49 CRC                   1C4CBA2F (474790447)
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│ │ │ │ +3AA55 Filename Length       0013 (19)
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│ │ │ │ +#
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│ │ │ │ +3AA75   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +3C4D9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3C4DA General Purpose Flag  0000 (0)
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│ │ │ │ +3C4DE Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +3C4E2 CRC                   B885C195 (3095773589)
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│ │ │ │ +3C4EE Filename Length       0010 (16)
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│ │ │ │ +3C4F2 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
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│ │ │ │ +3C50B   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +3C50F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +3CEC8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3CEC9 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +3CECD Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +3CED1 CRC                   297E5B60 (696146784)
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│ │ │ │ +3CED9 Uncompressed Size     00001565 (5477)
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│ │ │ │ +3CEE1 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +3CEFC   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +3D5CB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +3D5CC General Purpose Flag  0000 (0)
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│ │ │ │ +3D5D0 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +3D5D4 CRC                   DBF03C4C (3689954380)
│ │ │ │ +3D5D8 Compressed Size       00002A1A (10778)
│ │ │ │ +3D5DC Uncompressed Size     0000B1C5 (45509)
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│ │ │ │ +3D5E4 Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
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│ │ │ │ +3D5FD   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +3D601 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +4002F Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +40034 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +40038 CRC                   1DC19E6D (499228269)
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│ │ │ │ +40046 Extra Length          001C (28)
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│ │ │ │ +#
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│ │ │ │ +40063   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +41F09 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +41F0A General Purpose Flag  0000 (0)
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│ │ │ │ +41F0E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +41F12 CRC                   B76D57E0 (3077396448)
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│ │ │ │ +41F43   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +41F51   GID Size            04 (4)
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│ │ │ │ +41F56 PAYLOAD
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│ │ │ │ +433CF LOCAL HEADER #39      04034B50 (67324752)
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│ │ │ │ +433D4 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +433D5 General Purpose Flag  0000 (0)
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│ │ │ │ +433D9 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +433DD CRC                   5D4AAA0E (1565174286)
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│ │ │ │ +43415   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +43423   GID Size            04 (4)
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│ │ │ │ +43428 PAYLOAD
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│ │ │ │ +44CFA Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +44CFB General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +44CFF Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +44D03 CRC                   705BC16B (1885061483)
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│ │ │ │ +44D11 Extra Length          001C (28)
│ │ │ │ +44D13 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x44D13: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +44D31 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +44D36   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +44D3A   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +44D3E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +44D4D PAYLOAD
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│ │ │ │ +45148 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +45149 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4514A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4514C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4514E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +45152 CRC                   BAFC6D2D (3137105197)
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│ │ │ │ +4515A Uncompressed Size     0000D8DC (55516)
│ │ │ │ +4515E Filename Length       0013 (19)
│ │ │ │ +45160 Extra Length          001C (28)
│ │ │ │ +45162 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x45162: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +45175 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +4517A   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +4517E   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +49428 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +49429 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4942A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4942C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4942E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +49432 CRC                   732C5AC6 (1932286662)
│ │ │ │ +49436 Compressed Size       000026C5 (9925)
│ │ │ │ +4943A Uncompressed Size     00006E45 (28229)
│ │ │ │ +4943E Filename Length       0019 (25)
│ │ │ │ +49440 Extra Length          001C (28)
│ │ │ │ +49442 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x49442: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +4945B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +49464   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +49468 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +49473   GID                 00000000 (0)
│ │ │ │ +49477 PAYLOAD
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│ │ │ │ +4BB3C LOCAL HEADER #43      04034B50 (67324752)
│ │ │ │ +4BB40 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4BB41 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4BB42 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4BB44 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4BB46 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +4BB4A CRC                   063987F6 (104433654)
│ │ │ │ +4BB4E Compressed Size       0000273A (10042)
│ │ │ │ +4BB52 Uncompressed Size     00008B83 (35715)
│ │ │ │ +4BB56 Filename Length       0019 (25)
│ │ │ │ +4BB58 Extra Length          001C (28)
│ │ │ │ +4BB5A Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4BB5A: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4BB73 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +4BB75   Length              0009 (9)
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│ │ │ │ +4BB78   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +4BB7C   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +4BB80 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +4BB84   Version             01 (1)
│ │ │ │ +4BB85   UID Size            04 (4)
│ │ │ │ +4BB86   UID                 00000000 (0)
│ │ │ │ +4BB8A   GID Size            04 (4)
│ │ │ │ +4BB8B   GID                 00000000 (0)
│ │ │ │ +4BB8F PAYLOAD
│ │ │ │ +
│ │ │ │ +4E2C9 LOCAL HEADER #44      04034B50 (67324752)
│ │ │ │ +4E2CD Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4E2CE Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4E2CF General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4E2D1 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4E2D3 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +4E2D7 CRC                   5D3635A5 (1563833765)
│ │ │ │ +4E2DB Compressed Size       00000CF1 (3313)
│ │ │ │ +4E2DF Uncompressed Size     0000517A (20858)
│ │ │ │ +4E2E3 Filename Length       0021 (33)
│ │ │ │ +4E2E5 Extra Length          001C (28)
│ │ │ │ +4E2E7 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4E2E7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4E308 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +4E311   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +4E315 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +4E31F   GID Size            04 (4)
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│ │ │ │ +4E324 PAYLOAD
│ │ │ │ +
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│ │ │ │ +4F019 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4F01A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4F01B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +4F01D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +4F01F Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +4F023 CRC                   8C66FDEA (2355559914)
│ │ │ │ +4F027 Compressed Size       00000468 (1128)
│ │ │ │ +4F02B Uncompressed Size     00000931 (2353)
│ │ │ │ +4F02F Filename Length       001B (27)
│ │ │ │ +4F031 Extra Length          001C (28)
│ │ │ │ +4F033 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4F033: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +4F04E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +4F057   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +4F05B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +4F065   GID Size            04 (4)
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│ │ │ │ +4F06A PAYLOAD
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│ │ │ │ +4F4D6 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +4F4D7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +4F4D8 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +4F4DC Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +4F4E0 CRC                   3B22D9D4 (992139732)
│ │ │ │ +4F4E4 Compressed Size       000016F3 (5875)
│ │ │ │ +4F4E8 Uncompressed Size     00007A6D (31341)
│ │ │ │ +4F4EC Filename Length       001F (31)
│ │ │ │ +4F4EE Extra Length          001C (28)
│ │ │ │ +4F4F0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x4F4F0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +4F50F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +4F518   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +4F51C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +4F526   GID Size            04 (4)
│ │ │ │ +4F527   GID                 00000000 (0)
│ │ │ │ +4F52B PAYLOAD
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│ │ │ │ +50C1E LOCAL HEADER #47      04034B50 (67324752)
│ │ │ │ +50C22 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +50C23 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +50C24 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +50C26 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +50C28 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +50C2C CRC                   4B3DFBE8 (1262353384)
│ │ │ │ +50C30 Compressed Size       00004173 (16755)
│ │ │ │ +50C34 Uncompressed Size     0001CF93 (118675)
│ │ │ │ +50C38 Filename Length       0010 (16)
│ │ │ │ +50C3A Extra Length          001C (28)
│ │ │ │ +50C3C Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x50C3C: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +50C4C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +50C55   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +50C59 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +50C5F   UID                 00000000 (0)
│ │ │ │ +50C63   GID Size            04 (4)
│ │ │ │ +50C64   GID                 00000000 (0)
│ │ │ │ +50C68 PAYLOAD
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│ │ │ │ +54DDB LOCAL HEADER #48      04034B50 (67324752)
│ │ │ │ +54DDF Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +54DE0 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +54DE1 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +54DE3 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +54DE5 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +54DE9 CRC                   7903D415 (2030294037)
│ │ │ │ +54DED Compressed Size       00000A94 (2708)
│ │ │ │ +54DF1 Uncompressed Size     00002105 (8453)
│ │ │ │ +54DF5 Filename Length       0014 (20)
│ │ │ │ +54DF7 Extra Length          001C (28)
│ │ │ │ +54DF9 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x54DF9: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +54E0D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +54E16   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +54E1A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +54E1E   Version             01 (1)
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│ │ │ │ +54E25   GID                 00000000 (0)
│ │ │ │ +54E29 PAYLOAD
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│ │ │ │ +558BD LOCAL HEADER #49      04034B50 (67324752)
│ │ │ │ +558C1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +558C2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +558C3 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +558C7 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +558CB CRC                   C323E604 (3273909764)
│ │ │ │ +558CF Compressed Size       0000AC95 (44181)
│ │ │ │ +558D3 Uncompressed Size     0003E418 (255000)
│ │ │ │ +558D7 Filename Length       0017 (23)
│ │ │ │ +558D9 Extra Length          001C (28)
│ │ │ │ +558DB Filename              'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x558DB: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +558F2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +558F4   Length              0009 (9)
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│ │ │ │ +558F7   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +558FB   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +558FF Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +55901   Length              000B (11)
│ │ │ │ +55903   Version             01 (1)
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│ │ │ │ +55905   UID                 00000000 (0)
│ │ │ │ +55909   GID Size            04 (4)
│ │ │ │ +5590A   GID                 00000000 (0)
│ │ │ │ +5590E PAYLOAD
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│ │ │ │ +605A3 LOCAL HEADER #50      04034B50 (67324752)
│ │ │ │ +605A7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +605A8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +605A9 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +605AB Compression Method    0008 (8) 'Deflated'
│ │ │ │ +605AD Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +605B1 CRC                   99B8E58B (2579031435)
│ │ │ │ +605B5 Compressed Size       00000401 (1025)
│ │ │ │ +605B9 Uncompressed Size     0000093D (2365)
│ │ │ │ +605BD Filename Length       0013 (19)
│ │ │ │ +605BF Extra Length          001C (28)
│ │ │ │ +605C1 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x605C1: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +605D4 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +605D9   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +605DD   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +605E1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +605E5   Version             01 (1)
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│ │ │ │ +605EB   GID Size            04 (4)
│ │ │ │ +605EC   GID                 00000000 (0)
│ │ │ │ +605F0 PAYLOAD
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│ │ │ │ +609F1 LOCAL HEADER #51      04034B50 (67324752)
│ │ │ │ +609F5 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +609F6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +609F7 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +609F9 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +609FB Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +609FF CRC                   BD83713F (3179508031)
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│ │ │ │ +60A07 Uncompressed Size     0000687B (26747)
│ │ │ │ +60A0B Filename Length       0012 (18)
│ │ │ │ +60A0D Extra Length          001C (28)
│ │ │ │ +60A0F Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x60A0F: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +60A21 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +60A2A   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +60A2E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +60A32   Version             01 (1)
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│ │ │ │ +60A38   GID Size            04 (4)
│ │ │ │ +60A39   GID                 00000000 (0)
│ │ │ │ +60A3D PAYLOAD
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│ │ │ │ +61F1E LOCAL HEADER #52      04034B50 (67324752)
│ │ │ │ +61F22 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +61F23 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +61F24 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +61F26 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +61F28 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +61F2C CRC                   53B3812A (1404272938)
│ │ │ │ +61F30 Compressed Size       000011EB (4587)
│ │ │ │ +61F34 Uncompressed Size     000040F5 (16629)
│ │ │ │ +61F38 Filename Length       0012 (18)
│ │ │ │ +61F3A Extra Length          001C (28)
│ │ │ │ +61F3C Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x61F3C: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +61F4E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ +61F57   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +61F5B Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +61F5F   Version             01 (1)
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│ │ │ │ +61F65   GID Size            04 (4)
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│ │ │ │ +61F6A PAYLOAD
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│ │ │ │ +63155 LOCAL HEADER #53      04034B50 (67324752)
│ │ │ │ +63159 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +6315A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6315B General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +6315D Compression Method    0008 (8) 'Deflated'
│ │ │ │ +6315F Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +63163 CRC                   AB9B08FD (2879064317)
│ │ │ │ +63167 Compressed Size       000009DA (2522)
│ │ │ │ +6316B Uncompressed Size     00003529 (13609)
│ │ │ │ +6316F Filename Length       0019 (25)
│ │ │ │ +63171 Extra Length          001C (28)
│ │ │ │ +63173 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x63173: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +6318C Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +6318E   Length              0009 (9)
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│ │ │ │ +63191   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +63195   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +63199 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +6319B   Length              000B (11)
│ │ │ │ +6319D   Version             01 (1)
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│ │ │ │ +631A4   GID                 00000000 (0)
│ │ │ │ +631A8 PAYLOAD
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│ │ │ │ +63B82 LOCAL HEADER #54      04034B50 (67324752)
│ │ │ │ +63B86 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +63B87 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +63B88 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +63B8A Compression Method    0008 (8) 'Deflated'
│ │ │ │ +63B8C Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +63B90 CRC                   A925840A (2837808138)
│ │ │ │ +63B94 Compressed Size       000018B2 (6322)
│ │ │ │ +63B98 Uncompressed Size     0000A605 (42501)
│ │ │ │ +63B9C Filename Length       0019 (25)
│ │ │ │ +63B9E Extra Length          001C (28)
│ │ │ │ +63BA0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x63BA0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +63BB9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +63BBB   Length              0009 (9)
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│ │ │ │ +63BBE   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +63BC2   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +63BC6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +63BC8   Length              000B (11)
│ │ │ │ +63BCA   Version             01 (1)
│ │ │ │ +63BCB   UID Size            04 (4)
│ │ │ │ +63BCC   UID                 00000000 (0)
│ │ │ │ +63BD0   GID Size            04 (4)
│ │ │ │ +63BD1   GID                 00000000 (0)
│ │ │ │ +63BD5 PAYLOAD
│ │ │ │ +
│ │ │ │ +65487 LOCAL HEADER #55      04034B50 (67324752)
│ │ │ │ +6548B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +6548C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6548D General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +65491 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +65495 CRC                   80854D35 (2156219701)
│ │ │ │ +65499 Compressed Size       0000177D (6013)
│ │ │ │ +6549D Uncompressed Size     0000472C (18220)
│ │ │ │ +654A1 Filename Length       0014 (20)
│ │ │ │ +654A3 Extra Length          001C (28)
│ │ │ │ +654A5 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x654A5: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +654C2   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +654C6 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +66C57 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +66C58 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +66C5C Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +66C60 CRC                   8CE827B6 (2364024758)
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│ │ │ │ +66C68 Uncompressed Size     00000825 (2085)
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│ │ │ │ +66C6E Extra Length          001C (28)
│ │ │ │ +66C70 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +66C95   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +670B7 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +670B8 General Purpose Flag  0000 (0)
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│ │ │ │ +670BC Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +670C0 CRC                   EACCE274 (3939295860)
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│ │ │ │ +670C8 Uncompressed Size     0000B56F (46447)
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│ │ │ │ +670CE Extra Length          001C (28)
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│ │ │ │ +#
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +670F8   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +6958D Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6958E General Purpose Flag  0000 (0)
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│ │ │ │ +69590 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +69592 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +69596 CRC                   0F1C1DE9 (253500905)
│ │ │ │ +6959A Compressed Size       00000E7E (3710)
│ │ │ │ +6959E Uncompressed Size     000052D9 (21209)
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│ │ │ │ +#
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +695CE   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +6A464 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6A465 General Purpose Flag  0000 (0)
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│ │ │ │ +6A469 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +6A46D CRC                   B25A43FF (2992260095)
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│ │ │ │ +6A499   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +6AEF5 General Purpose Flag  0000 (0)
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│ │ │ │ +6AEF9 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +6D3CD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6D3CE General Purpose Flag  0000 (0)
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│ │ │ │ +6D3D2 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +6D3DE Uncompressed Size     00003A2C (14892)
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│ │ │ │ +6E325 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +6E326 General Purpose Flag  0000 (0)
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│ │ │ │ +6E32A Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +6FE3C Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +6FE40 CRC                   11E32AF1 (300100337)
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│ │ │ │ +6FE50 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +70D67 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +70D68 General Purpose Flag  0000 (0)
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│ │ │ │ +70D6C Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +70D70 CRC                   2DB7929F (767005343)
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +70DA4   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +70ECF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +70ED0 General Purpose Flag  0000 (0)
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│ │ │ │ +70ED4 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +70ED8 CRC                   6AE26CB1 (1793223857)
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│ │ │ │ +70EE8 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +727B6 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +727B7 General Purpose Flag  0000 (0)
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│ │ │ │ +727BB Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +727BF CRC                   5F656D2A (1600482602)
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│ │ │ │ +727E9   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +727ED   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +72800 PAYLOAD
│ │ │ │ +
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│ │ │ │ +73E51 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +73E52 General Purpose Flag  0000 (0)
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│ │ │ │ +73E56 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +73E5A CRC                   0806C373 (134660979)
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│ │ │ │ +73E62 Uncompressed Size     0001185B (71771)
│ │ │ │ +73E66 Filename Length       0016 (22)
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│ │ │ │ +73E6A Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x73E6A: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
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│ │ │ │ +73E89   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +73E9C PAYLOAD
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│ │ │ │ +779F2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +779F3 General Purpose Flag  0000 (0)
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│ │ │ │ +779F7 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +779FB CRC                   CA7EF696 (3397318294)
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│ │ │ │ +77A40 PAYLOAD
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│ │ │ │ +7B8CC Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7B8CD General Purpose Flag  0000 (0)
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│ │ │ │ +7B8D1 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +7B8D5 CRC                   9AA2E4F1 (2594366705)
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│ │ │ │ +7B8DD Uncompressed Size     00003383 (13187)
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│ │ │ │ +7B8FF   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +7B903 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ +7C150 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +7C151 General Purpose Flag  0000 (0)
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│ │ │ │ +7C155 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +7C159 CRC                   24F3A56F (619947375)
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│ │ │ │ +7C161 Uncompressed Size     0001FB6C (129900)
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│ │ │ │ +7C187   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +81321 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +81322 General Purpose Flag  0000 (0)
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│ │ │ │ +81326 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +8132A CRC                   91682113 (2439520531)
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│ │ │ │ +81332 Uncompressed Size     000081CF (33231)
│ │ │ │ +81336 Filename Length       0019 (25)
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│ │ │ │ +8135C   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +82E79 Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +82E7E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +82EB3   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +83C64 General Purpose Flag  0000 (0)
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│ │ │ │ +83C68 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
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│ │ │ │ +83E8E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +83E8F General Purpose Flag  0000 (0)
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│ │ │ │ +83E93 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +83E97 CRC                   3FD13568 (1070675304)
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│ │ │ │ +83EC9   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +845A3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +845A4 General Purpose Flag  0000 (0)
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│ │ │ │ +845A8 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +845AC CRC                   C30A498C (3272231308)
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│ │ │ │ +845DD   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +8617E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +8617F General Purpose Flag  0000 (0)
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│ │ │ │ +86183 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +86187 CRC                   BF2A02F8 (3207201528)
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│ │ │ │ +# WARNING: Offset 0x86197: Filename 'XXXXXXXXXXXXXXXXXX'
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│ │ │ │ +861B2   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +878C3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +878C4 General Purpose Flag  0000 (0)
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│ │ │ │ +878C8 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +878CC CRC                   5572EFA1 (1433595809)
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│ │ │ │ +# WARNING: Offset 0x878DC: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +89722 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +89723 General Purpose Flag  0000 (0)
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│ │ │ │ +89727 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +8972B CRC                   8CF4315F (2364813663)
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│ │ │ │ +89739 Extra Length          001C (28)
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│ │ │ │ +# WARNING: Offset 0x8973B: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +8975E   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +8C120 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +8C121 General Purpose Flag  0000 (0)
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│ │ │ │ +8C125 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +8C129 CRC                   8546C52F (2236007727)
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│ │ │ │ +8C131 Uncompressed Size     00001DB6 (7606)
│ │ │ │ +8C135 Filename Length       0018 (24)
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│ │ │ │ +# WARNING: Offset 0x8C139: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +8CB1E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +8CB1F General Purpose Flag  0000 (0)
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│ │ │ │ +8CB23 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +8CB27 CRC                   F5E2129F (4125233823)
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│ │ │ │ +8E229 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +8E22A General Purpose Flag  0000 (0)
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│ │ │ │ +8E22E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +8E232 CRC                   F5E2129F (4125233823)
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│ │ │ │ +8E267   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +8F93C General Purpose Flag  0000 (0)
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│ │ │ │ +8F944 CRC                   FC95F24B (4237685323)
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│ │ │ │ +9150F Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +91514 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +91518 CRC                   D0D71F86 (3503759238)
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│ │ │ │ +91524 Filename Length       0016 (22)
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│ │ │ │ +91547   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +920DA Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +920E3 CRC                   FFF9C4D2 (4294558930)
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│ │ │ │ +920EF Filename Length       0016 (22)
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│ │ │ │ +92112   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +934B9 Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +934C2 CRC                   A1037E8E (2701360782)
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +94970 CRC                   5E9E64F1 (1587438833)
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│ │ │ │ +952E3   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +97229 Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
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│ │ │ │ +9722E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +97232 CRC                   BB9BE575 (3147556213)
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│ │ │ │ +# WARNING: Offset 0x97242: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ +97265   Access Time         68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
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│ │ │ │ +9AFF3 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9AFF4 General Purpose Flag  0000 (0)
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│ │ │ │ +9AFF8 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +9AFFC CRC                   46C39BCE (1187224526)
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│ │ │ │ +#          Zero length filename
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│ │ │ │ +9DA05 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9DA06 General Purpose Flag  0000 (0)
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│ │ │ │ +9DA0A Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +9DA0E CRC                   DCB3B516 (3702764822)
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│ │ │ │ +# WARNING: Offset 0x9DA1E: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ -#          Zero length filename
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│ │ │ │ -# WARNING: Offset 0x9E1B1: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -#          Zero length filename
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│ │ │ │ -# WARNING: Offset 0x9E2D7: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
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│ │ │ │ -#          Zero length filename
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│ │ │ │ -# WARNING: Offset 0x9E3F2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -# WARNING: Offset 0x9E458: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -# WARNING: Offset 0x9E4B9: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -# WARNING: Offset 0x9E514: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -9E525 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9E52E Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E56B: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -9E57F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9E588 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9E5A3 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E5A7 CRC                   6E954352 (1855275858)
│ │ │ │ -9E5AB Compressed Size       00001262 (4706)
│ │ │ │ -9E5AF Uncompressed Size     00003469 (13417)
│ │ │ │ -9E5B3 Filename Length       0014 (20)
│ │ │ │ -9E5B5 Extra Length          0018 (24)
│ │ │ │ -9E5B7 Comment Length        0000 (0)
│ │ │ │ -9E5B9 Disk Start            0000 (0)
│ │ │ │ -9E5BB Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9E5BD Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E5C1 Local Header Offset   00036B42 (224066)
│ │ │ │ -9E5C5 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E5C5: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E5D9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E5DB   Length              0005 (5)
│ │ │ │ -9E5DD   Flags               01 (1) 'Modification'
│ │ │ │ -9E5DE   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E5E2 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E5E4   Length              000B (11)
│ │ │ │ -9E5E6   Version             01 (1)
│ │ │ │ -9E5E7   UID Size            04 (4)
│ │ │ │ -9E5E8   UID                 00000000 (0)
│ │ │ │ -9E5EC   GID Size            04 (4)
│ │ │ │ -9E5ED   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E5F1 CENTRAL HEADER #29    02014B50 (33639248)
│ │ │ │ -9E5F5 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9E5F6 Created OS            03 (3) 'Unix'
│ │ │ │ -9E5F7 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E5F8 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E5F9 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9E5FB Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9E5FD Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E601 CRC                   DB1D4E7B (3676130939)
│ │ │ │ -9E605 Compressed Size       00000ACF (2767)
│ │ │ │ -9E609 Uncompressed Size     000022FF (8959)
│ │ │ │ -9E60D Filename Length       001B (27)
│ │ │ │ -9E60F Extra Length          0018 (24)
│ │ │ │ -9E611 Comment Length        0000 (0)
│ │ │ │ -9E613 Disk Start            0000 (0)
│ │ │ │ -9E615 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9E617 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E61B Local Header Offset   00037DF2 (228850)
│ │ │ │ -9E61F Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E61F: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E63A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E63C   Length              0005 (5)
│ │ │ │ -9E63E   Flags               01 (1) 'Modification'
│ │ │ │ -9E63F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E643 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E645   Length              000B (11)
│ │ │ │ -9E647   Version             01 (1)
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│ │ │ │ -9E649   UID                 00000000 (0)
│ │ │ │ -9E64D   GID Size            04 (4)
│ │ │ │ -9E64E   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E652 CENTRAL HEADER #30    02014B50 (33639248)
│ │ │ │ -9E656 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9E657 Created OS            03 (3) 'Unix'
│ │ │ │ -9E658 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E659 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E65A General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9E65C Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9E65E Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E662 CRC                   B74B6217 (3075170839)
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│ │ │ │ -9E66A Uncompressed Size     0000237A (9082)
│ │ │ │ -9E66E Filename Length       0013 (19)
│ │ │ │ -9E670 Extra Length          0018 (24)
│ │ │ │ -9E672 Comment Length        0000 (0)
│ │ │ │ -9E674 Disk Start            0000 (0)
│ │ │ │ -9E676 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9E678 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E67C Local Header Offset   00038916 (231702)
│ │ │ │ -9E680 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E680: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E693 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E695   Length              0005 (5)
│ │ │ │ -9E697   Flags               01 (1) 'Modification'
│ │ │ │ -9E698   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E69C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E69E   Length              000B (11)
│ │ │ │ -9E6A0   Version             01 (1)
│ │ │ │ -9E6A1   UID Size            04 (4)
│ │ │ │ -9E6A2   UID                 00000000 (0)
│ │ │ │ -9E6A6   GID Size            04 (4)
│ │ │ │ -9E6A7   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E6AB CENTRAL HEADER #31    02014B50 (33639248)
│ │ │ │ -9E6AF Created Zip Spec      3D (61) '6.1'
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│ │ │ │ -9E6B1 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E6B2 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E6B3 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9E6B5 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9E6B7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E6BB CRC                   33B87EA3 (867729059)
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│ │ │ │ -9E6C3 Uncompressed Size     000036F1 (14065)
│ │ │ │ -9E6C7 Filename Length       000F (15)
│ │ │ │ -9E6C9 Extra Length          0018 (24)
│ │ │ │ -9E6CB Comment Length        0000 (0)
│ │ │ │ -9E6CD Disk Start            0000 (0)
│ │ │ │ -9E6CF Int File Attributes   0000 (0)
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│ │ │ │ -9E6D5 Local Header Offset   000393F1 (234481)
│ │ │ │ -9E6D9 Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E6D9: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E6E8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E6EA   Length              0005 (5)
│ │ │ │ -9E6EC   Flags               01 (1) 'Modification'
│ │ │ │ -9E6ED   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E6F1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E6F3   Length              000B (11)
│ │ │ │ -9E6F5   Version             01 (1)
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│ │ │ │ -9E6F7   UID                 00000000 (0)
│ │ │ │ -9E6FB   GID Size            04 (4)
│ │ │ │ -9E6FC   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E700 CENTRAL HEADER #32    02014B50 (33639248)
│ │ │ │ -9E704 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9E705 Created OS            03 (3) 'Unix'
│ │ │ │ -9E706 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E707 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E708 General Purpose Flag  0000 (0)
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│ │ │ │ -9E70C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E710 CRC                   7FB04E29 (2142260777)
│ │ │ │ -9E714 Compressed Size       0000066A (1642)
│ │ │ │ -9E718 Uncompressed Size     000018DF (6367)
│ │ │ │ -9E71C Filename Length       000F (15)
│ │ │ │ -9E71E Extra Length          0018 (24)
│ │ │ │ -9E720 Comment Length        0000 (0)
│ │ │ │ -9E722 Disk Start            0000 (0)
│ │ │ │ -9E724 Int File Attributes   0000 (0)
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│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E72A Local Header Offset   0003A382 (238466)
│ │ │ │ -9E72E Filename              'XXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E72E: Filename 'XXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E73D Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E73F   Length              0005 (5)
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│ │ │ │ -9E746 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E748   Length              000B (11)
│ │ │ │ -9E74A   Version             01 (1)
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│ │ │ │ -9E74C   UID                 00000000 (0)
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│ │ │ │ -9E751   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E755 CENTRAL HEADER #33    02014B50 (33639248)
│ │ │ │ -9E759 Created Zip Spec      3D (61) '6.1'
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│ │ │ │ -9E75B Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E75C Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E75D General Purpose Flag  0000 (0)
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│ │ │ │ -9E761 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E765 CRC                   5FF08021 (1609596961)
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│ │ │ │ -9E771 Filename Length       0013 (19)
│ │ │ │ -9E773 Extra Length          0018 (24)
│ │ │ │ -9E775 Comment Length        0000 (0)
│ │ │ │ -9E777 Disk Start            0000 (0)
│ │ │ │ -9E779 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9E77B Ext File Attributes   01A40000 (27525120)
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│ │ │ │ -9E77F Local Header Offset   0003AA35 (240181)
│ │ │ │ -9E783 Filename              'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E783: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E796 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E798   Length              0005 (5)
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│ │ │ │ -9E79B   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E79F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E7A1   Length              000B (11)
│ │ │ │ -9E7A3   Version             01 (1)
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│ │ │ │ -9E7A5   UID                 00000000 (0)
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│ │ │ │ -9E7B5 Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ -9E7BA Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E7BE CRC                   B885C195 (3095773589)
│ │ │ │ -9E7C2 Compressed Size       000009A5 (2469)
│ │ │ │ -9E7C6 Uncompressed Size     00001B64 (7012)
│ │ │ │ -9E7CA Filename Length       0010 (16)
│ │ │ │ -9E7CC Extra Length          0018 (24)
│ │ │ │ -9E7CE Comment Length        0000 (0)
│ │ │ │ -9E7D0 Disk Start            0000 (0)
│ │ │ │ -9E7D2 Int File Attributes   0000 (0)
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│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E7D8 Local Header Offset   0003C4CC (246988)
│ │ │ │ -9E7DC Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E7DC: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E7EC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E7EE   Length              0005 (5)
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│ │ │ │ -9E7F1   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E7F5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E7F7   Length              000B (11)
│ │ │ │ -9E7F9   Version             01 (1)
│ │ │ │ -9E7FA   UID Size            04 (4)
│ │ │ │ -9E7FB   UID                 00000000 (0)
│ │ │ │ -9E7FF   GID Size            04 (4)
│ │ │ │ -9E800   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E804 CENTRAL HEADER #35    02014B50 (33639248)
│ │ │ │ -9E808 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9E809 Created OS            03 (3) 'Unix'
│ │ │ │ -9E80A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E80B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E80C General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9E80E Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9E810 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E814 CRC                   297E5B60 (696146784)
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│ │ │ │ -9E81C Uncompressed Size     00001565 (5477)
│ │ │ │ -9E820 Filename Length       0012 (18)
│ │ │ │ -9E822 Extra Length          0018 (24)
│ │ │ │ -9E824 Comment Length        0000 (0)
│ │ │ │ -9E826 Disk Start            0000 (0)
│ │ │ │ -9E828 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9E82A Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E82E Local Header Offset   0003CEBB (249531)
│ │ │ │ -9E832 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E832: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E844 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E846   Length              0005 (5)
│ │ │ │ -9E848   Flags               01 (1) 'Modification'
│ │ │ │ -9E849   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E84D Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E84F   Length              000B (11)
│ │ │ │ -9E851   Version             01 (1)
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│ │ │ │ -9E853   UID                 00000000 (0)
│ │ │ │ -9E857   GID Size            04 (4)
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│ │ │ │ -
│ │ │ │ -9E85C CENTRAL HEADER #36    02014B50 (33639248)
│ │ │ │ -9E860 Created Zip Spec      3D (61) '6.1'
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│ │ │ │ -9E862 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E863 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E864 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9E866 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9E868 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E86C CRC                   963999A8 (2520357288)
│ │ │ │ -9E870 Compressed Size       00002A16 (10774)
│ │ │ │ -9E874 Uncompressed Size     0000B1C5 (45509)
│ │ │ │ -9E878 Filename Length       0010 (16)
│ │ │ │ -9E87A Extra Length          0018 (24)
│ │ │ │ -9E87C Comment Length        0000 (0)
│ │ │ │ -9E87E Disk Start            0000 (0)
│ │ │ │ -9E880 Int File Attributes   0000 (0)
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│ │ │ │ -9E882 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E886 Local Header Offset   0003D5BE (251326)
│ │ │ │ -9E88A Filename              'XXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E88A: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9E89A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9E89C   Length              0005 (5)
│ │ │ │ -9E89E   Flags               01 (1) 'Modification'
│ │ │ │ -9E89F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E8A3 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9E8A5   Length              000B (11)
│ │ │ │ -9E8A7   Version             01 (1)
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│ │ │ │ -9E8A9   UID                 00000000 (0)
│ │ │ │ -9E8AD   GID Size            04 (4)
│ │ │ │ -9E8AE   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9E8B2 CENTRAL HEADER #37    02014B50 (33639248)
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│ │ │ │ -9E8B7 Created OS            03 (3) 'Unix'
│ │ │ │ -9E8B8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9E8B9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9E8BA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9E8BC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9E8BE Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9E8C2 CRC                   412FC61A (1093649946)
│ │ │ │ -9E8C6 Compressed Size       00001E8C (7820)
│ │ │ │ -9E8CA Uncompressed Size     00009AAA (39594)
│ │ │ │ -9E8CE Filename Length       0012 (18)
│ │ │ │ -9E8D0 Extra Length          0018 (24)
│ │ │ │ -9E8D2 Comment Length        0000 (0)
│ │ │ │ -9E8D4 Disk Start            0000 (0)
│ │ │ │ -9E8D6 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9E8D8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9E8DC Local Header Offset   0004001E (262174)
│ │ │ │ -9E8E0 Filename              'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9E8E0: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
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│ │ │ │ -# WARNING: Offset 0x9EC3E: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -9EC81 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9EC85 CRC                   6703890F (1728284943)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9ECA3: Filename 'XXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9ECB3 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9ECB8   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9ECBC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9ECD7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9ECDB CRC                   7903D415 (2030294037)
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│ │ │ │ -#
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│ │ │ │ -#          Zero length filename
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9ED53: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9ED6A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9ED73 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9ED92 CRC                   73C7E563 (1942480227)
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│ │ │ │ -9ED9E Filename Length       0013 (19)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EDB0: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
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│ │ │ │ -9EDCC Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9EDE7 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9EDEB CRC                   7EF400B8 (2129920184)
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│ │ │ │ -9EDF7 Filename Length       0012 (18)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EE09: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9EE1B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9EE24 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9EE43 CRC                   693EF524 (1765733668)
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│ │ │ │ -9EE4F Filename Length       0012 (18)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EE61: Filename 'XXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9EE73 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9EE7C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9EE9B CRC                   23CF3462 (600781922)
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│ │ │ │ -9EEA7 Filename Length       0019 (25)
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│ │ │ │ -9EEAD Disk Start            0000 (0)
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│ │ │ │ -9EEB5 Local Header Offset   00063152 (405842)
│ │ │ │ -9EEB9 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EEB9: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9EED2 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9EEDB Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9EEFA CRC                   3E165161 (1041650017)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EF18: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9EF31 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9EF3A Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9EF49 CENTRAL HEADER #55    02014B50 (33639248)
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│ │ │ │ -9EF59 CRC                   80854D35 (2156219701)
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│ │ │ │ -9EF65 Filename Length       0014 (20)
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│ │ │ │ -9EF73 Local Header Offset   00065482 (414850)
│ │ │ │ -9EF77 Filename              'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EF77: Filename 'XXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9EF8B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9EF94 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9EFAF Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9EFB3 CRC                   8CE827B6 (2364024758)
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│ │ │ │ -9EFBB Uncompressed Size     00000825 (2085)
│ │ │ │ -9EFBF Filename Length       001C (28)
│ │ │ │ -9EFC1 Extra Length          0018 (24)
│ │ │ │ -9EFC3 Comment Length        0000 (0)
│ │ │ │ -9EFC5 Disk Start            0000 (0)
│ │ │ │ -9EFC7 Int File Attributes   0000 (0)
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│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9EFCD Local Header Offset   00066C4D (420941)
│ │ │ │ -9EFD1 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9EFD1: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9EFED Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9F015 CRC                   060C597A (101472634)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F033: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -#          Zero length filename
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F0FD: Filename 'XXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -9F134 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F138 CRC                   1E73B85F (510900319)
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F156: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
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│ │ │ │ -# WARNING: Offset 0x9F1B5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F21F: Filename 'XXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F236 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9F23F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F27C: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F29F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9F2D3 Filename Length       001B (27)
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│ │ │ │ -9F2E5 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F2E5: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F300 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9F309 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
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│ │ │ │ -9F31F Extract OS            00 (0) 'MS-DOS'
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│ │ │ │ -9F324 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F328 CRC                   AA7430BF (2859741375)
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│ │ │ │ -9F334 Filename Length       001D (29)
│ │ │ │ -9F336 Extra Length          0018 (24)
│ │ │ │ -9F338 Comment Length        0000 (0)
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│ │ │ │ -9F33C Int File Attributes   0000 (0)
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│ │ │ │ -9F342 Local Header Offset   00070EC4 (462532)
│ │ │ │ -9F346 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F346: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F363 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
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│ │ │ │ -9F36C Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F36E   Length              000B (11)
│ │ │ │ -9F370   Version             01 (1)
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│ │ │ │ -9F381 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F382 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F383 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F385 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F387 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F38B CRC                   5F656D2A (1600482602)
│ │ │ │ -9F38F Compressed Size       0000164C (5708)
│ │ │ │ -9F393 Uncompressed Size     00003A9B (15003)
│ │ │ │ -9F397 Filename Length       0015 (21)
│ │ │ │ -9F399 Extra Length          0018 (24)
│ │ │ │ -9F39B Comment Length        0000 (0)
│ │ │ │ -9F39D Disk Start            0000 (0)
│ │ │ │ -9F39F Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F3A1 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F3A5 Local Header Offset   000727AB (468907)
│ │ │ │ -9F3A9 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F3A9: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F3BE Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F3C0   Length              0005 (5)
│ │ │ │ -9F3C2   Flags               01 (1) 'Modification'
│ │ │ │ -9F3C3   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F3C7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F3C9   Length              000B (11)
│ │ │ │ -9F3CB   Version             01 (1)
│ │ │ │ -9F3CC   UID Size            04 (4)
│ │ │ │ -9F3CD   UID                 00000000 (0)
│ │ │ │ -9F3D1   GID Size            04 (4)
│ │ │ │ -9F3D2   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F3D6 CENTRAL HEADER #67    02014B50 (33639248)
│ │ │ │ -9F3DA Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F3DB Created OS            03 (3) 'Unix'
│ │ │ │ -9F3DC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F3DD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F3DE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F3E0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F3E2 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F3E6 CRC                   DBD9148D (3688436877)
│ │ │ │ -9F3EA Compressed Size       00003B4F (15183)
│ │ │ │ -9F3EE Uncompressed Size     0001185B (71771)
│ │ │ │ -9F3F2 Filename Length       0016 (22)
│ │ │ │ -9F3F4 Extra Length          0018 (24)
│ │ │ │ -9F3F6 Comment Length        0000 (0)
│ │ │ │ -9F3F8 Disk Start            0000 (0)
│ │ │ │ -9F3FA Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F3FC Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F400 Local Header Offset   00073E46 (474694)
│ │ │ │ -9F404 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F404: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F41A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F41C   Length              0005 (5)
│ │ │ │ -9F41E   Flags               01 (1) 'Modification'
│ │ │ │ -9F41F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F423 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F425   Length              000B (11)
│ │ │ │ -9F427   Version             01 (1)
│ │ │ │ -9F428   UID Size            04 (4)
│ │ │ │ -9F429   UID                 00000000 (0)
│ │ │ │ -9F42D   GID Size            04 (4)
│ │ │ │ -9F42E   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F432 CENTRAL HEADER #68    02014B50 (33639248)
│ │ │ │ -9F436 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F437 Created OS            03 (3) 'Unix'
│ │ │ │ -9F438 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F439 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F43A General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F43C Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F43E Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F442 CRC                   C7B6EF21 (3350654753)
│ │ │ │ -9F446 Compressed Size       00003E88 (16008)
│ │ │ │ -9F44A Uncompressed Size     0001C17B (115067)
│ │ │ │ -9F44E Filename Length       0019 (25)
│ │ │ │ -9F450 Extra Length          0018 (24)
│ │ │ │ -9F452 Comment Length        0000 (0)
│ │ │ │ -9F454 Disk Start            0000 (0)
│ │ │ │ -9F456 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F458 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F45C Local Header Offset   000779E5 (489957)
│ │ │ │ -9F460 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F460: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F479 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F47B   Length              0005 (5)
│ │ │ │ -9F47D   Flags               01 (1) 'Modification'
│ │ │ │ -9F47E   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F482 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F484   Length              000B (11)
│ │ │ │ -9F486   Version             01 (1)
│ │ │ │ -9F487   UID Size            04 (4)
│ │ │ │ -9F488   UID                 00000000 (0)
│ │ │ │ -9F48C   GID Size            04 (4)
│ │ │ │ -9F48D   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F491 CENTRAL HEADER #69    02014B50 (33639248)
│ │ │ │ -9F495 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F496 Created OS            03 (3) 'Unix'
│ │ │ │ -9F497 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F498 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F499 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F49B Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F49D Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F4A1 CRC                   59E53244 (1508192836)
│ │ │ │ -9F4A5 Compressed Size       00000835 (2101)
│ │ │ │ -9F4A9 Uncompressed Size     00003383 (13187)
│ │ │ │ -9F4AD Filename Length       0011 (17)
│ │ │ │ -9F4AF Extra Length          0018 (24)
│ │ │ │ -9F4B1 Comment Length        0000 (0)
│ │ │ │ -9F4B3 Disk Start            0000 (0)
│ │ │ │ -9F4B5 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F4B7 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F4BB Local Header Offset   0007B8C0 (506048)
│ │ │ │ -9F4BF Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F4BF: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F4D0 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F4D2   Length              0005 (5)
│ │ │ │ -9F4D4   Flags               01 (1) 'Modification'
│ │ │ │ -9F4D5   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F4D9 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F4DB   Length              000B (11)
│ │ │ │ -9F4DD   Version             01 (1)
│ │ │ │ -9F4DE   UID Size            04 (4)
│ │ │ │ -9F4DF   UID                 00000000 (0)
│ │ │ │ -9F4E3   GID Size            04 (4)
│ │ │ │ -9F4E4   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F4E8 CENTRAL HEADER #70    02014B50 (33639248)
│ │ │ │ -9F4EC Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F4ED Created OS            03 (3) 'Unix'
│ │ │ │ -9F4EE Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F4EF Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F4F0 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F4F2 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F4F4 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F4F8 CRC                   D1DF86DD (3521087197)
│ │ │ │ -9F4FC Compressed Size       00005184 (20868)
│ │ │ │ -9F500 Uncompressed Size     0001FB6C (129900)
│ │ │ │ -9F504 Filename Length       0015 (21)
│ │ │ │ -9F506 Extra Length          0018 (24)
│ │ │ │ -9F508 Comment Length        0000 (0)
│ │ │ │ -9F50A Disk Start            0000 (0)
│ │ │ │ -9F50C Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F50E Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F512 Local Header Offset   0007C140 (508224)
│ │ │ │ -9F516 Filename              'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F516: Filename 'XXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F52B Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F52D   Length              0005 (5)
│ │ │ │ -9F52F   Flags               01 (1) 'Modification'
│ │ │ │ -9F530   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F534 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F536   Length              000B (11)
│ │ │ │ -9F538   Version             01 (1)
│ │ │ │ -9F539   UID Size            04 (4)
│ │ │ │ -9F53A   UID                 00000000 (0)
│ │ │ │ -9F53E   GID Size            04 (4)
│ │ │ │ -9F53F   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F543 CENTRAL HEADER #71    02014B50 (33639248)
│ │ │ │ -9F547 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F548 Created OS            03 (3) 'Unix'
│ │ │ │ -9F549 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F54A Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F54B General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F54D Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F54F Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F553 CRC                   419D467F (1100826239)
│ │ │ │ -9F557 Compressed Size       00001B0A (6922)
│ │ │ │ -9F55B Uncompressed Size     000081CF (33231)
│ │ │ │ -9F55F Filename Length       0019 (25)
│ │ │ │ -9F561 Extra Length          0018 (24)
│ │ │ │ -9F563 Comment Length        0000 (0)
│ │ │ │ -9F565 Disk Start            0000 (0)
│ │ │ │ -9F567 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F569 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F56D Local Header Offset   00081313 (529171)
│ │ │ │ -9F571 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F571: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F58A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F58C   Length              0005 (5)
│ │ │ │ -9F58E   Flags               01 (1) 'Modification'
│ │ │ │ -9F58F   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F593 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F595   Length              000B (11)
│ │ │ │ -9F597   Version             01 (1)
│ │ │ │ -9F598   UID Size            04 (4)
│ │ │ │ -9F599   UID                 00000000 (0)
│ │ │ │ -9F59D   GID Size            04 (4)
│ │ │ │ -9F59E   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F5A2 CENTRAL HEADER #72    02014B50 (33639248)
│ │ │ │ -9F5A6 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F5A7 Created OS            03 (3) 'Unix'
│ │ │ │ -9F5A8 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F5A9 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F5AA General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F5AC Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F5AE Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F5B2 CRC                   49C11139 (1237389625)
│ │ │ │ -9F5B6 Compressed Size       00000D97 (3479)
│ │ │ │ -9F5BA Uncompressed Size     00002E9F (11935)
│ │ │ │ -9F5BE Filename Length       0018 (24)
│ │ │ │ -9F5C0 Extra Length          0018 (24)
│ │ │ │ -9F5C2 Comment Length        0000 (0)
│ │ │ │ -9F5C4 Disk Start            0000 (0)
│ │ │ │ -9F5C6 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F5C8 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F5CC Local Header Offset   00082E70 (536176)
│ │ │ │ -9F5D0 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F5D0: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F5E8 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F5EA   Length              0005 (5)
│ │ │ │ -9F5EC   Flags               01 (1) 'Modification'
│ │ │ │ -9F5ED   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F5F1 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F5F3   Length              000B (11)
│ │ │ │ -9F5F5   Version             01 (1)
│ │ │ │ -9F5F6   UID Size            04 (4)
│ │ │ │ -9F5F7   UID                 00000000 (0)
│ │ │ │ -9F5FB   GID Size            04 (4)
│ │ │ │ -9F5FC   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F600 CENTRAL HEADER #73    02014B50 (33639248)
│ │ │ │ -9F604 Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F605 Created OS            03 (3) 'Unix'
│ │ │ │ -9F606 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F607 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F608 General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F60A Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F60C Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F610 CRC                   0350D61E (55629342)
│ │ │ │ -9F614 Compressed Size       000001E0 (480)
│ │ │ │ -9F618 Uncompressed Size     00000323 (803)
│ │ │ │ -9F61C Filename Length       0011 (17)
│ │ │ │ -9F61E Extra Length          0018 (24)
│ │ │ │ -9F620 Comment Length        0000 (0)
│ │ │ │ -9F622 Disk Start            0000 (0)
│ │ │ │ -9F624 Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F626 Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F62A Local Header Offset   00083C59 (539737)
│ │ │ │ -9F62E Filename              'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F62E: Filename 'XXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F63F Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F641   Length              0005 (5)
│ │ │ │ -9F643   Flags               01 (1) 'Modification'
│ │ │ │ -9F644   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F648 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F64A   Length              000B (11)
│ │ │ │ -9F64C   Version             01 (1)
│ │ │ │ -9F64D   UID Size            04 (4)
│ │ │ │ -9F64E   UID                 00000000 (0)
│ │ │ │ -9F652   GID Size            04 (4)
│ │ │ │ -9F653   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F657 CENTRAL HEADER #74    02014B50 (33639248)
│ │ │ │ -9F65B Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F65C Created OS            03 (3) 'Unix'
│ │ │ │ -9F65D Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F65E Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F65F General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F661 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F663 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F667 CRC                   3FD13568 (1070675304)
│ │ │ │ -9F66B Compressed Size       000006C2 (1730)
│ │ │ │ -9F66F Uncompressed Size     00001439 (5177)
│ │ │ │ -9F673 Filename Length       0019 (25)
│ │ │ │ -9F675 Extra Length          0018 (24)
│ │ │ │ -9F677 Comment Length        0000 (0)
│ │ │ │ -9F679 Disk Start            0000 (0)
│ │ │ │ -9F67B Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F67D Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F681 Local Header Offset   00083E84 (540292)
│ │ │ │ -9F685 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#
│ │ │ │ -# WARNING: Offset 0x9F685: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ -#          Zero length filename
│ │ │ │ -#
│ │ │ │ -9F69E Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ -9F6A0   Length              0005 (5)
│ │ │ │ -9F6A2   Flags               01 (1) 'Modification'
│ │ │ │ -9F6A3   Modification Time   68C84154 (1757954388) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F6A7 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ -9F6A9   Length              000B (11)
│ │ │ │ -9F6AB   Version             01 (1)
│ │ │ │ -9F6AC   UID Size            04 (4)
│ │ │ │ -9F6AD   UID                 00000000 (0)
│ │ │ │ -9F6B1   GID Size            04 (4)
│ │ │ │ -9F6B2   GID                 00000000 (0)
│ │ │ │ -
│ │ │ │ -9F6B6 CENTRAL HEADER #75    02014B50 (33639248)
│ │ │ │ -9F6BA Created Zip Spec      3D (61) '6.1'
│ │ │ │ -9F6BB Created OS            03 (3) 'Unix'
│ │ │ │ -9F6BC Extract Zip Spec      14 (20) '2.0'
│ │ │ │ -9F6BD Extract OS            00 (0) 'MS-DOS'
│ │ │ │ -9F6BE General Purpose Flag  0000 (0)
│ │ │ │ -      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ -9F6C0 Compression Method    0008 (8) 'Deflated'
│ │ │ │ -9F6C2 Modification Time     5B2F84F8 (1529840888) 'Mon Sep 15 16:39:48 2025'
│ │ │ │ -9F6C6 CRC                   89473D13 (2303147283)
│ │ │ │ -9F6CA Compressed Size       00001B8B (7051)
│ │ │ │ -9F6CE Uncompressed Size     00009F03 (40707)
│ │ │ │ -9F6D2 Filename Length       0018 (24)
│ │ │ │ -9F6D4 Extra Length          0018 (24)
│ │ │ │ -9F6D6 Comment Length        0000 (0)
│ │ │ │ -9F6D8 Disk Start            0000 (0)
│ │ │ │ -9F6DA Int File Attributes   0000 (0)
│ │ │ │ -      [Bit 0]               0 'Binary Data'
│ │ │ │ -9F6DC Ext File Attributes   01A40000 (27525120)
│ │ │ │ -      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ -9F6E0 Local Header Offset   00084599 (542105)
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│ │ │ │ +
│ │ │ │ +9FB84 CENTRAL HEADER #88    02014B50 (33639248)
│ │ │ │ +9FB88 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +9FB89 Created OS            03 (3) 'Unix'
│ │ │ │ +9FB8A Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +9FB8B Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9FB8C General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9FB8E Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9FB90 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +9FB94 CRC                   BB9BE575 (3147556213)
│ │ │ │ +9FB98 Compressed Size       00003D76 (15734)
│ │ │ │ +9FB9C Uncompressed Size     00016649 (91721)
│ │ │ │ +9FBA0 Filename Length       001A (26)
│ │ │ │ +9FBA2 Extra Length          0018 (24)
│ │ │ │ +9FBA4 Comment Length        0000 (0)
│ │ │ │ +9FBA6 Disk Start            0000 (0)
│ │ │ │ +9FBA8 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +9FBAA Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +9FBAE Local Header Offset   00097224 (619044)
│ │ │ │ +9FBB2 Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x9FBB2: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9FBCC Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9FBCE   Length              0005 (5)
│ │ │ │ +9FBD0   Flags               01 (1) 'Modification'
│ │ │ │ +9FBD1   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +9FBD5 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9FBD7   Length              000B (11)
│ │ │ │ +9FBD9   Version             01 (1)
│ │ │ │ +9FBDA   UID Size            04 (4)
│ │ │ │ +9FBDB   UID                 00000000 (0)
│ │ │ │ +9FBDF   GID Size            04 (4)
│ │ │ │ +9FBE0   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +9FBE4 CENTRAL HEADER #89    02014B50 (33639248)
│ │ │ │ +9FBE8 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +9FBE9 Created OS            03 (3) 'Unix'
│ │ │ │ +9FBEA Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +9FBEB Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9FBEC General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9FBEE Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9FBF0 Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +9FBF4 CRC                   46C39BCE (1187224526)
│ │ │ │ +9FBF8 Compressed Size       000029C0 (10688)
│ │ │ │ +9FBFC Uncompressed Size     0000BA6A (47722)
│ │ │ │ +9FC00 Filename Length       0018 (24)
│ │ │ │ +9FC02 Extra Length          0018 (24)
│ │ │ │ +9FC04 Comment Length        0000 (0)
│ │ │ │ +9FC06 Disk Start            0000 (0)
│ │ │ │ +9FC08 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +9FC0A Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +9FC0E Local Header Offset   0009AFEE (634862)
│ │ │ │ +9FC12 Filename              'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x9FC12: Filename 'XXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9FC2A Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9FC2C   Length              0005 (5)
│ │ │ │ +9FC2E   Flags               01 (1) 'Modification'
│ │ │ │ +9FC2F   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +9FC33 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9FC35   Length              000B (11)
│ │ │ │ +9FC37   Version             01 (1)
│ │ │ │ +9FC38   UID Size            04 (4)
│ │ │ │ +9FC39   UID                 00000000 (0)
│ │ │ │ +9FC3D   GID Size            04 (4)
│ │ │ │ +9FC3E   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +9FC42 CENTRAL HEADER #90    02014B50 (33639248)
│ │ │ │ +9FC46 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +9FC47 Created OS            03 (3) 'Unix'
│ │ │ │ +9FC48 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +9FC49 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9FC4A General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9FC4C Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9FC4E Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +9FC52 CRC                   DCB3B516 (3702764822)
│ │ │ │ +9FC56 Compressed Size       000000AE (174)
│ │ │ │ +9FC5A Uncompressed Size     000000FC (252)
│ │ │ │ +9FC5E Filename Length       0016 (22)
│ │ │ │ +9FC60 Extra Length          0018 (24)
│ │ │ │ +9FC62 Comment Length        0000 (0)
│ │ │ │ +9FC64 Disk Start            0000 (0)
│ │ │ │ +9FC66 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +9FC68 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +9FC6C Local Header Offset   0009DA00 (645632)
│ │ │ │ +9FC70 Filename              'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x9FC70: Filename 'XXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9FC86 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9FC88   Length              0005 (5)
│ │ │ │ +9FC8A   Flags               01 (1) 'Modification'
│ │ │ │ +9FC8B   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +9FC8F Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9FC91   Length              000B (11)
│ │ │ │ +9FC93   Version             01 (1)
│ │ │ │ +9FC94   UID Size            04 (4)
│ │ │ │ +9FC95   UID                 00000000 (0)
│ │ │ │ +9FC99   GID Size            04 (4)
│ │ │ │ +9FC9A   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +9FC9E CENTRAL HEADER #91    02014B50 (33639248)
│ │ │ │ +9FCA2 Created Zip Spec      3D (61) '6.1'
│ │ │ │ +9FCA3 Created OS            03 (3) 'Unix'
│ │ │ │ +9FCA4 Extract Zip Spec      14 (20) '2.0'
│ │ │ │ +9FCA5 Extract OS            00 (0) 'MS-DOS'
│ │ │ │ +9FCA6 General Purpose Flag  0000 (0)
│ │ │ │ +      [Bits 1-2]            0 'Normal Compression'
│ │ │ │ +9FCA8 Compression Method    0008 (8) 'Deflated'
│ │ │ │ +9FCAA Modification Time     5B445D10 (1531206928) 'Sat Oct  4 11:40:32 2025'
│ │ │ │ +9FCAE CRC                   58439733 (1480824627)
│ │ │ │ +9FCB2 Compressed Size       00000077 (119)
│ │ │ │ +9FCB6 Uncompressed Size     000000A2 (162)
│ │ │ │ +9FCBA Filename Length       002D (45)
│ │ │ │ +9FCBC Extra Length          0018 (24)
│ │ │ │ +9FCBE Comment Length        0000 (0)
│ │ │ │ +9FCC0 Disk Start            0000 (0)
│ │ │ │ +9FCC2 Int File Attributes   0000 (0)
│ │ │ │ +      [Bit 0]               0 'Binary Data'
│ │ │ │ +9FCC4 Ext File Attributes   01A40000 (27525120)
│ │ │ │ +      [Bits 16-24]          01A4 (420) 'Unix attrib: rw-r--r--'
│ │ │ │ +9FCC8 Local Header Offset   0009DAFE (645886)
│ │ │ │ +9FCCC Filename              'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#
│ │ │ │ +# WARNING: Offset 0x9FCCC: Filename 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
│ │ │ │ +#          Zero length filename
│ │ │ │ +#
│ │ │ │ +9FCF9 Extra ID #1           5455 (21589) 'Extended Timestamp [UT]'
│ │ │ │ +9FCFB   Length              0005 (5)
│ │ │ │ +9FCFD   Flags               01 (1) 'Modification'
│ │ │ │ +9FCFE   Modification Time   68E107B1 (1759578033) 'Sat Oct  4 11:40:33 2025'
│ │ │ │ +9FD02 Extra ID #2           7875 (30837) 'Unix Extra type 3 [ux]'
│ │ │ │ +9FD04   Length              000B (11)
│ │ │ │ +9FD06   Version             01 (1)
│ │ │ │ +9FD07   UID Size            04 (4)
│ │ │ │ +9FD08   UID                 00000000 (0)
│ │ │ │ +9FD0C   GID Size            04 (4)
│ │ │ │ +9FD0D   GID                 00000000 (0)
│ │ │ │ +
│ │ │ │ +9FD11 END CENTRAL HEADER    06054B50 (101010256)
│ │ │ │ +9FD15 Number of this disk   0000 (0)
│ │ │ │ +9FD17 Central Dir Disk no   0000 (0)
│ │ │ │ +9FD19 Entries in this disk  005B (91)
│ │ │ │ +9FD1B Total Entries         005B (91)
│ │ │ │ +9FD1D Size of Central Dir   00002135 (8501)
│ │ │ │ +9FD21 Offset to Central Dir 0009DBDC (646108)
│ │ │ │ +9FD25 Comment Length        0000 (0)
│ │ │ │  #
│ │ │ │  # Warning Count: 182
│ │ │ │  #
│ │ │ │  # Done
│ │ │ ├── filetype from file(1)
│ │ │ │ @@ -1 +1 @@
│ │ │ │ -Zip archive data, made by v6.1 UNIX, extract using at least v1.0, last modified Sep 15 2025 16:39:48, uncompressed size 20, method=store
│ │ │ │ +Zip archive data, made by v6.1 UNIX, extract using at least v1.0, last modified Oct 04 2025 11:40:32, uncompressed size 20, method=store
│ │ │ ├── OEBPS/typespec.xhtml
│ │ │ │ @@ -143,122 +143,122 @@
│ │ │ │  and optional <code class="inline">(=&gt;)</code> association types. If an association type is mandatory, an
│ │ │ │  association with that type needs to be present. In the case of an optional
│ │ │ │  association type it is not required for the key type to be present.</p><p>The notation <code class="inline">#{}</code> specifies the singleton type for the empty map. Note that
│ │ │ │  this notation is not a shorthand for the <a href="../../../lib/../erts/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a> type.</p><p>For convenience, the following types are also built-in. They can be thought as
│ │ │ │  predefined aliases for the type unions also shown in the table.</p><p><a href="" id="builtin_types"></a></p><table><thead><tr><th style="text-align: left;"><em>Built-in type</em></th><th style="text-align: left;"><em>Defined as</em></th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:binary/0"><code class="inline">binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_binary/0"><code class="inline">nonempty_binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:8, _:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:bitstring/0"><code class="inline">bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_bitstring/0"><code class="inline">nonempty_bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:1, _:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a></td><td style="text-align: left;"><code class="inline">'false'</code> | <code class="inline">'true'</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:byte/0"><code class="inline">byte/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:char/0"><code class="inline">char/0</code></a></td><td style="text-align: left;"><code class="inline">0..16#10ffff</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nil/0"><code class="inline">nil/0</code></a></td><td style="text-align: left;"><code class="inline">[]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:number/0"><code class="inline">number/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:integer/0"><code class="inline">integer/0</code></a> | <a href="../../../lib/../erts/doc/html/erlang.html#t:float/0"><code class="inline">float/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:list/0"><code class="inline">list/0</code></a></td><td style="text-align: left;"><code class="inline">[any()]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:maybe_improper_list/0"><code class="inline">maybe_improper_list/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:maybe_improper_list/2"><code class="inline">maybe_improper_list(any(), any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_list/0"><code class="inline">nonempty_list/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_list/1"><code class="inline">nonempty_list(any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:string/0"><code class="inline">string/0</code></a></td><td style="text-align: left;"><code class="inline">[char()]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:nonempty_string/0"><code class="inline">nonempty_string/0</code></a></td><td style="text-align: left;"><code class="inline">[char(),...]</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:iodata/0"><code class="inline">iodata/0</code></a></td><td style="text-align: left;"><code class="inline">iolist()</code> | <code class="inline">binary()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:iolist/0"><code class="inline">iolist/0</code></a></td><td style="text-align: left;"><code class="inline">maybe_improper_list(byte()</code> | <code class="inline">binary()</code> | <code class="inline">iolist(), binary()</code> | <code class="inline">[])</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a></td><td style="text-align: left;"><code class="inline">#{any() =&gt; any()}</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:function/0"><code class="inline">function/0</code></a></td><td style="text-align: left;"><code class="inline">fun()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:module/0"><code class="inline">module/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:mfa/0"><code class="inline">mfa/0</code></a></td><td style="text-align: left;"><code class="inline">{module(),atom(),arity()}</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:arity/0"><code class="inline">arity/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:identifier/0"><code class="inline">identifier/0</code></a></td><td style="text-align: left;"><code class="inline">pid()</code> | <code class="inline">port()</code> | <code class="inline">reference()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#node/0"><code class="inline">node/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:timeout/0"><code class="inline">timeout/0</code></a></td><td style="text-align: left;"><code class="inline">'infinity'</code> | <code class="inline">non_neg_integer()</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a></td><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:none/0"><code class="inline">none/0</code></a></td></tr></tbody></table><p><em>Table: Built-in types, predefined aliases</em></p><p>In addition, the following three built-in types exist and can be thought as
│ │ │ │  defined below, though strictly their &quot;type definition&quot; is not valid syntax
│ │ │ │  according to the type language defined above.</p><table><thead><tr><th style="text-align: left;"><em>Built-in type</em></th><th style="text-align: left;"><em>Can be thought defined by the syntax</em></th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:non_neg_integer/0"><code class="inline">non_neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">0..</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:pos_integer/0"><code class="inline">pos_integer/0</code></a></td><td style="text-align: left;"><code class="inline">1..</code></td></tr><tr><td style="text-align: left;"><a href="../../../lib/../erts/doc/html/erlang.html#t:neg_integer/0"><code class="inline">neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">..-1</code></td></tr></tbody></table><p><em>Table: Additional built-in types</em></p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The following built-in list types also exist, but they are expected to be
│ │ │ │ -rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2460425917-1">(</span><span class="p" data-group-id="2460425917-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2460425917-2">(</span><span class="nf">any</span><span class="p" data-group-id="2460425917-3">(</span><span class="p" data-group-id="2460425917-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2460425917-4">(</span><span class="p" data-group-id="2460425917-4">)</span><span class="p" data-group-id="2460425917-2">)</span><span class="w">
│ │ │ │ -</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="2460425917-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2460425917-5">)</span><span class="w">
│ │ │ │ -</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="2460425917-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="2460425917-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ │ -shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="6112468503-1">{</span><span class="p" data-group-id="6112468503-1">}</span><span class="w">
│ │ │ │ -        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="6112468503-2">{</span><span class="n">Fields</span><span class="p" data-group-id="6112468503-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │ │ +rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="6514027194-1">(</span><span class="p" data-group-id="6514027194-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="6514027194-2">(</span><span class="nf">any</span><span class="p" data-group-id="6514027194-3">(</span><span class="p" data-group-id="6514027194-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="6514027194-4">(</span><span class="p" data-group-id="6514027194-4">)</span><span class="p" data-group-id="6514027194-2">)</span><span class="w">
│ │ │ │ +</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="6514027194-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="6514027194-5">)</span><span class="w">
│ │ │ │ +</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="6514027194-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="6514027194-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ │ +shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="5188403893-1">{</span><span class="p" data-group-id="5188403893-1">}</span><span class="w">
│ │ │ │ +        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="5188403893-2">{</span><span class="n">Fields</span><span class="p" data-group-id="5188403893-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │ │  <a href="typespec.xhtml#typeinrecords">Type Information in Record Declarations</a>.</p><h3 id="redefining-built-in-types" class="section-heading">
│ │ │ │    <a href="#redefining-built-in-types" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Redefining built-in types</span>
│ │ │ │  </h3>
│ │ │ │  <section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, it is permitted to define a type having the same
│ │ │ │  name as a built-in type.</p></section><p>It is recommended to avoid deliberately reusing built-in names because it can be
│ │ │ │  confusing. However, when an Erlang/OTP release introduces a new type, code that
│ │ │ │  happened to define its own type having the same name will continue to work.</p><p>As an example, imagine that the Erlang/OTP 42 release introduces a new type
│ │ │ │ -<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="5677984558-1">(</span><span class="p" data-group-id="5677984558-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5677984558-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="5677984558-3">(</span><span class="p" data-group-id="5677984558-3">)</span><span class="p" data-group-id="5677984558-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="6248810724-1">(</span><span class="p" data-group-id="6248810724-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6248810724-2">#{</span><span class="p" data-group-id="6248810724-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │ │ +<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="3079746717-1">(</span><span class="p" data-group-id="3079746717-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3079746717-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="3079746717-3">(</span><span class="p" data-group-id="3079746717-3">)</span><span class="p" data-group-id="3079746717-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="2892610011-1">(</span><span class="p" data-group-id="2892610011-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2892610011-2">#{</span><span class="p" data-group-id="2892610011-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │ │  warning), and Dialyzer will not emit any additional warnings.</p><h2 id="type-declarations-of-user-defined-types" class="section-heading">
│ │ │ │    <a href="#type-declarations-of-user-defined-types" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Declarations of User-Defined Types</span>
│ │ │ │  </h2>
│ │ │ │  <p>As seen, the basic syntax of a type is an atom followed by closed parentheses.
│ │ │ │  New types are declared using <code class="inline">-type</code> and <code class="inline">-opaque</code> attributes as in the
│ │ │ │ -following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="2545197543-1">(</span><span class="p" data-group-id="2545197543-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="2545197543-2">(</span><span class="p" data-group-id="2545197543-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │ │ +following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="1993269317-1">(</span><span class="p" data-group-id="1993269317-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="1993269317-2">(</span><span class="p" data-group-id="1993269317-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │ │  type as defined in the previous section. A current restriction is that <code class="inline">Type</code>
│ │ │ │  can contain only predefined types, or user-defined types which are either of the
│ │ │ │  following:</p><ul><li>Module-local type, that is, with a definition that is present in the code of
│ │ │ │  the module</li><li>Remote type, that is, type defined in, and exported by, other modules; more
│ │ │ │  about this soon.</li></ul><p>For module-local types, the restriction that their definition exists in the
│ │ │ │  module is enforced by the compiler and results in a compilation error. (A
│ │ │ │  similar restriction currently exists for records.)</p><p>Type declarations can also be parameterized by including type variables between
│ │ │ │  the parentheses. The syntax of type variables is the same as Erlang variables,
│ │ │ │  that is, starts with an upper-case letter. These variables is to
│ │ │ │ -appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="9528893358-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="9528893358-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9528893358-2">[</span><span class="p" data-group-id="9528893358-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="9528893358-3">}</span><span class="p" data-group-id="9528893358-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ │ -refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="1465095895-1">(</span><span class="p" data-group-id="1465095895-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="1465095895-2">]</span><span class="p" data-group-id="1465095895-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arguments.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="4542139570-1">(</span><span class="p" data-group-id="4542139570-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4542139570-2">]</span><span class="p" data-group-id="4542139570-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ │ -them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="6762302084-1">(</span><span class="p" data-group-id="6762302084-1">)</span><span class="w">
│ │ │ │ -</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="6762302084-2">(</span><span class="nf">atom</span><span class="p" data-group-id="6762302084-3">(</span><span class="p" data-group-id="6762302084-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6762302084-4">(</span><span class="p" data-group-id="6762302084-4">)</span><span class="p" data-group-id="6762302084-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │ │ +appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="2711598373-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="2711598373-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2711598373-2">[</span><span class="p" data-group-id="2711598373-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="2711598373-3">}</span><span class="p" data-group-id="2711598373-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ │ +refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="0682675680-1">(</span><span class="p" data-group-id="0682675680-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="0682675680-2">]</span><span class="p" data-group-id="0682675680-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arguments.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="6007595216-1">(</span><span class="p" data-group-id="6007595216-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6007595216-2">]</span><span class="p" data-group-id="6007595216-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ │ +them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="6219212490-1">(</span><span class="p" data-group-id="6219212490-1">)</span><span class="w">
│ │ │ │ +</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="6219212490-2">(</span><span class="nf">atom</span><span class="p" data-group-id="6219212490-3">(</span><span class="p" data-group-id="6219212490-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6219212490-4">(</span><span class="p" data-group-id="6219212490-4">)</span><span class="p" data-group-id="6219212490-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │ │  supposed to be visible from outside of their defining module. That is, only the
│ │ │ │  module defining them is allowed to depend on their term structure. Consequently,
│ │ │ │  such types do not make much sense as module local - module local types are not
│ │ │ │  accessible by other modules anyway - and is always to be exported.</p><p>Read more on <a href="opaques.xhtml">Opaques</a></p><p><a href="" id="typeinrecords"></a></p><h2 id="type-information-in-record-declarations" class="section-heading">
│ │ │ │    <a href="#type-information-in-record-declarations" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Information in Record Declarations</span>
│ │ │ │  </h2>
│ │ │ │  <p>The types of record fields can be specified in the declaration of the record.
│ │ │ │ -The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2373410270-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2373410270-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="2373410270-2">}</span><span class="p" data-group-id="2373410270-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ │ -previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5006048017-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5006048017-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="5006048017-3">(</span><span class="p" data-group-id="5006048017-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="5006048017-2">}</span><span class="p" data-group-id="5006048017-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ │ -the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4240866347-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4240866347-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4240866347-3">[</span><span class="p" data-group-id="4240866347-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="4240866347-2">}</span><span class="p" data-group-id="4240866347-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │ │ +The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8504556637-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8504556637-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="8504556637-2">}</span><span class="p" data-group-id="8504556637-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ │ +previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2875518582-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2875518582-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="2875518582-3">(</span><span class="p" data-group-id="2875518582-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="2875518582-2">}</span><span class="p" data-group-id="2875518582-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ │ +the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9304932490-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9304932490-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9304932490-3">[</span><span class="p" data-group-id="9304932490-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="9304932490-2">}</span><span class="p" data-group-id="9304932490-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │ │  the corresponding types. This is checked by the compiler and results in a
│ │ │ │  compilation error if a violation is detected.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, for fields without initial values, the singleton type
│ │ │ │  <code class="inline">'undefined'</code> was added to all declared types. In other words, the following
│ │ │ │ -two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3575018208-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3575018208-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3575018208-3">(</span><span class="p" data-group-id="3575018208-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="3575018208-4">(</span><span class="p" data-group-id="3575018208-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="3575018208-2">}</span><span class="p" data-group-id="3575018208-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9754216989-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9754216989-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9754216989-3">(</span><span class="p" data-group-id="9754216989-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="9754216989-4">(</span><span class="p" data-group-id="9754216989-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="9754216989-2">}</span><span class="p" data-group-id="9754216989-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3575018208-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3575018208-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3575018208-7">(</span><span class="p" data-group-id="3575018208-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="3575018208-8">(</span><span class="p" data-group-id="3575018208-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="3575018208-6">}</span><span class="p" data-group-id="3575018208-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9754216989-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9754216989-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9754216989-7">(</span><span class="p" data-group-id="9754216989-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="9754216989-8">(</span><span class="p" data-group-id="9754216989-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="9754216989-6">}</span><span class="p" data-group-id="9754216989-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │ │  type, you must explicitly add it to the typespec, as in the 2nd example.</p></section><p>Any record, containing type information or not, once defined, can be used as a
│ │ │ │  type using the following syntax:</p><pre><code class="text">#rec{}</code></pre><p>In addition, the record fields can be further specified when using a record type
│ │ │ │  by adding type information about the field as follows:</p><pre><code class="text">#rec{some_field :: Type}</code></pre><p>Any unspecified fields are assumed to have the type in the original record
│ │ │ │  declaration.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>When records are used to create patterns for ETS and Mnesia match functions,
│ │ │ │ -Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="6900824101-1">(</span><span class="p" data-group-id="6900824101-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="6900824101-2">(</span><span class="p" data-group-id="6900824101-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6900824101-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6900824101-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="6900824101-5">(</span><span class="p" data-group-id="6900824101-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="6900824101-6">(</span><span class="p" data-group-id="6900824101-6">)</span><span class="p" data-group-id="6900824101-4">}</span><span class="p" data-group-id="6900824101-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="9952376375-1">(</span><span class="p" data-group-id="9952376375-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="9952376375-2">(</span><span class="p" data-group-id="9952376375-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9952376375-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9952376375-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="9952376375-5">(</span><span class="p" data-group-id="9952376375-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="9952376375-6">(</span><span class="p" data-group-id="9952376375-6">)</span><span class="p" data-group-id="9952376375-4">}</span><span class="p" data-group-id="9952376375-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="6900824101-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="6900824101-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="6900824101-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6900824101-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="6900824101-9">}</span><span class="p" data-group-id="6900824101-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="9952376375-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="9952376375-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="9952376375-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9952376375-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9952376375-9">}</span><span class="p" data-group-id="9952376375-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │ │  <code class="inline">height</code>.</p><p>The recommended way of dealing with this is to declare the smallest record
│ │ │ │  field types to accommodate all your needs, and then create refinements as
│ │ │ │ -needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8302328413-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8302328413-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="8302328413-3">(</span><span class="p" data-group-id="8302328413-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="8302328413-4">(</span><span class="p" data-group-id="8302328413-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="8302328413-2">}</span><span class="p" data-group-id="8302328413-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1867766593-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1867766593-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="1867766593-3">(</span><span class="p" data-group-id="1867766593-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1867766593-4">(</span><span class="p" data-group-id="1867766593-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1867766593-2">}</span><span class="p" data-group-id="1867766593-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="8302328413-5">(</span><span class="p" data-group-id="8302328413-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8302328413-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="8302328413-7">(</span><span class="p" data-group-id="8302328413-7">)</span><span class="p" data-group-id="8302328413-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="1867766593-5">(</span><span class="p" data-group-id="1867766593-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1867766593-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1867766593-7">(</span><span class="p" data-group-id="1867766593-7">)</span><span class="p" data-group-id="1867766593-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │ │  before <code class="inline">#person{}</code>.</p></section><h2 id="specifications-for-functions" class="section-heading">
│ │ │ │    <a href="#specifications-for-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Specifications for Functions</span>
│ │ │ │  </h2>
│ │ │ │  <p>A specification (or contract) for a function is given using the <code class="inline">-spec</code>
│ │ │ │  attribute. The general format is as follows:</p><pre><code class="text">-spec Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>An implementation of the function with the same name <code class="inline">Function</code> must exist in
│ │ │ │  the current module, and the arity of the function must match the number of
│ │ │ │  arguments, otherwise the compilation fails.</p><p>The following longer format with module name is also valid as long as <code class="inline">Module</code>
│ │ │ │  is the name of the current module. This can be useful for documentation
│ │ │ │  purposes.</p><pre><code class="text">-spec Module:Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>Also, for documentation purposes, argument names can be given:</p><pre><code class="text">-spec Function(ArgName1 :: Type1, ..., ArgNameN :: TypeN) -&gt; RT.</code></pre><p>A function specification can be overloaded. That is, it can have several types,
│ │ │ │ -separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="1337372705-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="1337372705-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="1337372705-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="1337372705-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │ │ +separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7553332740-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="7553332740-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="7553332740-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="7553332740-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │ │  the domains of the argument types cannot overlap. For example, the following
│ │ │ │ -specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0012238744-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="0012238744-2">(</span><span class="p" data-group-id="0012238744-2">)</span><span class="p" data-group-id="0012238744-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="0012238744-3">(</span><span class="p" data-group-id="0012238744-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="0012238744-4">(</span><span class="nf">integer</span><span class="p" data-group-id="0012238744-5">(</span><span class="p" data-group-id="0012238744-5">)</span><span class="p" data-group-id="0012238744-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0012238744-6">(</span><span class="p" data-group-id="0012238744-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │ │ +specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8007859226-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="8007859226-2">(</span><span class="p" data-group-id="8007859226-2">)</span><span class="p" data-group-id="8007859226-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="8007859226-3">(</span><span class="p" data-group-id="8007859226-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="8007859226-4">(</span><span class="nf">integer</span><span class="p" data-group-id="8007859226-5">(</span><span class="p" data-group-id="8007859226-5">)</span><span class="p" data-group-id="8007859226-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8007859226-6">(</span><span class="p" data-group-id="8007859226-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │ │  and output arguments of a function. For example, the following specification
│ │ │ │  defines the type of a polymorphic identity function:</p><pre><code class="text">-spec id(X) -&gt; X.</code></pre><p>Notice that the above specification does not restrict the input and output type
│ │ │ │  in any way. These types can be constrained by guard-like subtype constraints and
│ │ │ │ -provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="4842206455-1">(</span><span class="n">X</span><span class="p" data-group-id="4842206455-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="4842206455-2">(</span><span class="p" data-group-id="4842206455-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │ │ +provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="5111478220-1">(</span><span class="n">X</span><span class="p" data-group-id="5111478220-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="5111478220-2">(</span><span class="p" data-group-id="5111478220-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │ │  constraint that can be used in the <code class="inline">when</code> part of a <code class="inline">-spec</code> attribute.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The above function specification uses multiple occurrences of the same type
│ │ │ │  variable. That provides more type information than the following function
│ │ │ │ -specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="0449662429-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="0449662429-2">(</span><span class="p" data-group-id="0449662429-2">)</span><span class="p" data-group-id="0449662429-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="0449662429-3">(</span><span class="p" data-group-id="0449662429-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │ │ +specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="0118432002-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="0118432002-2">(</span><span class="p" data-group-id="0118432002-2">)</span><span class="p" data-group-id="0118432002-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="0118432002-3">(</span><span class="p" data-group-id="0118432002-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │ │  some tuple. The specification with the <code class="inline">X</code> type variable specifies that the
│ │ │ │  function takes a tuple and returns <em>the same</em> tuple.</p><p>However, it is up to the tools that process the specifications to choose
│ │ │ │  whether to take this extra information into account or not.</p></section><p>The scope of a <code class="inline">::</code> constraint is the <code class="inline">(...) -&gt; RetType</code> specification after
│ │ │ │  which it appears. To avoid confusion, it is suggested that different variables
│ │ │ │  are used in different constituents of an overloaded contract, as shown in the
│ │ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="2126434998-1">(</span><span class="p" data-group-id="2126434998-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2126434998-3">(</span><span class="p" data-group-id="2126434998-3">)</span><span class="p" data-group-id="2126434998-2">}</span><span class="p" data-group-id="2126434998-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="2126434998-4">(</span><span class="p" data-group-id="2126434998-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="2126434998-5">(</span><span class="p" data-group-id="2126434998-6">[</span><span class="n">Y</span><span class="p" data-group-id="2126434998-6">]</span><span class="p" data-group-id="2126434998-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2126434998-7">(</span><span class="p" data-group-id="2126434998-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="7531568665-1">(</span><span class="p" data-group-id="7531568665-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7531568665-3">(</span><span class="p" data-group-id="7531568665-3">)</span><span class="p" data-group-id="7531568665-2">}</span><span class="p" data-group-id="7531568665-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="7531568665-4">(</span><span class="p" data-group-id="7531568665-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="7531568665-5">(</span><span class="p" data-group-id="7531568665-6">[</span><span class="n">Y</span><span class="p" data-group-id="7531568665-6">]</span><span class="p" data-group-id="7531568665-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7531568665-7">(</span><span class="p" data-group-id="7531568665-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │ │  servers or because they are used to throw exceptions, as in the following
│ │ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="9957444928-1">(</span><span class="n">Err</span><span class="p" data-group-id="9957444928-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="9957444928-2">(</span><span class="p" data-group-id="9957444928-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="9957444928-3">}</span><span class="p" data-group-id="9957444928-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../../lib/../erts/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="8468453911-1">(</span><span class="n">Err</span><span class="p" data-group-id="8468453911-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="8468453911-2">(</span><span class="p" data-group-id="8468453911-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="8468453911-3">}</span><span class="p" data-group-id="8468453911-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../../lib/../erts/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │ │  for their &quot;return&quot;, through a contract of the following form:</p><pre><code class="text">-spec my_error(term()) -&gt; no_return().</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Erlang uses the shorthand version <code class="inline">_</code> as an anonymous type variable equivalent
│ │ │ │  to <a href="../../../lib/../erts/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a> or <a href="../../../lib/../erts/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a>. For example, the following function</p><pre><code class="text">-spec Function(string(), _) -&gt; string().</code></pre><p>is equivalent to:</p><pre><code class="text">-spec Function(string(), any()) -&gt; string().</code></pre></section>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/tablesdatabases.xhtml
│ │ │ │ @@ -51,73 +51,73 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deleting an Element</span>
│ │ │ │  </h3>
│ │ │ │  <p>The <code class="inline">delete</code> operation is considered successful if the element was not present
│ │ │ │  in the table. Hence all attempts to check that the element is present in the
│ │ │ │  Ets/Mnesia table before deletion are unnecessary. Here follows an example for
│ │ │ │ -Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2784960064-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2784960064-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2784960064-2">[</span><span class="p" data-group-id="2784960064-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="9975361598-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9975361598-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9975361598-2">[</span><span class="p" data-group-id="9975361598-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2784960064-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="2784960064-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="2784960064-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2784960064-4">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9975361598-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="9975361598-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="9975361598-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9975361598-4">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><h3 id="fetching-data" class="section-heading">
│ │ │ │    <a href="#fetching-data" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Fetching Data</span>
│ │ │ │  </h3>
│ │ │ │  <p>Do not fetch data that you already have.</p><p>Consider that you have a module that handles the abstract data type <code class="inline">Person</code>.
│ │ │ │  You export the interface function <code class="inline">print_person/1</code>, which uses the internal
│ │ │ │  functions <code class="inline">print_name/1</code>, <code class="inline">print_age/1</code>, and <code class="inline">print_occupation/1</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If the function <code class="inline">print_name/1</code>, and so on, had been interface functions, the
│ │ │ │  situation would have been different, as you do not want the user of the
│ │ │ │  interface to know about the internal data representation.</p></section><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="3860790396-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="3860790396-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="3469492371-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="3469492371-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3860790396-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3860790396-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3860790396-3">[</span><span class="n">Person</span><span class="p" data-group-id="3860790396-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="3860790396-4">(</span><span class="n">Person</span><span class="p" data-group-id="3860790396-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="3860790396-5">(</span><span class="n">Person</span><span class="p" data-group-id="3860790396-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="3860790396-6">(</span><span class="n">Person</span><span class="p" data-group-id="3860790396-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3860790396-7">[</span><span class="p" data-group-id="3860790396-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3860790396-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3860790396-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="3860790396-9">]</span><span class="p" data-group-id="3860790396-8">)</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3469492371-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3469492371-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3469492371-3">[</span><span class="n">Person</span><span class="p" data-group-id="3469492371-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="3469492371-4">(</span><span class="n">Person</span><span class="p" data-group-id="3469492371-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="3469492371-5">(</span><span class="n">Person</span><span class="p" data-group-id="3469492371-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="3469492371-6">(</span><span class="n">Person</span><span class="p" data-group-id="3469492371-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3469492371-7">[</span><span class="p" data-group-id="3469492371-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3469492371-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3469492371-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="3469492371-9">]</span><span class="p" data-group-id="3469492371-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="3860790396-10">(</span><span class="n">Person</span><span class="p" data-group-id="3860790396-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3860790396-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3860790396-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="3860790396-12">]</span><span class="p" data-group-id="3860790396-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="3469492371-10">(</span><span class="n">Person</span><span class="p" data-group-id="3469492371-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3469492371-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3469492371-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="3469492371-12">]</span><span class="p" data-group-id="3469492371-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="3860790396-13">(</span><span class="n">Person</span><span class="p" data-group-id="3860790396-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3860790396-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3860790396-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3860790396-15">]</span><span class="p" data-group-id="3860790396-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="3469492371-13">(</span><span class="n">Person</span><span class="p" data-group-id="3469492371-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3469492371-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3469492371-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3469492371-15">]</span><span class="p" data-group-id="3469492371-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="3860790396-16">(</span><span class="n">Person</span><span class="p" data-group-id="3860790396-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3860790396-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3860790396-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="3860790396-18">]</span><span class="p" data-group-id="3860790396-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="4415909685-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="4415909685-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="3469492371-16">(</span><span class="n">Person</span><span class="p" data-group-id="3469492371-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3469492371-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3469492371-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="3469492371-18">]</span><span class="p" data-group-id="3469492371-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="3661461777-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="3661461777-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="4415909685-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="4415909685-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4415909685-3">[</span><span class="n">Person</span><span class="p" data-group-id="4415909685-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="4415909685-4">(</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="4415909685-5">(</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="4415909685-6">(</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4415909685-7">[</span><span class="p" data-group-id="4415909685-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4415909685-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4415909685-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-9">]</span><span class="p" data-group-id="4415909685-8">)</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3661461777-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3661461777-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3661461777-3">[</span><span class="n">Person</span><span class="p" data-group-id="3661461777-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="3661461777-4">(</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="3661461777-5">(</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="3661461777-6">(</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3661461777-7">[</span><span class="p" data-group-id="3661461777-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3661461777-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3661461777-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-9">]</span><span class="p" data-group-id="3661461777-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="4415909685-10">(</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4415909685-11">[</span><span class="n">Person</span><span class="p" data-group-id="4415909685-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="4415909685-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="4415909685-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4415909685-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4415909685-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="4415909685-14">]</span><span class="p" data-group-id="4415909685-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="4415909685-15">(</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4415909685-16">[</span><span class="n">Person</span><span class="p" data-group-id="4415909685-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="4415909685-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="4415909685-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4415909685-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4415909685-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="4415909685-19">]</span><span class="p" data-group-id="4415909685-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="4415909685-20">(</span><span class="n">PersonID</span><span class="p" data-group-id="4415909685-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4415909685-21">[</span><span class="n">Person</span><span class="p" data-group-id="4415909685-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="4415909685-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="4415909685-22">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4415909685-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4415909685-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="4415909685-24">]</span><span class="p" data-group-id="4415909685-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="3661461777-10">(</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3661461777-11">[</span><span class="n">Person</span><span class="p" data-group-id="3661461777-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3661461777-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3661461777-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3661461777-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3661461777-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="3661461777-14">]</span><span class="p" data-group-id="3661461777-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="3661461777-15">(</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3661461777-16">[</span><span class="n">Person</span><span class="p" data-group-id="3661461777-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3661461777-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3661461777-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3661461777-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3661461777-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3661461777-19">]</span><span class="p" data-group-id="3661461777-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="3661461777-20">(</span><span class="n">PersonID</span><span class="p" data-group-id="3661461777-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3661461777-21">[</span><span class="n">Person</span><span class="p" data-group-id="3661461777-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3661461777-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3661461777-22">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3661461777-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3661461777-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="3661461777-24">]</span><span class="p" data-group-id="3661461777-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │ │    <a href="#non-persistent-database-storage" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Non-Persistent Database Storage</span>
│ │ │ │  </h3>
│ │ │ │  <p>For non-persistent database storage, prefer Ets tables over Mnesia
│ │ │ │  <code class="inline">local_content</code> tables. Even the Mnesia <code class="inline">dirty_write</code> operations carry a fixed
│ │ │ │ @@ -131,38 +131,38 @@
│ │ │ │  </h3>
│ │ │ │  <p>Assuming an Ets table that uses <code class="inline">idno</code> as key and contains the following:</p><pre><code class="text">[#person{idno = 1, name = &quot;Adam&quot;,  age = 31, occupation = &quot;mailman&quot;},
│ │ │ │   #person{idno = 2, name = &quot;Bryan&quot;, age = 31, occupation = &quot;cashier&quot;},
│ │ │ │   #person{idno = 3, name = &quot;Bryan&quot;, age = 35, occupation = &quot;banker&quot;},
│ │ │ │   #person{idno = 4, name = &quot;Carl&quot;,  age = 25, occupation = &quot;mailman&quot;}]</code></pre><p>If you <em>must</em> return all data stored in the Ets table, you can use
│ │ │ │  <a href="../../../lib/stdlib/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a>. However, usually you are only interested in a subset of the
│ │ │ │  information in which case <a href="../../../lib/stdlib/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a> is expensive. If you only want to
│ │ │ │ -extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="5558163761-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5558163761-2">[</span><span class="p" data-group-id="5558163761-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5558163761-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ +extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="4787979333-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4787979333-2">[</span><span class="p" data-group-id="4787979333-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4787979333-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5558163761-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="5558163761-5">[</span><span class="p" data-group-id="5558163761-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="5558163761-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="5558163761-6">]</span><span class="p" data-group-id="5558163761-3">}</span><span class="p" data-group-id="5558163761-2">]</span><span class="p" data-group-id="5558163761-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="0400865367-1">(</span><span class="n">Tab</span><span class="p" data-group-id="0400865367-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0400865367-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0400865367-3">(</span><span class="n">X</span><span class="p" data-group-id="0400865367-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="0400865367-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="5156665052-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5156665052-2">[</span><span class="p" data-group-id="5156665052-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5156665052-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="4787979333-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="4787979333-5">[</span><span class="p" data-group-id="4787979333-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="4787979333-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="4787979333-6">]</span><span class="p" data-group-id="4787979333-3">}</span><span class="p" data-group-id="4787979333-2">]</span><span class="p" data-group-id="4787979333-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="6916823616-1">(</span><span class="n">Tab</span><span class="p" data-group-id="6916823616-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="6916823616-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6916823616-3">(</span><span class="n">X</span><span class="p" data-group-id="6916823616-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="6916823616-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="3335495081-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3335495081-2">[</span><span class="p" data-group-id="3335495081-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3335495081-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5156665052-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="5156665052-5">[</span><span class="p" data-group-id="5156665052-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="5156665052-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="5156665052-6">]</span><span class="p" data-group-id="5156665052-3">}</span><span class="p" data-group-id="5156665052-2">]</span><span class="p" data-group-id="5156665052-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="3441821170-1">(</span><span class="n">Tab</span><span class="p" data-group-id="3441821170-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="3441821170-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3441821170-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3441821170-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="3335495081-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="3335495081-5">[</span><span class="p" data-group-id="3335495081-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="3335495081-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="3335495081-6">]</span><span class="p" data-group-id="3335495081-3">}</span><span class="p" data-group-id="3335495081-2">]</span><span class="p" data-group-id="3335495081-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="6690048302-1">(</span><span class="n">Tab</span><span class="p" data-group-id="6690048302-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="6690048302-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6690048302-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6690048302-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │                                  </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="3441821170-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="3441821170-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="6690048302-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="6690048302-4">]</span><span class="p">;</span><span class="w">
│ │ │ │                                   </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                       </span><span class="n">Acc</span><span class="w">
│ │ │ │                             </span><span class="k">end</span><span class="w">
│ │ │ │ -             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3441821170-5">[</span><span class="p" data-group-id="3441821170-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="3441821170-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ │ -then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="5843258905-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5843258905-2">[</span><span class="p" data-group-id="5843258905-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5843258905-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6690048302-5">[</span><span class="p" data-group-id="6690048302-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="6690048302-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ │ +then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="7888019307-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7888019307-2">[</span><span class="p" data-group-id="7888019307-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7888019307-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5843258905-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5843258905-5">[</span><span class="p" data-group-id="5843258905-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5843258905-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="5843258905-6">]</span><span class="p" data-group-id="5843258905-3">}</span><span class="p" data-group-id="5843258905-2">]</span><span class="p" data-group-id="5843258905-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="9714539823-1">(</span><span class="n">Tab</span><span class="p" data-group-id="9714539823-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9714539823-2">(</span><span class="nf">fun</span><span class="p" data-group-id="9714539823-3">(</span><span class="n">X</span><span class="p" data-group-id="9714539823-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="9714539823-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="7888019307-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7888019307-5">[</span><span class="p" data-group-id="7888019307-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7888019307-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="7888019307-6">]</span><span class="p" data-group-id="7888019307-3">}</span><span class="p" data-group-id="7888019307-2">]</span><span class="p" data-group-id="7888019307-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="6279635375-1">(</span><span class="n">Tab</span><span class="p" data-group-id="6279635375-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="6279635375-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6279635375-3">(</span><span class="n">X</span><span class="p" data-group-id="6279635375-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="6279635375-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │ │    <a href="#ordered_set-tables" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text"><code class="inline">ordered_set</code> Tables</span>
│ │ │ │  </h3>
│ │ │ │  <p>If the data in the table is to be accessed so that the order of the keys in the
│ │ │ │  table is significant, the table type <code class="inline">ordered_set</code> can be used instead of the
│ │ │ │ @@ -198,20 +198,20 @@
│ │ │ │  Clearly, the second table would have to be kept consistent with the master
│ │ │ │  table. Mnesia can do this for you, but a home-brew index table can be very
│ │ │ │  efficient compared to the overhead involved in using Mnesia.</p><p>An index table for the table in the previous examples would have to be a bag (as
│ │ │ │  keys would appear more than once) and can have the following contents:</p><pre><code class="text">[#index_entry{name=&quot;Adam&quot;, idno=1},
│ │ │ │   #index_entry{name=&quot;Bryan&quot;, idno=2},
│ │ │ │   #index_entry{name=&quot;Bryan&quot;, idno=3},
│ │ │ │   #index_entry{name=&quot;Carl&quot;, idno=4}]</code></pre><p>Given this index table, a lookup of the <code class="inline">age</code> fields for all persons named
│ │ │ │ -&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5944209019-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="5944209019-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="5944209019-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5944209019-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="5944209019-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="5944209019-4">}</span><span class="p" data-group-id="5944209019-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="5944209019-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5944209019-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="5944209019-6">}</span><span class="p" data-group-id="5944209019-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="5944209019-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="5944209019-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1102706918-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="1102706918-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1102706918-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1102706918-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="1102706918-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="1102706918-4">}</span><span class="p" data-group-id="1102706918-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="1102706918-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1102706918-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="1102706918-6">}</span><span class="p" data-group-id="1102706918-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1102706918-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="1102706918-7">)</span><span class="p">,</span><span class="w">
│ │ │ │                   </span><span class="n">Age</span><span class="w">
│ │ │ │            </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="5944209019-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │ │ +          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="1102706918-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │ │  <a href="../../../lib/stdlib/doc/html/ets.html#lookup/2"><code class="inline">ets:lookup/2</code></a> call. The <a href="../../../lib/stdlib/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> call is only used to traverse the <code class="inline">idno</code>s
│ │ │ │  matching the name &quot;Bryan&quot; in the table; thus the number of lookups in the master
│ │ │ │  table is minimized.</p><p>Keeping an index table introduces some overhead when inserting records in the
│ │ │ │  table. The number of operations gained from the table must therefore be compared
│ │ │ │  against the number of operations inserting objects in the table. However, notice
│ │ │ │  that the gain is significant when the key can be used to lookup elements.</p><h2 id="mnesia" class="section-heading">
│ │ │ │    <a href="#mnesia" class="hover-link">
│ │ │ │ @@ -226,47 +226,47 @@
│ │ │ │    <span class="text">Secondary Index</span>
│ │ │ │  </h3>
│ │ │ │  <p>If you frequently do lookups on a field that is not the key of the table, you
│ │ │ │  lose performance using <a href="../../../lib/mnesia/doc/html/mnesia.html#select/3">mnesia:select()</a> or
│ │ │ │  <a href="../../../lib/mnesia/doc/html/mnesia.html#match_object/1"><code class="inline">mnesia:match_object()</code></a> as these function traverse
│ │ │ │  the whole table. Instead, you can create a secondary index and use
│ │ │ │  <a href="../../../lib/mnesia/doc/html/mnesia.html#index_read/3"><code class="inline">mnesia:index_read/3</code></a> to get faster access at the expense of using more
│ │ │ │ -memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4918887434-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4918887434-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="4918887434-2">}</span><span class="p" data-group-id="4918887434-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3008123586-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3008123586-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="3008123586-2">}</span><span class="p" data-group-id="3008123586-1">)</span><span class="p">.</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4918887434-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="4918887434-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="4918887434-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4918887434-5">[</span><span class="p" data-group-id="4918887434-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="4918887434-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="4918887434-7">]</span><span class="p" data-group-id="4918887434-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                              </span><span class="p" data-group-id="4918887434-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="nf">record_info</span><span class="p" data-group-id="4918887434-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="4918887434-9">)</span><span class="p" data-group-id="4918887434-8">}</span><span class="p" data-group-id="4918887434-5">]</span><span class="p" data-group-id="4918887434-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4918887434-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="4918887434-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="4918887434-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="4918887434-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3008123586-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="3008123586-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ +</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="3008123586-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3008123586-5">[</span><span class="p" data-group-id="3008123586-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="3008123586-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3008123586-7">]</span><span class="p" data-group-id="3008123586-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                              </span><span class="p" data-group-id="3008123586-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="nf">record_info</span><span class="p" data-group-id="3008123586-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="3008123586-9">)</span><span class="p" data-group-id="3008123586-8">}</span><span class="p" data-group-id="3008123586-5">]</span><span class="p" data-group-id="3008123586-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3008123586-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="3008123586-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="3008123586-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="3008123586-11">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="n">PersonsAge42</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="4918887434-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="4918887434-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │ │ +     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="3008123586-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3008123586-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │ │    <a href="#transactions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Transactions</span>
│ │ │ │  </h3>
│ │ │ │  <p>Using transactions is a way to guarantee that the distributed Mnesia database
│ │ │ │  remains consistent, even when many different processes update it in parallel.
│ │ │ │  However, if you have real-time requirements it is recommended to use dirtry
│ │ │ │  operations instead of transactions. When using dirty operations, you lose the
│ │ │ │  consistency guarantee; this is usually solved by only letting one process update
│ │ │ │  the table. Other processes must send update requests to that process.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Using transaction</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4983872217-1">(</span><span class="p" data-group-id="4983872217-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="4983872217-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="4983872217-3">(</span><span class="p" data-group-id="4983872217-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="4983872217-4">}</span><span class="p" data-group-id="4983872217-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="4983872217-5">(</span><span class="p" data-group-id="4983872217-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="4983872217-6">}</span><span class="p" data-group-id="4983872217-5">)</span><span class="p" data-group-id="4983872217-2">]</span><span class="w">
│ │ │ │ +</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4541593981-1">(</span><span class="p" data-group-id="4541593981-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="4541593981-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="4541593981-3">(</span><span class="p" data-group-id="4541593981-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="4541593981-4">}</span><span class="p" data-group-id="4541593981-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="4541593981-5">(</span><span class="p" data-group-id="4541593981-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="4541593981-6">}</span><span class="p" data-group-id="4541593981-5">)</span><span class="p" data-group-id="4541593981-2">]</span><span class="w">
│ │ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="4983872217-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4983872217-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="4983872217-8">]</span><span class="p" data-group-id="4983872217-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="4983872217-9">(</span><span class="n">Fun</span><span class="p" data-group-id="4983872217-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4541593981-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4541593981-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="4541593981-8">]</span><span class="p" data-group-id="4541593981-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="4541593981-9">(</span><span class="n">Fun</span><span class="p" data-group-id="4541593981-9">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Same thing using dirty operations</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="4983872217-10">(</span><span class="p" data-group-id="4983872217-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="4983872217-11">}</span><span class="p" data-group-id="4983872217-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="4983872217-12">(</span><span class="p" data-group-id="4983872217-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="4983872217-13">}</span><span class="p" data-group-id="4983872217-12">)</span><span class="p">,</span></code></pre>
│ │ │ │ +</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="4541593981-10">(</span><span class="p" data-group-id="4541593981-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="4541593981-11">}</span><span class="p" data-group-id="4541593981-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="4541593981-12">(</span><span class="p" data-group-id="4541593981-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="4541593981-13">}</span><span class="p" data-group-id="4541593981-12">)</span><span class="p">,</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/sup_princ.xhtml
│ │ │ │ @@ -33,48 +33,48 @@
│ │ │ │  the order specified by this list, and are terminated in the reverse order.</p><h2 id="example" class="section-heading">
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>The callback module for a supervisor starting the server from
│ │ │ │ -<a href="gen_server_concepts.xhtml#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2189424829-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="2189424829-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2189424829-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="2189424829-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="gen_server_concepts.xhtml#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7874621634-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="7874621634-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7874621634-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="7874621634-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2189424829-3">(</span><span class="p" data-group-id="2189424829-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2189424829-4">]</span><span class="p" data-group-id="2189424829-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2189424829-5">(</span><span class="p" data-group-id="2189424829-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2189424829-6">]</span><span class="p" data-group-id="2189424829-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7874621634-3">(</span><span class="p" data-group-id="7874621634-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7874621634-4">]</span><span class="p" data-group-id="7874621634-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7874621634-5">(</span><span class="p" data-group-id="7874621634-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7874621634-6">]</span><span class="p" data-group-id="7874621634-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="2189424829-7">(</span><span class="p" data-group-id="2189424829-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2189424829-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2189424829-9">[</span><span class="p" data-group-id="2189424829-9">]</span><span class="p" data-group-id="2189424829-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="7874621634-7">(</span><span class="p" data-group-id="7874621634-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7874621634-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7874621634-9">[</span><span class="p" data-group-id="7874621634-9">]</span><span class="p" data-group-id="7874621634-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="2189424829-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2189424829-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2189424829-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2189424829-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2189424829-12">[</span><span class="p" data-group-id="2189424829-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2189424829-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2189424829-15">[</span><span class="p" data-group-id="2189424829-15">]</span><span class="p" data-group-id="2189424829-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7874621634-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7874621634-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7874621634-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="7874621634-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7874621634-12">[</span><span class="p" data-group-id="7874621634-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7874621634-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7874621634-15">[</span><span class="p" data-group-id="7874621634-15">]</span><span class="p" data-group-id="7874621634-14">}</span><span class="p">,</span><span class="w">
│ │ │ │                      </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │ │                      </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │ │                      </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2189424829-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="2189424829-16">]</span><span class="p" data-group-id="2189424829-13">}</span><span class="p" data-group-id="2189424829-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2189424829-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2189424829-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="2189424829-18">}</span><span class="p" data-group-id="2189424829-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │ │ +                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7874621634-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="7874621634-16">]</span><span class="p" data-group-id="7874621634-13">}</span><span class="p" data-group-id="7874621634-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7874621634-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7874621634-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="7874621634-18">}</span><span class="p" data-group-id="7874621634-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │ │  <a href="sup_princ.xhtml#flags">supervisor flags</a>.</p><p>The <code class="inline">ChildSpecs</code> variable in the return value from <code class="inline">init/1</code> is a list of
│ │ │ │  <a href="sup_princ.xhtml#spec">child specifications</a>.</p><p><a href="" id="flags"></a></p><h2 id="supervisor-flags" class="section-heading">
│ │ │ │    <a href="#supervisor-flags" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Supervisor Flags</span>
│ │ │ │  </h2>
│ │ │ │ -<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="3524776698-1">(</span><span class="p" data-group-id="3524776698-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3524776698-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="3524776698-3">(</span><span class="p" data-group-id="3524776698-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3524776698-4">(</span><span class="p" data-group-id="3524776698-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="3524776698-5">(</span><span class="p" data-group-id="3524776698-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="3524776698-6">(</span><span class="p" data-group-id="3524776698-6">)</span><span class="p" data-group-id="3524776698-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -    </span><span class="nf">strategy</span><span class="p" data-group-id="3524776698-7">(</span><span class="p" data-group-id="3524776698-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │ │ +<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="8422503371-1">(</span><span class="p" data-group-id="8422503371-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8422503371-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="8422503371-3">(</span><span class="p" data-group-id="8422503371-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8422503371-4">(</span><span class="p" data-group-id="8422503371-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="8422503371-5">(</span><span class="p" data-group-id="8422503371-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="8422503371-6">(</span><span class="p" data-group-id="8422503371-6">)</span><span class="p" data-group-id="8422503371-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +    </span><span class="nf">strategy</span><span class="p" data-group-id="8422503371-7">(</span><span class="p" data-group-id="8422503371-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">one_for_one</span><span class="w">
│ │ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">rest_for_one</span><span class="w">
│ │ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="w">
│ │ │ │ -    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="3524776698-8">(</span><span class="p" data-group-id="3524776698-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │ │ +    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="8422503371-8">(</span><span class="p" data-group-id="8422503371-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">any_significant</span><span class="w">
│ │ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">all_significant</span></code></pre><ul><li><code class="inline">strategy</code> specifies the <a href="sup_princ.xhtml#strategy">restart strategy</a>.</li><li><code class="inline">intensity</code> and <code class="inline">period</code> specify the
│ │ │ │  <a href="sup_princ.xhtml#max_intensity">maximum restart intensity</a>.</li><li><code class="inline">auto_shutdown</code> specifies whether and when a supervisor should
│ │ │ │  <a href="sup_princ.xhtml#automatic-shutdown">automatically shut itself down</a>.</li></ul><p><a href="" id="strategy"></a></p><h2 id="restart-strategy" class="section-heading">
│ │ │ │    <a href="#restart-strategy" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -313,28 +313,28 @@
│ │ │ │  exhaust the <a href="sup_princ.xhtml#max_intensity">Maximum Restart Intensity</a> of the
│ │ │ │  parent supervisor.</p></section><p><a href="" id="spec"></a></p><h2 id="child-specification" class="section-heading">
│ │ │ │    <a href="#child-specification" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Child Specification</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="1012249072-1">(</span><span class="p" data-group-id="1012249072-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1012249072-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="1012249072-3">(</span><span class="p" data-group-id="1012249072-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ -                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="1012249072-4">(</span><span class="p" data-group-id="1012249072-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ -                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="1012249072-5">(</span><span class="p" data-group-id="1012249072-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="1012249072-6">(</span><span class="p" data-group-id="1012249072-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="1012249072-7">(</span><span class="p" data-group-id="1012249072-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="1012249072-8">(</span><span class="p" data-group-id="1012249072-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="1012249072-9">(</span><span class="p" data-group-id="1012249072-9">)</span><span class="p" data-group-id="1012249072-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ -    </span><span class="nf">child_id</span><span class="p" data-group-id="1012249072-10">(</span><span class="p" data-group-id="1012249072-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1012249072-11">(</span><span class="p" data-group-id="1012249072-11">)</span><span class="w">
│ │ │ │ -    </span><span class="nf">mfargs</span><span class="p" data-group-id="1012249072-12">(</span><span class="p" data-group-id="1012249072-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1012249072-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="1012249072-14">(</span><span class="p" data-group-id="1012249072-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="1012249072-15">(</span><span class="p" data-group-id="1012249072-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1012249072-16">[</span><span class="nf">term</span><span class="p" data-group-id="1012249072-17">(</span><span class="p" data-group-id="1012249072-17">)</span><span class="p" data-group-id="1012249072-16">]</span><span class="p" data-group-id="1012249072-13">}</span><span class="w">
│ │ │ │ -    </span><span class="nf">modules</span><span class="p" data-group-id="1012249072-18">(</span><span class="p" data-group-id="1012249072-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1012249072-19">[</span><span class="nf">module</span><span class="p" data-group-id="1012249072-20">(</span><span class="p" data-group-id="1012249072-20">)</span><span class="p" data-group-id="1012249072-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ │ -    </span><span class="nf">restart</span><span class="p" data-group-id="1012249072-21">(</span><span class="p" data-group-id="1012249072-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ │ -    </span><span class="nf">significant</span><span class="p" data-group-id="1012249072-22">(</span><span class="p" data-group-id="1012249072-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="1012249072-23">(</span><span class="p" data-group-id="1012249072-23">)</span><span class="w">
│ │ │ │ -    </span><span class="nf">shutdown</span><span class="p" data-group-id="1012249072-24">(</span><span class="p" data-group-id="1012249072-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="1012249072-25">(</span><span class="p" data-group-id="1012249072-25">)</span><span class="w">
│ │ │ │ -    </span><span class="nf">worker</span><span class="p" data-group-id="1012249072-26">(</span><span class="p" data-group-id="1012249072-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │ │ +<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="2645841824-1">(</span><span class="p" data-group-id="2645841824-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2645841824-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="2645841824-3">(</span><span class="p" data-group-id="2645841824-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ +                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="2645841824-4">(</span><span class="p" data-group-id="2645841824-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ │ +                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="2645841824-5">(</span><span class="p" data-group-id="2645841824-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="2645841824-6">(</span><span class="p" data-group-id="2645841824-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="2645841824-7">(</span><span class="p" data-group-id="2645841824-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="2645841824-8">(</span><span class="p" data-group-id="2645841824-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="2645841824-9">(</span><span class="p" data-group-id="2645841824-9">)</span><span class="p" data-group-id="2645841824-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ │ +    </span><span class="nf">child_id</span><span class="p" data-group-id="2645841824-10">(</span><span class="p" data-group-id="2645841824-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="2645841824-11">(</span><span class="p" data-group-id="2645841824-11">)</span><span class="w">
│ │ │ │ +    </span><span class="nf">mfargs</span><span class="p" data-group-id="2645841824-12">(</span><span class="p" data-group-id="2645841824-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2645841824-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="2645841824-14">(</span><span class="p" data-group-id="2645841824-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="2645841824-15">(</span><span class="p" data-group-id="2645841824-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2645841824-16">[</span><span class="nf">term</span><span class="p" data-group-id="2645841824-17">(</span><span class="p" data-group-id="2645841824-17">)</span><span class="p" data-group-id="2645841824-16">]</span><span class="p" data-group-id="2645841824-13">}</span><span class="w">
│ │ │ │ +    </span><span class="nf">modules</span><span class="p" data-group-id="2645841824-18">(</span><span class="p" data-group-id="2645841824-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2645841824-19">[</span><span class="nf">module</span><span class="p" data-group-id="2645841824-20">(</span><span class="p" data-group-id="2645841824-20">)</span><span class="p" data-group-id="2645841824-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ │ +    </span><span class="nf">restart</span><span class="p" data-group-id="2645841824-21">(</span><span class="p" data-group-id="2645841824-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ │ +    </span><span class="nf">significant</span><span class="p" data-group-id="2645841824-22">(</span><span class="p" data-group-id="2645841824-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="2645841824-23">(</span><span class="p" data-group-id="2645841824-23">)</span><span class="w">
│ │ │ │ +    </span><span class="nf">shutdown</span><span class="p" data-group-id="2645841824-24">(</span><span class="p" data-group-id="2645841824-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="2645841824-25">(</span><span class="p" data-group-id="2645841824-25">)</span><span class="w">
│ │ │ │ +    </span><span class="nf">worker</span><span class="p" data-group-id="2645841824-26">(</span><span class="p" data-group-id="2645841824-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │ │  possible, the terms &quot;identifier&quot; or &quot;id&quot; are now used but in order to keep
│ │ │ │  backwards compatibility, some occurrences of &quot;name&quot; can still be found, for
│ │ │ │  example in error messages.</p></li><li><p><code class="inline">start</code> defines the function call used to start the child process. It is a
│ │ │ │  module-function-arguments tuple used as <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A)</code></a>.</p><p>It is to be (or result in) a call to any of the following:</p><ul><li><a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/2,3</code></a></li><li><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/3,4</code></a></li><li><a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/3,4</code></a></li><li><a href="../../../lib/stdlib/doc/html/gen_event.html#start_link/2"><code class="inline">gen_event:start_link/0,1,2</code></a></li><li>A function compliant with these functions. For details, see
│ │ │ │  <a href="../../../lib/stdlib/doc/html/supervisor.html"><code class="inline">supervisor</code></a>.</li></ul><p>The <code class="inline">start</code> key is mandatory.</p></li><li><p><a href="" id="restart"></a> <code class="inline">restart</code> defines when a terminated child process is to be
│ │ │ │  restarted.</p><ul><li>A <code class="inline">permanent</code> child process is always restarted.</li><li>A <code class="inline">temporary</code> child process is never restarted (not even when the supervisor
│ │ │ │  restart strategy is <code class="inline">rest_for_one</code> or <code class="inline">one_for_all</code> and a sibling death
│ │ │ │ @@ -362,53 +362,53 @@
│ │ │ │  <code class="inline">supervisor</code>, the default value <code class="inline">infinity</code> will be used.</p></li><li><p><code class="inline">type</code> specifies whether the child process is a supervisor or a worker.</p><p>The <code class="inline">type</code> key is optional. If it is not given, the default value <code class="inline">worker</code>
│ │ │ │  will be used.</p></li><li><p><code class="inline">modules</code> has to be a list consisting of a single element. The value
│ │ │ │  of that element depends on the behaviour of the process:</p><ul><li>If the child process is a <code class="inline">gen_event</code>, the element has to be the atom
│ │ │ │  <code class="inline">dynamic</code>.</li><li>Otherwise, the element should be <code class="inline">Module</code>, where <code class="inline">Module</code> is the
│ │ │ │  name of the callback module.</li></ul><p>This information is used by the release handler during upgrades and
│ │ │ │  downgrades; see <a href="release_handling.xhtml">Release Handling</a>.</p><p>The <code class="inline">modules</code> key is optional. If it is not given, it defaults to <code class="inline">[M]</code>, where
│ │ │ │  <code class="inline">M</code> comes from the child's start <code class="inline">{M,F,A}</code>.</p></li></ul><p><em>Example:</em> The child specification to start the server <code class="inline">ch3</code> in the previous
│ │ │ │ -example look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8704014115-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8704014115-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8704014115-3">[</span><span class="p" data-group-id="8704014115-3">]</span><span class="p" data-group-id="8704014115-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +example look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4748606938-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4748606938-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4748606938-3">[</span><span class="p" data-group-id="4748606938-3">]</span><span class="p" data-group-id="4748606938-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8704014115-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="8704014115-4">]</span><span class="p" data-group-id="8704014115-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4748606938-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="4748606938-4">]</span><span class="p" data-group-id="4748606938-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │ │    start =&gt; {ch3, start_link, []},
│ │ │ │    shutdown =&gt; brutal_kill}</code></pre><p>Example: A child specification to start the event manager from the chapter about
│ │ │ │ -<a href="events.xhtml#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6454943498-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6454943498-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6454943498-3">[</span><span class="p" data-group-id="6454943498-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="6454943498-4">}</span><span class="p" data-group-id="6454943498-3">]</span><span class="p" data-group-id="6454943498-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="6454943498-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │ │ +<a href="events.xhtml#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5330091009-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5330091009-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5330091009-3">[</span><span class="p" data-group-id="5330091009-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="5330091009-4">}</span><span class="p" data-group-id="5330091009-3">]</span><span class="p" data-group-id="5330091009-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="5330091009-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │ │  be always accessible. Thus they are specified to be <code class="inline">permanent</code>.</p><p><code class="inline">ch3</code> does not need to do any cleaning up before termination. Thus, no shutdown
│ │ │ │  time is needed, but <code class="inline">brutal_kill</code> is sufficient. <code class="inline">error_man</code> can need some time
│ │ │ │  for the event handlers to clean up, thus the shutdown time is set to 5000 ms
│ │ │ │ -(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9023345995-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9023345995-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9023345995-3">[</span><span class="p" data-group-id="9023345995-3">]</span><span class="p" data-group-id="9023345995-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6872415512-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6872415512-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6872415512-3">[</span><span class="p" data-group-id="6872415512-3">]</span><span class="p" data-group-id="6872415512-2">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">transient</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9023345995-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │ │ +  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="6872415512-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │ │    <a href="#starting-a-supervisor" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting a Supervisor</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the previous example, the supervisor is started by calling
│ │ │ │ -<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="1911426369-1">(</span><span class="p" data-group-id="1911426369-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1911426369-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1911426369-3">[</span><span class="p" data-group-id="1911426369-3">]</span><span class="p" data-group-id="1911426369-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │ │ +<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="1900242268-1">(</span><span class="p" data-group-id="1900242268-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1900242268-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1900242268-3">[</span><span class="p" data-group-id="1900242268-3">]</span><span class="p" data-group-id="1900242268-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │ │  links to a new process, a supervisor.</p><ul><li>The first argument, <code class="inline">ch_sup</code>, is the name of the callback module, that is, the
│ │ │ │  module where the <code class="inline">init</code> callback function is located.</li><li>The second argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any data and ignores the argument.</li></ul><p>In this case, the supervisor is not registered. Instead its pid must be used. A
│ │ │ │  name can be specified by calling
│ │ │ │  <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({local, Name}, Module, Args)</code></a>
│ │ │ │  or
│ │ │ │  <a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({global, Name}, Module, Args)</code></a>.</p><p>The new supervisor process calls the callback function <code class="inline">ch_sup:init([])</code>. <code class="inline">init</code>
│ │ │ │ -has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6945939210-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6945939210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6945939210-2">#{</span><span class="p" data-group-id="6945939210-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6945939210-3">[</span><span class="p" data-group-id="6945939210-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6945939210-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6945939210-6">[</span><span class="p" data-group-id="6945939210-6">]</span><span class="p" data-group-id="6945939210-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="6945939210-4">}</span><span class="p" data-group-id="6945939210-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6945939210-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6945939210-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="6945939210-8">}</span><span class="p" data-group-id="6945939210-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │ │ +has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6181217094-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6181217094-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6181217094-2">#{</span><span class="p" data-group-id="6181217094-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6181217094-3">[</span><span class="p" data-group-id="6181217094-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6181217094-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6181217094-6">[</span><span class="p" data-group-id="6181217094-6">]</span><span class="p" data-group-id="6181217094-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="6181217094-4">}</span><span class="p" data-group-id="6181217094-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6181217094-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6181217094-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="6181217094-8">}</span><span class="p" data-group-id="6181217094-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │ │  specifications in the start specification. In this case there is a single child
│ │ │ │  process, called <code class="inline">ch3</code>.</p><p><a href="../../../lib/stdlib/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/3</code></a> is synchronous. It does not return until all child
│ │ │ │  processes have been started.</p><h2 id="adding-a-child-process" class="section-heading">
│ │ │ │    <a href="#adding-a-child-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding a Child Process</span>
│ │ │ │ @@ -437,31 +437,31 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simplified one_for_one Supervisors</span>
│ │ │ │  </h2>
│ │ │ │  <p>A supervisor with restart strategy <code class="inline">simple_one_for_one</code> is a simplified
│ │ │ │  <code class="inline">one_for_one</code> supervisor, where all child processes are dynamically added
│ │ │ │  instances of the same process.</p><p>The following is an example of a callback module for a <code class="inline">simple_one_for_one</code>
│ │ │ │ -supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7196840603-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="7196840603-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7196840603-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="7196840603-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6918682813-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="6918682813-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6918682813-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="6918682813-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7196840603-3">(</span><span class="p" data-group-id="7196840603-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7196840603-4">]</span><span class="p" data-group-id="7196840603-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7196840603-5">(</span><span class="p" data-group-id="7196840603-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7196840603-6">]</span><span class="p" data-group-id="7196840603-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6918682813-3">(</span><span class="p" data-group-id="6918682813-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6918682813-4">]</span><span class="p" data-group-id="6918682813-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6918682813-5">(</span><span class="p" data-group-id="6918682813-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6918682813-6">]</span><span class="p" data-group-id="6918682813-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="7196840603-7">(</span><span class="p" data-group-id="7196840603-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7196840603-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7196840603-9">[</span><span class="p" data-group-id="7196840603-9">]</span><span class="p" data-group-id="7196840603-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="6918682813-7">(</span><span class="p" data-group-id="6918682813-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6918682813-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6918682813-9">[</span><span class="p" data-group-id="6918682813-9">]</span><span class="p" data-group-id="6918682813-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="7196840603-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7196840603-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7196840603-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="6918682813-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6918682813-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6918682813-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │ │                   </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7196840603-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7196840603-12">[</span><span class="p" data-group-id="7196840603-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7196840603-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7196840603-15">[</span><span class="p" data-group-id="7196840603-15">]</span><span class="p" data-group-id="7196840603-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="7196840603-13">}</span><span class="p" data-group-id="7196840603-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7196840603-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7196840603-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="7196840603-17">}</span><span class="p" data-group-id="7196840603-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │ │ +                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6918682813-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6918682813-12">[</span><span class="p" data-group-id="6918682813-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6918682813-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6918682813-15">[</span><span class="p" data-group-id="6918682813-15">]</span><span class="p" data-group-id="6918682813-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="6918682813-13">}</span><span class="p" data-group-id="6918682813-12">]</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6918682813-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6918682813-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="6918682813-17">}</span><span class="p" data-group-id="6918682813-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │ │  processes. Instead, all child processes need to be added dynamically by
│ │ │ │  calling <a href="../../../lib/stdlib/doc/html/supervisor.html#start_child/2"><code class="inline">supervisor:start_child(Sup, List)</code></a>.</p><p><code class="inline">Sup</code> is the pid, or name, of the supervisor. <code class="inline">List</code> is an arbitrary list of
│ │ │ │  terms, which are added to the list of arguments specified in the child
│ │ │ │  specification. If the start function is specified as <code class="inline">{M, F, A}</code>, the child
│ │ │ │  process is started by calling <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A++List)</code></a>.</p><p>For example, adding a child to <code class="inline">simple_sup</code> above:</p><pre><code class="text">supervisor:start_child(Pid, [id1])</code></pre><p>The result is that the child process is started by calling
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply(call, start_link, []++[id1])</code></a>, or actually:</p><pre><code class="text">call:start_link(id1)</code></pre><p>A child under a <code class="inline">simple_one_for_one</code> supervisor can be terminated with the
│ │ │ │  following:</p><pre><code class="text">supervisor:terminate_child(Sup, Pid)</code></pre><p><code class="inline">Sup</code> is the pid, or name, of the supervisor and <code class="inline">Pid</code> is the pid of the child.</p><p>Because a <code class="inline">simple_one_for_one</code> supervisor can have many children, it shuts them
│ │ │ ├── OEBPS/statem.xhtml
│ │ │ │ @@ -29,15 +29,15 @@
│ │ │ │  </h2>
│ │ │ │  <p>Established Automata Theory does not deal much with how a <em>state transition</em>
│ │ │ │  is triggered, but assumes that the output is a function of the input
│ │ │ │  (and the state) and that they are some kind of values.</p><p>For an Event-Driven State Machine, the input is an <em>event</em> that triggers
│ │ │ │  a <em>state transition</em> and the output is actions executed during
│ │ │ │  the <em>state transition</em>.  Analogously to the mathematical model
│ │ │ │  of a Finite State Machine, it can be described as a set of relations
│ │ │ │ -of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="5567276866-1">(</span><span class="n">S</span><span class="p" data-group-id="5567276866-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="5567276866-2">(</span><span class="n">E</span><span class="p" data-group-id="5567276866-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="5567276866-3">(</span><span class="n">A</span><span class="p" data-group-id="5567276866-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5567276866-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="5567276866-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │ │ +of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="6926990118-1">(</span><span class="n">S</span><span class="p" data-group-id="6926990118-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="6926990118-2">(</span><span class="n">E</span><span class="p" data-group-id="6926990118-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="6926990118-3">(</span><span class="n">A</span><span class="p" data-group-id="6926990118-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6926990118-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="6926990118-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │ │  and event <code class="inline">E</code> occurs, we are to perform actions <code class="inline">A</code>, and make a transition
│ │ │ │  to state <code class="inline">S'</code>.  Notice that <code class="inline">S'</code> can be equal to <code class="inline">S</code>,
│ │ │ │  and that <code class="inline">A</code> can be empty.</p><p>In <code class="inline">gen_statem</code> we define a <em>state change</em> as a <em>state transition</em> in which the
│ │ │ │  new state <code class="inline">S'</code> is different from the current state <code class="inline">S</code>, where &quot;different&quot; means
│ │ │ │  Erlang's strict inequality: <code class="inline">=/=</code> also known as &quot;does not match&quot;. <code class="inline">gen_statem</code>
│ │ │ │  does more things during <em>state changes</em> than during other <em>state transitions</em>.</p><p>As <code class="inline">A</code> and <code class="inline">S'</code> depend only on <code class="inline">S</code> and <code class="inline">E</code>, the kind of state machine described
│ │ │ │  here is a Mealy machine (see, for example, the Wikipedia article
│ │ │ │ @@ -310,20 +310,20 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">State Enter Calls</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">gen_statem</code> behaviour can, if this is enabled, regardless of <em>callback
│ │ │ │  mode</em>, automatically call the <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:state_enter/0"><em>state callback</em></a>
│ │ │ │  with special arguments whenever the state changes, so you can write
│ │ │ │  state enter actions near the rest of the <em>state transition</em> rules.
│ │ │ │ -It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="0633096948-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0633096948-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="7511263193-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7511263193-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">enter</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0633096948-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="0633096948-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="n">StateName</span><span class="p" data-group-id="0633096948-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0633096948-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7511263193-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="7511263193-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="n">StateName</span><span class="p" data-group-id="7511263193-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7511263193-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0633096948-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="0633096948-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │ │ +    </span><span class="p" data-group-id="7511263193-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="7511263193-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │ │  allowed return value and state <a href="#transition-actions"><em>transition actions</em></a>.
│ │ │ │  You must not change the state, <a href="#postponing-events">postpone</a> this non-event,
│ │ │ │  <a href="#inserted-events">insert any events</a>, or change the
│ │ │ │  <a href="#callback-module"><em>callback module</em></a>.</p><p>The first state that is entered after <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:init/1"><code class="inline">gen_statem:init/1</code></a> will get
│ │ │ │  a <em>state enter call</em> with <code class="inline">OldState</code> equal to the current state.</p><p>You may repeat the <em>state enter call</em> using the <code class="inline">{repeat_state,...}</code> return
│ │ │ │  value from the <a href="#state-callback"><em>state callback</em></a>. In this case
│ │ │ │  <code class="inline">OldState</code> will also be equal to the current state.</p><p>Depending on how your state machine is specified, this can be a very useful
│ │ │ │ @@ -404,72 +404,72 @@
│ │ │ │  
│ │ │ │      locked      --&gt; check_code : {button, Button}\n* Collect Buttons
│ │ │ │      check_code  --&gt; locked     : Incorrect code
│ │ │ │      check_code  --&gt; open       : Correct code\n* do_unlock()\n* Clear Buttons\n* Set state_timeout 10 s
│ │ │ │  
│ │ │ │      open        --&gt; open   : {button, Digit}
│ │ │ │      open        --&gt; locked : state_timeout\n* do_lock()</code></pre><p>This code lock state machine can be implemented using <a href="../../../lib/stdlib/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a> with
│ │ │ │ -the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6552868952-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="6552868952-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6552868952-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="6552868952-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6552868952-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="6552868952-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5866591012-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="5866591012-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5866591012-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="5866591012-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5866591012-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="5866591012-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6552868952-4">(</span><span class="p" data-group-id="6552868952-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6552868952-5">]</span><span class="p" data-group-id="6552868952-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6552868952-6">(</span><span class="p" data-group-id="6552868952-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6552868952-7">]</span><span class="p" data-group-id="6552868952-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6552868952-8">(</span><span class="p" data-group-id="6552868952-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6552868952-9">]</span><span class="p" data-group-id="6552868952-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6552868952-10">(</span><span class="p" data-group-id="6552868952-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6552868952-11">]</span><span class="p" data-group-id="6552868952-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="6552868952-12">(</span><span class="n">Code</span><span class="p" data-group-id="6552868952-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6552868952-13">(</span><span class="p" data-group-id="6552868952-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6552868952-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552868952-15">[</span><span class="p" data-group-id="6552868952-15">]</span><span class="p" data-group-id="6552868952-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="6552868952-16">(</span><span class="n">Button</span><span class="p" data-group-id="6552868952-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6552868952-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6552868952-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6552868952-18">}</span><span class="p" data-group-id="6552868952-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6552868952-19">(</span><span class="n">Code</span><span class="p" data-group-id="6552868952-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6552868952-20">(</span><span class="p" data-group-id="6552868952-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6552868952-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6552868952-22">(</span><span class="n">Code</span><span class="p" data-group-id="6552868952-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6552868952-23">[</span><span class="p" data-group-id="6552868952-23">]</span><span class="p" data-group-id="6552868952-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6552868952-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6552868952-24">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="6552868952-25">(</span><span class="p" data-group-id="6552868952-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="0084339876-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0084339876-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0084339876-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="0084339876-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0084339876-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0084339876-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5866591012-4">(</span><span class="p" data-group-id="5866591012-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5866591012-5">]</span><span class="p" data-group-id="5866591012-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5866591012-6">(</span><span class="p" data-group-id="5866591012-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5866591012-7">]</span><span class="p" data-group-id="5866591012-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5866591012-8">(</span><span class="p" data-group-id="5866591012-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5866591012-9">]</span><span class="p" data-group-id="5866591012-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5866591012-10">(</span><span class="p" data-group-id="5866591012-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5866591012-11">]</span><span class="p" data-group-id="5866591012-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="5866591012-12">(</span><span class="n">Code</span><span class="p" data-group-id="5866591012-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5866591012-13">(</span><span class="p" data-group-id="5866591012-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="5866591012-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5866591012-15">[</span><span class="p" data-group-id="5866591012-15">]</span><span class="p" data-group-id="5866591012-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="5866591012-16">(</span><span class="n">Button</span><span class="p" data-group-id="5866591012-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5866591012-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5866591012-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5866591012-18">}</span><span class="p" data-group-id="5866591012-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="5866591012-19">(</span><span class="n">Code</span><span class="p" data-group-id="5866591012-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="5866591012-20">(</span><span class="p" data-group-id="5866591012-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5866591012-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5866591012-22">(</span><span class="n">Code</span><span class="p" data-group-id="5866591012-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5866591012-23">[</span><span class="p" data-group-id="5866591012-23">]</span><span class="p" data-group-id="5866591012-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5866591012-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5866591012-24">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="5866591012-25">(</span><span class="p" data-group-id="5866591012-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="1661739373-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1661739373-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1661739373-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1661739373-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1661739373-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1661739373-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="0084339876-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="0084339876-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1661739373-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="1661739373-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="0084339876-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="0084339876-5">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="0084339876-6">[</span><span class="n">Button</span><span class="p" data-group-id="0084339876-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1661739373-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="1661739373-5">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1661739373-6">[</span><span class="n">Button</span><span class="p" data-group-id="1661739373-6">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0084339876-7">(</span><span class="p" data-group-id="0084339876-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0084339876-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0084339876-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0084339876-10">[</span><span class="p" data-group-id="0084339876-10">]</span><span class="p" data-group-id="0084339876-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="0084339876-11">[</span><span class="p" data-group-id="0084339876-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0084339876-12">}</span><span class="p" data-group-id="0084339876-11">]</span><span class="p" data-group-id="0084339876-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1661739373-7">(</span><span class="p" data-group-id="1661739373-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1661739373-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1661739373-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1661739373-10">[</span><span class="p" data-group-id="1661739373-10">]</span><span class="p" data-group-id="1661739373-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="1661739373-11">[</span><span class="p" data-group-id="1661739373-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1661739373-12">}</span><span class="p" data-group-id="1661739373-11">]</span><span class="p" data-group-id="1661739373-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0084339876-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0084339876-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="0084339876-14">}</span><span class="p" data-group-id="0084339876-13">}</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="6268611675-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="6268611675-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6268611675-2">(</span><span class="p" data-group-id="6268611675-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6268611675-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6268611675-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="6268611675-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6268611675-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6268611675-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6268611675-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6268611675-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6268611675-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="5224280720-1">(</span><span class="p" data-group-id="5224280720-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5224280720-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224280720-3">[</span><span class="p" data-group-id="5224280720-3">]</span><span class="p" data-group-id="5224280720-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="5224280720-4">(</span><span class="p" data-group-id="5224280720-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5224280720-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224280720-6">[</span><span class="p" data-group-id="5224280720-6">]</span><span class="p" data-group-id="5224280720-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1661739373-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1661739373-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1661739373-14">}</span><span class="p" data-group-id="1661739373-13">}</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="6168079236-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="6168079236-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="6168079236-2">(</span><span class="p" data-group-id="6168079236-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6168079236-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6168079236-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="6168079236-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6168079236-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6168079236-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6168079236-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6168079236-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6168079236-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="0755542619-1">(</span><span class="p" data-group-id="0755542619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0755542619-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0755542619-3">[</span><span class="p" data-group-id="0755542619-3">]</span><span class="p" data-group-id="0755542619-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="0755542619-4">(</span><span class="p" data-group-id="0755542619-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0755542619-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0755542619-6">[</span><span class="p" data-group-id="0755542619-6">]</span><span class="p" data-group-id="0755542619-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="5224280720-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5224280720-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="5224280720-8">(</span><span class="p" data-group-id="5224280720-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="0755542619-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0755542619-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="0755542619-8">(</span><span class="p" data-group-id="0755542619-8">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-gen_statem" class="section-heading">
│ │ │ │    <a href="#starting-gen_statem" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting gen_statem</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the example in the previous section, <code class="inline">gen_statem</code> is started by calling
│ │ │ │ -<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="0832633361-1">(</span><span class="n">Code</span><span class="p" data-group-id="0832633361-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0832633361-2">(</span><span class="p" data-group-id="0832633361-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0832633361-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0832633361-4">[</span><span class="p" data-group-id="0832633361-4">]</span><span class="p" data-group-id="0832633361-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │ │ +<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="6976303569-1">(</span><span class="n">Code</span><span class="p" data-group-id="6976303569-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6976303569-2">(</span><span class="p" data-group-id="6976303569-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6976303569-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6976303569-4">[</span><span class="p" data-group-id="6976303569-4">]</span><span class="p" data-group-id="6976303569-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │ │  which spawns and links to a new process, a <code class="inline">gen_statem</code>.</p><ul><li><p>The first argument, <code class="inline">{local,?NAME}</code>, specifies the name. In this case, the
│ │ │ │  <code class="inline">gen_statem</code> is locally registered as <code class="inline">code_lock</code> through the macro <code class="inline">?NAME</code>.</p><p>If the name is omitted, the <code class="inline">gen_statem</code> is not registered. Instead its pid
│ │ │ │  must be used. The name can also be specified as <code class="inline">{global, Name}</code>, then the
│ │ │ │  <code class="inline">gen_statem</code> is registered using <a href="../../../lib/kernel/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a> in Kernel.</p></li><li><p>The second argument, <code class="inline">?MODULE</code>, is the name of the <em>callback module</em>,
│ │ │ │  that is, the module where the callback functions are located,
│ │ │ │  which is this module.</p><p>The interface functions (<code class="inline">start_link/1</code> and <code class="inline">button/1</code>) are located in the
│ │ │ │  same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">locked/3</code>, and <code class="inline">open/3</code>).
│ │ │ │ @@ -479,184 +479,184 @@
│ │ │ │  see <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3</code></a>.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_statem</code> process calls callback
│ │ │ │  function <code class="inline">code_lock:init(Code)</code>. This function is expected to return
│ │ │ │  <code class="inline">{ok, State, Data}</code>, where <code class="inline">State</code> is the initial state of the <code class="inline">gen_statem</code>,
│ │ │ │  in this case <code class="inline">locked</code>; assuming that the door is locked to begin with.
│ │ │ │  <code class="inline">Data</code> is the internal server data of the <code class="inline">gen_statem</code>. Here the server data
│ │ │ │  is a <a href="../../../lib/stdlib/doc/html/maps.html"><code class="inline">map()</code></a> with key <code class="inline">code</code> that stores the correct
│ │ │ │  button sequence, key <code class="inline">length</code> store its length, and key <code class="inline">buttons</code>
│ │ │ │ -that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7357226804-1">(</span><span class="n">Code</span><span class="p" data-group-id="7357226804-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="7357226804-2">(</span><span class="p" data-group-id="7357226804-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7357226804-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7357226804-4">(</span><span class="n">Code</span><span class="p" data-group-id="7357226804-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7357226804-5">[</span><span class="p" data-group-id="7357226804-5">]</span><span class="p" data-group-id="7357226804-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7357226804-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7357226804-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ │ +that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1673430584-1">(</span><span class="n">Code</span><span class="p" data-group-id="1673430584-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1673430584-2">(</span><span class="p" data-group-id="1673430584-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1673430584-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1673430584-4">(</span><span class="n">Code</span><span class="p" data-group-id="1673430584-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1673430584-5">[</span><span class="p" data-group-id="1673430584-5">]</span><span class="p" data-group-id="1673430584-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1673430584-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1673430584-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ │  is synchronous. It does not return until the <code class="inline">gen_statem</code> is initialized
│ │ │ │  and is ready to receive events.</p><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ │  must be used if the <code class="inline">gen_statem</code> is part of a supervision tree, that is,
│ │ │ │  started by a supervisor.  Function,
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#start/3"><code class="inline">gen_statem:start/3,4</code></a> can be used to start
│ │ │ │  a standalone <code class="inline">gen_statem</code>, meaning it is not part of a supervision tree.</p><p>Function <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">Module:callback_mode/0</code></a> selects
│ │ │ │  the <a href="#callback-modes"><code class="inline">CallbackMode</code></a> for the <em>callback module</em>,
│ │ │ │  in this case <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">state_functions</code></a>.
│ │ │ │ -That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="2140028527-1">(</span><span class="p" data-group-id="2140028527-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="8441219351-1">(</span><span class="p" data-group-id="8441219351-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><h2 id="handling-events" class="section-heading">
│ │ │ │    <a href="#handling-events" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling Events</span>
│ │ │ │  </h2>
│ │ │ │  <p>The function notifying the code lock about a button event is implemented using
│ │ │ │ -<a href="../../../lib/stdlib/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="7003408602-1">(</span><span class="n">Button</span><span class="p" data-group-id="7003408602-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7003408602-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7003408602-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7003408602-3">}</span><span class="p" data-group-id="7003408602-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │ │ +<a href="../../../lib/stdlib/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="4660150278-1">(</span><span class="n">Button</span><span class="p" data-group-id="4660150278-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4660150278-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4660150278-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4660150278-3">}</span><span class="p" data-group-id="4660150278-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │ │  the name used to start it. So, we use the same macro <code class="inline">?NAME</code> as when starting.
│ │ │ │  <code class="inline">{button, Button}</code> is the event content.</p><p>The event is sent to the <code class="inline">gen_statem</code>. When the event is received, the
│ │ │ │  <code class="inline">gen_statem</code> calls <code class="inline">StateName(cast, Event, Data)</code>, which is expected
│ │ │ │  to return a tuple <code class="inline">{next_state, NewStateName, NewData}</code>, or
│ │ │ │  <code class="inline">{next_state, NewStateName, NewData, Actions}</code>. <code class="inline">StateName</code> is the name
│ │ │ │  of the current state and <code class="inline">NewStateName</code> is the name of the next state.
│ │ │ │  <code class="inline">NewData</code> is a new value for the server data of the <code class="inline">gen_statem</code>,
│ │ │ │ -and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="6686509593-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6686509593-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6686509593-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6686509593-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6686509593-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6686509593-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="3681073741-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3681073741-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3681073741-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3681073741-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3681073741-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3681073741-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="6686509593-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="6686509593-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="3681073741-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="3681073741-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="6686509593-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="6686509593-5">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6686509593-6">[</span><span class="n">Button</span><span class="p" data-group-id="6686509593-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="3681073741-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="3681073741-5">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3681073741-6">[</span><span class="n">Button</span><span class="p" data-group-id="3681073741-6">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6686509593-7">(</span><span class="p" data-group-id="6686509593-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6686509593-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6686509593-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6686509593-10">[</span><span class="p" data-group-id="6686509593-10">]</span><span class="p" data-group-id="6686509593-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="6686509593-11">[</span><span class="p" data-group-id="6686509593-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="6686509593-12">}</span><span class="p" data-group-id="6686509593-11">]</span><span class="p" data-group-id="6686509593-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3681073741-7">(</span><span class="p" data-group-id="3681073741-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3681073741-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3681073741-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3681073741-10">[</span><span class="p" data-group-id="3681073741-10">]</span><span class="p" data-group-id="3681073741-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="3681073741-11">[</span><span class="p" data-group-id="3681073741-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3681073741-12">}</span><span class="p" data-group-id="3681073741-11">]</span><span class="p" data-group-id="3681073741-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6686509593-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6686509593-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="6686509593-14">}</span><span class="p" data-group-id="6686509593-13">}</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3681073741-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3681073741-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3681073741-14">}</span><span class="p" data-group-id="3681073741-13">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>In state <code class="inline">locked</code>, when a button is pressed, it is collected with the
│ │ │ │  previously pressed buttons up to the length of the correct code, then
│ │ │ │  compared with the correct code. Depending on the result, the door is
│ │ │ │  either unlocked and the <code class="inline">gen_statem</code> goes to state <code class="inline">open</code>, or the door
│ │ │ │  remains in state <code class="inline">locked</code>.</p><p>When changing to state <code class="inline">open</code>, the collected buttons are reset, the lock
│ │ │ │ -unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="1715029301-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715029301-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1715029301-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1715029301-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1715029301-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1715029301-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │ │ +unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="1078395450-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1078395450-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1078395450-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1078395450-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1078395450-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1078395450-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │ │  This can also be done by returning <code class="inline">{keep_state, Data}</code>, or in this case
│ │ │ │  since <code class="inline">Data</code> is unchanged, by returning <code class="inline">keep_state_and_data</code>.</p><h2 id="state-time-outs" class="section-heading">
│ │ │ │    <a href="#state-time-outs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">State Time-Outs</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a correct code has been given, the door is unlocked and the following
│ │ │ │ -tuple is returned from <code class="inline">locked/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2935312769-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2935312769-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2935312769-3">[</span><span class="p" data-group-id="2935312769-3">]</span><span class="p" data-group-id="2935312769-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2935312769-4">[</span><span class="p" data-group-id="2935312769-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2935312769-5">}</span><span class="p" data-group-id="2935312769-4">]</span><span class="p" data-group-id="2935312769-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │ │ +tuple is returned from <code class="inline">locked/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2011622156-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2011622156-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2011622156-3">[</span><span class="p" data-group-id="2011622156-3">]</span><span class="p" data-group-id="2011622156-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2011622156-4">[</span><span class="p" data-group-id="2011622156-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2011622156-5">}</span><span class="p" data-group-id="2011622156-4">]</span><span class="p" data-group-id="2011622156-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │ │  a time-out occurs. Then, <code class="inline">StateName(state_timeout, lock, Data)</code> is called.
│ │ │ │  The time-out occurs when the door has been in state <code class="inline">open</code> for 10 seconds.
│ │ │ │ -After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="8655746133-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="8655746133-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="8655746133-2">(</span><span class="p" data-group-id="8655746133-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8655746133-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8655746133-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │ │ +After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="1305984521-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="1305984521-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1305984521-2">(</span><span class="p" data-group-id="1305984521-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1305984521-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1305984521-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │ │  the state machine does a <em>state change</em>.</p><p>You can restart, cancel, or update a <em>state time-out</em>. See section
│ │ │ │  <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="all-state-events" class="section-heading">
│ │ │ │    <a href="#all-state-events" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">All State Events</span>
│ │ │ │  </h2>
│ │ │ │  <p>Sometimes events can arrive in any state of the <code class="inline">gen_statem</code>. It is convenient
│ │ │ │  to handle these in a common state handler function that all state functions
│ │ │ │  call for events not specific to the state.</p><p>Consider a <code class="inline">code_length/0</code> function that returns the length
│ │ │ │  of the correct code.  We dispatch all events that are not state-specific
│ │ │ │  to the common function <code class="inline">handle_common/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8389910095-1">(</span><span class="p" data-group-id="8389910095-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8389910095-2">]</span><span class="p" data-group-id="8389910095-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0622315657-1">(</span><span class="p" data-group-id="0622315657-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0622315657-2">]</span><span class="p" data-group-id="0622315657-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="8389910095-3">(</span><span class="p" data-group-id="8389910095-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="8389910095-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="8389910095-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="0622315657-3">(</span><span class="p" data-group-id="0622315657-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0622315657-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="0622315657-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="8389910095-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8389910095-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="8389910095-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8389910095-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="8389910095-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8389910095-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="0622315657-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0622315657-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="0622315657-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0622315657-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="0622315657-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0622315657-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="8389910095-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8389910095-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="8389910095-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8389910095-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="8389910095-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8389910095-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="8389910095-11">(</span><span class="p" data-group-id="8389910095-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="8389910095-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8389910095-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8389910095-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8389910095-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8389910095-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="8389910095-15">[</span><span class="p" data-group-id="8389910095-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="8389910095-17">(</span><span class="n">Code</span><span class="p" data-group-id="8389910095-17">)</span><span class="p" data-group-id="8389910095-16">}</span><span class="p" data-group-id="8389910095-15">]</span><span class="p" data-group-id="8389910095-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4433246620-1">(</span><span class="p" data-group-id="4433246620-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4433246620-2">]</span><span class="p" data-group-id="4433246620-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0622315657-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0622315657-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0622315657-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0622315657-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="0622315657-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0622315657-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="0622315657-11">(</span><span class="p" data-group-id="0622315657-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="0622315657-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0622315657-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="0622315657-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0622315657-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0622315657-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0622315657-15">[</span><span class="p" data-group-id="0622315657-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="0622315657-17">(</span><span class="n">Code</span><span class="p" data-group-id="0622315657-17">)</span><span class="p" data-group-id="0622315657-16">}</span><span class="p" data-group-id="0622315657-15">]</span><span class="p" data-group-id="0622315657-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6630167316-1">(</span><span class="p" data-group-id="6630167316-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6630167316-2">]</span><span class="p" data-group-id="6630167316-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="4433246620-3">(</span><span class="p" data-group-id="4433246620-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4433246620-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="4433246620-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="6630167316-3">(</span><span class="p" data-group-id="6630167316-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6630167316-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="6630167316-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4433246620-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="4433246620-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="4433246620-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="4433246620-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="4433246620-7">)</span><span class="p" data-group-id="4433246620-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6630167316-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="6630167316-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6630167316-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="6630167316-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="6630167316-7">)</span><span class="p" data-group-id="6630167316-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="4433246620-8">(</span><span class="p" data-group-id="4433246620-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4433246620-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4433246620-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="4433246620-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4433246620-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4433246620-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="4433246620-12">[</span><span class="p" data-group-id="4433246620-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="4433246620-14">(</span><span class="n">Code</span><span class="p" data-group-id="4433246620-14">)</span><span class="p" data-group-id="4433246620-13">}</span><span class="p" data-group-id="4433246620-12">]</span><span class="p" data-group-id="4433246620-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="6630167316-8">(</span><span class="p" data-group-id="6630167316-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="6630167316-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6630167316-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="6630167316-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6630167316-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6630167316-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="6630167316-12">[</span><span class="p" data-group-id="6630167316-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="6630167316-14">(</span><span class="n">Code</span><span class="p" data-group-id="6630167316-14">)</span><span class="p" data-group-id="6630167316-13">}</span><span class="p" data-group-id="6630167316-12">]</span><span class="p" data-group-id="6630167316-11">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="4433246620-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4433246620-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="6630167316-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6630167316-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="4433246620-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4433246620-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="6630167316-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6630167316-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><p>This example uses <a href="../../../lib/stdlib/doc/html/gen_statem.html#call/2"><code class="inline">gen_statem:call/2</code></a>, which waits for a reply from the server.
│ │ │ │  The reply is sent with a <code class="inline">{reply, From, Reply}</code> tuple in an action list in the
│ │ │ │  <code class="inline">{keep_state, ...}</code> tuple that retains the current state. This return form is
│ │ │ │  convenient when you want to stay in the current state but do not know or care
│ │ │ │  about what it is.</p><p>If the common <em>state callback</em> needs to know the current state a function
│ │ │ │ -<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1988898880-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="1988898880-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="1988898880-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="1988898880-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="1988898880-3">)</span><span class="p" data-group-id="1988898880-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │ │ +<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2988335519-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="2988335519-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="2988335519-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="2988335519-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="2988335519-3">)</span><span class="p" data-group-id="2988335519-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │ │    <a href="#one-state-callback" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">One State Callback</span>
│ │ │ │  </h2>
│ │ │ │  <p>If <a href="#callback-modes"><em>callback mode</em></a> <code class="inline">handle_event_function</code> is used,
│ │ │ │  all events are handled in
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:handle_event/4"><code class="inline">Module:handle_event/4</code></a> and we can
│ │ │ │  (but do not have to) use an event-centered approach where we first branch
│ │ │ │  depending on event and then depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1345508288-1">(</span><span class="p" data-group-id="1345508288-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="1345508288-2">]</span><span class="p" data-group-id="1345508288-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1455815085-1">(</span><span class="p" data-group-id="1455815085-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="1455815085-2">]</span><span class="p" data-group-id="1455815085-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="1345508288-3">(</span><span class="p" data-group-id="1345508288-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="1455815085-3">(</span><span class="p" data-group-id="1455815085-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">handle_event_function</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1345508288-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1345508288-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1345508288-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1345508288-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1345508288-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1345508288-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1455815085-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1455815085-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1455815085-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1455815085-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1455815085-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1455815085-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │  	</span><span class="ss">locked</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1345508288-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1345508288-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1455815085-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1455815085-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="1345508288-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="1345508288-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="1455815085-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="1455815085-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="1345508288-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="1345508288-9">)</span><span class="w">
│ │ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1345508288-10">[</span><span class="n">Button</span><span class="p" data-group-id="1345508288-10">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="1455815085-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="1455815085-9">)</span><span class="w">
│ │ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1455815085-10">[</span><span class="n">Button</span><span class="p" data-group-id="1455815085-10">]</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="k">if</span><span class="w">
│ │ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1345508288-11">(</span><span class="p" data-group-id="1345508288-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="1345508288-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1345508288-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1345508288-14">[</span><span class="p" data-group-id="1345508288-14">]</span><span class="p" data-group-id="1345508288-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="p" data-group-id="1345508288-15">[</span><span class="p" data-group-id="1345508288-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1345508288-16">}</span><span class="p" data-group-id="1345508288-15">]</span><span class="p" data-group-id="1345508288-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1455815085-11">(</span><span class="p" data-group-id="1455815085-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="1455815085-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1455815085-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1455815085-14">[</span><span class="p" data-group-id="1455815085-14">]</span><span class="p" data-group-id="1455815085-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="p" data-group-id="1455815085-15">[</span><span class="p" data-group-id="1455815085-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1455815085-16">}</span><span class="p" data-group-id="1455815085-15">]</span><span class="p" data-group-id="1455815085-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="1345508288-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1345508288-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1345508288-18">}</span><span class="p" data-group-id="1345508288-17">}</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="1455815085-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1455815085-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1455815085-18">}</span><span class="p" data-group-id="1455815085-17">}</span><span class="w">
│ │ │ │              </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">open</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1345508288-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1345508288-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="1345508288-20">(</span><span class="p" data-group-id="1345508288-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1345508288-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1345508288-21">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1345508288-22">(</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1345508288-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="1345508288-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1345508288-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1345508288-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1345508288-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1345508288-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="1345508288-26">[</span><span class="p" data-group-id="1345508288-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="1345508288-28">(</span><span class="n">Code</span><span class="p" data-group-id="1345508288-28">)</span><span class="p" data-group-id="1345508288-27">}</span><span class="p" data-group-id="1345508288-26">]</span><span class="p" data-group-id="1345508288-25">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1455815085-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1455815085-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1455815085-20">(</span><span class="p" data-group-id="1455815085-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1455815085-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1455815085-21">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1455815085-22">(</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1455815085-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="1455815085-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1455815085-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1455815085-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1455815085-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1455815085-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="1455815085-26">[</span><span class="p" data-group-id="1455815085-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="1455815085-28">(</span><span class="n">Code</span><span class="p" data-group-id="1455815085-28">)</span><span class="p" data-group-id="1455815085-27">}</span><span class="p" data-group-id="1455815085-26">]</span><span class="p" data-group-id="1455815085-25">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ │    <a href="#stopping" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stopping</span>
│ │ │ │  </h2>
│ │ │ │ @@ -668,59 +668,59 @@
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_statem</code> is part of a supervision tree, no stop function is needed.
│ │ │ │  The <code class="inline">gen_statem</code> is automatically terminated by its supervisor. Exactly how
│ │ │ │  this is done is defined by a <a href="sup_princ.xhtml#shutdown">shutdown strategy</a>
│ │ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │ │  must be a time-out value and the <code class="inline">gen_statem</code> must in function <code class="inline">init/1</code>
│ │ │ │  set itself to trap exit signals by calling
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3280899464-1">(</span><span class="n">Args</span><span class="p" data-group-id="3280899464-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="3280899464-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3280899464-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="3280899464-3">(</span><span class="p" data-group-id="3280899464-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0173389475-1">(</span><span class="n">Args</span><span class="p" data-group-id="0173389475-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="0173389475-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0173389475-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="0173389475-3">(</span><span class="p" data-group-id="0173389475-3">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When ordered to shut down, the <code class="inline">gen_statem</code> then calls callback function
│ │ │ │  <code class="inline">terminate(shutdown, State, Data)</code>.</p><p>In this example, function <code class="inline">terminate/3</code> locks the door if it is open,
│ │ │ │  so we do not accidentally leave the door open
│ │ │ │ -when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="3799051079-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="3799051079-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="3799051079-2">(</span><span class="p" data-group-id="3799051079-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="6024912229-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6024912229-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="6024912229-2">(</span><span class="p" data-group-id="6024912229-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_statem" class="section-heading">
│ │ │ │    <a href="#standalone-gen_statem" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standalone gen_statem</span>
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_statem</code> is not part of a supervision tree, it can be stopped
│ │ │ │  using <a href="../../../lib/stdlib/doc/html/gen_statem.html#stop/1"><code class="inline">gen_statem:stop/1</code></a>, preferably through
│ │ │ │  an API function:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0741048636-1">(</span><span class="p" data-group-id="0741048636-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0741048636-2">]</span><span class="p" data-group-id="0741048636-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2173857736-1">(</span><span class="p" data-group-id="2173857736-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2173857736-2">]</span><span class="p" data-group-id="2173857736-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0741048636-3">(</span><span class="p" data-group-id="0741048636-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0741048636-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0741048636-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="2173857736-3">(</span><span class="p" data-group-id="2173857736-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2173857736-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="2173857736-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │ │  for a supervised server and waits for the process to terminate.</p><h2 id="event-time-outs" class="section-heading">
│ │ │ │    <a href="#event-time-outs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Event Time-Outs</span>
│ │ │ │  </h2>
│ │ │ │  <p>A time-out feature inherited from <code class="inline">gen_statem</code>'s predecessor <a href="../../../lib/stdlib/doc/html/gen_fsm.html"><code class="inline">gen_fsm</code></a>,
│ │ │ │  is an <em>event time-out</em>, that is, if an event arrives the timer is canceled.
│ │ │ │  You get either an event or a time-out, but not both.</p><p>It is ordered by the
│ │ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">{timeout, Time, EventContent}</code>,
│ │ │ │  or just an integer <code class="inline">Time</code>, even without the enclosing actions list (the latter
│ │ │ │  is a form inherited from <code class="inline">gen_fsm</code>).</p><p>This type of time-out is useful, for example, to act on inactivity.
│ │ │ │  Let's restart the code sequence if no button is pressed for say 30 seconds:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1721368328-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1721368328-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1721368328-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1721368328-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1721368328-4">[</span><span class="p" data-group-id="1721368328-4">]</span><span class="p" data-group-id="1721368328-3">}</span><span class="p" data-group-id="1721368328-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1721368328-5">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1721368328-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1721368328-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1721368328-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1721368328-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1721368328-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4719168863-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4719168863-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4719168863-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4719168863-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="4719168863-4">[</span><span class="p" data-group-id="4719168863-4">]</span><span class="p" data-group-id="4719168863-3">}</span><span class="p" data-group-id="4719168863-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4719168863-5">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4719168863-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4719168863-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4719168863-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="4719168863-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4719168863-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1721368328-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1721368328-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1721368328-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="1721368328-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="4719168863-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4719168863-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="4719168863-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="4719168863-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Whenever we receive a button event we start an <em>event time-out</em> of 30 seconds,
│ │ │ │  and if we get an <em>event type</em> of <code class="inline">timeout</code> we reset the remaining
│ │ │ │  code sequence.</p><p>An <em>event time-out</em> is canceled by any other event so you either get
│ │ │ │  some other event or the time-out event. Therefore, canceling,
│ │ │ │  restarting, or updating an <em>event time-out</em> is neither possible nor
│ │ │ │  necessary. Whatever event you act on has already canceled
│ │ │ │  the <em>event time-out</em>, so there is never a running <em>event time-out</em>
│ │ │ │ @@ -739,30 +739,30 @@
│ │ │ │  another, maybe cancel the time-out without changing states, or perhaps run
│ │ │ │  multiple time-outs in parallel. All this can be accomplished with
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:generic_timeout/0"><em>generic time-outs</em></a>. They may look a little
│ │ │ │  bit like <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:event_timeout/0"><em>event time-outs</em></a> but contain
│ │ │ │  a name to allow for any number of them simultaneously and they are
│ │ │ │  not automatically canceled.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │ │  by instead using a <em>generic time-out</em> named for example <code class="inline">open</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="7583238792-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7583238792-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7583238792-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7583238792-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7583238792-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7583238792-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="9920583742-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9920583742-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9920583742-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9920583742-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9920583742-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9920583742-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7583238792-4">(</span><span class="p" data-group-id="7583238792-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7583238792-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7583238792-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7583238792-7">[</span><span class="p" data-group-id="7583238792-7">]</span><span class="p" data-group-id="7583238792-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="7583238792-8">[</span><span class="p" data-group-id="7583238792-9">{</span><span class="p" data-group-id="7583238792-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="7583238792-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7583238792-9">}</span><span class="p" data-group-id="7583238792-8">]</span><span class="p" data-group-id="7583238792-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9920583742-4">(</span><span class="p" data-group-id="9920583742-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9920583742-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9920583742-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9920583742-7">[</span><span class="p" data-group-id="9920583742-7">]</span><span class="p" data-group-id="9920583742-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="9920583742-8">[</span><span class="p" data-group-id="9920583742-9">{</span><span class="p" data-group-id="9920583742-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="9920583742-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9920583742-9">}</span><span class="p" data-group-id="9920583742-8">]</span><span class="p" data-group-id="9920583742-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="7583238792-11">(</span><span class="p" data-group-id="7583238792-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="7583238792-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7583238792-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="7583238792-13">(</span><span class="p" data-group-id="7583238792-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7583238792-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="7583238792-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="7583238792-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7583238792-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7583238792-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7583238792-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7583238792-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="7583238792-17">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9920583742-11">(</span><span class="p" data-group-id="9920583742-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="9920583742-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9920583742-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="9920583742-13">(</span><span class="p" data-group-id="9920583742-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9920583742-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9920583742-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9920583742-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9920583742-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9920583742-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9920583742-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9920583742-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9920583742-17">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Specific <em>generic time-outs</em> can just as <a href="#state-time-outs"><em>state time-outs</em></a>
│ │ │ │  be restarted or canceled by setting it to a new time or <code class="inline">infinity</code>.</p><p>In this particular case we do not need to cancel the time-out since
│ │ │ │  the time-out event is the only possible reason to do a <em>state change</em>
│ │ │ │  from <code class="inline">open</code> to <code class="inline">locked</code>.</p><p>Instead of bothering with when to cancel a time-out, a late time-out event
│ │ │ │  can be handled by ignoring it if it arrives in a state
│ │ │ │  where it is known to be late.</p><p>You can restart, cancel, or update a <em>generic time-out</em>.
│ │ │ │  See section <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="erlang-timers" class="section-heading">
│ │ │ │ @@ -774,32 +774,32 @@
│ │ │ │  <p>The most versatile way to handle time-outs is to use Erlang Timers; see
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#start_timer/4"><code class="inline">erlang:start_timer/3,4</code></a>. Most time-out tasks
│ │ │ │  can be performed with the time-out features in <a href="../../../lib/stdlib/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a>,
│ │ │ │  but an example of one that cannot is if you should need the return value
│ │ │ │  from <a href="../../../lib/../erts/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>, that is,
│ │ │ │  the remaining time of the timer.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │ │  by instead using an Erlang Timer:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="2852134645-1">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2852134645-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2852134645-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2852134645-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2852134645-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2852134645-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="5390983101-1">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5390983101-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5390983101-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="5390983101-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="5390983101-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5390983101-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2852134645-4">(</span><span class="p" data-group-id="2852134645-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5390983101-4">(</span><span class="p" data-group-id="5390983101-4">)</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="n">Tref</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="2852134645-5">(</span><span class="w">
│ │ │ │ -                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2852134645-6">(</span><span class="p" data-group-id="2852134645-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="2852134645-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="2852134645-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2852134645-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2852134645-9">[</span><span class="p" data-group-id="2852134645-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="2852134645-8">}</span><span class="p" data-group-id="2852134645-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="5390983101-5">(</span><span class="w">
│ │ │ │ +                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5390983101-6">(</span><span class="p" data-group-id="5390983101-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="5390983101-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="5390983101-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5390983101-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5390983101-9">[</span><span class="p" data-group-id="5390983101-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="5390983101-8">}</span><span class="p" data-group-id="5390983101-7">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2852134645-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2852134645-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2852134645-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2852134645-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="2852134645-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2852134645-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="2852134645-13">(</span><span class="p" data-group-id="2852134645-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2852134645-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="2852134645-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2852134645-15">)</span><span class="p" data-group-id="2852134645-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2852134645-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2852134645-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2852134645-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2852134645-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2852134645-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="2852134645-18">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="5390983101-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5390983101-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5390983101-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5390983101-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="5390983101-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5390983101-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="5390983101-13">(</span><span class="p" data-group-id="5390983101-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5390983101-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="5390983101-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5390983101-15">)</span><span class="p" data-group-id="5390983101-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="5390983101-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5390983101-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5390983101-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5390983101-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5390983101-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="5390983101-18">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Removing the <code class="inline">timer</code> key from the map when we do a <em>state change</em> to <code class="inline">locked</code>
│ │ │ │  is not strictly necessary since we can only get into state <code class="inline">open</code>
│ │ │ │  with an updated <code class="inline">timer</code> map value. But it can be nice to not have
│ │ │ │  outdated values in the state <code class="inline">Data</code>.</p><p>If you need to cancel a timer because of some other event, you can use
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>. Note that no time-out
│ │ │ │  message will arrive after this (because the timer has been
│ │ │ │  explicitly canceled), unless you have already postponed one earlier
│ │ │ │ @@ -815,16 +815,16 @@
│ │ │ │    <span class="text">Postponing Events</span>
│ │ │ │  </h2>
│ │ │ │  <p>If you want to ignore a particular event in the current state and handle it
│ │ │ │  in a future state, you can postpone the event. A postponed event
│ │ │ │  is retried after a <em>state change</em>, that is, <code class="inline">OldState =/= NewState</code>.</p><p>Postponing is ordered by the
│ │ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">postpone</code>.</p><p>In this example, instead of ignoring button events while in the <code class="inline">open</code> state,
│ │ │ │  we can postpone them handle them later in the <code class="inline">locked</code> state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="8995741770-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8995741770-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8995741770-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8995741770-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8995741770-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="8995741770-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="8995741770-4">]</span><span class="p" data-group-id="8995741770-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="1469428128-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1469428128-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1469428128-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1469428128-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1469428128-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="1469428128-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="1469428128-4">]</span><span class="p" data-group-id="1469428128-3">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Since a postponed event is only retried after a <em>state change</em>, you have to
│ │ │ │  think about where to keep a state data item. You can keep it in the server
│ │ │ │  <code class="inline">Data</code> or in the <code class="inline">State</code> itself, for example by having two more or less
│ │ │ │  identical states to keep a boolean value, or by using a complex state (see
│ │ │ │  section <a href="#complex-state"><em>Complex State</em></a>) with
│ │ │ │  <a href="#callback-modes"><em>callback mode</em></a>
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">handle_event_function</code></a>. If a change
│ │ │ │ @@ -845,55 +845,55 @@
│ │ │ │    <a href="#selective-receive" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Selective Receive</span>
│ │ │ │  </h3>
│ │ │ │  <p>Erlang's selective <code class="inline">receive</code> statement is often used to describe simple state
│ │ │ │  machine examples in straightforward Erlang code. The following is a possible
│ │ │ │ -implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6399160993-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="6399160993-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6399160993-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="6399160993-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6399160993-3">(</span><span class="p" data-group-id="6399160993-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6399160993-4">]</span><span class="p" data-group-id="6399160993-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="6399160993-5">(</span><span class="n">Code</span><span class="p" data-group-id="6399160993-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6399160993-6">(</span><span class="w">
│ │ │ │ -      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6399160993-7">(</span><span class="p" data-group-id="6399160993-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="6399160993-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6399160993-9">(</span><span class="p" data-group-id="6399160993-9">)</span><span class="p" data-group-id="6399160993-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="nf">do_lock</span><span class="p" data-group-id="6399160993-10">(</span><span class="p" data-group-id="6399160993-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="nf">locked</span><span class="p" data-group-id="6399160993-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6399160993-12">(</span><span class="n">Code</span><span class="p" data-group-id="6399160993-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6399160993-13">[</span><span class="p" data-group-id="6399160993-13">]</span><span class="p" data-group-id="6399160993-11">)</span><span class="w">
│ │ │ │ -      </span><span class="k">end</span><span class="p" data-group-id="6399160993-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5280685974-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="5280685974-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5280685974-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="5280685974-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5280685974-3">(</span><span class="p" data-group-id="5280685974-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5280685974-4">]</span><span class="p" data-group-id="5280685974-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="5280685974-5">(</span><span class="n">Code</span><span class="p" data-group-id="5280685974-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5280685974-6">(</span><span class="w">
│ │ │ │ +      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5280685974-7">(</span><span class="p" data-group-id="5280685974-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="5280685974-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5280685974-9">(</span><span class="p" data-group-id="5280685974-9">)</span><span class="p" data-group-id="5280685974-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="nf">do_lock</span><span class="p" data-group-id="5280685974-10">(</span><span class="p" data-group-id="5280685974-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="nf">locked</span><span class="p" data-group-id="5280685974-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5280685974-12">(</span><span class="n">Code</span><span class="p" data-group-id="5280685974-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5280685974-13">[</span><span class="p" data-group-id="5280685974-13">]</span><span class="p" data-group-id="5280685974-11">)</span><span class="w">
│ │ │ │ +      </span><span class="k">end</span><span class="p" data-group-id="5280685974-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="6399160993-14">(</span><span class="n">Button</span><span class="p" data-group-id="6399160993-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6399160993-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6399160993-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="1242220104-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1242220104-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="5280685974-14">(</span><span class="n">Button</span><span class="p" data-group-id="5280685974-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5280685974-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5280685974-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="3152521494-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3152521494-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1242220104-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1242220104-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3152521494-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3152521494-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="1242220104-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="1242220104-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="3152521494-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="3152521494-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="1242220104-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="1242220104-4">)</span><span class="w">
│ │ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1242220104-5">[</span><span class="n">Button</span><span class="p" data-group-id="1242220104-5">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="3152521494-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="3152521494-4">)</span><span class="w">
│ │ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3152521494-5">[</span><span class="n">Button</span><span class="p" data-group-id="3152521494-5">]</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="k">if</span><span class="w">
│ │ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1242220104-6">(</span><span class="p" data-group-id="1242220104-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -		    </span><span class="nf">open</span><span class="p" data-group-id="1242220104-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="1242220104-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3152521494-6">(</span><span class="p" data-group-id="3152521494-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +		    </span><span class="nf">open</span><span class="p" data-group-id="3152521494-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="3152521494-7">)</span><span class="p">;</span><span class="w">
│ │ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -                    </span><span class="nf">locked</span><span class="p" data-group-id="1242220104-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1242220104-8">)</span><span class="w">
│ │ │ │ +                    </span><span class="nf">locked</span><span class="p" data-group-id="3152521494-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3152521494-8">)</span><span class="w">
│ │ │ │              </span><span class="k">end</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="9793917051-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="9793917051-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="7657794733-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="7657794733-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -	    </span><span class="nf">do_lock</span><span class="p" data-group-id="9793917051-2">(</span><span class="p" data-group-id="9793917051-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">locked</span><span class="p" data-group-id="9793917051-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9793917051-4">[</span><span class="p" data-group-id="9793917051-4">]</span><span class="p" data-group-id="9793917051-3">)</span><span class="w">
│ │ │ │ +	    </span><span class="nf">do_lock</span><span class="p" data-group-id="7657794733-2">(</span><span class="p" data-group-id="7657794733-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="nf">locked</span><span class="p" data-group-id="7657794733-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7657794733-4">[</span><span class="p" data-group-id="7657794733-4">]</span><span class="p" data-group-id="7657794733-3">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="9793917051-5">(</span><span class="p" data-group-id="9793917051-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9793917051-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9793917051-7">[</span><span class="p" data-group-id="9793917051-7">]</span><span class="p" data-group-id="9793917051-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="9793917051-8">(</span><span class="p" data-group-id="9793917051-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9793917051-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9793917051-10">[</span><span class="p" data-group-id="9793917051-10">]</span><span class="p" data-group-id="9793917051-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="7657794733-5">(</span><span class="p" data-group-id="7657794733-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7657794733-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7657794733-7">[</span><span class="p" data-group-id="7657794733-7">]</span><span class="p" data-group-id="7657794733-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="7657794733-8">(</span><span class="p" data-group-id="7657794733-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7657794733-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7657794733-10">[</span><span class="p" data-group-id="7657794733-10">]</span><span class="p" data-group-id="7657794733-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │ │  events to the <code class="inline">locked</code> state.</p><p>A catch-all receive should never be used from a <code class="inline">gen_statem</code> behaviour
│ │ │ │  (or from any <code class="inline">gen_*</code> behaviour), as the receive statement is within
│ │ │ │  the <code class="inline">gen_*</code> engine itself. <a href="../../../lib/stdlib/doc/html/sys.html"><code class="inline">sys</code></a>-compatible behaviours must respond to
│ │ │ │  system messages and therefore do that in their engine receive loop,
│ │ │ │  passing non-system messages to the <em>callback module</em>. Using a catch-all
│ │ │ │  receive can result in system messages being discarded, which in turn
│ │ │ │  can lead to unexpected behaviour. If a selective receive must be used,
│ │ │ │ @@ -916,40 +916,40 @@
│ │ │ │  section), especially if only one or a few states have state enter actions,
│ │ │ │  this is a perfect use case for the built in
│ │ │ │  <a href="#state-enter-calls"><em>state enter calls</em></a>.</p><p>You return a list containing <code class="inline">state_enter</code> from your
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">callback_mode/0</code></a> function and the
│ │ │ │  <code class="inline">gen_statem</code> engine will call your <em>state callback</em> once with an event
│ │ │ │  <code class="inline">(enter, OldState, ...)</code> whenever it does a <em>state change</em>. Then you
│ │ │ │  just need to handle these event-like calls in all states.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1611307811-1">(</span><span class="n">Code</span><span class="p" data-group-id="1611307811-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="1611307811-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1611307811-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1611307811-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1611307811-4">(</span><span class="n">Code</span><span class="p" data-group-id="1611307811-4">)</span><span class="p" data-group-id="1611307811-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1611307811-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1611307811-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="1611307811-6">(</span><span class="p" data-group-id="1611307811-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1611307811-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="1611307811-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1611307811-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1611307811-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="1611307811-9">(</span><span class="p" data-group-id="1611307811-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1611307811-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1611307811-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1611307811-12">[</span><span class="p" data-group-id="1611307811-12">]</span><span class="p" data-group-id="1611307811-11">}</span><span class="p" data-group-id="1611307811-10">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1611307811-13">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1611307811-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1611307811-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1611307811-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1611307811-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1611307811-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2259820404-1">(</span><span class="n">Code</span><span class="p" data-group-id="2259820404-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="2259820404-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2259820404-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2259820404-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="2259820404-4">(</span><span class="n">Code</span><span class="p" data-group-id="2259820404-4">)</span><span class="p" data-group-id="2259820404-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2259820404-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2259820404-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="2259820404-6">(</span><span class="p" data-group-id="2259820404-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2259820404-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="2259820404-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2259820404-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2259820404-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="2259820404-9">(</span><span class="p" data-group-id="2259820404-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2259820404-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="2259820404-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2259820404-12">[</span><span class="p" data-group-id="2259820404-12">]</span><span class="p" data-group-id="2259820404-11">}</span><span class="p" data-group-id="2259820404-10">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2259820404-13">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2259820404-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2259820404-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2259820404-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2259820404-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2259820404-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1611307811-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1611307811-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2259820404-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2259820404-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1611307811-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1611307811-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1611307811-18">(</span><span class="p" data-group-id="1611307811-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1611307811-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="1611307811-20">[</span><span class="p" data-group-id="1611307811-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1611307811-21">}</span><span class="p" data-group-id="1611307811-20">]</span><span class="p" data-group-id="1611307811-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1611307811-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1611307811-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1611307811-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1611307811-23">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="2259820404-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2259820404-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2259820404-18">(</span><span class="p" data-group-id="2259820404-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2259820404-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="2259820404-20">[</span><span class="p" data-group-id="2259820404-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2259820404-21">}</span><span class="p" data-group-id="2259820404-20">]</span><span class="p" data-group-id="2259820404-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="2259820404-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2259820404-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2259820404-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2259820404-23">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>You can repeat the state enter code by returning one of
│ │ │ │  <code class="inline">{repeat_state, ...}</code>,<code class="inline">{repeat_state_and_data, _}</code>,
│ │ │ │  or <code class="inline">repeat_state_and_data</code> that otherwise behaves exactly like their
│ │ │ │  <code class="inline">keep_state</code> siblings.  See the type
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:state_callback_result/2"><code class="inline">state_callback_result()</code></a>
│ │ │ │  in the Reference Manual.</p><h2 id="inserted-events" class="section-heading">
│ │ │ │    <a href="#inserted-events" class="hover-link">
│ │ │ │ @@ -971,44 +971,44 @@
│ │ │ │  to dispatch pre-processed events as internal events to the main state
│ │ │ │  machine.</p><p>Using internal events also can make it easier to synchronize the state
│ │ │ │  machines.</p><p>A variant of this is to use a <a href="#complex-state">complex state</a> with
│ │ │ │  <a href="#one-state-callback">one state callback</a>, modeling the state
│ │ │ │  with, for example, a tuple <code class="inline">{MainFSMState, SubFSMState}</code>.</p><p>To illustrate this we make up an example where the buttons instead generate
│ │ │ │  down and up (press and release) events, and the lock responds
│ │ │ │  to an up event only after the corresponding down event.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3516549929-1">(</span><span class="p" data-group-id="3516549929-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3516549929-2">]</span><span class="p" data-group-id="3516549929-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4948526356-1">(</span><span class="p" data-group-id="4948526356-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4948526356-2">]</span><span class="p" data-group-id="4948526356-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="3516549929-3">(</span><span class="n">Button</span><span class="p" data-group-id="3516549929-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3516549929-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3516549929-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3516549929-5">}</span><span class="p" data-group-id="3516549929-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="4948526356-3">(</span><span class="n">Button</span><span class="p" data-group-id="4948526356-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4948526356-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4948526356-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4948526356-5">}</span><span class="p" data-group-id="4948526356-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="3516549929-6">(</span><span class="n">Button</span><span class="p" data-group-id="3516549929-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3516549929-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3516549929-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3516549929-8">}</span><span class="p" data-group-id="3516549929-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="4948526356-6">(</span><span class="n">Button</span><span class="p" data-group-id="4948526356-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4948526356-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4948526356-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4948526356-8">}</span><span class="p" data-group-id="4948526356-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="3516549929-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3516549929-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="3516549929-10">(</span><span class="p" data-group-id="3516549929-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3516549929-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3516549929-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3516549929-13">[</span><span class="p" data-group-id="3516549929-13">]</span><span class="p" data-group-id="3516549929-12">}</span><span class="p" data-group-id="3516549929-11">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="3516549929-14">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3516549929-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3516549929-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3516549929-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3516549929-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3516549929-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="0845661158-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0845661158-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0845661158-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0845661158-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0845661158-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0845661158-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0845661158-4">}</span><span class="p" data-group-id="0845661158-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="0845661158-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0845661158-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0845661158-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0845661158-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4948526356-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4948526356-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="4948526356-10">(</span><span class="p" data-group-id="4948526356-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4948526356-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="4948526356-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4948526356-13">[</span><span class="p" data-group-id="4948526356-13">]</span><span class="p" data-group-id="4948526356-12">}</span><span class="p" data-group-id="4948526356-11">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4948526356-14">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4948526356-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4948526356-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4948526356-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="4948526356-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4948526356-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="3879057902-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3879057902-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3879057902-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3879057902-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3879057902-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3879057902-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="3879057902-4">}</span><span class="p" data-group-id="3879057902-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="3879057902-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3879057902-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3879057902-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3879057902-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0845661158-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0845661158-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0845661158-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="0845661158-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0845661158-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="0845661158-10">[</span><span class="p" data-group-id="0845661158-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="0845661158-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0845661158-12">}</span><span class="p" data-group-id="0845661158-11">}</span><span class="p" data-group-id="0845661158-10">]</span><span class="p" data-group-id="0845661158-8">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0845661158-13">#{</span><span class="p" data-group-id="0845661158-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3879057902-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="3879057902-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3879057902-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="3879057902-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3879057902-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="3879057902-10">[</span><span class="p" data-group-id="3879057902-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="3879057902-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3879057902-12">}</span><span class="p" data-group-id="3879057902-11">}</span><span class="p" data-group-id="3879057902-10">]</span><span class="p" data-group-id="3879057902-8">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3879057902-13">#{</span><span class="p" data-group-id="3879057902-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="0845661158-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0845661158-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0845661158-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0845661158-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0845661158-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="0845661158-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="0845661158-17">]</span><span class="p" data-group-id="0845661158-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3879057902-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3879057902-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3879057902-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3879057902-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3879057902-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="3879057902-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="3879057902-17">]</span><span class="p" data-group-id="3879057902-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>If you start this program with <code class="inline">code_lock:start([17])</code> you can unlock with
│ │ │ │  <code class="inline">code_lock:down(17), code_lock:up(17).</code></p><h2 id="example-revisited" class="section-heading">
│ │ │ │    <a href="#example-revisited" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example Revisited</span>
│ │ │ │  </h2>
│ │ │ │ @@ -1036,152 +1036,152 @@
│ │ │ │  Also, the state diagram does not show that the <code class="inline">code_length/0</code> call
│ │ │ │  must be handled in every state.</p><h3 id="callback-mode-state_functions" class="section-heading">
│ │ │ │    <a href="#callback-mode-state_functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Callback Mode: state_functions</span>
│ │ │ │  </h3>
│ │ │ │ -<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0851965068-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="0851965068-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0851965068-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="0851965068-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0851965068-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="0851965068-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5303008774-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="5303008774-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5303008774-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="5303008774-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5303008774-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="5303008774-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0851965068-4">(</span><span class="p" data-group-id="0851965068-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0851965068-5">]</span><span class="p" data-group-id="0851965068-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0851965068-6">(</span><span class="p" data-group-id="0851965068-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0851965068-7">]</span><span class="p" data-group-id="0851965068-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0851965068-8">(</span><span class="p" data-group-id="0851965068-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="0851965068-9">]</span><span class="p" data-group-id="0851965068-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0851965068-10">(</span><span class="p" data-group-id="0851965068-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="0851965068-11">]</span><span class="p" data-group-id="0851965068-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="0851965068-12">(</span><span class="n">Code</span><span class="p" data-group-id="0851965068-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0851965068-13">(</span><span class="p" data-group-id="0851965068-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0851965068-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0851965068-15">[</span><span class="p" data-group-id="0851965068-15">]</span><span class="p" data-group-id="0851965068-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0851965068-16">(</span><span class="p" data-group-id="0851965068-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0851965068-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0851965068-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="0851965068-18">(</span><span class="n">Button</span><span class="p" data-group-id="0851965068-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0851965068-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0851965068-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0851965068-20">}</span><span class="p" data-group-id="0851965068-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="0851965068-21">(</span><span class="n">Button</span><span class="p" data-group-id="0851965068-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0851965068-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0851965068-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0851965068-23">}</span><span class="p" data-group-id="0851965068-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="0851965068-24">(</span><span class="p" data-group-id="0851965068-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0851965068-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="0851965068-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9879579112-1">(</span><span class="n">Code</span><span class="p" data-group-id="9879579112-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="9879579112-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9879579112-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9879579112-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9879579112-4">(</span><span class="n">Code</span><span class="p" data-group-id="9879579112-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9879579112-5">[</span><span class="p" data-group-id="9879579112-5">]</span><span class="p" data-group-id="9879579112-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9879579112-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9879579112-6">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5303008774-4">(</span><span class="p" data-group-id="5303008774-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5303008774-5">]</span><span class="p" data-group-id="5303008774-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5303008774-6">(</span><span class="p" data-group-id="5303008774-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5303008774-7">]</span><span class="p" data-group-id="5303008774-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5303008774-8">(</span><span class="p" data-group-id="5303008774-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5303008774-9">]</span><span class="p" data-group-id="5303008774-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5303008774-10">(</span><span class="p" data-group-id="5303008774-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5303008774-11">]</span><span class="p" data-group-id="5303008774-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="5303008774-12">(</span><span class="n">Code</span><span class="p" data-group-id="5303008774-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5303008774-13">(</span><span class="p" data-group-id="5303008774-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="5303008774-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5303008774-15">[</span><span class="p" data-group-id="5303008774-15">]</span><span class="p" data-group-id="5303008774-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="5303008774-16">(</span><span class="p" data-group-id="5303008774-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="5303008774-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="5303008774-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="5303008774-18">(</span><span class="n">Button</span><span class="p" data-group-id="5303008774-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5303008774-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5303008774-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5303008774-20">}</span><span class="p" data-group-id="5303008774-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="5303008774-21">(</span><span class="n">Button</span><span class="p" data-group-id="5303008774-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5303008774-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5303008774-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5303008774-23">}</span><span class="p" data-group-id="5303008774-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="5303008774-24">(</span><span class="p" data-group-id="5303008774-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="5303008774-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="5303008774-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0668316922-1">(</span><span class="n">Code</span><span class="p" data-group-id="0668316922-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="0668316922-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0668316922-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0668316922-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="0668316922-4">(</span><span class="n">Code</span><span class="p" data-group-id="0668316922-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0668316922-5">[</span><span class="p" data-group-id="0668316922-5">]</span><span class="p" data-group-id="0668316922-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0668316922-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0668316922-6">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="9879579112-7">(</span><span class="p" data-group-id="9879579112-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9879579112-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="9879579112-8">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="0668316922-7">(</span><span class="p" data-group-id="0668316922-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0668316922-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="0668316922-8">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9879579112-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="9879579112-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="9879579112-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="9879579112-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="9879579112-11">)</span><span class="p" data-group-id="9879579112-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0668316922-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="0668316922-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0668316922-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="0668316922-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0668316922-11">)</span><span class="p" data-group-id="0668316922-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="9879579112-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9879579112-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9879579112-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9879579112-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9879579112-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9879579112-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9879579112-15">}</span><span class="p" data-group-id="9879579112-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="9879579112-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9879579112-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9879579112-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9879579112-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="0668316922-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0668316922-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0668316922-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0668316922-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0668316922-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0668316922-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0668316922-15">}</span><span class="p" data-group-id="0668316922-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="0668316922-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0668316922-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0668316922-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0668316922-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9879579112-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9879579112-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9879579112-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="9879579112-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9879579112-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="9879579112-21">[</span><span class="p" data-group-id="9879579112-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="9879579112-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9879579112-23">}</span><span class="p" data-group-id="9879579112-22">}</span><span class="p" data-group-id="9879579112-21">]</span><span class="p" data-group-id="9879579112-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9879579112-24">#{</span><span class="p" data-group-id="9879579112-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0668316922-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0668316922-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0668316922-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="0668316922-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0668316922-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="0668316922-21">[</span><span class="p" data-group-id="0668316922-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="0668316922-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0668316922-23">}</span><span class="p" data-group-id="0668316922-22">}</span><span class="p" data-group-id="0668316922-21">]</span><span class="p" data-group-id="0668316922-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0668316922-24">#{</span><span class="p" data-group-id="0668316922-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="9879579112-25">(</span><span class="p" data-group-id="9879579112-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="9879579112-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9879579112-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="9879579112-27">}</span><span class="p" data-group-id="9879579112-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9879579112-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="9879579112-29">[</span><span class="p" data-group-id="9879579112-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="9879579112-31">(</span><span class="n">Code</span><span class="p" data-group-id="9879579112-31">)</span><span class="p" data-group-id="9879579112-30">}</span><span class="p" data-group-id="9879579112-29">]</span><span class="p" data-group-id="9879579112-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="5074339944-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="5074339944-2">(</span><span class="p" data-group-id="5074339944-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5074339944-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5074339944-5">[</span><span class="p" data-group-id="5074339944-5">]</span><span class="p" data-group-id="5074339944-4">}</span><span class="p" data-group-id="5074339944-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="5074339944-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5074339944-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5074339944-9">[</span><span class="p" data-group-id="5074339944-9">]</span><span class="p" data-group-id="5074339944-8">}</span><span class="p" data-group-id="5074339944-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="5074339944-10">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5074339944-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5074339944-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5074339944-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="5074339944-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="0668316922-25">(</span><span class="p" data-group-id="0668316922-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="0668316922-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0668316922-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="0668316922-27">}</span><span class="p" data-group-id="0668316922-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0668316922-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="0668316922-29">[</span><span class="p" data-group-id="0668316922-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="0668316922-31">(</span><span class="n">Code</span><span class="p" data-group-id="0668316922-31">)</span><span class="p" data-group-id="0668316922-30">}</span><span class="p" data-group-id="0668316922-29">]</span><span class="p" data-group-id="0668316922-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="7585719753-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="7585719753-2">(</span><span class="p" data-group-id="7585719753-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7585719753-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7585719753-5">[</span><span class="p" data-group-id="7585719753-5">]</span><span class="p" data-group-id="7585719753-4">}</span><span class="p" data-group-id="7585719753-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="7585719753-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7585719753-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7585719753-9">[</span><span class="p" data-group-id="7585719753-9">]</span><span class="p" data-group-id="7585719753-8">}</span><span class="p" data-group-id="7585719753-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="7585719753-10">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7585719753-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7585719753-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7585719753-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7585719753-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="5074339944-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="5074339944-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="7585719753-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="7585719753-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="5074339944-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="5074339944-14">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5074339944-15">[</span><span class="n">Button</span><span class="p" data-group-id="5074339944-15">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="7585719753-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="7585719753-14">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7585719753-15">[</span><span class="n">Button</span><span class="p" data-group-id="7585719753-15">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5074339944-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="7585719753-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5074339944-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5074339944-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="5074339944-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="5074339944-19">[</span><span class="p" data-group-id="5074339944-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="5074339944-20">}</span><span class="p" data-group-id="5074339944-19">]</span><span class="p" data-group-id="5074339944-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="7585719753-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7585719753-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="7585719753-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="7585719753-19">[</span><span class="p" data-group-id="7585719753-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="7585719753-20">}</span><span class="p" data-group-id="7585719753-19">]</span><span class="p" data-group-id="7585719753-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="2889471753-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2889471753-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="2889471753-2">(</span><span class="p" data-group-id="2889471753-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2889471753-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="2889471753-4">[</span><span class="p" data-group-id="2889471753-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="2889471753-5">}</span><span class="p" data-group-id="2889471753-4">]</span><span class="p" data-group-id="2889471753-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2889471753-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2889471753-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2889471753-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2889471753-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2889471753-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2889471753-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2889471753-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2889471753-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2889471753-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2889471753-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="2889471753-11">]</span><span class="p" data-group-id="2889471753-10">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="9365826149-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9365826149-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9365826149-2">(</span><span class="p" data-group-id="9365826149-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9365826149-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="9365826149-4">[</span><span class="p" data-group-id="9365826149-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9365826149-5">}</span><span class="p" data-group-id="9365826149-4">]</span><span class="p" data-group-id="9365826149-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9365826149-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9365826149-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9365826149-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9365826149-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="9365826149-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9365826149-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9365826149-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9365826149-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9365826149-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9365826149-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="9365826149-11">]</span><span class="p" data-group-id="9365826149-10">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="2889471753-12">(</span><span class="p" data-group-id="2889471753-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2889471753-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2889471753-14">[</span><span class="p" data-group-id="2889471753-14">]</span><span class="p" data-group-id="2889471753-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="2889471753-15">(</span><span class="p" data-group-id="2889471753-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2889471753-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2889471753-17">[</span><span class="p" data-group-id="2889471753-17">]</span><span class="p" data-group-id="2889471753-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="9365826149-12">(</span><span class="p" data-group-id="9365826149-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9365826149-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9365826149-14">[</span><span class="p" data-group-id="9365826149-14">]</span><span class="p" data-group-id="9365826149-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="9365826149-15">(</span><span class="p" data-group-id="9365826149-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9365826149-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9365826149-17">[</span><span class="p" data-group-id="9365826149-17">]</span><span class="p" data-group-id="9365826149-16">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="2889471753-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="2889471753-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="2889471753-19">(</span><span class="p" data-group-id="2889471753-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="9365826149-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9365826149-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="9365826149-19">(</span><span class="p" data-group-id="9365826149-19">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="callback-mode-handle_event_function" class="section-heading">
│ │ │ │    <a href="#callback-mode-handle_event_function" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Callback Mode: handle_event_function</span>
│ │ │ │  </h3>
│ │ │ │  <p>This section describes what to change in the example to use one
│ │ │ │  <code class="inline">handle_event/4</code> function.  The previously used approach to first branch
│ │ │ │  depending on event does not work that well here because of
│ │ │ │ -the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1774552766-1">(</span><span class="p" data-group-id="1774552766-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="1774552766-2">]</span><span class="p" data-group-id="1774552766-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="4434895252-1">(</span><span class="p" data-group-id="4434895252-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4434895252-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="4434895252-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │ +the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5161921122-1">(</span><span class="p" data-group-id="5161921122-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="5161921122-2">]</span><span class="p" data-group-id="5161921122-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="0884644631-1">(</span><span class="p" data-group-id="0884644631-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0884644631-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="0884644631-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="9767452912-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="9767452912-2">(</span><span class="p" data-group-id="9767452912-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9767452912-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9767452912-5">[</span><span class="p" data-group-id="9767452912-5">]</span><span class="p" data-group-id="9767452912-4">}</span><span class="p" data-group-id="9767452912-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="9767452912-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9767452912-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9767452912-9">[</span><span class="p" data-group-id="9767452912-9">]</span><span class="p" data-group-id="9767452912-8">}</span><span class="p" data-group-id="9767452912-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="9767452912-10">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9767452912-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9767452912-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9767452912-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9767452912-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8842409002-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8842409002-2">(</span><span class="p" data-group-id="8842409002-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8842409002-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8842409002-5">[</span><span class="p" data-group-id="8842409002-5">]</span><span class="p" data-group-id="8842409002-4">}</span><span class="p" data-group-id="8842409002-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8842409002-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8842409002-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8842409002-9">[</span><span class="p" data-group-id="8842409002-9">]</span><span class="p" data-group-id="8842409002-8">}</span><span class="p" data-group-id="8842409002-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8842409002-10">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8842409002-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8842409002-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8842409002-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8842409002-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="9767452912-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="9767452912-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="8842409002-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="8842409002-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="9767452912-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="9767452912-14">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9767452912-15">[</span><span class="n">Button</span><span class="p" data-group-id="9767452912-15">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="8842409002-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="8842409002-14">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8842409002-15">[</span><span class="n">Button</span><span class="p" data-group-id="8842409002-15">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9767452912-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-16">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8842409002-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-16">}</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9767452912-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9767452912-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9767452912-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="9767452912-19">[</span><span class="p" data-group-id="9767452912-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="9767452912-20">}</span><span class="p" data-group-id="9767452912-19">]</span><span class="p" data-group-id="9767452912-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8842409002-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8842409002-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8842409002-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="8842409002-19">[</span><span class="p" data-group-id="8842409002-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="8842409002-20">}</span><span class="p" data-group-id="8842409002-19">]</span><span class="p" data-group-id="8842409002-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7958341534-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="7958341534-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7958341534-2">(</span><span class="p" data-group-id="7958341534-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7958341534-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7958341534-4">[</span><span class="p" data-group-id="7958341534-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7958341534-5">}</span><span class="p" data-group-id="7958341534-4">]</span><span class="p" data-group-id="7958341534-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7958341534-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7958341534-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7958341534-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7958341534-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7958341534-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7958341534-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7958341534-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7958341534-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7958341534-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="7958341534-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="7958341534-11">]</span><span class="p" data-group-id="7958341534-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6495094214-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6495094214-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6495094214-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6495094214-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6495094214-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6495094214-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="6495094214-4">}</span><span class="p" data-group-id="6495094214-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6495094214-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6495094214-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6495094214-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6495094214-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4632276941-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4632276941-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="4632276941-2">(</span><span class="p" data-group-id="4632276941-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4632276941-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4632276941-4">[</span><span class="p" data-group-id="4632276941-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4632276941-5">}</span><span class="p" data-group-id="4632276941-4">]</span><span class="p" data-group-id="4632276941-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4632276941-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4632276941-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4632276941-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4632276941-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4632276941-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4632276941-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4632276941-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4632276941-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4632276941-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="4632276941-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="4632276941-11">]</span><span class="p" data-group-id="4632276941-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5156826911-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5156826911-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5156826911-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5156826911-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5156826911-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5156826911-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="5156826911-4">}</span><span class="p" data-group-id="5156826911-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5156826911-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5156826911-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5156826911-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5156826911-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6495094214-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="6495094214-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6495094214-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="6495094214-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6495094214-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="6495094214-10">[</span><span class="p" data-group-id="6495094214-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="6495094214-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6495094214-12">}</span><span class="p" data-group-id="6495094214-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="6495094214-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="6495094214-13">}</span><span class="p" data-group-id="6495094214-10">]</span><span class="p" data-group-id="6495094214-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6495094214-14">#{</span><span class="p" data-group-id="6495094214-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5156826911-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="5156826911-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="5156826911-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="5156826911-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5156826911-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="5156826911-10">[</span><span class="p" data-group-id="5156826911-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="5156826911-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5156826911-12">}</span><span class="p" data-group-id="5156826911-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="5156826911-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="5156826911-13">}</span><span class="p" data-group-id="5156826911-10">]</span><span class="p" data-group-id="5156826911-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5156826911-14">#{</span><span class="p" data-group-id="5156826911-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6495094214-15">(</span><span class="p" data-group-id="6495094214-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="6495094214-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6495094214-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="6495094214-17">}</span><span class="p" data-group-id="6495094214-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6495094214-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="6495094214-19">[</span><span class="p" data-group-id="6495094214-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="6495094214-20">}</span><span class="p" data-group-id="6495094214-19">]</span><span class="p" data-group-id="6495094214-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="5156826911-15">(</span><span class="p" data-group-id="5156826911-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="5156826911-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5156826911-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="5156826911-17">}</span><span class="p" data-group-id="5156826911-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5156826911-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="5156826911-19">[</span><span class="p" data-group-id="5156826911-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="5156826911-20">}</span><span class="p" data-group-id="5156826911-19">]</span><span class="p" data-group-id="5156826911-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │ │  seems like a strange thing to do for a code lock, but it at least
│ │ │ │  illustrates event postponing.</p><h2 id="filter-the-state" class="section-heading">
│ │ │ │    <a href="#filter-the-state" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Filter the State</span>
│ │ │ │  </h2>
│ │ │ │ @@ -1191,30 +1191,30 @@
│ │ │ │  and which digits that remain to unlock.</p><p>This state data can be regarded as sensitive, and maybe not what you want
│ │ │ │  in the error log because of some unpredictable event.</p><p>Another reason to filter the state can be that the state is too large to print,
│ │ │ │  as it fills the error log with uninteresting details.</p><p>To avoid this, you can format the internal state that gets in the error log
│ │ │ │  and gets returned from <a href="../../../lib/stdlib/doc/html/sys.html#get_status/1"><code class="inline">sys:get_status/1,2</code></a>
│ │ │ │  by implementing function
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a>,
│ │ │ │  for example like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6119846834-1">(</span><span class="p" data-group-id="6119846834-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6119846834-2">]</span><span class="p" data-group-id="6119846834-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3573885882-1">(</span><span class="p" data-group-id="3573885882-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3573885882-2">]</span><span class="p" data-group-id="3573885882-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">format_status</span><span class="p" data-group-id="6119846834-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6119846834-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="6119846834-4">]</span><span class="p" data-group-id="6119846834-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">format_status</span><span class="p" data-group-id="3573885882-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3573885882-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3573885882-4">]</span><span class="p" data-group-id="3573885882-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">StateData</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="6119846834-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ │ -	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="6119846834-6">(</span><span class="w">
│ │ │ │ -	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6119846834-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6119846834-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ │ -	       </span><span class="p" data-group-id="6119846834-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6119846834-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="3573885882-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ │ +	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="3573885882-6">(</span><span class="w">
│ │ │ │ +	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3573885882-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3573885882-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ │ +	       </span><span class="p" data-group-id="3573885882-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3573885882-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │ │  	   </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	   </span><span class="n">Data</span><span class="p" data-group-id="6119846834-6">)</span><span class="p" data-group-id="6119846834-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	   </span><span class="n">Data</span><span class="p" data-group-id="3573885882-6">)</span><span class="p" data-group-id="3573885882-5">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Opt</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │  	</span><span class="ss">terminate</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">StateData</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">normal</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="p" data-group-id="6119846834-9">[</span><span class="p" data-group-id="6119846834-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="6119846834-11">[</span><span class="p" data-group-id="6119846834-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="6119846834-12">}</span><span class="p" data-group-id="6119846834-11">]</span><span class="p" data-group-id="6119846834-10">}</span><span class="p" data-group-id="6119846834-9">]</span><span class="w">
│ │ │ │ +	    </span><span class="p" data-group-id="3573885882-9">[</span><span class="p" data-group-id="3573885882-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="3573885882-11">[</span><span class="p" data-group-id="3573885882-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="3573885882-12">}</span><span class="p" data-group-id="3573885882-11">]</span><span class="p" data-group-id="3573885882-10">}</span><span class="p" data-group-id="3573885882-9">]</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is not mandatory to implement a
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a> function.
│ │ │ │  If you do not, a default implementation is used that does the same
│ │ │ │  as this example function without filtering the <code class="inline">Data</code> term, that is,
│ │ │ │  <code class="inline">StateData = {State, Data}</code>, in this example containing sensitive information.</p><h2 id="complex-state" class="section-heading">
│ │ │ │    <a href="#complex-state" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -1227,104 +1227,104 @@
│ │ │ │  like a tuple.</p><p>One reason to use this is when you have a state item that when changed
│ │ │ │  should cancel the <a href="#state-time-outs"><em>state time-out</em></a>, or one that affects
│ │ │ │  the event handling in combination with postponing events. We will go for
│ │ │ │  the latter and complicate the previous example by introducing
│ │ │ │  a configurable lock button (this is the state item in question),
│ │ │ │  which in the <code class="inline">open</code> state immediately locks the door, and an API function
│ │ │ │  <code class="inline">set_lock_button/1</code> to set the lock button.</p><p>Suppose now that we call <code class="inline">set_lock_button</code> while the door is open,
│ │ │ │ -and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5090863436-1">(</span><span class="p" data-group-id="5090863436-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5090863436-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="5090863436-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5090863436-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5090863436-3">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5090863436-4">(</span><span class="ss">a</span><span class="p" data-group-id="5090863436-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9592448323-1">(</span><span class="p" data-group-id="9592448323-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="9592448323-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="9592448323-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9592448323-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9592448323-3">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9592448323-4">(</span><span class="ss">a</span><span class="p" data-group-id="9592448323-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5090863436-5">(</span><span class="ss">b</span><span class="p" data-group-id="5090863436-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9592448323-5">(</span><span class="ss">b</span><span class="p" data-group-id="9592448323-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5090863436-6">(</span><span class="ss">c</span><span class="p" data-group-id="5090863436-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9592448323-6">(</span><span class="ss">c</span><span class="p" data-group-id="9592448323-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="n">Open</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5090863436-7">(</span><span class="ss">y</span><span class="p" data-group-id="5090863436-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9592448323-7">(</span><span class="ss">y</span><span class="p" data-group-id="9592448323-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="5090863436-8">(</span><span class="ss">y</span><span class="p" data-group-id="5090863436-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="9592448323-8">(</span><span class="ss">y</span><span class="p" data-group-id="9592448323-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">x</span><span class="w">
│ │ │ │  </span><span class="c1">% What should happen here?  Immediate lock or nothing?</span></code></pre><p>We could say that the button was pressed too early so it should not be
│ │ │ │  recognized as the lock button. Or we can make the lock button part of
│ │ │ │  the state so when we then change the lock button in the locked state,
│ │ │ │  the change becomes a <em>state change</em> and all postponed events are retried,
│ │ │ │  therefore the lock is immediately locked!</p><p>We define the state as <code class="inline">{StateName, LockButton}</code>, where <code class="inline">StateName</code>
│ │ │ │ -is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3422298776-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="3422298776-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3422298776-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="3422298776-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3422298776-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="3422298776-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0404593391-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="0404593391-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0404593391-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="0404593391-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0404593391-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="0404593391-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3422298776-4">(</span><span class="p" data-group-id="3422298776-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3422298776-5">]</span><span class="p" data-group-id="3422298776-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3422298776-6">(</span><span class="p" data-group-id="3422298776-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3422298776-7">]</span><span class="p" data-group-id="3422298776-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3422298776-8">(</span><span class="p" data-group-id="3422298776-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="3422298776-9">]</span><span class="p" data-group-id="3422298776-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3422298776-10">(</span><span class="p" data-group-id="3422298776-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="3422298776-11">]</span><span class="p" data-group-id="3422298776-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="3422298776-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="3422298776-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3422298776-13">(</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3422298776-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="3422298776-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3422298776-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="3422298776-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3422298776-16">[</span><span class="p" data-group-id="3422298776-16">]</span><span class="p" data-group-id="3422298776-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="3422298776-17">(</span><span class="p" data-group-id="3422298776-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3422298776-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="3422298776-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="3422298776-19">(</span><span class="n">Button</span><span class="p" data-group-id="3422298776-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3422298776-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3422298776-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3422298776-21">}</span><span class="p" data-group-id="3422298776-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">set_lock_button</span><span class="p" data-group-id="3422298776-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="3422298776-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="3422298776-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3422298776-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="3422298776-24">}</span><span class="p" data-group-id="3422298776-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6430032047-1">(</span><span class="p" data-group-id="6430032047-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6430032047-2">}</span><span class="p" data-group-id="6430032047-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="6430032047-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6430032047-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6430032047-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6430032047-5">(</span><span class="n">Code</span><span class="p" data-group-id="6430032047-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6430032047-6">[</span><span class="p" data-group-id="6430032047-6">]</span><span class="p" data-group-id="6430032047-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6430032047-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430032047-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6430032047-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-7">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0404593391-4">(</span><span class="p" data-group-id="0404593391-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0404593391-5">]</span><span class="p" data-group-id="0404593391-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0404593391-6">(</span><span class="p" data-group-id="0404593391-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0404593391-7">]</span><span class="p" data-group-id="0404593391-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0404593391-8">(</span><span class="p" data-group-id="0404593391-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="0404593391-9">]</span><span class="p" data-group-id="0404593391-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0404593391-10">(</span><span class="p" data-group-id="0404593391-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="0404593391-11">]</span><span class="p" data-group-id="0404593391-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="0404593391-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="0404593391-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0404593391-13">(</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0404593391-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0404593391-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0404593391-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0404593391-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0404593391-16">[</span><span class="p" data-group-id="0404593391-16">]</span><span class="p" data-group-id="0404593391-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="0404593391-17">(</span><span class="p" data-group-id="0404593391-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0404593391-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="0404593391-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="0404593391-19">(</span><span class="n">Button</span><span class="p" data-group-id="0404593391-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0404593391-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0404593391-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0404593391-21">}</span><span class="p" data-group-id="0404593391-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">set_lock_button</span><span class="p" data-group-id="0404593391-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="0404593391-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0404593391-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0404593391-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="0404593391-24">}</span><span class="p" data-group-id="0404593391-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8979147996-1">(</span><span class="p" data-group-id="8979147996-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="8979147996-2">}</span><span class="p" data-group-id="8979147996-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="8979147996-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8979147996-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8979147996-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8979147996-5">(</span><span class="n">Code</span><span class="p" data-group-id="8979147996-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8979147996-6">[</span><span class="p" data-group-id="8979147996-6">]</span><span class="p" data-group-id="8979147996-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8979147996-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979147996-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="8979147996-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-7">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="6430032047-9">(</span><span class="p" data-group-id="6430032047-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6430032047-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="6430032047-10">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="8979147996-9">(</span><span class="p" data-group-id="8979147996-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8979147996-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="8979147996-10">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6430032047-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430032047-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6430032047-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6430032047-13">(</span><span class="p" data-group-id="6430032047-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6430032047-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6430032047-16">[</span><span class="p" data-group-id="6430032047-16">]</span><span class="p" data-group-id="6430032047-15">}</span><span class="p" data-group-id="6430032047-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6430032047-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430032047-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6430032047-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6430032047-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6430032047-21">[</span><span class="p" data-group-id="6430032047-21">]</span><span class="p" data-group-id="6430032047-20">}</span><span class="p" data-group-id="6430032047-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6430032047-22">(</span><span class="w">
│ │ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430032047-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6430032047-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430032047-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6430032047-24">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6430032047-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6430032047-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8979147996-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979147996-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8979147996-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8979147996-13">(</span><span class="p" data-group-id="8979147996-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8979147996-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8979147996-16">[</span><span class="p" data-group-id="8979147996-16">]</span><span class="p" data-group-id="8979147996-15">}</span><span class="p" data-group-id="8979147996-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8979147996-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979147996-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8979147996-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8979147996-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8979147996-21">[</span><span class="p" data-group-id="8979147996-21">]</span><span class="p" data-group-id="8979147996-20">}</span><span class="p" data-group-id="8979147996-19">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8979147996-22">(</span><span class="w">
│ │ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979147996-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8979147996-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979147996-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="8979147996-24">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8979147996-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8979147996-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │          </span><span class="k">if</span><span class="w">
│ │ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="6430032047-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="6430032047-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="8979147996-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="8979147996-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="6430032047-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="6430032047-27">)</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6430032047-28">[</span><span class="n">Button</span><span class="p" data-group-id="6430032047-28">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="8979147996-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="8979147996-27">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8979147996-28">[</span><span class="n">Button</span><span class="p" data-group-id="8979147996-28">]</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6430032047-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6430032047-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6430032047-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-29">}</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8979147996-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8979147996-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="8979147996-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-29">}</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6430032047-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6430032047-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="6430032047-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="6430032047-33">[</span><span class="p" data-group-id="6430032047-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="6430032047-34">}</span><span class="p" data-group-id="6430032047-33">]</span><span class="p" data-group-id="6430032047-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="8979147996-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8979147996-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8979147996-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="8979147996-33">[</span><span class="p" data-group-id="8979147996-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="8979147996-34">}</span><span class="p" data-group-id="8979147996-33">]</span><span class="p" data-group-id="8979147996-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1004604805-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1004604805-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1004604805-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1004604805-3">(</span><span class="p" data-group-id="1004604805-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1004604805-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="1004604805-5">[</span><span class="p" data-group-id="1004604805-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1004604805-6">}</span><span class="p" data-group-id="1004604805-5">]</span><span class="p" data-group-id="1004604805-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1004604805-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1004604805-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1004604805-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1004604805-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1004604805-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1004604805-9">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1004604805-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1004604805-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1004604805-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1004604805-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1004604805-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1004604805-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1004604805-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="1004604805-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1004604805-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004604805-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1004604805-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1004604805-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1004604805-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="1004604805-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="1004604805-20">]</span><span class="p" data-group-id="1004604805-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6280842709-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6280842709-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6280842709-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="6280842709-3">(</span><span class="p" data-group-id="6280842709-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6280842709-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="6280842709-5">[</span><span class="p" data-group-id="6280842709-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="6280842709-6">}</span><span class="p" data-group-id="6280842709-5">]</span><span class="p" data-group-id="6280842709-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6280842709-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6280842709-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6280842709-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6280842709-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6280842709-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6280842709-9">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6280842709-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6280842709-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6280842709-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6280842709-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6280842709-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="6280842709-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6280842709-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="6280842709-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6280842709-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6280842709-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="6280842709-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6280842709-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6280842709-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="6280842709-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="6280842709-20">]</span><span class="p" data-group-id="6280842709-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% Common events</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="9620714268-1">(</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9620714268-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="9620714268-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9620714268-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="9620714268-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9620714268-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="9620714268-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9620714268-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9620714268-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9620714268-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="9620714268-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="9620714268-7">[</span><span class="p" data-group-id="9620714268-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="9620714268-8">}</span><span class="p" data-group-id="9620714268-7">]</span><span class="p" data-group-id="9620714268-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="6871618563-1">(</span><span class="p" data-group-id="6871618563-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6871618563-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6871618563-3">[</span><span class="p" data-group-id="6871618563-3">]</span><span class="p" data-group-id="6871618563-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="6871618563-4">(</span><span class="p" data-group-id="6871618563-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6871618563-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6871618563-6">[</span><span class="p" data-group-id="6871618563-6">]</span><span class="p" data-group-id="6871618563-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="7303370707-1">(</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7303370707-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7303370707-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7303370707-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="7303370707-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7303370707-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="7303370707-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7303370707-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7303370707-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7303370707-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="7303370707-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="7303370707-7">[</span><span class="p" data-group-id="7303370707-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="7303370707-8">}</span><span class="p" data-group-id="7303370707-7">]</span><span class="p" data-group-id="7303370707-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="0768852560-1">(</span><span class="p" data-group-id="0768852560-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0768852560-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0768852560-3">[</span><span class="p" data-group-id="0768852560-3">]</span><span class="p" data-group-id="0768852560-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="0768852560-4">(</span><span class="p" data-group-id="0768852560-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0768852560-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0768852560-6">[</span><span class="p" data-group-id="0768852560-6">]</span><span class="p" data-group-id="0768852560-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="6871618563-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="6871618563-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="6871618563-8">(</span><span class="p" data-group-id="6871618563-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="0768852560-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0768852560-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="0768852560-8">(</span><span class="p" data-group-id="0768852560-8">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="hibernation" class="section-heading">
│ │ │ │    <a href="#hibernation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Hibernation</span>
│ │ │ │  </h2>
│ │ │ │  <p>If you have many servers in one node and they have some state(s) in their
│ │ │ │ @@ -1333,19 +1333,19 @@
│ │ │ │  footprint of a server can be minimized by hibernating it through
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#hibernate/3"><code class="inline">proc_lib:hibernate/3</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is rather costly to hibernate a process; see <a href="../../../lib/../erts/doc/html/erlang.html#hibernate/3"><code class="inline">erlang:hibernate/3</code></a>. It is
│ │ │ │  not something you want to do after every event.</p></section><p>We can in this example hibernate in the <code class="inline">{open, _}</code> state,
│ │ │ │  because what normally occurs in that state is that the <em>state time-out</em>
│ │ │ │  after a while triggers a transition to <code class="inline">{locked, _}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5609761716-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5609761716-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5609761716-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5609761716-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5609761716-3">(</span><span class="p" data-group-id="5609761716-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5609761716-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="5609761716-5">[</span><span class="p" data-group-id="5609761716-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5609761716-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ -      </span><span class="ss">hibernate</span><span class="p" data-group-id="5609761716-5">]</span><span class="p" data-group-id="5609761716-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="9005672096-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9005672096-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9005672096-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9005672096-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9005672096-3">(</span><span class="p" data-group-id="9005672096-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9005672096-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="9005672096-5">[</span><span class="p" data-group-id="9005672096-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9005672096-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ │ +      </span><span class="ss">hibernate</span><span class="p" data-group-id="9005672096-5">]</span><span class="p" data-group-id="9005672096-4">}</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The atom <a href="../../../lib/stdlib/doc/html/gen_statem.html#t:hibernate/0"><code class="inline">hibernate</code></a> in the action list on the
│ │ │ │  last line when entering the <code class="inline">{open, _}</code> state is the only change. If any event
│ │ │ │  arrives in the <code class="inline">{open, _},</code> state, we do not bother to rehibernate,
│ │ │ │  so the server stays awake after any event.</p><p>To change that we would need to insert action <code class="inline">hibernate</code> in more places.
│ │ │ │  For example, the state-independent <code class="inline">set_lock_button</code> operation
│ │ │ │  would have to use <code class="inline">hibernate</code> but only in the <code class="inline">{open, _}</code> state,
│ │ │ │  which would clutter the code.</p><p>Another not uncommon scenario is to use the
│ │ │ ├── OEBPS/spec_proc.xhtml
│ │ │ │ @@ -28,72 +28,72 @@
│ │ │ │    <a href="#simple-debugging" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simple Debugging</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <a href="../../../lib/stdlib/doc/html/sys.html"><code class="inline">sys</code></a> module has functions for simple debugging of processes implemented
│ │ │ │  using behaviours. The <code class="inline">code_lock</code> example from
│ │ │ │ -<a href="statem.xhtml#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="8694512216-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="8694512216-1">]</span><span class="w"> </span><span class="p" data-group-id="8694512216-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="8694512216-2">]</span><span class="w"> </span><span class="p" data-group-id="8694512216-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8694512216-3">]</span><span class="w"> </span><span class="p" data-group-id="8694512216-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="8694512216-4">]</span><span class="w"> </span><span class="p" data-group-id="8694512216-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8694512216-5">]</span><span class="w"> </span><span class="p" data-group-id="8694512216-6">[</span><span class="ss">jit</span><span class="p" data-group-id="8694512216-6">]</span><span class="w">
│ │ │ │ +<a href="statem.xhtml#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="4300115907-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="4300115907-1">]</span><span class="w"> </span><span class="p" data-group-id="4300115907-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4300115907-2">]</span><span class="w"> </span><span class="p" data-group-id="4300115907-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4300115907-3">]</span><span class="w"> </span><span class="p" data-group-id="4300115907-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4300115907-4">]</span><span class="w"> </span><span class="p" data-group-id="4300115907-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4300115907-5">]</span><span class="w"> </span><span class="p" data-group-id="4300115907-6">[</span><span class="ss">jit</span><span class="p" data-group-id="4300115907-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="8694512216-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="8694512216-8">(</span><span class="p" data-group-id="8694512216-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="8694512216-7">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8694512216-9">(</span><span class="p" data-group-id="8694512216-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8694512216-10">]</span><span class="p" data-group-id="8694512216-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="4300115907-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4300115907-8">(</span><span class="p" data-group-id="4300115907-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4300115907-7">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4300115907-9">(</span><span class="p" data-group-id="4300115907-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4300115907-10">]</span><span class="p" data-group-id="4300115907-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8694512216-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="8694512216-11">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="8694512216-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8694512216-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4300115907-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4300115907-11">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4300115907-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4300115907-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="8694512216-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8694512216-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="4300115907-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4300115907-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="8694512216-14">(</span><span class="mi">1</span><span class="p" data-group-id="8694512216-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8694512216-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4300115907-14">(</span><span class="mi">1</span><span class="p" data-group-id="4300115907-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4300115907-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8694512216-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="8694512216-17">(</span><span class="mi">2</span><span class="p" data-group-id="8694512216-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8694512216-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4300115907-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ +5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4300115907-17">(</span><span class="mi">2</span><span class="p" data-group-id="4300115907-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4300115907-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8694512216-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="8694512216-20">(</span><span class="mi">3</span><span class="p" data-group-id="8694512216-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8694512216-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4300115907-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ +6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4300115907-20">(</span><span class="mi">3</span><span class="p" data-group-id="4300115907-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4300115907-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8694512216-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="8694512216-23">(</span><span class="mi">4</span><span class="p" data-group-id="8694512216-23">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8694512216-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4300115907-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ +7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="4300115907-23">(</span><span class="mi">4</span><span class="p" data-group-id="4300115907-23">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4300115907-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="n">Unlock</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="8694512216-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8694512216-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="8694512216-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="8694512216-27">[</span><span class="p" data-group-id="8694512216-27">]</span><span class="p" data-group-id="8694512216-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="4300115907-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4300115907-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="4300115907-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="4300115907-27">[</span><span class="p" data-group-id="4300115907-27">]</span><span class="p" data-group-id="4300115907-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ │ -8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="8694512216-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="8694512216-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8694512216-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8694512216-30">[</span><span class="p" data-group-id="8694512216-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="8694512216-32">{</span><span class="p" data-group-id="8694512216-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8694512216-33">}</span><span class="p">,</span><span class="p" data-group-id="8694512216-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8694512216-34">}</span><span class="p" data-group-id="8694512216-32">}</span><span class="p" data-group-id="8694512216-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="8694512216-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="8694512216-36">{</span><span class="p" data-group-id="8694512216-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8694512216-37">}</span><span class="p">,</span><span class="p" data-group-id="8694512216-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="8694512216-38">}</span><span class="p" data-group-id="8694512216-36">}</span><span class="p" data-group-id="8694512216-35">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="8694512216-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="8694512216-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="8694512216-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8694512216-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="8694512216-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="8694512216-41">}</span><span class="p" data-group-id="8694512216-30">]</span><span class="p" data-group-id="8694512216-29">}</span><span class="gp unselectable">
│ │ │ │ -9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="8694512216-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="8694512216-42">)</span><span class="p">.</span><span class="w">
│ │ │ │ +8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4300115907-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="4300115907-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4300115907-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="4300115907-30">[</span><span class="p" data-group-id="4300115907-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="4300115907-32">{</span><span class="p" data-group-id="4300115907-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4300115907-33">}</span><span class="p">,</span><span class="p" data-group-id="4300115907-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4300115907-34">}</span><span class="p" data-group-id="4300115907-32">}</span><span class="p" data-group-id="4300115907-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4300115907-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="4300115907-36">{</span><span class="p" data-group-id="4300115907-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4300115907-37">}</span><span class="p">,</span><span class="p" data-group-id="4300115907-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="4300115907-38">}</span><span class="p" data-group-id="4300115907-36">}</span><span class="p" data-group-id="4300115907-35">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4300115907-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="4300115907-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4300115907-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4300115907-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4300115907-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4300115907-41">}</span><span class="p" data-group-id="4300115907-30">]</span><span class="p" data-group-id="4300115907-29">}</span><span class="gp unselectable">
│ │ │ │ +9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4300115907-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4300115907-42">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="8694512216-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="8694512216-43">)</span><span class="p">.</span><span class="w">
│ │ │ │ +10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="4300115907-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4300115907-43">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="8694512216-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="8694512216-44">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8694512216-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8694512216-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="8694512216-46">}</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8694512216-47">[</span><span class="p" data-group-id="8694512216-48">[</span><span class="p" data-group-id="8694512216-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="8694512216-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8694512216-50">}</span><span class="p" data-group-id="8694512216-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="8694512216-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="8694512216-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="8694512216-52">]</span><span class="p" data-group-id="8694512216-51">}</span><span class="p" data-group-id="8694512216-48">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="8694512216-53">[</span><span class="p" data-group-id="8694512216-53">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="8694512216-54">[</span><span class="p" data-group-id="8694512216-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="8694512216-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="8694512216-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="8694512216-57">[</span><span class="p" data-group-id="8694512216-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="8694512216-58">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="8694512216-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="8694512216-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="8694512216-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="8694512216-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="8694512216-61">]</span><span class="p" data-group-id="8694512216-60">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="8694512216-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="8694512216-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="8694512216-64">[</span><span class="p" data-group-id="8694512216-64">]</span><span class="p" data-group-id="8694512216-63">}</span><span class="p" data-group-id="8694512216-62">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="8694512216-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="8694512216-66">[</span><span class="p" data-group-id="8694512216-66">]</span><span class="p" data-group-id="8694512216-65">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                 </span><span class="p" data-group-id="8694512216-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="8694512216-68">[</span><span class="p" data-group-id="8694512216-68">]</span><span class="p" data-group-id="8694512216-67">}</span><span class="p" data-group-id="8694512216-57">]</span><span class="p" data-group-id="8694512216-56">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="8694512216-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="8694512216-70">[</span><span class="p" data-group-id="8694512216-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -                  </span><span class="p" data-group-id="8694512216-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="8694512216-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8694512216-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8694512216-74">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8694512216-75">[</span><span class="p" data-group-id="8694512216-75">]</span><span class="p" data-group-id="8694512216-73">}</span><span class="p" data-group-id="8694512216-72">}</span><span class="p" data-group-id="8694512216-71">}</span><span class="p" data-group-id="8694512216-70">]</span><span class="p" data-group-id="8694512216-69">}</span><span class="p" data-group-id="8694512216-54">]</span><span class="p" data-group-id="8694512216-47">]</span><span class="p" data-group-id="8694512216-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │ │ +11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="4300115907-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="4300115907-44">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4300115907-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4300115907-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="4300115907-46">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4300115907-47">[</span><span class="p" data-group-id="4300115907-48">[</span><span class="p" data-group-id="4300115907-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="4300115907-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4300115907-50">}</span><span class="p" data-group-id="4300115907-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="4300115907-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="4300115907-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4300115907-52">]</span><span class="p" data-group-id="4300115907-51">}</span><span class="p" data-group-id="4300115907-48">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="4300115907-53">[</span><span class="p" data-group-id="4300115907-53">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="4300115907-54">[</span><span class="p" data-group-id="4300115907-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="4300115907-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="4300115907-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="4300115907-57">[</span><span class="p" data-group-id="4300115907-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="4300115907-58">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="4300115907-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="4300115907-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="4300115907-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="4300115907-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="4300115907-61">]</span><span class="p" data-group-id="4300115907-60">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="4300115907-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="4300115907-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="4300115907-64">[</span><span class="p" data-group-id="4300115907-64">]</span><span class="p" data-group-id="4300115907-63">}</span><span class="p" data-group-id="4300115907-62">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="4300115907-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="4300115907-66">[</span><span class="p" data-group-id="4300115907-66">]</span><span class="p" data-group-id="4300115907-65">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                 </span><span class="p" data-group-id="4300115907-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="4300115907-68">[</span><span class="p" data-group-id="4300115907-68">]</span><span class="p" data-group-id="4300115907-67">}</span><span class="p" data-group-id="4300115907-57">]</span><span class="p" data-group-id="4300115907-56">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="4300115907-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="4300115907-70">[</span><span class="p" data-group-id="4300115907-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +                  </span><span class="p" data-group-id="4300115907-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="4300115907-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4300115907-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4300115907-74">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4300115907-75">[</span><span class="p" data-group-id="4300115907-75">]</span><span class="p" data-group-id="4300115907-73">}</span><span class="p" data-group-id="4300115907-72">}</span><span class="p" data-group-id="4300115907-71">}</span><span class="p" data-group-id="4300115907-70">]</span><span class="p" data-group-id="4300115907-69">}</span><span class="p" data-group-id="4300115907-54">]</span><span class="p" data-group-id="4300115907-47">]</span><span class="p" data-group-id="4300115907-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │ │    <a href="#special-processes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Special Processes</span>
│ │ │ │  </h2>
│ │ │ │  <p>This section describes how to write a process that complies to the OTP design
│ │ │ │  principles, without using a standard behaviour. Such a process is to:</p><ul><li>Be started in a way that makes the process fit into a supervision tree</li><li>Support the <code class="inline">sys</code> <a href="spec_proc.xhtml#debug">debug facilities</a></li><li>Take care of <a href="spec_proc.xhtml#msg">system messages</a>.</li></ul><p>System messages are messages with a special meaning, used in the supervision
│ │ │ │ @@ -103,238 +103,238 @@
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h3>
│ │ │ │  <p>Here follows the simple server from
│ │ │ │  <a href="design_principles.xhtml#ch1">Overview</a>,
│ │ │ │ -implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4939520013-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="4939520013-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4939520013-2">(</span><span class="p" data-group-id="4939520013-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4939520013-3">]</span><span class="p" data-group-id="4939520013-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4939520013-4">(</span><span class="p" data-group-id="4939520013-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4939520013-5">]</span><span class="p" data-group-id="4939520013-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4939520013-6">(</span><span class="p" data-group-id="4939520013-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4939520013-7">]</span><span class="p" data-group-id="4939520013-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4939520013-8">(</span><span class="p" data-group-id="4939520013-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │ │ +implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1485884472-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="1485884472-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1485884472-2">(</span><span class="p" data-group-id="1485884472-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1485884472-3">]</span><span class="p" data-group-id="1485884472-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1485884472-4">(</span><span class="p" data-group-id="1485884472-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1485884472-5">]</span><span class="p" data-group-id="1485884472-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1485884472-6">(</span><span class="p" data-group-id="1485884472-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1485884472-7">]</span><span class="p" data-group-id="1485884472-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1485884472-8">(</span><span class="p" data-group-id="1485884472-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │ │           </span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4939520013-9">]</span><span class="p" data-group-id="4939520013-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1485884472-9">]</span><span class="p" data-group-id="1485884472-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="4939520013-10">(</span><span class="p" data-group-id="4939520013-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4939520013-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-12">[</span><span class="nf">self</span><span class="p" data-group-id="4939520013-13">(</span><span class="p" data-group-id="4939520013-13">)</span><span class="p" data-group-id="4939520013-12">]</span><span class="p" data-group-id="4939520013-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1485884472-10">(</span><span class="p" data-group-id="1485884472-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1485884472-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-12">[</span><span class="nf">self</span><span class="p" data-group-id="1485884472-13">(</span><span class="p" data-group-id="1485884472-13">)</span><span class="p" data-group-id="1485884472-12">]</span><span class="p" data-group-id="1485884472-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="4939520013-14">(</span><span class="p" data-group-id="4939520013-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4939520013-15">{</span><span class="nf">self</span><span class="p" data-group-id="4939520013-16">(</span><span class="p" data-group-id="4939520013-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="4939520013-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="1485884472-14">(</span><span class="p" data-group-id="1485884472-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1485884472-15">{</span><span class="nf">self</span><span class="p" data-group-id="1485884472-16">(</span><span class="p" data-group-id="1485884472-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1485884472-15">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4939520013-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="4939520013-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1485884472-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="1485884472-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Res</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="4939520013-18">(</span><span class="n">Ch</span><span class="p" data-group-id="4939520013-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4939520013-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4939520013-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="1485884472-18">(</span><span class="n">Ch</span><span class="p" data-group-id="1485884472-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1485884472-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1485884472-19">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4939520013-20">(</span><span class="n">Parent</span><span class="p" data-group-id="4939520013-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4939520013-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4939520013-22">(</span><span class="p" data-group-id="4939520013-22">)</span><span class="p" data-group-id="4939520013-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="4939520013-23">(</span><span class="p" data-group-id="4939520013-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="4939520013-24">(</span><span class="p" data-group-id="4939520013-25">[</span><span class="p" data-group-id="4939520013-25">]</span><span class="p" data-group-id="4939520013-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="4939520013-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4939520013-28">(</span><span class="p" data-group-id="4939520013-28">)</span><span class="p" data-group-id="4939520013-27">}</span><span class="p" data-group-id="4939520013-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4939520013-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4939520013-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1485884472-20">(</span><span class="n">Parent</span><span class="p" data-group-id="1485884472-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="1485884472-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1485884472-22">(</span><span class="p" data-group-id="1485884472-22">)</span><span class="p" data-group-id="1485884472-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1485884472-23">(</span><span class="p" data-group-id="1485884472-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="1485884472-24">(</span><span class="p" data-group-id="1485884472-25">[</span><span class="p" data-group-id="1485884472-25">]</span><span class="p" data-group-id="1485884472-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="1485884472-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1485884472-28">(</span><span class="p" data-group-id="1485884472-28">)</span><span class="p" data-group-id="1485884472-27">}</span><span class="p" data-group-id="1485884472-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1485884472-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1485884472-29">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4939520013-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4939520013-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="1485884472-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1485884472-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4939520013-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="4939520013-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="4939520013-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="4939520013-33">}</span><span class="p" data-group-id="4939520013-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="4939520013-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4939520013-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="4939520013-35">(</span><span class="n">Chs</span><span class="p" data-group-id="4939520013-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4939520013-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4939520013-36">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="4939520013-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4939520013-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="4939520013-38">}</span><span class="p" data-group-id="4939520013-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="4939520013-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="4939520013-40">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4939520013-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4939520013-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="4939520013-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4939520013-44">}</span><span class="p" data-group-id="4939520013-43">}</span><span class="p" data-group-id="4939520013-42">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="4939520013-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4939520013-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="4939520013-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="4939520013-46">)</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -        </span><span class="p" data-group-id="4939520013-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="4939520013-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="4939520013-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4939520013-48">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1485884472-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1485884472-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1485884472-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="1485884472-33">}</span><span class="p" data-group-id="1485884472-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1485884472-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1485884472-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="1485884472-35">(</span><span class="n">Chs</span><span class="p" data-group-id="1485884472-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1485884472-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1485884472-36">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1485884472-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1485884472-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="1485884472-38">}</span><span class="p" data-group-id="1485884472-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="1485884472-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="1485884472-40">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1485884472-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1485884472-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1485884472-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1485884472-44">}</span><span class="p" data-group-id="1485884472-43">}</span><span class="p" data-group-id="1485884472-42">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="1485884472-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1485884472-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="1485884472-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="1485884472-46">)</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +        </span><span class="p" data-group-id="1485884472-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1485884472-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="1485884472-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1485884472-48">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="4939520013-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4939520013-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4939520013-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="4939520013-50">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="1485884472-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1485884472-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1485884472-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="1485884472-50">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="4939520013-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="4939520013-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="4939520013-52">(</span><span class="n">Reason</span><span class="p" data-group-id="4939520013-52">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="1485884472-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="1485884472-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="1485884472-52">(</span><span class="n">Reason</span><span class="p" data-group-id="1485884472-52">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="4939520013-53">(</span><span class="n">Chs</span><span class="p" data-group-id="4939520013-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4939520013-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4939520013-54">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="1485884472-53">(</span><span class="n">Chs</span><span class="p" data-group-id="1485884472-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1485884472-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1485884472-54">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="4939520013-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4939520013-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="4939520013-56">(</span><span class="n">Chs</span><span class="p" data-group-id="4939520013-56">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4939520013-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="4939520013-57">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="1485884472-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1485884472-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="1485884472-56">(</span><span class="n">Chs</span><span class="p" data-group-id="1485884472-56">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1485884472-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="1485884472-57">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="4939520013-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4939520013-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4939520013-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4939520013-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="4939520013-60">]</span><span class="p" data-group-id="4939520013-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="1485884472-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1485884472-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1485884472-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1485884472-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="1485884472-60">]</span><span class="p" data-group-id="1485884472-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │ │  omitted. To compile this example, the
│ │ │ │  <a href="design_principles.xhtml#channels-implementation">implementation of channel handling</a>
│ │ │ │  needs to be added to the module.</p><p>Here is an example showing how the debugging functions in the <code class="inline">sys</code>
│ │ │ │  module can be used for <code class="inline">ch4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="0982776229-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="0982776229-1">]</span><span class="w"> </span><span class="p" data-group-id="0982776229-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0982776229-2">]</span><span class="w"> </span><span class="p" data-group-id="0982776229-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0982776229-3">]</span><span class="w"> </span><span class="p" data-group-id="0982776229-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0982776229-4">]</span><span class="w"> </span><span class="p" data-group-id="0982776229-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0982776229-5">]</span><span class="w"> </span><span class="p" data-group-id="0982776229-6">[</span><span class="ss">jit</span><span class="p" data-group-id="0982776229-6">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="5582702456-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="5582702456-1">]</span><span class="w"> </span><span class="p" data-group-id="5582702456-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="5582702456-2">]</span><span class="w"> </span><span class="p" data-group-id="5582702456-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="5582702456-3">]</span><span class="w"> </span><span class="p" data-group-id="5582702456-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="5582702456-4">]</span><span class="w"> </span><span class="p" data-group-id="5582702456-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5582702456-5">]</span><span class="w"> </span><span class="p" data-group-id="5582702456-6">[</span><span class="ss">jit</span><span class="p" data-group-id="5582702456-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="0982776229-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="0982776229-8">(</span><span class="p" data-group-id="0982776229-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="0982776229-7">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0982776229-9">(</span><span class="p" data-group-id="0982776229-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0982776229-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0982776229-10">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0982776229-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0982776229-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="5582702456-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="5582702456-8">(</span><span class="p" data-group-id="5582702456-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="5582702456-7">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5582702456-9">(</span><span class="p" data-group-id="5582702456-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5582702456-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5582702456-10">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="5582702456-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5582702456-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0982776229-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0982776229-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="5582702456-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5582702456-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="0982776229-13">(</span><span class="p" data-group-id="0982776229-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0982776229-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0982776229-14">}</span><span class="w">
│ │ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0982776229-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="0982776229-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0982776229-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0982776229-15">}</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="5582702456-13">(</span><span class="p" data-group-id="5582702456-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5582702456-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5582702456-14">}</span><span class="w">
│ │ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5582702456-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="5582702456-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5582702456-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5582702456-15">}</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="0982776229-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="0982776229-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0982776229-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="0982776229-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="0982776229-19">}</span><span class="p" data-group-id="0982776229-18">}</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="5582702456-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="5582702456-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5582702456-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="5582702456-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="5582702456-19">}</span><span class="p" data-group-id="5582702456-18">}</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0982776229-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="0982776229-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0982776229-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0982776229-22">[</span><span class="p" data-group-id="0982776229-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="0982776229-24">{</span><span class="p" data-group-id="0982776229-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0982776229-25">}</span><span class="p">,</span><span class="p" data-group-id="0982776229-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="0982776229-26">}</span><span class="p" data-group-id="0982776229-24">}</span><span class="p" data-group-id="0982776229-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="0982776229-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="0982776229-28">{</span><span class="p" data-group-id="0982776229-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0982776229-29">}</span><span class="p">,</span><span class="p" data-group-id="0982776229-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="0982776229-30">}</span><span class="p" data-group-id="0982776229-28">}</span><span class="p" data-group-id="0982776229-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="0982776229-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="0982776229-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="0982776229-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0982776229-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="0982776229-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0982776229-33">}</span><span class="p" data-group-id="0982776229-22">]</span><span class="p" data-group-id="0982776229-21">}</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="0982776229-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="0982776229-34">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="5582702456-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="5582702456-20">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5582702456-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="5582702456-22">[</span><span class="p" data-group-id="5582702456-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="5582702456-24">{</span><span class="p" data-group-id="5582702456-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5582702456-25">}</span><span class="p">,</span><span class="p" data-group-id="5582702456-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="5582702456-26">}</span><span class="p" data-group-id="5582702456-24">}</span><span class="p" data-group-id="5582702456-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="5582702456-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="5582702456-28">{</span><span class="p" data-group-id="5582702456-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5582702456-29">}</span><span class="p">,</span><span class="p" data-group-id="5582702456-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="5582702456-30">}</span><span class="p" data-group-id="5582702456-28">}</span><span class="p" data-group-id="5582702456-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="5582702456-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="5582702456-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="5582702456-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5582702456-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="5582702456-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5582702456-33">}</span><span class="p" data-group-id="5582702456-22">]</span><span class="p" data-group-id="5582702456-21">}</span><span class="gp unselectable">
│ │ │ │ +7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="5582702456-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5582702456-34">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0982776229-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="0982776229-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ +8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="5582702456-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5582702456-35">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="0982776229-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="0982776229-36">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0982776229-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0982776229-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="0982776229-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0982776229-39">[</span><span class="p" data-group-id="0982776229-40">[</span><span class="p" data-group-id="0982776229-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="0982776229-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0982776229-42">}</span><span class="p" data-group-id="0982776229-41">}</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="0982776229-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="0982776229-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0982776229-44">]</span><span class="p" data-group-id="0982776229-43">}</span><span class="p" data-group-id="0982776229-40">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="0982776229-45">[</span><span class="p" data-group-id="0982776229-45">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="0982776229-46">{</span><span class="p" data-group-id="0982776229-47">[</span><span class="mi">1</span><span class="p" data-group-id="0982776229-47">]</span><span class="p">,</span><span class="p" data-group-id="0982776229-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0982776229-48">]</span><span class="p" data-group-id="0982776229-46">}</span><span class="p" data-group-id="0982776229-39">]</span><span class="p" data-group-id="0982776229-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │ │ +9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="5582702456-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="5582702456-36">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5582702456-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5582702456-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="5582702456-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5582702456-39">[</span><span class="p" data-group-id="5582702456-40">[</span><span class="p" data-group-id="5582702456-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="5582702456-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5582702456-42">}</span><span class="p" data-group-id="5582702456-41">}</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="5582702456-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="5582702456-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5582702456-44">]</span><span class="p" data-group-id="5582702456-43">}</span><span class="p" data-group-id="5582702456-40">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="5582702456-45">[</span><span class="p" data-group-id="5582702456-45">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="5582702456-46">{</span><span class="p" data-group-id="5582702456-47">[</span><span class="mi">1</span><span class="p" data-group-id="5582702456-47">]</span><span class="p">,</span><span class="p" data-group-id="5582702456-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5582702456-48">]</span><span class="p" data-group-id="5582702456-46">}</span><span class="p" data-group-id="5582702456-39">]</span><span class="p" data-group-id="5582702456-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │ │    <a href="#starting-the-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting the Process</span>
│ │ │ │  </h3>
│ │ │ │  <p>A function in the <a href="../../../lib/stdlib/doc/html/proc_lib.html"><code class="inline">proc_lib</code></a> module is to be used to start the process. Several
│ │ │ │  functions are available, for example,
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#spawn_link/4"><code class="inline">proc_lib:spawn_link/3,4</code></a>
│ │ │ │  for asynchronous start and
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/5"><code class="inline">proc_lib:start_link/3,4,5</code></a> for synchronous start.</p><p>Information necessary for a process within a supervision tree, such as
│ │ │ │  details on ancestors and the initial call, is stored when a process
│ │ │ │  is started through one of these functions.</p><p>If the process terminates with a reason other than <code class="inline">normal</code> or <code class="inline">shutdown</code>, a
│ │ │ │  crash report is generated. For more information about the crash report, see
│ │ │ │  <a href="../../../lib/kernel/doc/html/logger_chapter.xhtml">Logging</a> in Kernel User's Guide.</p><p>In the example, synchronous start is used. The process starts by calling
│ │ │ │ -<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="2611970417-1">(</span><span class="p" data-group-id="2611970417-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2611970417-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2611970417-3">[</span><span class="nf">self</span><span class="p" data-group-id="2611970417-4">(</span><span class="p" data-group-id="2611970417-4">)</span><span class="p" data-group-id="2611970417-3">]</span><span class="p" data-group-id="2611970417-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │ │ +<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="9308637067-1">(</span><span class="p" data-group-id="9308637067-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9308637067-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9308637067-3">[</span><span class="nf">self</span><span class="p" data-group-id="9308637067-4">(</span><span class="p" data-group-id="9308637067-4">)</span><span class="p" data-group-id="9308637067-3">]</span><span class="p" data-group-id="9308637067-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │ │  name, a function name, and an argument list as arguments. It then
│ │ │ │  spawns a new process and establishes a link. The new process starts
│ │ │ │  by executing the given function, here <code class="inline">ch4:init(Pid)</code>, where <code class="inline">Pid</code> is
│ │ │ │  the pid of the parent process (obtained by the call to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self()</code></a> in the call to <a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>).</p><p>All initialization, including name registration, is done in <code class="inline">init/1</code>. The new
│ │ │ │ -process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3276365553-1">(</span><span class="n">Parent</span><span class="p" data-group-id="3276365553-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6980072782-1">(</span><span class="n">Parent</span><span class="p" data-group-id="6980072782-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="3276365553-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3276365553-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3276365553-4">(</span><span class="p" data-group-id="3276365553-4">)</span><span class="p" data-group-id="3276365553-3">}</span><span class="p" data-group-id="3276365553-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3276365553-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3276365553-5">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="6980072782-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6980072782-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6980072782-4">(</span><span class="p" data-group-id="6980072782-4">)</span><span class="p" data-group-id="6980072782-3">}</span><span class="p" data-group-id="6980072782-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6980072782-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6980072782-5">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#init_ack/2"><code class="inline">proc_lib:init_ack/1,2</code></a> or
│ │ │ │  <a href="../../../lib/stdlib/doc/html/proc_lib.html#init_fail/3"><code class="inline">proc_lib:init_fail/2,3</code></a> has been called,
│ │ │ │  or the process has exited.</p><p><a href="" id="debug"></a></p><h3 id="debugging" class="section-heading">
│ │ │ │    <a href="#debugging" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Debugging</span>
│ │ │ │  </h3>
│ │ │ │  <p>To support the debug facilities in <code class="inline">sys</code>, a <em>debug structure</em> is needed. The
│ │ │ │ -<code class="inline">Deb</code> term is initialized using <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8839398491-1">(</span><span class="n">Parent</span><span class="p" data-group-id="8839398491-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<code class="inline">Deb</code> term is initialized using <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2071088227-1">(</span><span class="n">Parent</span><span class="p" data-group-id="2071088227-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="8839398491-2">(</span><span class="p" data-group-id="8839398491-3">[</span><span class="p" data-group-id="8839398491-3">]</span><span class="p" data-group-id="8839398491-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="2071088227-2">(</span><span class="p" data-group-id="2071088227-3">[</span><span class="p" data-group-id="2071088227-3">]</span><span class="p" data-group-id="2071088227-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8839398491-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="8839398491-4">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2071088227-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="2071088227-4">)</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │ │  example means that debugging is initially disabled. For information about the
│ │ │ │  possible options, see <a href="../../../lib/stdlib/doc/html/sys.html"><code class="inline">sys</code></a> in STDLIB.</p><p>For each <em>system event</em> to be logged or traced, the following function
│ │ │ │ -is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="0237090972-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="0237090972-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the follow meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │ │ +is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1763254561-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="1763254561-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the follow meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../../lib/stdlib/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │ │  output. For each system event, the format function is called as
│ │ │ │  <code class="inline">Func(Dev, Event, Info)</code>, where:<ul><li><code class="inline">Dev</code> is the I/O device to which the output is to be printed. See <a href="../../../lib/stdlib/doc/html/io.html"><code class="inline">io</code></a>
│ │ │ │  in STDLIB.</li><li><code class="inline">Event</code> and <code class="inline">Info</code> are passed as-is from the call to <a href="../../../lib/stdlib/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a>.</li></ul></li><li><code class="inline">Info</code> is used to pass more information to <code class="inline">Func</code>. It can be any term, and it
│ │ │ │  is passed as-is.</li><li><code class="inline">Event</code> is the system event. It is up to the user to define what a system
│ │ │ │  event is and how it is to be represented. Typically, at least incoming and
│ │ │ │  outgoing messages are considered system events and represented by the tuples
│ │ │ │  <code class="inline">{in,Msg[,From]}</code> and <code class="inline">{out,Msg,To[,State]}</code>, respectively.</li></ul><p><a href="../../../lib/stdlib/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> returns an updated debug structure <code class="inline">Deb1</code>.</p><p>In the example, <a href="../../../lib/stdlib/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> is called for each incoming and
│ │ │ │  outgoing message. The format function <code class="inline">Func</code> is the function
│ │ │ │ -<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../../lib/stdlib/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="9216041581-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="9216041581-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../../lib/stdlib/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2648405100-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="2648405100-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9216041581-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9216041581-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="9216041581-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9216041581-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="9216041581-4">}</span><span class="p" data-group-id="9216041581-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9216041581-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9216041581-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9216041581-6">(</span><span class="n">Chs</span><span class="p" data-group-id="9216041581-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9216041581-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9216041581-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="9216041581-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9216041581-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9216041581-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9216041581-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="9216041581-9">}</span><span class="p" data-group-id="9216041581-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9216041581-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="9216041581-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9216041581-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9216041581-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="9216041581-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9216041581-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9216041581-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9216041581-15">}</span><span class="p" data-group-id="9216041581-14">}</span><span class="p" data-group-id="9216041581-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9216041581-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9216041581-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9216041581-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="9216041581-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2648405100-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2648405100-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="2648405100-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2648405100-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="2648405100-4">}</span><span class="p" data-group-id="2648405100-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2648405100-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2648405100-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="2648405100-6">(</span><span class="n">Chs</span><span class="p" data-group-id="2648405100-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2648405100-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2648405100-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="2648405100-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2648405100-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2648405100-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2648405100-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="2648405100-9">}</span><span class="p" data-group-id="2648405100-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2648405100-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="2648405100-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2648405100-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2648405100-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="2648405100-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2648405100-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2648405100-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2648405100-15">}</span><span class="p" data-group-id="2648405100-14">}</span><span class="p" data-group-id="2648405100-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2648405100-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2648405100-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2648405100-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="2648405100-17">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="9216041581-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9216041581-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9216041581-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9216041581-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="9216041581-20">]</span><span class="p" data-group-id="9216041581-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="2648405100-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2648405100-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2648405100-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2648405100-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="2648405100-20">]</span><span class="p" data-group-id="2648405100-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │ │    <a href="#handling-system-messages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling System Messages</span>
│ │ │ │  </h3>
│ │ │ │  <p><em>System messages</em> are received as:</p><pre><code class="text">{system, From, Request}</code></pre><p>The content and meaning of these messages are not to be interpreted by the
│ │ │ │ -process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="7984931935-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7984931935-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │ │ +process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="9296646746-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9296646746-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │ │  passed as-is to the call to <a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a>.</li><li><code class="inline">Parent</code> is the pid of the parent process.</li><li><code class="inline">Module</code> is the name of the module implementing the speciall process.</li><li><code class="inline">Deb</code> is the debug structure.</li><li><code class="inline">State</code> is a term describing the internal state and is passed on to
│ │ │ │  <code class="inline">Module:system_continue/3</code>, <code class="inline">Module:system_terminate/4</code>/
│ │ │ │  <code class="inline">Module:system_get_state/1</code>, and <code class="inline">Module:system_replace_state/2</code>.</li></ul><p><a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> does not return. It handles the system
│ │ │ │  message and <em>eventually</em> calls either of the following functions:</p><ul><li><p><code class="inline">Module:system_continue(Parent, Deb, State)</code> - if process execution is to
│ │ │ │  continue.</p></li><li><p><code class="inline">Module:system_terminate(Reason, Parent, Deb, State)</code> - if the
│ │ │ │  process is to terminate.</p></li></ul><p>While handling the system message, <a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> can call
│ │ │ │  one of the following functions:</p><ul><li><p><code class="inline">Module:system_get_state(State)</code> - if the process is to return its state.</p></li><li><p><code class="inline">Module:system_replace_state(StateFun, State)</code> - if the process is
│ │ │ │  to replace its state using the fun <code class="inline">StateFun</code> fun. See <a href="../../../lib/stdlib/doc/html/sys.html#replace_state/3"><code class="inline">sys:replace_state/3</code></a>
│ │ │ │  for more information.</p></li><li><p><code class="inline">system_code_change(Misc, Module, OldVsn, Extra)</code> - if the process is to
│ │ │ │  perform a code change.</p></li></ul><p>A process in a supervision tree is expected to terminate with the same reason as
│ │ │ │ -its parent.</p><p>In the example, system messages are handed by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3557584843-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3557584843-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +its parent.</p><p>In the example, system messages are handed by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="6753746952-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6753746952-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -        </span><span class="p" data-group-id="3557584843-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3557584843-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="3557584843-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3557584843-3">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6753746952-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="6753746952-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="6753746952-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6753746952-3">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="3557584843-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3557584843-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3557584843-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3557584843-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="6753746952-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6753746952-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6753746952-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="6753746952-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="3557584843-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3557584843-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="3557584843-7">(</span><span class="n">Reason</span><span class="p" data-group-id="3557584843-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="6753746952-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6753746952-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="6753746952-7">(</span><span class="n">Reason</span><span class="p" data-group-id="6753746952-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="3557584843-8">(</span><span class="n">Chs</span><span class="p" data-group-id="3557584843-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3557584843-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3557584843-9">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="6753746952-8">(</span><span class="n">Chs</span><span class="p" data-group-id="6753746952-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6753746952-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6753746952-9">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="3557584843-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3557584843-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="3557584843-11">(</span><span class="n">Chs</span><span class="p" data-group-id="3557584843-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3557584843-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="3557584843-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="6753746952-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="6753746952-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="6753746952-11">(</span><span class="n">Chs</span><span class="p" data-group-id="6753746952-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6753746952-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="6753746952-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │ │  of 'EXIT' messages from its parent process and terminate using the
│ │ │ │ -same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2374896930-1">(</span><span class="n">Parent</span><span class="p" data-group-id="2374896930-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2964430898-1">(</span><span class="n">Parent</span><span class="p" data-group-id="2964430898-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="2374896930-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2374896930-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="2964430898-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2964430898-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="2374896930-3">(</span><span class="n">Parent</span><span class="p" data-group-id="2374896930-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2964430898-3">(</span><span class="n">Parent</span><span class="p" data-group-id="2964430898-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="2374896930-4">(</span><span class="n">Parent</span><span class="p" data-group-id="2374896930-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="2964430898-4">(</span><span class="n">Parent</span><span class="p" data-group-id="2964430898-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2374896930-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2374896930-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2964430898-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2964430898-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="c1">%% Clean up here, if needed.</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="2374896930-6">(</span><span class="n">Reason</span><span class="p" data-group-id="2374896930-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="2964430898-6">(</span><span class="n">Reason</span><span class="p" data-group-id="2964430898-6">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="user-defined-behaviours" class="section-heading">
│ │ │ │    <a href="#user-defined-behaviours" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">User-Defined Behaviours</span>
│ │ │ │  </h2>
│ │ │ │ @@ -353,69 +353,69 @@
│ │ │ │  function. Note that the <code class="inline">-optional_callbacks</code> attribute is to be used together
│ │ │ │  with the <code class="inline">-callback</code> attribute; it cannot be combined with the
│ │ │ │  <code class="inline">behaviour_info()</code> function described below.</p><p>Tools that need to know about optional callback functions can call
│ │ │ │  <code class="inline">Behaviour:behaviour_info(optional_callbacks)</code> to get a list of all optional
│ │ │ │  callback functions.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>We recommend using the <code class="inline">-callback</code> attribute rather than the
│ │ │ │  <code class="inline">behaviour_info()</code> function. The reason is that the extra type information can
│ │ │ │  be used by tools to produce documentation or find discrepancies.</p></section><p>As an alternative to the <code class="inline">-callback</code> and <code class="inline">-optional_callbacks</code> attributes you
│ │ │ │ -may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="7642313462-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="7642313462-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7642313462-2">[</span><span class="p" data-group-id="7642313462-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="7642313462-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="7642313462-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="7642313462-4">}</span><span class="p" data-group-id="7642313462-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │ │ +may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="8448992710-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="8448992710-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8448992710-2">[</span><span class="p" data-group-id="8448992710-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="8448992710-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="8448992710-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="8448992710-4">}</span><span class="p" data-group-id="8448992710-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │ │  This function is otherwise automatically generated by the compiler using the
│ │ │ │  <code class="inline">-callback</code> attributes.</p><p>When the compiler encounters the module attribute <code class="inline">-behaviour(Behaviour).</code> in a
│ │ │ │  module <code class="inline">Mod</code>, it calls <code class="inline">Behaviour:behaviour_info(callbacks)</code> and compares the
│ │ │ │  result with the set of functions actually exported from <code class="inline">Mod</code>, and issues a
│ │ │ │  warning if any callback function is missing.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% User-defined behaviour module</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1593723672-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="1593723672-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1593723672-2">(</span><span class="p" data-group-id="1593723672-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1593723672-3">]</span><span class="p" data-group-id="1593723672-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4907278316-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="4907278316-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4907278316-2">(</span><span class="p" data-group-id="4907278316-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4907278316-3">]</span><span class="p" data-group-id="4907278316-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="1593723672-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1593723672-5">(</span><span class="p" data-group-id="1593723672-5">)</span><span class="p" data-group-id="1593723672-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="1593723672-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1593723672-7">(</span><span class="p" data-group-id="1593723672-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1593723672-8">(</span><span class="p" data-group-id="1593723672-8">)</span><span class="p" data-group-id="1593723672-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1593723672-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1593723672-10">(</span><span class="p" data-group-id="1593723672-10">)</span><span class="p" data-group-id="1593723672-9">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="1593723672-11">(</span><span class="p" data-group-id="1593723672-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="1593723672-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1593723672-13">(</span><span class="p" data-group-id="1593723672-13">)</span><span class="p" data-group-id="1593723672-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1593723672-14">(</span><span class="p" data-group-id="1593723672-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="4907278316-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4907278316-5">(</span><span class="p" data-group-id="4907278316-5">)</span><span class="p" data-group-id="4907278316-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="4907278316-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4907278316-7">(</span><span class="p" data-group-id="4907278316-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4907278316-8">(</span><span class="p" data-group-id="4907278316-8">)</span><span class="p" data-group-id="4907278316-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4907278316-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4907278316-10">(</span><span class="p" data-group-id="4907278316-10">)</span><span class="p" data-group-id="4907278316-9">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="4907278316-11">(</span><span class="p" data-group-id="4907278316-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="4907278316-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4907278316-13">(</span><span class="p" data-group-id="4907278316-13">)</span><span class="p" data-group-id="4907278316-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4907278316-14">(</span><span class="p" data-group-id="4907278316-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="1593723672-15">(</span><span class="p" data-group-id="1593723672-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1593723672-16">]</span><span class="p" data-group-id="1593723672-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="4907278316-15">(</span><span class="p" data-group-id="4907278316-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4907278316-16">]</span><span class="p" data-group-id="4907278316-15">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Alternatively you may define:</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │  </span><span class="c1">%% -export([behaviour_info/1]).</span><span class="w">
│ │ │ │  </span><span class="c1">%% behaviour_info(callbacks) -&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%%     [{init,1},</span><span class="w">
│ │ │ │  </span><span class="c1">%%      {handle_req,2},</span><span class="w">
│ │ │ │  </span><span class="c1">%%      {terminate,0}].</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="1593723672-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1593723672-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1593723672-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1593723672-19">[</span><span class="nf">self</span><span class="p" data-group-id="1593723672-20">(</span><span class="p" data-group-id="1593723672-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1593723672-19">]</span><span class="p" data-group-id="1593723672-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="4907278316-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="4907278316-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4907278316-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4907278316-19">[</span><span class="nf">self</span><span class="p" data-group-id="4907278316-20">(</span><span class="p" data-group-id="4907278316-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="4907278316-19">]</span><span class="p" data-group-id="4907278316-18">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1593723672-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1593723672-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1593723672-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1593723672-23">(</span><span class="p" data-group-id="1593723672-23">)</span><span class="p" data-group-id="1593723672-22">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4907278316-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="4907278316-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4907278316-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4907278316-23">(</span><span class="p" data-group-id="4907278316-23">)</span><span class="p" data-group-id="4907278316-22">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="1593723672-24">(</span><span class="p" data-group-id="1593723672-25">[</span><span class="p" data-group-id="1593723672-25">]</span><span class="p" data-group-id="1593723672-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="1593723672-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1593723672-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1593723672-28">(</span><span class="p" data-group-id="1593723672-28">)</span><span class="p" data-group-id="1593723672-27">}</span><span class="p" data-group-id="1593723672-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="1593723672-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1593723672-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="4907278316-24">(</span><span class="p" data-group-id="4907278316-25">[</span><span class="p" data-group-id="4907278316-25">]</span><span class="p" data-group-id="4907278316-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="4907278316-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4907278316-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4907278316-28">(</span><span class="p" data-group-id="4907278316-28">)</span><span class="p" data-group-id="4907278316-27">}</span><span class="p" data-group-id="4907278316-26">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4907278316-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4907278316-29">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9286475772-1">(</span><span class="ss">db</span><span class="p" data-group-id="9286475772-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9286475772-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="9286475772-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8084409456-1">(</span><span class="ss">db</span><span class="p" data-group-id="8084409456-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8084409456-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="8084409456-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9286475772-3">(</span><span class="p" data-group-id="9286475772-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9286475772-4">]</span><span class="p" data-group-id="9286475772-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8084409456-3">(</span><span class="p" data-group-id="8084409456-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8084409456-4">]</span><span class="p" data-group-id="8084409456-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The contracts specified with <code class="inline">-callback</code> attributes in behaviour modules can be
│ │ │ │  further refined by adding <code class="inline">-spec</code> attributes in callback modules. This can be
│ │ │ │  useful as <code class="inline">-callback</code> contracts are usually generic. The same callback module
│ │ │ │ -with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3864064699-1">(</span><span class="ss">db</span><span class="p" data-group-id="3864064699-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3864064699-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="3864064699-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5911143099-1">(</span><span class="ss">db</span><span class="p" data-group-id="5911143099-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="5911143099-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="5911143099-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3864064699-3">(</span><span class="p" data-group-id="3864064699-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3864064699-4">]</span><span class="p" data-group-id="3864064699-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5911143099-3">(</span><span class="p" data-group-id="5911143099-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5911143099-4">]</span><span class="p" data-group-id="5911143099-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3864064699-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3864064699-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3864064699-7">[</span><span class="nf">atom</span><span class="p" data-group-id="3864064699-8">(</span><span class="p" data-group-id="3864064699-8">)</span><span class="p" data-group-id="3864064699-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3864064699-9">(</span><span class="p" data-group-id="3864064699-9">)</span><span class="p" data-group-id="3864064699-6">}</span><span class="p" data-group-id="3864064699-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5911143099-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5911143099-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5911143099-7">[</span><span class="nf">atom</span><span class="p" data-group-id="5911143099-8">(</span><span class="p" data-group-id="5911143099-8">)</span><span class="p" data-group-id="5911143099-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5911143099-9">(</span><span class="p" data-group-id="5911143099-9">)</span><span class="p" data-group-id="5911143099-6">}</span><span class="p" data-group-id="5911143099-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="3864064699-10">(</span><span class="p" data-group-id="3864064699-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="3864064699-11">{</span><span class="p" data-group-id="3864064699-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="3864064699-12">(</span><span class="p" data-group-id="3864064699-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3864064699-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3864064699-14">(</span><span class="p" data-group-id="3864064699-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3864064699-15">(</span><span class="p" data-group-id="3864064699-15">)</span><span class="p" data-group-id="3864064699-13">}</span><span class="p">;</span><span class="w">
│ │ │ │ -                   </span><span class="p" data-group-id="3864064699-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3864064699-17">(</span><span class="p" data-group-id="3864064699-17">)</span><span class="p" data-group-id="3864064699-16">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="5911143099-10">(</span><span class="p" data-group-id="5911143099-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="5911143099-11">{</span><span class="p" data-group-id="5911143099-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="5911143099-12">(</span><span class="p" data-group-id="5911143099-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="5911143099-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5911143099-14">(</span><span class="p" data-group-id="5911143099-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5911143099-15">(</span><span class="p" data-group-id="5911143099-15">)</span><span class="p" data-group-id="5911143099-13">}</span><span class="p">;</span><span class="w">
│ │ │ │ +                   </span><span class="p" data-group-id="5911143099-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5911143099-17">(</span><span class="p" data-group-id="5911143099-17">)</span><span class="p" data-group-id="5911143099-16">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="3864064699-18">(</span><span class="nf">request</span><span class="p" data-group-id="3864064699-19">(</span><span class="p" data-group-id="3864064699-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="3864064699-20">(</span><span class="p" data-group-id="3864064699-20">)</span><span class="p" data-group-id="3864064699-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3864064699-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3864064699-22">(</span><span class="p" data-group-id="3864064699-22">)</span><span class="p" data-group-id="3864064699-21">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="5911143099-18">(</span><span class="nf">request</span><span class="p" data-group-id="5911143099-19">(</span><span class="p" data-group-id="5911143099-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="5911143099-20">(</span><span class="p" data-group-id="5911143099-20">)</span><span class="p" data-group-id="5911143099-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5911143099-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5911143099-22">(</span><span class="p" data-group-id="5911143099-22">)</span><span class="p" data-group-id="5911143099-21">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Each <code class="inline">-spec</code> contract is to be a subtype of the respective <code class="inline">-callback</code> contract.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/seq_prog.xhtml
│ │ │ │ @@ -41,293 +41,293 @@
│ │ │ │  </span><span class="mi">7</span><span class="gp unselectable">
│ │ │ │  2&gt; </span></code></pre><p>As shown, the Erlang shell numbers the lines that can be entered, (as 1&gt; 2&gt;) and
│ │ │ │  that it correctly says that 2 + 5 is 7. If you make writing mistakes in the
│ │ │ │  shell, you can delete with the backspace key, as in most shells. There are many
│ │ │ │  more editing commands in the shell (see
│ │ │ │  <a href="../../../lib/../erts/doc/html/tty.xhtml">tty - A command line interface</a> in ERTS User's Guide).</p><p>(Notice that many line numbers given by the shell in the following examples are
│ │ │ │  out of sequence. This is because this tutorial was written and code-tested in
│ │ │ │ -separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="2928227850-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="2928227850-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │ +separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="5754082472-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="5754082472-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">2618.0</span></code></pre><p>Notice the use of brackets, the multiplication operator <code class="inline">*</code>, and the division
│ │ │ │  operator <code class="inline">/</code>, as in normal arithmetic (see
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml">Expressions</a>).</p><p>Press Control-C to shut down the Erlang system and the Erlang shell.</p><p>The following output is shown:</p><pre><code class="text">BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
│ │ │ │         (v)ersion (k)ill (D)b-tables (d)istribution
│ │ │ │  a
│ │ │ │ -$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../../lib/../erts/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="1862646622-1">(</span><span class="p" data-group-id="1862646622-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../../lib/../erts/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="9672032960-1">(</span><span class="p" data-group-id="9672032960-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="err">$</span></code></pre><h2 id="modules-and-functions" class="section-heading">
│ │ │ │    <a href="#modules-and-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Modules and Functions</span>
│ │ │ │  </h2>
│ │ │ │  <p>A programming language is not much use if you only can run code from the shell.
│ │ │ │  So here is a small Erlang program. Enter it into a file named <code class="inline">tut.erl</code> using a
│ │ │ │  suitable text editor. The file name <code class="inline">tut.erl</code> is important, and also that it is
│ │ │ │  in the same directory as the one where you started <code class="inline">erl</code>). If you are lucky your
│ │ │ │  editor has an Erlang mode that makes it easier for you to enter and format your
│ │ │ │  code nicely (see <a href="../../../lib/tools/doc/html/erlang_mode_chapter.xhtml">The Erlang mode for Emacs</a>
│ │ │ │  in Tools User's Guide), but you can manage perfectly well without. Here is the
│ │ │ │ -code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8076656466-1">(</span><span class="ss">tut</span><span class="p" data-group-id="8076656466-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8076656466-2">(</span><span class="p" data-group-id="8076656466-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8076656466-3">]</span><span class="p" data-group-id="8076656466-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9580086096-1">(</span><span class="ss">tut</span><span class="p" data-group-id="9580086096-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9580086096-2">(</span><span class="p" data-group-id="9580086096-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9580086096-3">]</span><span class="p" data-group-id="9580086096-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="8076656466-4">(</span><span class="n">X</span><span class="p" data-group-id="8076656466-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="9580086096-4">(</span><span class="n">X</span><span class="p" data-group-id="9580086096-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="p">.</span></code></pre><p>It is not hard to guess that this program doubles the value of numbers. The
│ │ │ │  first two lines of the code are described later. Let us compile the program.
│ │ │ │ -This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="8629674966-1">(</span><span class="ss">tut</span><span class="p" data-group-id="8629674966-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8629674966-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="8629674966-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │ │ +This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="5292072802-1">(</span><span class="ss">tut</span><span class="p" data-group-id="5292072802-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5292072802-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="5292072802-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │ │  that there is some mistake in the text that you entered. Additional error
│ │ │ │  messages gives an idea to what is wrong so you can modify the text and then try
│ │ │ │ -to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="6133101591-1">(</span><span class="mi">10</span><span class="p" data-group-id="6133101591-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="2121952492-1">(</span><span class="mi">10</span><span class="p" data-group-id="2121952492-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">20</span></code></pre><p>As expected, double of 10 is 20.</p><p>Now let us get back to the first two lines of the code. Erlang programs are
│ │ │ │  written in files. Each file contains an Erlang <em>module</em>. The first line of code
│ │ │ │ -in the module is the module name (see <a href="../../../lib/../system/doc/html/modules.xhtml">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6084530566-1">(</span><span class="ss">tut</span><span class="p" data-group-id="6084530566-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │ │ +in the module is the module name (see <a href="../../../lib/../system/doc/html/modules.xhtml">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3004915832-1">(</span><span class="ss">tut</span><span class="p" data-group-id="3004915832-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │ │  line. The files which are used to store the module must have the same name as
│ │ │ │  the module but with the extension <code class="inline">.erl</code>. In this case the file name is
│ │ │ │  <code class="inline">tut.erl</code>. When using a function in another module, the syntax
│ │ │ │  <code class="inline">module_name:function_name(arguments)</code> is used. So the following means call
│ │ │ │ -function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="8605695392-1">(</span><span class="mi">10</span><span class="p" data-group-id="8605695392-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ │ -which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4506802253-1">(</span><span class="p" data-group-id="4506802253-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4506802253-2">]</span><span class="p" data-group-id="4506802253-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │ │ +function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="1647071328-1">(</span><span class="mi">10</span><span class="p" data-group-id="1647071328-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ │ +which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2702700925-1">(</span><span class="p" data-group-id="2702700925-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2702700925-2">]</span><span class="p" data-group-id="2702700925-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │ │  module <code class="inline">tut</code>. More about this later. Again, notice the <code class="inline">.</code> at the end of the
│ │ │ │  line.</p><p>Now for a more complicated example, the factorial of a number. For example, the
│ │ │ │ -factorial of 4 is 4 <em> 3 </em> 2 * 1, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9224983243-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="9224983243-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9224983243-2">(</span><span class="p" data-group-id="9224983243-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9224983243-3">]</span><span class="p" data-group-id="9224983243-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +factorial of 4 is 4 <em> 3 </em> 2 * 1, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6160270491-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="6160270491-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6160270491-2">(</span><span class="p" data-group-id="6160270491-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6160270491-3">]</span><span class="p" data-group-id="6160270491-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="9224983243-4">(</span><span class="mi">1</span><span class="p" data-group-id="9224983243-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="6160270491-4">(</span><span class="mi">1</span><span class="p" data-group-id="6160270491-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="9224983243-5">(</span><span class="n">N</span><span class="p" data-group-id="9224983243-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="9224983243-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9224983243-6">)</span><span class="p">.</span></code></pre><p>So this is a module, called <code class="inline">tut1</code> that contains a function called <code class="inline">fac&gt;</code>, which
│ │ │ │ -takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1.:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="3619950490-1">(</span><span class="mi">1</span><span class="p" data-group-id="3619950490-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="6160270491-5">(</span><span class="n">N</span><span class="p" data-group-id="6160270491-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="6160270491-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6160270491-6">)</span><span class="p">.</span></code></pre><p>So this is a module, called <code class="inline">tut1</code> that contains a function called <code class="inline">fac&gt;</code>, which
│ │ │ │ +takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1.:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="1933921912-1">(</span><span class="mi">1</span><span class="p" data-group-id="1933921912-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">;</span></code></pre><p>Notice that this part ends with a semicolon <code class="inline">;</code> that indicates that there is
│ │ │ │  more of the function <code class="inline">fac&gt;</code> to come.</p><p>The second part says that the factorial of N is N multiplied by the factorial of
│ │ │ │ -N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="6839816069-1">(</span><span class="n">N</span><span class="p" data-group-id="6839816069-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="6839816069-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6839816069-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ │ -this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="4767245918-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="4767245918-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4767245918-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="4767245918-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="4687031876-1">(</span><span class="mi">4</span><span class="p" data-group-id="4687031876-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="3332688195-1">(</span><span class="n">N</span><span class="p" data-group-id="3332688195-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="3332688195-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3332688195-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ │ +this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="1394189535-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1394189535-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1394189535-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="1394189535-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="0975709067-1">(</span><span class="mi">4</span><span class="p" data-group-id="0975709067-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">24</span></code></pre><p>Here the function <code class="inline">fac&gt;</code> in module <code class="inline">tut1</code> is called with argument <code class="inline">4</code>.</p><p>A function can have many arguments. Let us expand the module <code class="inline">tut1</code> with the
│ │ │ │ -function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7747360938-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="7747360938-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7747360938-2">(</span><span class="p" data-group-id="7747360938-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7747360938-3">]</span><span class="p" data-group-id="7747360938-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2845312579-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="2845312579-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2845312579-2">(</span><span class="p" data-group-id="2845312579-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2845312579-3">]</span><span class="p" data-group-id="2845312579-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="7747360938-4">(</span><span class="mi">1</span><span class="p" data-group-id="7747360938-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="2845312579-4">(</span><span class="mi">1</span><span class="p" data-group-id="2845312579-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="7747360938-5">(</span><span class="n">N</span><span class="p" data-group-id="7747360938-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="7747360938-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7747360938-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="2845312579-5">(</span><span class="n">N</span><span class="p" data-group-id="2845312579-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="2845312579-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2845312579-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">mult</span><span class="p" data-group-id="7747360938-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7747360938-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">mult</span><span class="p" data-group-id="2845312579-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2845312579-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>Notice that it is also required to expand the <code class="inline">-export</code> line with the
│ │ │ │ -information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="1020316256-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1020316256-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1020316256-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="1020316256-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="5950128706-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5950128706-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="1929917295-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1929917295-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1929917295-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="1929917295-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="9185761839-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9185761839-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">12</span></code></pre><p>In this example the numbers are integers and the arguments in the functions in
│ │ │ │  the code <code class="inline">N</code>, <code class="inline">X</code>, and <code class="inline">Y</code> are called variables. Variables must start with a
│ │ │ │  capital letter (see <a href="../../../lib/../system/doc/html/expressions.xhtml">Variables</a>). Examples of
│ │ │ │  variables are <code class="inline">Number</code>, <code class="inline">ShoeSize</code>, and <code class="inline">Age</code>.</p><h2 id="atoms" class="section-heading">
│ │ │ │    <a href="#atoms" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Atoms</span>
│ │ │ │  </h2>
│ │ │ │  <p>Atom is another data type in Erlang. Atoms start with a small letter (see
│ │ │ │  <a href="../../../lib/../system/doc/html/data_types.xhtml">Atom</a>), for example, <code class="inline">charles</code>, <code class="inline">centimeter</code>, and
│ │ │ │  <code class="inline">inch</code>. Atoms are simply names, nothing else. They are not like variables, which
│ │ │ │  can have a value.</p><p>Enter the next program in a file named <code class="inline">tut2.erl</code>). It can be useful for
│ │ │ │ -converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9483370823-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="9483370823-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9483370823-2">(</span><span class="p" data-group-id="9483370823-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9483370823-3">]</span><span class="p" data-group-id="9483370823-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3945658788-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="3945658788-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3945658788-2">(</span><span class="p" data-group-id="3945658788-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3945658788-3">]</span><span class="p" data-group-id="3945658788-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="9483370823-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="9483370823-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="3945658788-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="3945658788-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">M</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="9483370823-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="9483370823-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="6332386331-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="6332386331-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6332386331-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="6332386331-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="8277695466-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="8277695466-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="3945658788-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="3945658788-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="6935902201-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="6935902201-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6935902201-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="6935902201-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="0095274879-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="0095274879-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">1.1811023622047243</span><span class="gp unselectable">
│ │ │ │ -11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="8277695466-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="8277695466-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="0095274879-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="0095274879-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">17.78</span></code></pre><p>Notice the introduction of decimals (floating point numbers) without any
│ │ │ │  explanation. Hopefully you can cope with that.</p><p>Let us see what happens if something other than <code class="inline">centimeter</code> or <code class="inline">inch</code> is
│ │ │ │ -entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="7504003968-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="7504003968-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="8230444447-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="8230444447-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no function clause matching tut2:convert(3,miles) (tut2.erl, line 4)</span></code></pre><p>The two parts of the <code class="inline">convert</code> function are called its clauses. As shown,
│ │ │ │  <code class="inline">miles</code> is not part of either of the clauses. The Erlang system cannot <em>match</em>
│ │ │ │  either of the clauses so an error message <code class="inline">function_clause</code> is returned. The
│ │ │ │  shell formats the error message nicely, but the error tuple is saved in the
│ │ │ │ -shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="6208071614-1">(</span><span class="mi">12</span><span class="p" data-group-id="6208071614-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6208071614-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6208071614-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="6208071614-4">[</span><span class="p" data-group-id="6208071614-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ │ -                                </span><span class="p" data-group-id="6208071614-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="6208071614-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                                </span><span class="p" data-group-id="6208071614-7">[</span><span class="p" data-group-id="6208071614-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="6208071614-8">}</span><span class="p">,</span><span class="p" data-group-id="6208071614-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6208071614-9">}</span><span class="p" data-group-id="6208071614-7">]</span><span class="p" data-group-id="6208071614-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="6208071614-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="6208071614-11">[</span><span class="p" data-group-id="6208071614-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="6208071614-12">}</span><span class="p">,</span><span class="p" data-group-id="6208071614-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="6208071614-13">}</span><span class="p" data-group-id="6208071614-11">]</span><span class="p" data-group-id="6208071614-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="6208071614-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="6208071614-15">[</span><span class="p" data-group-id="6208071614-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="6208071614-16">}</span><span class="p">,</span><span class="p" data-group-id="6208071614-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="6208071614-17">}</span><span class="p" data-group-id="6208071614-15">]</span><span class="p" data-group-id="6208071614-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="6208071614-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="6208071614-19">[</span><span class="p" data-group-id="6208071614-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="6208071614-20">}</span><span class="p">,</span><span class="p" data-group-id="6208071614-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="6208071614-21">}</span><span class="p" data-group-id="6208071614-19">]</span><span class="p" data-group-id="6208071614-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="p" data-group-id="6208071614-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ -                                 </span><span class="p" data-group-id="6208071614-23">[</span><span class="p" data-group-id="6208071614-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="6208071614-24">}</span><span class="p">,</span><span class="p" data-group-id="6208071614-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="6208071614-25">}</span><span class="p" data-group-id="6208071614-23">]</span><span class="p" data-group-id="6208071614-22">}</span><span class="p" data-group-id="6208071614-4">]</span><span class="p" data-group-id="6208071614-3">}</span><span class="p" data-group-id="6208071614-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │ │ +shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="5721466361-1">(</span><span class="mi">12</span><span class="p" data-group-id="5721466361-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5721466361-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="5721466361-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="5721466361-4">[</span><span class="p" data-group-id="5721466361-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ │ +                                </span><span class="p" data-group-id="5721466361-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="5721466361-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                                </span><span class="p" data-group-id="5721466361-7">[</span><span class="p" data-group-id="5721466361-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="5721466361-8">}</span><span class="p">,</span><span class="p" data-group-id="5721466361-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5721466361-9">}</span><span class="p" data-group-id="5721466361-7">]</span><span class="p" data-group-id="5721466361-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="5721466361-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="5721466361-11">[</span><span class="p" data-group-id="5721466361-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="5721466361-12">}</span><span class="p">,</span><span class="p" data-group-id="5721466361-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="5721466361-13">}</span><span class="p" data-group-id="5721466361-11">]</span><span class="p" data-group-id="5721466361-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="5721466361-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="5721466361-15">[</span><span class="p" data-group-id="5721466361-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5721466361-16">}</span><span class="p">,</span><span class="p" data-group-id="5721466361-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="5721466361-17">}</span><span class="p" data-group-id="5721466361-15">]</span><span class="p" data-group-id="5721466361-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="5721466361-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="5721466361-19">[</span><span class="p" data-group-id="5721466361-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5721466361-20">}</span><span class="p">,</span><span class="p" data-group-id="5721466361-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="5721466361-21">}</span><span class="p" data-group-id="5721466361-19">]</span><span class="p" data-group-id="5721466361-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="p" data-group-id="5721466361-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ │ +                                 </span><span class="p" data-group-id="5721466361-23">[</span><span class="p" data-group-id="5721466361-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5721466361-24">}</span><span class="p">,</span><span class="p" data-group-id="5721466361-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="5721466361-25">}</span><span class="p" data-group-id="5721466361-23">]</span><span class="p" data-group-id="5721466361-22">}</span><span class="p" data-group-id="5721466361-4">]</span><span class="p" data-group-id="5721466361-3">}</span><span class="p" data-group-id="5721466361-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │ │    <a href="#tuples" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Tuples</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="1422735375-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="1422735375-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │ │ +<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="5668958469-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="5668958469-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │ │  is to be converted to inches? Erlang has a way to group things together to make
│ │ │ │  things more understandable. These are called <em>tuples</em> and are surrounded by
│ │ │ │  curly brackets, <code class="inline">{</code> and <code class="inline">}</code>.</p><p>So, <code class="inline">{inch,3}</code> denotes 3 inches and <code class="inline">{centimeter,5}</code> denotes 5 centimeters. Now
│ │ │ │  let us write a new program that converts centimeters to inches and conversely.
│ │ │ │ -Enter the following code in a file called <code class="inline">tut3.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8259176761-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="8259176761-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8259176761-2">(</span><span class="p" data-group-id="8259176761-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8259176761-3">]</span><span class="p" data-group-id="8259176761-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +Enter the following code in a file called <code class="inline">tut3.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6703696770-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="6703696770-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6703696770-2">(</span><span class="p" data-group-id="6703696770-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6703696770-3">]</span><span class="p" data-group-id="6703696770-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="8259176761-4">(</span><span class="p" data-group-id="8259176761-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8259176761-5">}</span><span class="p" data-group-id="8259176761-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8259176761-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="8259176761-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="8259176761-7">(</span><span class="p" data-group-id="8259176761-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8259176761-8">}</span><span class="p" data-group-id="8259176761-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8259176761-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="8259176761-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="2427158070-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="2427158070-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2427158070-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="2427158070-2">}</span><span class="gp unselectable">
│ │ │ │ -15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2427158070-3">(</span><span class="p" data-group-id="2427158070-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2427158070-4">}</span><span class="p" data-group-id="2427158070-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2427158070-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="2427158070-5">}</span><span class="gp unselectable">
│ │ │ │ -16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2427158070-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2427158070-7">(</span><span class="p" data-group-id="2427158070-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2427158070-8">}</span><span class="p" data-group-id="2427158070-7">)</span><span class="p" data-group-id="2427158070-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2427158070-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="2427158070-9">}</span></code></pre><p>Notice on line 16 that 5 inches is converted to centimeters and back again and
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="6703696770-4">(</span><span class="p" data-group-id="6703696770-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6703696770-5">}</span><span class="p" data-group-id="6703696770-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6703696770-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="6703696770-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="6703696770-7">(</span><span class="p" data-group-id="6703696770-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6703696770-8">}</span><span class="p" data-group-id="6703696770-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6703696770-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="6703696770-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="0345542914-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="0345542914-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0345542914-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="0345542914-2">}</span><span class="gp unselectable">
│ │ │ │ +15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="0345542914-3">(</span><span class="p" data-group-id="0345542914-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="0345542914-4">}</span><span class="p" data-group-id="0345542914-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0345542914-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="0345542914-5">}</span><span class="gp unselectable">
│ │ │ │ +16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="0345542914-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="0345542914-7">(</span><span class="p" data-group-id="0345542914-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="0345542914-8">}</span><span class="p" data-group-id="0345542914-7">)</span><span class="p" data-group-id="0345542914-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0345542914-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="0345542914-9">}</span></code></pre><p>Notice on line 16 that 5 inches is converted to centimeters and back again and
│ │ │ │  reassuringly get back to the original value. That is, the argument to a function
│ │ │ │  can be the result of another function. Consider how line 16 (above) works. The
│ │ │ │  argument given to the function <code class="inline">{inch,5}</code> is first matched against the first
│ │ │ │  head clause of <code class="inline">convert_length</code>, that is, <code class="inline">convert_length({centimeter,X})</code>. It
│ │ │ │  can be seen that <code class="inline">{centimeter,X}</code> does not match <code class="inline">{inch,5}</code> (the head is the bit
│ │ │ │  before the <code class="inline">-&gt;</code>). This having failed, let us try the head of the next clause
│ │ │ │  that is, <code class="inline">convert_length({inch,Y})</code>. This matches, and <code class="inline">Y</code> gets the value 5.</p><p>Tuples can have more than two parts, in fact as many parts as you want, and
│ │ │ │  contain any valid Erlang <em>term</em>. For example, to represent the temperature of
│ │ │ │ -various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1181503285-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1181503285-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1181503285-2">}</span><span class="p" data-group-id="1181503285-1">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1181503285-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1181503285-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="1181503285-4">}</span><span class="p" data-group-id="1181503285-3">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1181503285-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1181503285-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="1181503285-6">}</span><span class="p" data-group-id="1181503285-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │ │ +various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6988272025-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988272025-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="6988272025-2">}</span><span class="p" data-group-id="6988272025-1">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6988272025-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988272025-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="6988272025-4">}</span><span class="p" data-group-id="6988272025-3">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6988272025-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988272025-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="6988272025-6">}</span><span class="p" data-group-id="6988272025-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │ │  <em>element</em>. In the tuple <code class="inline">{moscow,{c,-10}}</code>, element 1 is <code class="inline">moscow</code> and element 2
│ │ │ │  is <code class="inline">{c,-10}</code>. Here <code class="inline">c</code> represents Celsius and <code class="inline">f</code> Fahrenheit.</p><h2 id="lists" class="section-heading">
│ │ │ │    <a href="#lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Lists</span>
│ │ │ │  </h2>
│ │ │ │  <p>Whereas tuples group things together, it is also needed to represent lists of
│ │ │ │  things. Lists in Erlang are surrounded by square brackets, <code class="inline">[</code> and <code class="inline">]</code>. For
│ │ │ │ -example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5971730249-1">[</span><span class="p" data-group-id="5971730249-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5971730249-3">}</span><span class="p" data-group-id="5971730249-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5971730249-5">}</span><span class="p" data-group-id="5971730249-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5971730249-7">}</span><span class="p" data-group-id="5971730249-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5971730249-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5971730249-9">}</span><span class="p" data-group-id="5971730249-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5971730249-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5971730249-11">}</span><span class="p" data-group-id="5971730249-10">}</span><span class="p" data-group-id="5971730249-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │ │ +example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9630110966-1">[</span><span class="p" data-group-id="9630110966-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9630110966-3">}</span><span class="p" data-group-id="9630110966-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9630110966-5">}</span><span class="p" data-group-id="9630110966-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9630110966-7">}</span><span class="p" data-group-id="9630110966-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9630110966-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9630110966-9">}</span><span class="p" data-group-id="9630110966-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9630110966-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9630110966-11">}</span><span class="p" data-group-id="9630110966-10">}</span><span class="p" data-group-id="9630110966-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │ │  matter, Erlang allows line breaks at all &quot;sensible places&quot; but not, for example,
│ │ │ │  in the middle of atoms, integers, and others.</p><p>A useful way of looking at parts of lists, is by using <code class="inline">|</code>. This is best
│ │ │ │ -explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="5440347706-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="5440347706-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5440347706-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5440347706-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5440347706-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5440347706-3">]</span><span class="gp unselectable">
│ │ │ │ +explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="5168975834-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="5168975834-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5168975834-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5168975834-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5168975834-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5168975834-3">]</span><span class="gp unselectable">
│ │ │ │  18&gt; </span><span class="n">First</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ │  19&gt; </span><span class="n">TheRest</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5440347706-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5440347706-4">]</span></code></pre><p>To separate the first elements of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ │ -used. <code class="inline">First</code> has got value <code class="inline">1</code> and <code class="inline">TheRest</code> has got the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="7737744256-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="7737744256-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7737744256-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="7737744256-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7737744256-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="7737744256-3">]</span><span class="gp unselectable">
│ │ │ │ +</span><span class="p" data-group-id="5168975834-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5168975834-4">]</span></code></pre><p>To separate the first elements of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ │ +used. <code class="inline">First</code> has got value <code class="inline">1</code> and <code class="inline">TheRest</code> has got the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="3604035703-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="3604035703-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3604035703-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3604035703-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3604035703-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3604035703-3">]</span><span class="gp unselectable">
│ │ │ │  21&gt; </span><span class="n">E1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ │  22&gt; </span><span class="n">E2</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="gp unselectable">
│ │ │ │  23&gt; </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7737744256-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="7737744256-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │ │ +</span><span class="p" data-group-id="3604035703-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3604035703-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │ │  try to get more elements from the list than there are elements in the list, an
│ │ │ │  error is returned. Notice also the special case of the list with no elements,
│ │ │ │ -<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="4843144235-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="4843144235-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4843144235-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4843144235-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4843144235-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4843144235-3">]</span><span class="gp unselectable">
│ │ │ │ +<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="2379208621-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="2379208621-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2379208621-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2379208621-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2379208621-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2379208621-3">]</span><span class="gp unselectable">
│ │ │ │  25&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ │  26&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="gp unselectable">
│ │ │ │  27&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4843144235-4">[</span><span class="p" data-group-id="4843144235-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │ │ +</span><span class="p" data-group-id="2379208621-4">[</span><span class="p" data-group-id="2379208621-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │ │  old ones: <code class="inline">First</code>, <code class="inline">TheRest</code>, <code class="inline">E1</code>, <code class="inline">E2</code>, <code class="inline">R</code>, <code class="inline">A</code>, <code class="inline">B</code>, and <code class="inline">C</code>. The reason for
│ │ │ │  this is that a variable can only be given a value once in its context (scope).
│ │ │ │  More about this later.</p><p>The following example shows how to find the length of a list. Enter the
│ │ │ │ -following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6406116063-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="6406116063-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3660928574-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="3660928574-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6406116063-2">(</span><span class="p" data-group-id="6406116063-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6406116063-3">]</span><span class="p" data-group-id="6406116063-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3660928574-2">(</span><span class="p" data-group-id="3660928574-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3660928574-3">]</span><span class="p" data-group-id="3660928574-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="6406116063-4">(</span><span class="p" data-group-id="6406116063-5">[</span><span class="p" data-group-id="6406116063-5">]</span><span class="p" data-group-id="6406116063-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="3660928574-4">(</span><span class="p" data-group-id="3660928574-5">[</span><span class="p" data-group-id="3660928574-5">]</span><span class="p" data-group-id="3660928574-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="6406116063-6">(</span><span class="p" data-group-id="6406116063-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="6406116063-7">]</span><span class="p" data-group-id="6406116063-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="6406116063-8">(</span><span class="n">Rest</span><span class="p" data-group-id="6406116063-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="2133792370-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="2133792370-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2133792370-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="2133792370-2">}</span><span class="gp unselectable">
│ │ │ │ -29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="2133792370-3">(</span><span class="p" data-group-id="2133792370-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2133792370-4">]</span><span class="p" data-group-id="2133792370-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="0296350169-1">(</span><span class="p" data-group-id="0296350169-2">[</span><span class="p" data-group-id="0296350169-2">]</span><span class="p" data-group-id="0296350169-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="7228167580-1">(</span><span class="p" data-group-id="7228167580-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7228167580-2">]</span><span class="p" data-group-id="7228167580-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="7228167580-3">(</span><span class="n">Rest</span><span class="p" data-group-id="7228167580-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="3660928574-6">(</span><span class="p" data-group-id="3660928574-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3660928574-7">]</span><span class="p" data-group-id="3660928574-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="3660928574-8">(</span><span class="n">Rest</span><span class="p" data-group-id="3660928574-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="1222742375-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="1222742375-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1222742375-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="1222742375-2">}</span><span class="gp unselectable">
│ │ │ │ +29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="1222742375-3">(</span><span class="p" data-group-id="1222742375-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1222742375-4">]</span><span class="p" data-group-id="1222742375-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="8751649258-1">(</span><span class="p" data-group-id="8751649258-2">[</span><span class="p" data-group-id="8751649258-2">]</span><span class="p" data-group-id="8751649258-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="3182297860-1">(</span><span class="p" data-group-id="3182297860-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3182297860-2">]</span><span class="p" data-group-id="3182297860-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="3182297860-3">(</span><span class="n">Rest</span><span class="p" data-group-id="3182297860-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │ │  <code class="inline">Rest</code> is 1 + the length of <code class="inline">Rest</code>.</p><p>(Advanced readers only: This is not tail recursive, there is a better way to
│ │ │ │  write this function.)</p><p>In general, tuples are used where &quot;records&quot; or &quot;structs&quot; are used in other
│ │ │ │  languages. Also, lists are used when representing things with varying sizes,
│ │ │ │  that is, where linked lists are used in other languages.</p><p>Erlang does not have a string data type. Instead, strings can be represented by
│ │ │ │  lists of Unicode characters. This implies for example that the list <code class="inline">[97,98,99]</code>
│ │ │ │  is equivalent to <code class="inline">&quot;abc&quot;</code>. The Erlang shell is &quot;clever&quot; and guesses what list you
│ │ │ │ -mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="7528990725-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="7528990725-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="2818484719-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="2818484719-1">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;abc&quot;</span></code></pre><h2 id="maps" class="section-heading">
│ │ │ │    <a href="#maps" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Maps</span>
│ │ │ │  </h2>
│ │ │ │  <p>Maps are a set of key to value associations. These associations are encapsulated
│ │ │ │ -with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5428231610-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="5428231610-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5428231610-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="5428231610-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │ │ +with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3090575679-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="3090575679-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3090575679-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="3090575679-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │ │  features.</p><p>The following example shows how to calculate alpha blending using maps to
│ │ │ │ -reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8955990696-1">(</span><span class="ss">color</span><span class="p" data-group-id="8955990696-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7283466390-1">(</span><span class="ss">color</span><span class="p" data-group-id="7283466390-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8955990696-2">(</span><span class="p" data-group-id="8955990696-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8955990696-3">]</span><span class="p" data-group-id="8955990696-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7283466390-2">(</span><span class="p" data-group-id="7283466390-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7283466390-3">]</span><span class="p" data-group-id="7283466390-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8955990696-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="8955990696-5">(</span><span class="n">V</span><span class="p" data-group-id="8955990696-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8955990696-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="8955990696-7">(</span><span class="n">V</span><span class="p" data-group-id="8955990696-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="8955990696-6">)</span><span class="p" data-group-id="8955990696-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7283466390-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="7283466390-5">(</span><span class="n">V</span><span class="p" data-group-id="7283466390-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7283466390-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="7283466390-7">(</span><span class="n">V</span><span class="p" data-group-id="7283466390-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="7283466390-6">)</span><span class="p" data-group-id="7283466390-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="8955990696-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="8955990696-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8955990696-9">(</span><span class="n">R</span><span class="p" data-group-id="8955990696-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8955990696-10">(</span><span class="n">G</span><span class="p" data-group-id="8955990696-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8955990696-11">(</span><span class="n">B</span><span class="p" data-group-id="8955990696-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8955990696-12">(</span><span class="n">A</span><span class="p" data-group-id="8955990696-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8955990696-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8955990696-13">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="8955990696-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8955990696-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">blend</span><span class="p" data-group-id="8955990696-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="8955990696-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8955990696-16">)</span><span class="p" data-group-id="8955990696-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="8955990696-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="8955990696-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="8955990696-18">#{</span><span class="w">
│ │ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="8955990696-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8955990696-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="8955990696-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8955990696-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="8955990696-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="8955990696-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="7283466390-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="7283466390-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="7283466390-9">(</span><span class="n">R</span><span class="p" data-group-id="7283466390-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="7283466390-10">(</span><span class="n">G</span><span class="p" data-group-id="7283466390-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="7283466390-11">(</span><span class="n">B</span><span class="p" data-group-id="7283466390-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="7283466390-12">(</span><span class="n">A</span><span class="p" data-group-id="7283466390-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7283466390-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="7283466390-13">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="7283466390-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7283466390-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">blend</span><span class="p" data-group-id="7283466390-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="7283466390-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7283466390-16">)</span><span class="p" data-group-id="7283466390-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="7283466390-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="7283466390-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="7283466390-18">#{</span><span class="w">
│ │ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="7283466390-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7283466390-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="7283466390-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7283466390-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="7283466390-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7283466390-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8955990696-18">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="8955990696-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8955990696-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="8955990696-23">#{</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7283466390-18">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="7283466390-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7283466390-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="7283466390-23">#{</span><span class="w">
│ │ │ │          </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8955990696-23">}</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7283466390-23">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alpha</span><span class="p" data-group-id="8955990696-24">(</span><span class="p" data-group-id="8955990696-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8955990696-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8955990696-26">}</span><span class="p" data-group-id="8955990696-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8955990696-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alpha</span><span class="p" data-group-id="7283466390-24">(</span><span class="p" data-group-id="7283466390-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7283466390-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="7283466390-26">}</span><span class="p" data-group-id="7283466390-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="7283466390-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-27">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">red</span><span class="p" data-group-id="8955990696-28">(</span><span class="p" data-group-id="8955990696-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8955990696-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8955990696-30">}</span><span class="p" data-group-id="8955990696-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8955990696-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-31">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">green</span><span class="p" data-group-id="8955990696-32">(</span><span class="p" data-group-id="8955990696-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8955990696-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8955990696-34">}</span><span class="p" data-group-id="8955990696-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8955990696-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">blue</span><span class="p" data-group-id="8955990696-36">(</span><span class="p" data-group-id="8955990696-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8955990696-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8955990696-38">}</span><span class="p" data-group-id="8955990696-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8955990696-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8955990696-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="0486077006-1">(</span><span class="ss">color</span><span class="p" data-group-id="0486077006-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0486077006-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="0486077006-2">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0486077006-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="0486077006-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0486077006-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="0486077006-4">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0486077006-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="0486077006-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0486077006-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="0486077006-6">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="0486077006-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="0486077006-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0486077006-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="0486077006-8">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="0486077006-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="0486077006-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0486077006-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="0486077006-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9162918323-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="9162918323-2">(</span><span class="n">V</span><span class="p" data-group-id="9162918323-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9162918323-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="9162918323-4">(</span><span class="n">V</span><span class="p" data-group-id="9162918323-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="9162918323-3">)</span><span class="p" data-group-id="9162918323-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │ │ +</span><span class="nf">red</span><span class="p" data-group-id="7283466390-28">(</span><span class="p" data-group-id="7283466390-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7283466390-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="7283466390-30">}</span><span class="p" data-group-id="7283466390-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="7283466390-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-31">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">green</span><span class="p" data-group-id="7283466390-32">(</span><span class="p" data-group-id="7283466390-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7283466390-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="7283466390-34">}</span><span class="p" data-group-id="7283466390-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="7283466390-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-35">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">blue</span><span class="p" data-group-id="7283466390-36">(</span><span class="p" data-group-id="7283466390-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7283466390-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="7283466390-38">}</span><span class="p" data-group-id="7283466390-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="7283466390-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="7283466390-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="3511030495-1">(</span><span class="ss">color</span><span class="p" data-group-id="3511030495-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3511030495-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="3511030495-2">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="3511030495-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="3511030495-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3511030495-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="3511030495-4">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="3511030495-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="3511030495-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3511030495-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="3511030495-6">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="3511030495-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="3511030495-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3511030495-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="3511030495-8">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="3511030495-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="3511030495-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3511030495-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="3511030495-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9712072091-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="9712072091-2">(</span><span class="n">V</span><span class="p" data-group-id="9712072091-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9712072091-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="9712072091-4">(</span><span class="n">V</span><span class="p" data-group-id="9712072091-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="9712072091-3">)</span><span class="p" data-group-id="9712072091-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │ │  here for convenience and to reduce syntax cluttering. For more information about
│ │ │ │ -macros, see <a href="../../../lib/../system/doc/html/macros.xhtml">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="8311352799-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="8311352799-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8311352799-2">(</span><span class="n">R</span><span class="p" data-group-id="8311352799-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8311352799-3">(</span><span class="n">G</span><span class="p" data-group-id="8311352799-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8311352799-4">(</span><span class="n">B</span><span class="p" data-group-id="8311352799-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="8311352799-5">(</span><span class="n">A</span><span class="p" data-group-id="8311352799-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8311352799-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8311352799-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │ │ +macros, see <a href="../../../lib/../system/doc/html/macros.xhtml">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="5588999989-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="5588999989-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5588999989-2">(</span><span class="n">R</span><span class="p" data-group-id="5588999989-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5588999989-3">(</span><span class="n">G</span><span class="p" data-group-id="5588999989-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5588999989-4">(</span><span class="n">B</span><span class="p" data-group-id="5588999989-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5588999989-5">(</span><span class="n">A</span><span class="p" data-group-id="5588999989-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5588999989-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5588999989-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │ │  <code class="inline">blue</code>, and <code class="inline">alpha</code> be associated with an initial value. In this case, only
│ │ │ │  float values between and including 0.0 and 1.0 are allowed, as ensured by the
│ │ │ │  <code class="inline">?is_channel/1</code> macro for each argument. Only the <code class="inline">=&gt;</code> operator is allowed when
│ │ │ │  creating a new map.</p><p>By calling <code class="inline">blend/2</code> on any color term created by <code class="inline">new/4</code>, the resulting color
│ │ │ │ -can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="5087320891-1">(</span><span class="p" data-group-id="5087320891-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5087320891-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5087320891-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="5087320891-3">}</span><span class="p" data-group-id="5087320891-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="5087320891-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5087320891-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │ │ +can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="0960790159-1">(</span><span class="p" data-group-id="0960790159-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0960790159-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0960790159-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0960790159-3">}</span><span class="p" data-group-id="0960790159-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0960790159-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0960790159-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │ │  <code class="inline">:=</code> operator. The other keys in the map are ignored, only the key <code class="inline">alpha</code> is
│ │ │ │ -required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="8631076917-1">(</span><span class="p" data-group-id="8631076917-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8631076917-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8631076917-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8631076917-3">}</span><span class="p" data-group-id="8631076917-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8631076917-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8631076917-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ │ -The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="9226007818-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="9226007818-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="9226007818-2">#{</span><span class="w">
│ │ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="9226007818-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9226007818-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="9226007818-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9226007818-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="9226007818-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9226007818-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="9260110399-1">(</span><span class="p" data-group-id="9260110399-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9260110399-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9260110399-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="9260110399-3">}</span><span class="p" data-group-id="9260110399-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="9260110399-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9260110399-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ │ +The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="4192364575-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="4192364575-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="4192364575-2">#{</span><span class="w">
│ │ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="4192364575-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4192364575-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="4192364575-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4192364575-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="4192364575-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="4192364575-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9226007818-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │ │ +    </span><span class="p" data-group-id="4192364575-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │ │  existing key with a new value is with the <code class="inline">:=</code> operator.</p><h2 id="standard-modules-and-manual-pages" class="section-heading">
│ │ │ │    <a href="#standard-modules-and-manual-pages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standard Modules and Manual Pages</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang has many standard modules to help you do things. For example, the module
│ │ │ │ @@ -347,24 +347,24 @@
│ │ │ │    <a href="#writing-output-to-a-terminal" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Writing Output to a Terminal</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is nice to be able to do formatted output in examples, so the next example
│ │ │ │  shows a simple way to use the <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function. Like all other exported
│ │ │ │ -functions, you can test the <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2689523461-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2689523461-2">[</span><span class="p" data-group-id="2689523461-2">]</span><span class="p" data-group-id="2689523461-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +functions, you can test the <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9916723989-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9916723989-2">[</span><span class="p" data-group-id="9916723989-2">]</span><span class="p" data-group-id="9916723989-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2689523461-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2689523461-4">[</span><span class="ss">hello</span><span class="p" data-group-id="2689523461-4">]</span><span class="p" data-group-id="2689523461-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9916723989-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9916723989-4">[</span><span class="ss">hello</span><span class="p" data-group-id="9916723989-4">]</span><span class="p" data-group-id="9916723989-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">one</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">term</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2689523461-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2689523461-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="2689523461-6">]</span><span class="p" data-group-id="2689523461-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9916723989-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9916723989-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="9916723989-6">]</span><span class="p" data-group-id="9916723989-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">helloworld</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2689523461-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2689523461-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="2689523461-8">]</span><span class="p" data-group-id="2689523461-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9916723989-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9916723989-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="9916723989-8">]</span><span class="p" data-group-id="9916723989-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>The function <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> (that is, <code class="inline">format</code> with two arguments) takes two lists.
│ │ │ │  The first one is nearly always a list written between <code class="inline">&quot; &quot;</code>. This list is printed
│ │ │ │  out as it is, except that each <code class="inline">~w</code> is replaced by a term taken in order from the
│ │ │ │  second list. Each ~n is replaced by a new line. The <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function
│ │ │ │  itself returns the atom <code class="inline">ok</code> if everything goes as planned. Like other functions
│ │ │ │  in Erlang, it crashes if an error occurs. This is not a fault in Erlang, it is a
│ │ │ │ @@ -378,34 +378,34 @@
│ │ │ │    <span class="text">A Larger Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>Now for a larger example to consolidate what you have learnt so far. Assume that
│ │ │ │  you have a list of temperature readings from a number of cities in the world.
│ │ │ │  Some of them are in Celsius and some in Fahrenheit (as in the previous list).
│ │ │ │  First let us convert them all to Celsius, then let us print the data neatly.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% This module is in file tut5.erl</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9196960980-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="9196960980-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9196960980-2">(</span><span class="p" data-group-id="9196960980-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9196960980-3">]</span><span class="p" data-group-id="9196960980-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0642682026-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="0642682026-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0642682026-2">(</span><span class="p" data-group-id="0642682026-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0642682026-3">]</span><span class="p" data-group-id="0642682026-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Only this function is exported</span><span class="w">
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="9196960980-4">(</span><span class="p" data-group-id="9196960980-5">[</span><span class="p" data-group-id="9196960980-5">]</span><span class="p" data-group-id="9196960980-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="0642682026-4">(</span><span class="p" data-group-id="0642682026-5">[</span><span class="p" data-group-id="0642682026-5">]</span><span class="p" data-group-id="0642682026-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="9196960980-6">(</span><span class="p" data-group-id="9196960980-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9196960980-7">]</span><span class="p" data-group-id="9196960980-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="9196960980-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="9196960980-9">(</span><span class="n">City</span><span class="p" data-group-id="9196960980-9">)</span><span class="p" data-group-id="9196960980-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">format_temps</span><span class="p" data-group-id="9196960980-10">(</span><span class="n">Rest</span><span class="p" data-group-id="9196960980-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="9196960980-11">(</span><span class="p" data-group-id="9196960980-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9196960980-13">}</span><span class="p" data-group-id="9196960980-12">}</span><span class="p" data-group-id="9196960980-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9196960980-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9196960980-15">}</span><span class="p" data-group-id="9196960980-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="9196960980-16">(</span><span class="p" data-group-id="9196960980-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9196960980-18">}</span><span class="p" data-group-id="9196960980-17">}</span><span class="p" data-group-id="9196960980-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9196960980-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="9196960980-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="9196960980-20">}</span><span class="p" data-group-id="9196960980-19">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="9196960980-22">(</span><span class="p" data-group-id="9196960980-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9196960980-24">}</span><span class="p" data-group-id="9196960980-23">}</span><span class="p" data-group-id="9196960980-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9196960980-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9196960980-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9196960980-26">]</span><span class="p" data-group-id="9196960980-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="8406319566-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="8406319566-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8406319566-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="8406319566-2">}</span><span class="gp unselectable">
│ │ │ │ -36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="8406319566-3">(</span><span class="p" data-group-id="8406319566-4">[</span><span class="p" data-group-id="8406319566-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8406319566-6">}</span><span class="p" data-group-id="8406319566-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8406319566-8">}</span><span class="p" data-group-id="8406319566-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8406319566-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="8406319566-10">}</span><span class="p" data-group-id="8406319566-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8406319566-12">}</span><span class="p" data-group-id="8406319566-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8406319566-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="8406319566-14">}</span><span class="p" data-group-id="8406319566-13">}</span><span class="p" data-group-id="8406319566-4">]</span><span class="p" data-group-id="8406319566-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="0642682026-6">(</span><span class="p" data-group-id="0642682026-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0642682026-7">]</span><span class="p" data-group-id="0642682026-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="0642682026-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="0642682026-9">(</span><span class="n">City</span><span class="p" data-group-id="0642682026-9">)</span><span class="p" data-group-id="0642682026-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">format_temps</span><span class="p" data-group-id="0642682026-10">(</span><span class="n">Rest</span><span class="p" data-group-id="0642682026-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="0642682026-11">(</span><span class="p" data-group-id="0642682026-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0642682026-13">}</span><span class="p" data-group-id="0642682026-12">}</span><span class="p" data-group-id="0642682026-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0642682026-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0642682026-15">}</span><span class="p" data-group-id="0642682026-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="0642682026-16">(</span><span class="p" data-group-id="0642682026-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0642682026-18">}</span><span class="p" data-group-id="0642682026-17">}</span><span class="p" data-group-id="0642682026-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0642682026-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="0642682026-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="0642682026-20">}</span><span class="p" data-group-id="0642682026-19">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="0642682026-22">(</span><span class="p" data-group-id="0642682026-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0642682026-24">}</span><span class="p" data-group-id="0642682026-23">}</span><span class="p" data-group-id="0642682026-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0642682026-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0642682026-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0642682026-26">]</span><span class="p" data-group-id="0642682026-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="7149297316-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="7149297316-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7149297316-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="7149297316-2">}</span><span class="gp unselectable">
│ │ │ │ +36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="7149297316-3">(</span><span class="p" data-group-id="7149297316-4">[</span><span class="p" data-group-id="7149297316-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7149297316-6">}</span><span class="p" data-group-id="7149297316-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7149297316-8">}</span><span class="p" data-group-id="7149297316-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7149297316-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7149297316-10">}</span><span class="p" data-group-id="7149297316-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7149297316-12">}</span><span class="p" data-group-id="7149297316-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7149297316-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7149297316-14">}</span><span class="p" data-group-id="7149297316-13">}</span><span class="p" data-group-id="7149297316-4">]</span><span class="p" data-group-id="7149297316-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Before looking at how this program works, notice that a few comments are added
│ │ │ │  to the code. A comment starts with a %-character and goes on to the end of the
│ │ │ │ @@ -433,28 +433,28 @@
│ │ │ │    <a href="#matching-guards-and-scope-of-variables" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Matching, Guards, and Scope of Variables</span>
│ │ │ │  </h2>
│ │ │ │  <p>It can be useful to find the maximum and minimum temperature in lists like this.
│ │ │ │  Before extending the program to do this, let us look at functions for finding
│ │ │ │ -the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9260235779-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="9260235779-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9260235779-2">(</span><span class="p" data-group-id="9260235779-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9260235779-3">]</span><span class="p" data-group-id="9260235779-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7355229944-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="7355229944-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7355229944-2">(</span><span class="p" data-group-id="7355229944-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7355229944-3">]</span><span class="p" data-group-id="7355229944-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-4">(</span><span class="p" data-group-id="9260235779-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="9260235779-5">]</span><span class="p" data-group-id="9260235779-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="9260235779-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-4">(</span><span class="p" data-group-id="7355229944-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7355229944-5">]</span><span class="p" data-group-id="7355229944-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="7355229944-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-7">(</span><span class="p" data-group-id="9260235779-8">[</span><span class="p" data-group-id="9260235779-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="9260235779-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-7">(</span><span class="p" data-group-id="7355229944-8">[</span><span class="p" data-group-id="7355229944-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="7355229944-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Res</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-9">(</span><span class="p" data-group-id="9260235779-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="9260235779-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="9260235779-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="9260235779-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-12">(</span><span class="p" data-group-id="9260235779-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="9260235779-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="9260235779-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="9260235779-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="9260235779-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="5614594904-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="5614594904-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5614594904-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="5614594904-2">}</span><span class="gp unselectable">
│ │ │ │ -38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="5614594904-3">(</span><span class="p" data-group-id="5614594904-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5614594904-4">]</span><span class="p" data-group-id="5614594904-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-9">(</span><span class="p" data-group-id="7355229944-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7355229944-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7355229944-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="7355229944-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-12">(</span><span class="p" data-group-id="7355229944-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7355229944-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7355229944-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="7355229944-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7355229944-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="4014943724-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="4014943724-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4014943724-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="4014943724-2">}</span><span class="gp unselectable">
│ │ │ │ +38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="4014943724-3">(</span><span class="p" data-group-id="4014943724-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4014943724-4">]</span><span class="p" data-group-id="4014943724-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">7</span></code></pre><p>First notice that two functions have the same name, <code class="inline">list_max</code>. However, each of
│ │ │ │  these takes a different number of arguments (parameters). In Erlang these are
│ │ │ │  regarded as completely different functions. Where you need to distinguish
│ │ │ │  between these functions, you write Name/Arity, where Name is the function name
│ │ │ │  and Arity is the number of arguments, in this case <code class="inline">list_max/1</code> and
│ │ │ │  <code class="inline">list_max/2</code>.</p><p>In this example you walk through a list &quot;carrying&quot; a value, in this case
│ │ │ │  <code class="inline">Result_so_far</code>. <code class="inline">list_max/1</code> simply assumes that the max value of the list is
│ │ │ │ @@ -483,180 +483,180 @@
│ │ │ │  </span><span class="mi">5</span><span class="gp unselectable">
│ │ │ │  40&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="gp unselectable">
│ │ │ │  41&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="gp unselectable">
│ │ │ │  42&gt; </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">6</span></code></pre><p>The use of the match operator is particularly useful for pulling apart Erlang
│ │ │ │ -terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="3825658004-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3825658004-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3825658004-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3825658004-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="3825658004-3">}</span><span class="p" data-group-id="3825658004-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3825658004-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="3825658004-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="3825658004-5">}</span><span class="p" data-group-id="3825658004-4">}</span><span class="gp unselectable">
│ │ │ │ +terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="0694677564-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0694677564-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0694677564-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0694677564-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0694677564-3">}</span><span class="p" data-group-id="0694677564-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0694677564-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0694677564-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="0694677564-5">}</span><span class="p" data-group-id="0694677564-4">}</span><span class="gp unselectable">
│ │ │ │  44&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="gp unselectable">
│ │ │ │  45&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3825658004-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="3825658004-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="9896779982-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9896779982-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9896779982-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9896779982-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9896779982-3">}</span><span class="p" data-group-id="9896779982-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0694677564-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="0694677564-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="7240246310-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7240246310-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7240246310-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7240246310-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7240246310-3">}</span><span class="p" data-group-id="7240246310-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value {london,{f,36}}</span></code></pre><p>Variables can also be used to improve the readability of programs. For example,
│ │ │ │ -in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="7611826601-1">(</span><span class="p" data-group-id="7611826601-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7611826601-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7611826601-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="1978067906-1">(</span><span class="p" data-group-id="1978067906-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1978067906-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="1978067906-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">New_result_far</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Head</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="7611826601-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="7611826601-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="1978067906-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="1978067906-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │ │    <a href="#more-about-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">More About Lists</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="2196924518-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="2196924518-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2196924518-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="2196924518-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2196924518-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2196924518-3">]</span><span class="gp unselectable">
│ │ │ │ +<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="5435918978-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="5435918978-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5435918978-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="5435918978-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5435918978-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="5435918978-3">]</span><span class="gp unselectable">
│ │ │ │  48&gt; </span><span class="n">M1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="gp unselectable">
│ │ │ │  49&gt; </span><span class="n">T1</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2196924518-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2196924518-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7751909062-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7751909062-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7751909062-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7751909062-2">]</span><span class="gp unselectable">
│ │ │ │ +</span><span class="p" data-group-id="5435918978-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="5435918978-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3750690176-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="3750690176-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3750690176-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="3750690176-2">]</span><span class="gp unselectable">
│ │ │ │  51&gt; </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7751909062-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7751909062-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3546345673-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="3546345673-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3750690176-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="3750690176-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7651235878-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="7651235878-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3546345673-2">(</span><span class="p" data-group-id="3546345673-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3546345673-3">]</span><span class="p" data-group-id="3546345673-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7651235878-2">(</span><span class="p" data-group-id="7651235878-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7651235878-3">]</span><span class="p" data-group-id="7651235878-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="3546345673-4">(</span><span class="n">List</span><span class="p" data-group-id="3546345673-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="3546345673-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3546345673-6">[</span><span class="p" data-group-id="3546345673-6">]</span><span class="p" data-group-id="3546345673-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="7651235878-4">(</span><span class="n">List</span><span class="p" data-group-id="7651235878-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="7651235878-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7651235878-6">[</span><span class="p" data-group-id="7651235878-6">]</span><span class="p" data-group-id="7651235878-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="3546345673-7">(</span><span class="p" data-group-id="3546345673-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3546345673-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="3546345673-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="3546345673-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3546345673-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="3546345673-10">]</span><span class="p" data-group-id="3546345673-9">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="3546345673-11">(</span><span class="p" data-group-id="3546345673-12">[</span><span class="p" data-group-id="3546345673-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="3546345673-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="0641329094-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="0641329094-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0641329094-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="0641329094-2">}</span><span class="gp unselectable">
│ │ │ │ -53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="0641329094-3">(</span><span class="p" data-group-id="0641329094-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0641329094-4">]</span><span class="p" data-group-id="0641329094-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0641329094-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0641329094-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="7651235878-7">(</span><span class="p" data-group-id="7651235878-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7651235878-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="7651235878-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="7651235878-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7651235878-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="7651235878-10">]</span><span class="p" data-group-id="7651235878-9">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="7651235878-11">(</span><span class="p" data-group-id="7651235878-12">[</span><span class="p" data-group-id="7651235878-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="7651235878-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="3024062151-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="3024062151-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3024062151-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="3024062151-2">}</span><span class="gp unselectable">
│ │ │ │ +53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="3024062151-3">(</span><span class="p" data-group-id="3024062151-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3024062151-4">]</span><span class="p" data-group-id="3024062151-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3024062151-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3024062151-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │ │  heads are taken off of the list to be reversed and added to the the
│ │ │ │ -<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="7257043292-1">(</span><span class="p" data-group-id="7257043292-2">[</span><span class="mi">1</span><span class="p">|</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7257043292-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-3">[</span><span class="p" data-group-id="7257043292-3">]</span><span class="p" data-group-id="7257043292-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="7257043292-4">(</span><span class="p" data-group-id="7257043292-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7257043292-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-6">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="7257043292-7">[</span><span class="p" data-group-id="7257043292-7">]</span><span class="p" data-group-id="7257043292-6">]</span><span class="p" data-group-id="7257043292-4">)</span><span class="w">
│ │ │ │ +<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="9756511478-1">(</span><span class="p" data-group-id="9756511478-2">[</span><span class="mi">1</span><span class="p">|</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9756511478-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-3">[</span><span class="p" data-group-id="9756511478-3">]</span><span class="p" data-group-id="9756511478-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="9756511478-4">(</span><span class="p" data-group-id="9756511478-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9756511478-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-6">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="9756511478-7">[</span><span class="p" data-group-id="9756511478-7">]</span><span class="p" data-group-id="9756511478-6">]</span><span class="p" data-group-id="9756511478-4">)</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="7257043292-8">(</span><span class="p" data-group-id="7257043292-9">[</span><span class="mi">2</span><span class="p">|</span><span class="mi">3</span><span class="p" data-group-id="7257043292-9">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-10">[</span><span class="mi">1</span><span class="p" data-group-id="7257043292-10">]</span><span class="p" data-group-id="7257043292-8">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="7257043292-11">(</span><span class="p" data-group-id="7257043292-12">[</span><span class="mi">3</span><span class="p" data-group-id="7257043292-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-13">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="7257043292-14">[</span><span class="mi">1</span><span class="p" data-group-id="7257043292-14">]</span><span class="p">)</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="9756511478-8">(</span><span class="p" data-group-id="9756511478-9">[</span><span class="mi">2</span><span class="p">|</span><span class="mi">3</span><span class="p" data-group-id="9756511478-9">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-10">[</span><span class="mi">1</span><span class="p" data-group-id="9756511478-10">]</span><span class="p" data-group-id="9756511478-8">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="9756511478-11">(</span><span class="p" data-group-id="9756511478-12">[</span><span class="mi">3</span><span class="p" data-group-id="9756511478-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-13">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="9756511478-14">[</span><span class="mi">1</span><span class="p" data-group-id="9756511478-14">]</span><span class="p">)</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="7257043292-15">(</span><span class="p" data-group-id="7257043292-16">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="7257043292-17">[</span><span class="p" data-group-id="7257043292-17">]</span><span class="p" data-group-id="7257043292-16">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-18">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7257043292-18">]</span><span class="p" data-group-id="7257043292-15">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="7257043292-19">(</span><span class="p" data-group-id="7257043292-20">[</span><span class="p" data-group-id="7257043292-20">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-21">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="7257043292-22">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7257043292-22">]</span><span class="p" data-group-id="7257043292-21">]</span><span class="p" data-group-id="7257043292-19">)</span><span class="w">
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="9756511478-15">(</span><span class="p" data-group-id="9756511478-16">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="9756511478-17">[</span><span class="p" data-group-id="9756511478-17">]</span><span class="p" data-group-id="9756511478-16">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-18">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9756511478-18">]</span><span class="p" data-group-id="9756511478-15">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="9756511478-19">(</span><span class="p" data-group-id="9756511478-20">[</span><span class="p" data-group-id="9756511478-20">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-21">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="9756511478-22">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9756511478-22">]</span><span class="p" data-group-id="9756511478-21">]</span><span class="p" data-group-id="9756511478-19">)</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="7257043292-23">(</span><span class="p" data-group-id="7257043292-24">[</span><span class="p" data-group-id="7257043292-24">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7257043292-25">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7257043292-25">]</span><span class="p" data-group-id="7257043292-23">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7257043292-26">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7257043292-26">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="9756511478-23">(</span><span class="p" data-group-id="9756511478-24">[</span><span class="p" data-group-id="9756511478-24">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9756511478-25">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9756511478-25">]</span><span class="p" data-group-id="9756511478-23">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9756511478-26">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9756511478-26">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │ │  for reversing them. So before writing a list-manipulating function it is a good
│ │ │ │  idea to check if one not already is written for you (see the <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a> manual
│ │ │ │  page in STDLIB).</p><p>Now let us get back to the cities and temperatures, but take a more structured
│ │ │ │ -approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3823196799-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="3823196799-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3823196799-2">(</span><span class="p" data-group-id="3823196799-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3823196799-3">]</span><span class="p" data-group-id="3823196799-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3765549084-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="3765549084-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3765549084-2">(</span><span class="p" data-group-id="3765549084-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3765549084-3">]</span><span class="p" data-group-id="3765549084-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="3823196799-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3823196799-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3823196799-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3823196799-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="3765549084-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3765549084-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3765549084-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3765549084-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3823196799-6">(</span><span class="p" data-group-id="3823196799-7">[</span><span class="p" data-group-id="3823196799-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3823196799-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3823196799-9">}</span><span class="p" data-group-id="3823196799-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3823196799-7">]</span><span class="p" data-group-id="3823196799-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3823196799-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3823196799-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3823196799-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="3823196799-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3823196799-11">}</span><span class="p" data-group-id="3823196799-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3823196799-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3823196799-14">(</span><span class="n">Rest</span><span class="p" data-group-id="3823196799-14">)</span><span class="p" data-group-id="3823196799-13">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3823196799-15">(</span><span class="p" data-group-id="3823196799-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3823196799-16">]</span><span class="p" data-group-id="3823196799-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3823196799-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3823196799-18">(</span><span class="n">Rest</span><span class="p" data-group-id="3823196799-18">)</span><span class="p" data-group-id="3823196799-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3823196799-19">(</span><span class="p" data-group-id="3823196799-20">[</span><span class="p" data-group-id="3823196799-20">]</span><span class="p" data-group-id="3823196799-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3823196799-21">[</span><span class="p" data-group-id="3823196799-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="2091953367-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="2091953367-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2091953367-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="2091953367-2">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ -55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="2091953367-3">(</span><span class="p" data-group-id="2091953367-4">[</span><span class="p" data-group-id="2091953367-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="2091953367-6">}</span><span class="p" data-group-id="2091953367-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="2091953367-8">}</span><span class="p" data-group-id="2091953367-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2091953367-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="2091953367-10">}</span><span class="p" data-group-id="2091953367-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="2091953367-12">}</span><span class="p" data-group-id="2091953367-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2091953367-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="2091953367-14">}</span><span class="p" data-group-id="2091953367-13">}</span><span class="p" data-group-id="2091953367-4">]</span><span class="p" data-group-id="2091953367-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2091953367-15">[</span><span class="p" data-group-id="2091953367-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="2091953367-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="2091953367-17">}</span><span class="p" data-group-id="2091953367-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2091953367-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="2091953367-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="2091953367-19">}</span><span class="p" data-group-id="2091953367-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2091953367-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="2091953367-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="2091953367-21">}</span><span class="p" data-group-id="2091953367-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2091953367-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="2091953367-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="2091953367-23">}</span><span class="p" data-group-id="2091953367-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2091953367-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="2091953367-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="2091953367-25">}</span><span class="p" data-group-id="2091953367-24">}</span><span class="p" data-group-id="2091953367-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="6727477234-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="6727477234-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="6727477234-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="6727477234-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3765549084-6">(</span><span class="p" data-group-id="3765549084-7">[</span><span class="p" data-group-id="3765549084-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3765549084-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3765549084-9">}</span><span class="p" data-group-id="3765549084-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3765549084-7">]</span><span class="p" data-group-id="3765549084-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3765549084-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3765549084-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3765549084-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="3765549084-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3765549084-11">}</span><span class="p" data-group-id="3765549084-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3765549084-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3765549084-14">(</span><span class="n">Rest</span><span class="p" data-group-id="3765549084-14">)</span><span class="p" data-group-id="3765549084-13">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3765549084-15">(</span><span class="p" data-group-id="3765549084-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3765549084-16">]</span><span class="p" data-group-id="3765549084-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3765549084-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3765549084-18">(</span><span class="n">Rest</span><span class="p" data-group-id="3765549084-18">)</span><span class="p" data-group-id="3765549084-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3765549084-19">(</span><span class="p" data-group-id="3765549084-20">[</span><span class="p" data-group-id="3765549084-20">]</span><span class="p" data-group-id="3765549084-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3765549084-21">[</span><span class="p" data-group-id="3765549084-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="7291043927-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7291043927-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7291043927-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="7291043927-2">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ +55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="7291043927-3">(</span><span class="p" data-group-id="7291043927-4">[</span><span class="p" data-group-id="7291043927-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7291043927-6">}</span><span class="p" data-group-id="7291043927-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7291043927-8">}</span><span class="p" data-group-id="7291043927-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7291043927-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7291043927-10">}</span><span class="p" data-group-id="7291043927-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7291043927-12">}</span><span class="p" data-group-id="7291043927-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7291043927-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7291043927-14">}</span><span class="p" data-group-id="7291043927-13">}</span><span class="p" data-group-id="7291043927-4">]</span><span class="p" data-group-id="7291043927-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7291043927-15">[</span><span class="p" data-group-id="7291043927-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="7291043927-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7291043927-17">}</span><span class="p" data-group-id="7291043927-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7291043927-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="7291043927-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="7291043927-19">}</span><span class="p" data-group-id="7291043927-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7291043927-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="7291043927-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7291043927-21">}</span><span class="p" data-group-id="7291043927-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7291043927-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="7291043927-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="7291043927-23">}</span><span class="p" data-group-id="7291043927-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7291043927-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="7291043927-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="7291043927-25">}</span><span class="p" data-group-id="7291043927-24">}</span><span class="p" data-group-id="7291043927-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="5018878922-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5018878922-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5018878922-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5018878922-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │ │  off the head of the <code class="inline">List_of_cities</code>, converts it to Celsius if needed. The <code class="inline">|</code>
│ │ │ │ -operator is used to add the (maybe) converted to the converted rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1933480725-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1933480725-2">(</span><span class="n">Rest</span><span class="p" data-group-id="1933480725-2">)</span><span class="p" data-group-id="1933480725-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4353595177-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4353595177-2">(</span><span class="n">Rest</span><span class="p" data-group-id="4353595177-2">)</span><span class="p" data-group-id="4353595177-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1346705894-1">(</span><span class="p" data-group-id="1346705894-2">[</span><span class="p" data-group-id="1346705894-2">]</span><span class="p" data-group-id="1346705894-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1346705894-3">[</span><span class="p" data-group-id="1346705894-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7939940716-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7939940716-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7939940716-2">(</span><span class="p" data-group-id="7939940716-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7939940716-3">]</span><span class="p" data-group-id="7939940716-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7939940716-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7939940716-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7939940716-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7939940716-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7939940716-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="7939940716-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7939940716-7">(</span><span class="p" data-group-id="7939940716-8">[</span><span class="p" data-group-id="7939940716-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7939940716-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7939940716-10">}</span><span class="p" data-group-id="7939940716-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7939940716-8">]</span><span class="p" data-group-id="7939940716-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7939940716-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7939940716-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7939940716-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="7939940716-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7939940716-12">}</span><span class="p" data-group-id="7939940716-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7939940716-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7939940716-15">(</span><span class="n">Rest</span><span class="p" data-group-id="7939940716-15">)</span><span class="p" data-group-id="7939940716-14">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7939940716-16">(</span><span class="p" data-group-id="7939940716-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7939940716-17">]</span><span class="p" data-group-id="7939940716-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7939940716-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7939940716-19">(</span><span class="n">Rest</span><span class="p" data-group-id="7939940716-19">)</span><span class="p" data-group-id="7939940716-18">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7939940716-20">(</span><span class="p" data-group-id="7939940716-21">[</span><span class="p" data-group-id="7939940716-21">]</span><span class="p" data-group-id="7939940716-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7939940716-22">[</span><span class="p" data-group-id="7939940716-22">]</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7939940716-23">(</span><span class="p" data-group-id="7939940716-24">[</span><span class="p" data-group-id="7939940716-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7939940716-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7939940716-26">}</span><span class="p" data-group-id="7939940716-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7939940716-24">]</span><span class="p" data-group-id="7939940716-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7939940716-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7939940716-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7939940716-28">]</span><span class="p" data-group-id="7939940716-27">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7939940716-29">(</span><span class="n">Rest</span><span class="p" data-group-id="7939940716-29">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7939940716-30">(</span><span class="p" data-group-id="7939940716-31">[</span><span class="p" data-group-id="7939940716-31">]</span><span class="p" data-group-id="7939940716-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="0786290456-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0786290456-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0786290456-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="0786290456-2">}</span><span class="gp unselectable">
│ │ │ │ -57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="0786290456-3">(</span><span class="p" data-group-id="0786290456-4">[</span><span class="p" data-group-id="0786290456-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0786290456-6">}</span><span class="p" data-group-id="0786290456-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0786290456-8">}</span><span class="p" data-group-id="0786290456-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0786290456-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0786290456-10">}</span><span class="p" data-group-id="0786290456-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0786290456-12">}</span><span class="p" data-group-id="0786290456-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0786290456-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0786290456-14">}</span><span class="p" data-group-id="0786290456-13">}</span><span class="p" data-group-id="0786290456-4">]</span><span class="p" data-group-id="0786290456-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +operator is used to add the (maybe) converted to the converted rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4477967716-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4477967716-2">(</span><span class="n">Rest</span><span class="p" data-group-id="4477967716-2">)</span><span class="p" data-group-id="4477967716-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5867493332-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5867493332-2">(</span><span class="n">Rest</span><span class="p" data-group-id="5867493332-2">)</span><span class="p" data-group-id="5867493332-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1970342489-1">(</span><span class="p" data-group-id="1970342489-2">[</span><span class="p" data-group-id="1970342489-2">]</span><span class="p" data-group-id="1970342489-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1970342489-3">[</span><span class="p" data-group-id="1970342489-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9237818214-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="9237818214-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9237818214-2">(</span><span class="p" data-group-id="9237818214-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9237818214-3">]</span><span class="p" data-group-id="9237818214-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="9237818214-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="9237818214-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9237818214-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="9237818214-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="9237818214-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="9237818214-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9237818214-7">(</span><span class="p" data-group-id="9237818214-8">[</span><span class="p" data-group-id="9237818214-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9237818214-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="9237818214-10">}</span><span class="p" data-group-id="9237818214-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9237818214-8">]</span><span class="p" data-group-id="9237818214-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9237818214-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9237818214-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9237818214-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="9237818214-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="9237818214-12">}</span><span class="p" data-group-id="9237818214-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9237818214-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9237818214-15">(</span><span class="n">Rest</span><span class="p" data-group-id="9237818214-15">)</span><span class="p" data-group-id="9237818214-14">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9237818214-16">(</span><span class="p" data-group-id="9237818214-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9237818214-17">]</span><span class="p" data-group-id="9237818214-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9237818214-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9237818214-19">(</span><span class="n">Rest</span><span class="p" data-group-id="9237818214-19">)</span><span class="p" data-group-id="9237818214-18">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9237818214-20">(</span><span class="p" data-group-id="9237818214-21">[</span><span class="p" data-group-id="9237818214-21">]</span><span class="p" data-group-id="9237818214-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9237818214-22">[</span><span class="p" data-group-id="9237818214-22">]</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="9237818214-23">(</span><span class="p" data-group-id="9237818214-24">[</span><span class="p" data-group-id="9237818214-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9237818214-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9237818214-26">}</span><span class="p" data-group-id="9237818214-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9237818214-24">]</span><span class="p" data-group-id="9237818214-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9237818214-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9237818214-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9237818214-28">]</span><span class="p" data-group-id="9237818214-27">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="9237818214-29">(</span><span class="n">Rest</span><span class="p" data-group-id="9237818214-29">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="9237818214-30">(</span><span class="p" data-group-id="9237818214-31">[</span><span class="p" data-group-id="9237818214-31">]</span><span class="p" data-group-id="9237818214-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="1146632755-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="1146632755-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1146632755-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="1146632755-2">}</span><span class="gp unselectable">
│ │ │ │ +57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="1146632755-3">(</span><span class="p" data-group-id="1146632755-4">[</span><span class="p" data-group-id="1146632755-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1146632755-6">}</span><span class="p" data-group-id="1146632755-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="1146632755-8">}</span><span class="p" data-group-id="1146632755-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1146632755-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1146632755-10">}</span><span class="p" data-group-id="1146632755-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="1146632755-12">}</span><span class="p" data-group-id="1146632755-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1146632755-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="1146632755-14">}</span><span class="p" data-group-id="1146632755-13">}</span><span class="p" data-group-id="1146632755-4">]</span><span class="p" data-group-id="1146632755-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Now a function has to be added to find the cities with the maximum and minimum
│ │ │ │  temperatures. The following program is not the most efficient way of doing this
│ │ │ │  as you walk through the list of cities four times. But it is better to first
│ │ │ │  strive for clarity and correctness and to make programs efficient only if
│ │ │ │ -needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3163236132-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="3163236132-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3163236132-2">(</span><span class="p" data-group-id="3163236132-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3163236132-3">]</span><span class="p" data-group-id="3163236132-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5679008099-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5679008099-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5679008099-2">(</span><span class="p" data-group-id="5679008099-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5679008099-3">]</span><span class="p" data-group-id="5679008099-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="3163236132-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3163236132-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3163236132-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="3163236132-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="3163236132-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="3163236132-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3163236132-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="3163236132-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="3163236132-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="3163236132-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="3163236132-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="3163236132-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3163236132-10">(</span><span class="p" data-group-id="3163236132-11">[</span><span class="p" data-group-id="3163236132-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3163236132-13">}</span><span class="p" data-group-id="3163236132-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3163236132-11">]</span><span class="p" data-group-id="3163236132-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3163236132-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="3163236132-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3163236132-15">}</span><span class="p" data-group-id="3163236132-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3163236132-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3163236132-18">(</span><span class="n">Rest</span><span class="p" data-group-id="3163236132-18">)</span><span class="p" data-group-id="3163236132-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3163236132-19">(</span><span class="p" data-group-id="3163236132-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3163236132-20">]</span><span class="p" data-group-id="3163236132-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3163236132-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3163236132-22">(</span><span class="n">Rest</span><span class="p" data-group-id="3163236132-22">)</span><span class="p" data-group-id="3163236132-21">]</span><span class="p">;</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3163236132-23">(</span><span class="p" data-group-id="3163236132-24">[</span><span class="p" data-group-id="3163236132-24">]</span><span class="p" data-group-id="3163236132-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3163236132-25">[</span><span class="p" data-group-id="3163236132-25">]</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="3163236132-26">(</span><span class="p" data-group-id="3163236132-27">[</span><span class="p" data-group-id="3163236132-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3163236132-29">}</span><span class="p" data-group-id="3163236132-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3163236132-27">]</span><span class="p" data-group-id="3163236132-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3163236132-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3163236132-31">]</span><span class="p" data-group-id="3163236132-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="3163236132-32">(</span><span class="n">Rest</span><span class="p" data-group-id="3163236132-32">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="3163236132-33">(</span><span class="p" data-group-id="3163236132-34">[</span><span class="p" data-group-id="3163236132-34">]</span><span class="p" data-group-id="3163236132-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="5679008099-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5679008099-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5679008099-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="5679008099-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5679008099-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5679008099-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5679008099-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5679008099-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5679008099-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="5679008099-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5679008099-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="5679008099-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5679008099-10">(</span><span class="p" data-group-id="5679008099-11">[</span><span class="p" data-group-id="5679008099-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5679008099-13">}</span><span class="p" data-group-id="5679008099-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5679008099-11">]</span><span class="p" data-group-id="5679008099-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5679008099-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="5679008099-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5679008099-15">}</span><span class="p" data-group-id="5679008099-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5679008099-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5679008099-18">(</span><span class="n">Rest</span><span class="p" data-group-id="5679008099-18">)</span><span class="p" data-group-id="5679008099-17">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5679008099-19">(</span><span class="p" data-group-id="5679008099-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5679008099-20">]</span><span class="p" data-group-id="5679008099-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5679008099-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5679008099-22">(</span><span class="n">Rest</span><span class="p" data-group-id="5679008099-22">)</span><span class="p" data-group-id="5679008099-21">]</span><span class="p">;</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5679008099-23">(</span><span class="p" data-group-id="5679008099-24">[</span><span class="p" data-group-id="5679008099-24">]</span><span class="p" data-group-id="5679008099-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5679008099-25">[</span><span class="p" data-group-id="5679008099-25">]</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5679008099-26">(</span><span class="p" data-group-id="5679008099-27">[</span><span class="p" data-group-id="5679008099-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5679008099-29">}</span><span class="p" data-group-id="5679008099-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5679008099-27">]</span><span class="p" data-group-id="5679008099-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5679008099-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5679008099-31">]</span><span class="p" data-group-id="5679008099-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="5679008099-32">(</span><span class="n">Rest</span><span class="p" data-group-id="5679008099-32">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="5679008099-33">(</span><span class="p" data-group-id="5679008099-34">[</span><span class="p" data-group-id="5679008099-34">]</span><span class="p" data-group-id="5679008099-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="3163236132-35">(</span><span class="p" data-group-id="3163236132-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3163236132-36">]</span><span class="p" data-group-id="3163236132-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="3163236132-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="3163236132-37">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5679008099-35">(</span><span class="p" data-group-id="5679008099-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5679008099-36">]</span><span class="p" data-group-id="5679008099-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5679008099-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="5679008099-37">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="3163236132-38">(</span><span class="p" data-group-id="3163236132-39">[</span><span class="p" data-group-id="3163236132-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3163236132-41">}</span><span class="p" data-group-id="3163236132-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3163236132-39">]</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="3163236132-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="3163236132-43">}</span><span class="p" data-group-id="3163236132-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="3163236132-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="3163236132-45">}</span><span class="p" data-group-id="3163236132-44">}</span><span class="p" data-group-id="3163236132-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5679008099-38">(</span><span class="p" data-group-id="5679008099-39">[</span><span class="p" data-group-id="5679008099-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5679008099-41">}</span><span class="p" data-group-id="5679008099-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="5679008099-39">]</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="5679008099-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5679008099-43">}</span><span class="p" data-group-id="5679008099-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="5679008099-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5679008099-45">}</span><span class="p" data-group-id="5679008099-44">}</span><span class="p" data-group-id="5679008099-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">Temp</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Max_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3163236132-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3163236132-47">}</span><span class="p" data-group-id="3163236132-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5679008099-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5679008099-47">}</span><span class="p" data-group-id="5679008099-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3163236132-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="3163236132-49">}</span><span class="p" data-group-id="3163236132-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5679008099-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="5679008099-49">}</span><span class="p" data-group-id="5679008099-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │           </span><span class="n">Temp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Min_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3163236132-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3163236132-51">}</span><span class="p" data-group-id="3163236132-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5679008099-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5679008099-51">}</span><span class="p" data-group-id="5679008099-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3163236132-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="3163236132-53">}</span><span class="p" data-group-id="3163236132-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5679008099-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="5679008099-53">}</span><span class="p" data-group-id="5679008099-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="3163236132-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="3163236132-54">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5679008099-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5679008099-54">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="3163236132-55">(</span><span class="p" data-group-id="3163236132-56">[</span><span class="p" data-group-id="3163236132-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="3163236132-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3163236132-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="3163236132-57">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="5679008099-55">(</span><span class="p" data-group-id="5679008099-56">[</span><span class="p" data-group-id="5679008099-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5679008099-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5679008099-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="5679008099-57">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="3163236132-58">(</span><span class="p" data-group-id="3163236132-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="3163236132-60">}</span><span class="p" data-group-id="3163236132-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="3163236132-62">}</span><span class="p" data-group-id="3163236132-61">}</span><span class="p" data-group-id="3163236132-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3163236132-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="3163236132-64">]</span><span class="p" data-group-id="3163236132-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3163236132-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3163236132-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="3163236132-66">]</span><span class="p" data-group-id="3163236132-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="5008585027-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5008585027-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5008585027-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="5008585027-2">}</span><span class="gp unselectable">
│ │ │ │ -59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5008585027-3">(</span><span class="p" data-group-id="5008585027-4">[</span><span class="p" data-group-id="5008585027-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5008585027-6">}</span><span class="p" data-group-id="5008585027-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5008585027-8">}</span><span class="p" data-group-id="5008585027-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5008585027-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5008585027-10">}</span><span class="p" data-group-id="5008585027-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5008585027-12">}</span><span class="p" data-group-id="5008585027-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5008585027-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5008585027-14">}</span><span class="p" data-group-id="5008585027-13">}</span><span class="p" data-group-id="5008585027-4">]</span><span class="p" data-group-id="5008585027-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="5679008099-58">(</span><span class="p" data-group-id="5679008099-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="5679008099-60">}</span><span class="p" data-group-id="5679008099-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="5679008099-62">}</span><span class="p" data-group-id="5679008099-61">}</span><span class="p" data-group-id="5679008099-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5679008099-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="5679008099-64">]</span><span class="p" data-group-id="5679008099-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5679008099-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5679008099-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="5679008099-66">]</span><span class="p" data-group-id="5679008099-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="7234505299-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7234505299-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7234505299-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="7234505299-2">}</span><span class="gp unselectable">
│ │ │ │ +59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="7234505299-3">(</span><span class="p" data-group-id="7234505299-4">[</span><span class="p" data-group-id="7234505299-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7234505299-6">}</span><span class="p" data-group-id="7234505299-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7234505299-8">}</span><span class="p" data-group-id="7234505299-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7234505299-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7234505299-10">}</span><span class="p" data-group-id="7234505299-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7234505299-12">}</span><span class="p" data-group-id="7234505299-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7234505299-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7234505299-14">}</span><span class="p" data-group-id="7234505299-13">}</span><span class="p" data-group-id="7234505299-4">]</span><span class="p" data-group-id="7234505299-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │ │  </span><span class="n">Max</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">cape_town</span><span class="w">
│ │ │ │  </span><span class="n">Min</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">moscow</span><span class="w">
│ │ │ │ @@ -678,88 +678,88 @@
│ │ │ │          Action 4
│ │ │ │  end</code></pre><p>Notice that there is no <code class="inline">;</code> before <code class="inline">end</code>. Conditions do the same as guards, that
│ │ │ │  is, tests that succeed or fail. Erlang starts at the top and tests until it
│ │ │ │  finds a condition that succeeds. Then it evaluates (performs) the action
│ │ │ │  following the condition and ignores all other conditions and actions before the
│ │ │ │  <code class="inline">end</code>. If no condition matches, a run-time failure occurs. A condition that
│ │ │ │  always succeeds is the atom <code class="inline">true</code>. This is often used last in an <code class="inline">if</code>, meaning,
│ │ │ │ -do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8488457310-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="8488457310-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8488457310-2">(</span><span class="p" data-group-id="8488457310-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8488457310-3">]</span><span class="p" data-group-id="8488457310-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3936532397-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="3936532397-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3936532397-2">(</span><span class="p" data-group-id="3936532397-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3936532397-3">]</span><span class="p" data-group-id="3936532397-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">test_if</span><span class="p" data-group-id="8488457310-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8488457310-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">test_if</span><span class="p" data-group-id="3936532397-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3936532397-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8488457310-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8488457310-6">[</span><span class="p" data-group-id="8488457310-6">]</span><span class="p" data-group-id="8488457310-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3936532397-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3936532397-6">[</span><span class="p" data-group-id="3936532397-6">]</span><span class="p" data-group-id="3936532397-5">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">a_equals_5</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8488457310-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8488457310-8">[</span><span class="p" data-group-id="8488457310-8">]</span><span class="p" data-group-id="8488457310-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3936532397-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3936532397-8">[</span><span class="p" data-group-id="3936532397-8">]</span><span class="p" data-group-id="3936532397-7">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">b_equals_6</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                      </span><span class="c1">%That is A equals 2 and B equals 3</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8488457310-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8488457310-10">[</span><span class="p" data-group-id="8488457310-10">]</span><span class="p" data-group-id="8488457310-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3936532397-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3936532397-10">[</span><span class="p" data-group-id="3936532397-10">]</span><span class="p" data-group-id="3936532397-9">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">a_equals_2_b_equals_3</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                     </span><span class="c1">%That is A equals 1 or B equals 7</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8488457310-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8488457310-12">[</span><span class="p" data-group-id="8488457310-12">]</span><span class="p" data-group-id="8488457310-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3936532397-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3936532397-12">[</span><span class="p" data-group-id="3936532397-12">]</span><span class="p" data-group-id="3936532397-11">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="8238578779-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="8238578779-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8238578779-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="8238578779-2">}</span><span class="gp unselectable">
│ │ │ │ -61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="8238578779-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="8238578779-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="6990415280-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="6990415280-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6990415280-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="6990415280-2">}</span><span class="gp unselectable">
│ │ │ │ +61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="6990415280-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="6990415280-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_5</span><span class="gp unselectable">
│ │ │ │ -62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="8238578779-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8238578779-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="6990415280-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6990415280-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w">
│ │ │ │  </span><span class="ss">b_equals_6</span><span class="gp unselectable">
│ │ │ │ -63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="8238578779-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8238578779-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="6990415280-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6990415280-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_2_b_equals_3</span><span class="gp unselectable">
│ │ │ │ -64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="8238578779-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="8238578779-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="6990415280-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="6990415280-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="gp unselectable">
│ │ │ │ -65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="8238578779-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="8238578779-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="6990415280-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="6990415280-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="gp unselectable">
│ │ │ │ -66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="8238578779-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="8238578779-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="6990415280-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="6990415280-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no true branch found when evaluating an if expression
│ │ │ │       in function  tut9:test_if/2 (tut9.erl, line 5)</span></code></pre><p>Notice that <code class="inline">tut9:test_if(33,33)</code> does not cause any condition to succeed. This
│ │ │ │  leads to the run time error <code class="inline">if_clause</code>, here nicely formatted by the shell. See
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml">Guard Sequences</a> for details of the many guard tests
│ │ │ │  available.</p><p><code class="inline">case</code> is another construct in Erlang. Recall that the <code class="inline">convert_length</code> function
│ │ │ │ -was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="1615979947-1">(</span><span class="p" data-group-id="1615979947-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1615979947-2">}</span><span class="p" data-group-id="1615979947-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1615979947-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="1615979947-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="1615979947-4">(</span><span class="p" data-group-id="1615979947-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1615979947-5">}</span><span class="p" data-group-id="1615979947-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1615979947-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="1615979947-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0661659192-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="0661659192-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0661659192-2">(</span><span class="p" data-group-id="0661659192-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0661659192-3">]</span><span class="p" data-group-id="0661659192-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="7399682127-1">(</span><span class="p" data-group-id="7399682127-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7399682127-2">}</span><span class="p" data-group-id="7399682127-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7399682127-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7399682127-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="7399682127-4">(</span><span class="p" data-group-id="7399682127-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7399682127-5">}</span><span class="p" data-group-id="7399682127-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7399682127-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7399682127-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3478691540-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="3478691540-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3478691540-2">(</span><span class="p" data-group-id="3478691540-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3478691540-3">]</span><span class="p" data-group-id="3478691540-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="0661659192-4">(</span><span class="n">Length</span><span class="p" data-group-id="0661659192-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="3478691540-4">(</span><span class="n">Length</span><span class="p" data-group-id="3478691540-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0661659192-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0661659192-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0661659192-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="0661659192-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="0661659192-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0661659192-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="0661659192-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="0661659192-8">}</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="6844504342-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="6844504342-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6844504342-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="6844504342-2">}</span><span class="gp unselectable">
│ │ │ │ -68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="6844504342-3">(</span><span class="p" data-group-id="6844504342-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="6844504342-4">}</span><span class="p" data-group-id="6844504342-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6844504342-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="6844504342-5">}</span><span class="gp unselectable">
│ │ │ │ -69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="6844504342-6">(</span><span class="p" data-group-id="6844504342-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="6844504342-7">}</span><span class="p" data-group-id="6844504342-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6844504342-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="6844504342-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │ │ +        </span><span class="p" data-group-id="3478691540-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3478691540-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3478691540-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="3478691540-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3478691540-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3478691540-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3478691540-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="3478691540-8">}</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="5512489305-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="5512489305-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5512489305-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="5512489305-2">}</span><span class="gp unselectable">
│ │ │ │ +68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="5512489305-3">(</span><span class="p" data-group-id="5512489305-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="5512489305-4">}</span><span class="p" data-group-id="5512489305-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5512489305-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="5512489305-5">}</span><span class="gp unselectable">
│ │ │ │ +69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="5512489305-6">(</span><span class="p" data-group-id="5512489305-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="5512489305-7">}</span><span class="p" data-group-id="5512489305-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5512489305-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="5512489305-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │ │  returned either <code class="inline">{inch,X/2.54}</code> or <code class="inline">{centimeter,Y*2.54}</code>. The behaviour of
│ │ │ │  <code class="inline">case</code> can also be modified by using guards. The following example clarifies
│ │ │ │  this. It tells us the length of a month, given the year. The year must be known,
│ │ │ │ -since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8916391029-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="8916391029-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8916391029-2">(</span><span class="p" data-group-id="8916391029-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8916391029-3">]</span><span class="p" data-group-id="8916391029-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3909369133-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="3909369133-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3909369133-2">(</span><span class="p" data-group-id="3909369133-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3909369133-3">]</span><span class="p" data-group-id="3909369133-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">month_length</span><span class="p" data-group-id="8916391029-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="8916391029-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">month_length</span><span class="p" data-group-id="3909369133-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="3909369133-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% All years divisible by 400 are leap</span><span class="w">
│ │ │ │      </span><span class="c1">%% Years divisible by 100 are not leap (except the 400 rule above)</span><span class="w">
│ │ │ │      </span><span class="c1">%% Years divisible by 4 are leap (except the 100 rule above)</span><span class="w">
│ │ │ │      </span><span class="n">Leap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">if</span><span class="w">
│ │ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="8916391029-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="8916391029-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="3909369133-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="3909369133-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="8916391029-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="8916391029-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="3909369133-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="3909369133-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_leap</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="8916391029-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="8916391029-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="3909369133-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3909369133-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_leap</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Month</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">sep</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">apr</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │ │ @@ -770,151 +770,151 @@
│ │ │ │          </span><span class="ss">jan</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">mar</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">may</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">jul</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">aug</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">oct</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">dec</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="7784179866-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="7784179866-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7784179866-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="7784179866-2">}</span><span class="gp unselectable">
│ │ │ │ -71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="7784179866-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="7784179866-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="1000682403-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="1000682403-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1000682403-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="1000682403-2">}</span><span class="gp unselectable">
│ │ │ │ +71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="1000682403-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="1000682403-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">29</span><span class="gp unselectable">
│ │ │ │ -72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="7784179866-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="7784179866-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="1000682403-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="1000682403-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">28</span><span class="gp unselectable">
│ │ │ │ -73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="7784179866-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="7784179866-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="1000682403-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="1000682403-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">31</span></code></pre><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │ │  </h2>
│ │ │ │  <p>BIFs are functions that for some reason are built-in to the Erlang virtual
│ │ │ │  machine. BIFs often implement functionality that is impossible or is too
│ │ │ │  inefficient to implement in Erlang. Some BIFs can be called using the function
│ │ │ │  name only but they are by default belonging to the <code class="inline">erlang</code> module. For example,
│ │ │ │  the call to the BIF <code class="inline">trunc</code> below is equivalent to a call to <code class="inline">erlang:trunc</code>.</p><p>As shown, first it is checked if a year is leap. If a year is divisible by 400,
│ │ │ │  it is a leap year. To determine this, first divide the year by 400 and use the
│ │ │ │  BIF <code class="inline">trunc</code> (more about this later) to cut off any decimals. Then multiply by
│ │ │ │  400 again and see if the same value is returned again. For example, year 2004:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2004</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.01</span><span class="w">
│ │ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="2358975269-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="2358975269-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="3392954459-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="3392954459-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>2000 is not the same as 2004, so 2004 is not divisible by 400. Year 2000:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2000</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.0</span><span class="w">
│ │ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="9331981299-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="9331981299-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="1510734065-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="1510734065-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>That is, a leap year. The next two <code class="inline">trunc</code>-tests evaluate if the year is
│ │ │ │  divisible by 100 or 4 in the same way. The first <code class="inline">if</code> returns <code class="inline">leap</code> or
│ │ │ │  <code class="inline">not_leap</code>, which lands up in the variable <code class="inline">Leap</code>. This variable is used in the
│ │ │ │  guard for <code class="inline">feb</code> in the following <code class="inline">case</code> that tells us how long the month is.</p><p>This example showed the use of <code class="inline">trunc</code>. It is easier to use the Erlang operator
│ │ │ │  <code class="inline">rem</code> that gives the remainder after division, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">74&gt; </span><span class="mi">2004</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="3639800693-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="3639800693-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="0929438974-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="0929438974-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>it can be written:</p><pre><code class="makeup erlang" translate="no"><span class="n">Year</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>There are many other BIFs such as <code class="inline">trunc</code>. Only a few BIFs can be used in
│ │ │ │  guards, and you cannot use functions you have defined yourself in guards. (see
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml">Guard Sequences</a>) (For advanced readers: This is to
│ │ │ │  ensure that guards do not have side effects.) Let us play with a few of these
│ │ │ │ -functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="0376843056-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="0376843056-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="5797222569-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="5797222569-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">5</span><span class="gp unselectable">
│ │ │ │ -76&gt; </span><span class="nf">round</span><span class="p" data-group-id="0376843056-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="0376843056-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +76&gt; </span><span class="nf">round</span><span class="p" data-group-id="5797222569-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="5797222569-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">6</span><span class="gp unselectable">
│ │ │ │ -77&gt; </span><span class="nf">length</span><span class="p" data-group-id="0376843056-3">(</span><span class="p" data-group-id="0376843056-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="0376843056-4">]</span><span class="p" data-group-id="0376843056-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +77&gt; </span><span class="nf">length</span><span class="p" data-group-id="5797222569-3">(</span><span class="p" data-group-id="5797222569-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="5797222569-4">]</span><span class="p" data-group-id="5797222569-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ │ -78&gt; </span><span class="nf">float</span><span class="p" data-group-id="0376843056-5">(</span><span class="mi">5</span><span class="p" data-group-id="0376843056-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +78&gt; </span><span class="nf">float</span><span class="p" data-group-id="5797222569-5">(</span><span class="mi">5</span><span class="p" data-group-id="5797222569-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">5.0</span><span class="gp unselectable">
│ │ │ │ -79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="0376843056-6">(</span><span class="ss">hello</span><span class="p" data-group-id="0376843056-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="5797222569-6">(</span><span class="ss">hello</span><span class="p" data-group-id="5797222569-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="0376843056-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0376843056-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="5797222569-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5797222569-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │ -81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="0376843056-8">(</span><span class="p" data-group-id="0376843056-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376843056-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="0376843056-10">}</span><span class="p" data-group-id="0376843056-9">}</span><span class="p" data-group-id="0376843056-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="5797222569-8">(</span><span class="p" data-group-id="5797222569-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5797222569-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="5797222569-10">}</span><span class="p" data-group-id="5797222569-9">}</span><span class="p" data-group-id="5797222569-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="0376843056-11">(</span><span class="p" data-group-id="0376843056-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376843056-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="0376843056-13">}</span><span class="p" data-group-id="0376843056-12">]</span><span class="p" data-group-id="0376843056-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="5797222569-11">(</span><span class="p" data-group-id="5797222569-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5797222569-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="5797222569-13">}</span><span class="p" data-group-id="5797222569-12">]</span><span class="p" data-group-id="5797222569-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><p>All of these can be used in guards. Now for some BIFs that cannot be used in
│ │ │ │ -guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="4776435714-1">(</span><span class="ss">hello</span><span class="p" data-group-id="4776435714-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="4652016661-1">(</span><span class="ss">hello</span><span class="p" data-group-id="4652016661-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ │ -84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="4776435714-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="4776435714-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="4652016661-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="4652016661-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span><span class="gp unselectable">
│ │ │ │ -85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="4776435714-3">(</span><span class="mi">22</span><span class="p" data-group-id="4776435714-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="4652016661-3">(</span><span class="mi">22</span><span class="p" data-group-id="4652016661-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;22&quot;</span></code></pre><p>These three BIFs do conversions that would be difficult (or impossible) to do in
│ │ │ │  Erlang.</p><h2 id="higher-order-functions-funs" class="section-heading">
│ │ │ │    <a href="#higher-order-functions-funs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Higher-Order Functions (Funs)</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang, like most modern functional programming languages, has higher-order
│ │ │ │ -functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7811590314-1">(</span><span class="n">X</span><span class="p" data-group-id="7811590314-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0064602872-1">(</span><span class="n">X</span><span class="p" data-group-id="0064602872-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="7811590314-2">(</span><span class="mi">5</span><span class="p" data-group-id="7811590314-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="0064602872-2">(</span><span class="mi">5</span><span class="p" data-group-id="0064602872-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span></code></pre><p>Here is defined a function that doubles the value of a number and assigned this
│ │ │ │  function to a variable. Thus <code class="inline">Xf(5)</code> returns value 10. Two useful functions when
│ │ │ │ -working with lists are <code class="inline">foreach</code> and <code class="inline">map</code>, which are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1657857158-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1657857158-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1657857158-2">]</span><span class="p" data-group-id="1657857158-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Fun</span><span class="p" data-group-id="1657857158-3">(</span><span class="n">First</span><span class="p" data-group-id="1657857158-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="1657857158-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1657857158-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="1657857158-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1657857158-6">[</span><span class="p" data-group-id="1657857158-6">]</span><span class="p" data-group-id="1657857158-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +working with lists are <code class="inline">foreach</code> and <code class="inline">map</code>, which are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1573377140-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1573377140-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1573377140-2">]</span><span class="p" data-group-id="1573377140-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Fun</span><span class="p" data-group-id="1573377140-3">(</span><span class="n">First</span><span class="p" data-group-id="1573377140-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="1573377140-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1573377140-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="1573377140-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1573377140-6">[</span><span class="p" data-group-id="1573377140-6">]</span><span class="p" data-group-id="1573377140-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="1657857158-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1657857158-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1657857158-8">]</span><span class="p" data-group-id="1657857158-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1657857158-9">[</span><span class="n">Fun</span><span class="p" data-group-id="1657857158-10">(</span><span class="n">First</span><span class="p" data-group-id="1657857158-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="1657857158-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="1657857158-11">)</span><span class="p" data-group-id="1657857158-9">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="1657857158-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1657857158-13">[</span><span class="p" data-group-id="1657857158-13">]</span><span class="p" data-group-id="1657857158-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1657857158-14">[</span><span class="p" data-group-id="1657857158-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="1573377140-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1573377140-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1573377140-8">]</span><span class="p" data-group-id="1573377140-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1573377140-9">[</span><span class="n">Fun</span><span class="p" data-group-id="1573377140-10">(</span><span class="n">First</span><span class="p" data-group-id="1573377140-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="1573377140-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="1573377140-11">)</span><span class="p" data-group-id="1573377140-9">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="1573377140-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1573377140-13">[</span><span class="p" data-group-id="1573377140-13">]</span><span class="p" data-group-id="1573377140-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1573377140-14">[</span><span class="p" data-group-id="1573377140-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │ │  a list and applies a fun to every element in the list. <code class="inline">map</code> creates a new list
│ │ │ │  by applying a fun to every element in a list. Going back to the shell, <code class="inline">map</code> is
│ │ │ │ -used and a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6754188627-1">(</span><span class="n">X</span><span class="p" data-group-id="6754188627-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +used and a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5361829161-1">(</span><span class="n">X</span><span class="p" data-group-id="5361829161-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="6754188627-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6754188627-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6754188627-3">]</span><span class="p" data-group-id="6754188627-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6754188627-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6754188627-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8173025023-1">(</span><span class="p" data-group-id="8173025023-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8173025023-3">}</span><span class="p" data-group-id="8173025023-2">}</span><span class="p" data-group-id="8173025023-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8173025023-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8173025023-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8173025023-5">]</span><span class="p" data-group-id="8173025023-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="5361829161-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5361829161-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5361829161-3">]</span><span class="p" data-group-id="5361829161-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5361829161-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5361829161-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7867024259-1">(</span><span class="p" data-group-id="7867024259-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7867024259-3">}</span><span class="p" data-group-id="7867024259-2">}</span><span class="p" data-group-id="7867024259-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7867024259-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7867024259-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7867024259-5">]</span><span class="p" data-group-id="7867024259-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="8173025023-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-7">[</span><span class="p" data-group-id="8173025023-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8173025023-9">}</span><span class="p" data-group-id="8173025023-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8173025023-11">}</span><span class="p" data-group-id="8173025023-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8173025023-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="8173025023-13">}</span><span class="p" data-group-id="8173025023-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8173025023-15">}</span><span class="p" data-group-id="8173025023-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8173025023-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="8173025023-17">}</span><span class="p" data-group-id="8173025023-16">}</span><span class="p" data-group-id="8173025023-7">]</span><span class="p" data-group-id="8173025023-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7867024259-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-7">[</span><span class="p" data-group-id="7867024259-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7867024259-9">}</span><span class="p" data-group-id="7867024259-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7867024259-11">}</span><span class="p" data-group-id="7867024259-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7867024259-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7867024259-13">}</span><span class="p" data-group-id="7867024259-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7867024259-15">}</span><span class="p" data-group-id="7867024259-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867024259-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7867024259-17">}</span><span class="p" data-group-id="7867024259-16">}</span><span class="p" data-group-id="7867024259-7">]</span><span class="p" data-group-id="7867024259-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w">
│ │ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="ss">f</span><span class="w"> </span><span class="mi">70</span><span class="w">
│ │ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="w">
│ │ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="ss">f</span><span class="w"> </span><span class="mi">28</span><span class="w">
│ │ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="ss">f</span><span class="w"> </span><span class="mi">36</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Let us now define a fun that can be used to go through a list of cities and
│ │ │ │ -temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9555969941-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="9555969941-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3333047197-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="3333047197-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9555969941-2">(</span><span class="p" data-group-id="9555969941-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9555969941-3">]</span><span class="p" data-group-id="9555969941-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3333047197-2">(</span><span class="p" data-group-id="3333047197-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3333047197-3">]</span><span class="p" data-group-id="3333047197-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="9555969941-4">(</span><span class="p" data-group-id="9555969941-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9555969941-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9555969941-6">}</span><span class="p" data-group-id="9555969941-5">}</span><span class="p" data-group-id="9555969941-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9555969941-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9555969941-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="9555969941-9">(</span><span class="p" data-group-id="9555969941-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="9555969941-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="9555969941-9">)</span><span class="p" data-group-id="9555969941-8">}</span><span class="p" data-group-id="9555969941-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="9555969941-11">(</span><span class="p" data-group-id="9555969941-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9555969941-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9555969941-13">}</span><span class="p" data-group-id="9555969941-12">}</span><span class="p" data-group-id="9555969941-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9555969941-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9555969941-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9555969941-15">}</span><span class="p" data-group-id="9555969941-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9555969941-16">(</span><span class="n">List</span><span class="p" data-group-id="9555969941-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9555969941-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9555969941-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5830225539-1">(</span><span class="p" data-group-id="5830225539-2">[</span><span class="p" data-group-id="5830225539-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5830225539-4">}</span><span class="p" data-group-id="5830225539-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5830225539-6">}</span><span class="p" data-group-id="5830225539-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5830225539-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5830225539-8">}</span><span class="p" data-group-id="5830225539-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5830225539-10">}</span><span class="p" data-group-id="5830225539-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5830225539-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5830225539-12">}</span><span class="p" data-group-id="5830225539-11">}</span><span class="p" data-group-id="5830225539-2">]</span><span class="p" data-group-id="5830225539-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5830225539-13">[</span><span class="p" data-group-id="5830225539-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="5830225539-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5830225539-15">}</span><span class="p" data-group-id="5830225539-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5830225539-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="5830225539-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="5830225539-17">}</span><span class="p" data-group-id="5830225539-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5830225539-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="5830225539-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5830225539-19">}</span><span class="p" data-group-id="5830225539-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5830225539-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="5830225539-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="5830225539-21">}</span><span class="p" data-group-id="5830225539-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5830225539-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="5830225539-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5830225539-23">}</span><span class="p" data-group-id="5830225539-22">}</span><span class="p" data-group-id="5830225539-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1290811836-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1290811836-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="3333047197-4">(</span><span class="p" data-group-id="3333047197-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3333047197-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3333047197-6">}</span><span class="p" data-group-id="3333047197-5">}</span><span class="p" data-group-id="3333047197-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3333047197-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3333047197-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="3333047197-9">(</span><span class="p" data-group-id="3333047197-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="3333047197-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="3333047197-9">)</span><span class="p" data-group-id="3333047197-8">}</span><span class="p" data-group-id="3333047197-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="3333047197-11">(</span><span class="p" data-group-id="3333047197-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3333047197-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3333047197-13">}</span><span class="p" data-group-id="3333047197-12">}</span><span class="p" data-group-id="3333047197-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3333047197-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3333047197-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="3333047197-15">}</span><span class="p" data-group-id="3333047197-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3333047197-16">(</span><span class="n">List</span><span class="p" data-group-id="3333047197-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3333047197-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3333047197-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1764525353-1">(</span><span class="p" data-group-id="1764525353-2">[</span><span class="p" data-group-id="1764525353-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1764525353-4">}</span><span class="p" data-group-id="1764525353-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="1764525353-6">}</span><span class="p" data-group-id="1764525353-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1764525353-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1764525353-8">}</span><span class="p" data-group-id="1764525353-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="1764525353-10">}</span><span class="p" data-group-id="1764525353-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1764525353-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="1764525353-12">}</span><span class="p" data-group-id="1764525353-11">}</span><span class="p" data-group-id="1764525353-2">]</span><span class="p" data-group-id="1764525353-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1764525353-13">[</span><span class="p" data-group-id="1764525353-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="1764525353-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1764525353-15">}</span><span class="p" data-group-id="1764525353-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1764525353-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="1764525353-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="1764525353-17">}</span><span class="p" data-group-id="1764525353-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1764525353-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="1764525353-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1764525353-19">}</span><span class="p" data-group-id="1764525353-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1764525353-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="1764525353-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="1764525353-21">}</span><span class="p" data-group-id="1764525353-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1764525353-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="1764525353-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1764525353-23">}</span><span class="p" data-group-id="1764525353-22">}</span><span class="p" data-group-id="1764525353-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="5999024774-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5999024774-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │ │  <code class="inline">Function/Arity</code> (remember that <code class="inline">Arity</code> = number of arguments). So in the
│ │ │ │  <code class="inline">map</code>-call <code class="inline">lists:map(fun convert_to_c/1, List)</code> is written. As shown,
│ │ │ │  <code class="inline">convert_list_to_c</code> becomes much shorter and easier to understand.</p><p>The standard module <code class="inline">lists</code> also contains a function <code class="inline">sort(Fun, List)</code> where
│ │ │ │  <code class="inline">Fun</code> is a fun with two arguments. This fun returns <code class="inline">true</code> if the first argument
│ │ │ │  is less than the second argument, or else <code class="inline">false</code>. Sorting is added to the
│ │ │ │ -<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2686767334-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="2686767334-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1731098346-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="1731098346-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2686767334-2">(</span><span class="p" data-group-id="2686767334-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2686767334-3">]</span><span class="p" data-group-id="2686767334-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1731098346-2">(</span><span class="p" data-group-id="1731098346-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1731098346-3">]</span><span class="p" data-group-id="1731098346-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="2686767334-4">(</span><span class="p" data-group-id="2686767334-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="2686767334-6">}</span><span class="p" data-group-id="2686767334-5">}</span><span class="p" data-group-id="2686767334-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2686767334-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="2686767334-9">(</span><span class="p" data-group-id="2686767334-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="2686767334-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="2686767334-9">)</span><span class="p" data-group-id="2686767334-8">}</span><span class="p" data-group-id="2686767334-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="2686767334-11">(</span><span class="p" data-group-id="2686767334-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="2686767334-13">}</span><span class="p" data-group-id="2686767334-12">}</span><span class="p" data-group-id="2686767334-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2686767334-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="2686767334-15">}</span><span class="p" data-group-id="2686767334-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2686767334-16">(</span><span class="n">List</span><span class="p" data-group-id="2686767334-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2686767334-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2686767334-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="2686767334-18">(</span><span class="nf">fun</span><span class="p" data-group-id="2686767334-19">(</span><span class="p" data-group-id="2686767334-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="2686767334-21">}</span><span class="p" data-group-id="2686767334-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2686767334-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="2686767334-23">}</span><span class="p" data-group-id="2686767334-22">}</span><span class="p" data-group-id="2686767334-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="2686767334-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="7732978970-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="7732978970-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7732978970-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="7732978970-2">}</span><span class="gp unselectable">
│ │ │ │ -94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7732978970-3">(</span><span class="p" data-group-id="7732978970-4">[</span><span class="p" data-group-id="7732978970-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7732978970-6">}</span><span class="p" data-group-id="7732978970-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7732978970-8">}</span><span class="p" data-group-id="7732978970-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7732978970-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7732978970-10">}</span><span class="p" data-group-id="7732978970-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7732978970-12">}</span><span class="p" data-group-id="7732978970-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7732978970-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7732978970-14">}</span><span class="p" data-group-id="7732978970-13">}</span><span class="p" data-group-id="7732978970-4">]</span><span class="p" data-group-id="7732978970-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7732978970-15">[</span><span class="p" data-group-id="7732978970-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="7732978970-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7732978970-17">}</span><span class="p" data-group-id="7732978970-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7732978970-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="7732978970-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7732978970-19">}</span><span class="p" data-group-id="7732978970-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7732978970-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="7732978970-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="7732978970-21">}</span><span class="p" data-group-id="7732978970-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7732978970-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="7732978970-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7732978970-23">}</span><span class="p" data-group-id="7732978970-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7732978970-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="7732978970-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="7732978970-25">}</span><span class="p" data-group-id="7732978970-24">}</span><span class="p" data-group-id="7732978970-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="3802171142-1">(</span><span class="p" data-group-id="3802171142-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3802171142-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="3802171142-3">}</span><span class="p" data-group-id="3802171142-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3802171142-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3802171142-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="3802171142-5">}</span><span class="p" data-group-id="3802171142-4">}</span><span class="p" data-group-id="3802171142-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="1731098346-4">(</span><span class="p" data-group-id="1731098346-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1731098346-6">}</span><span class="p" data-group-id="1731098346-5">}</span><span class="p" data-group-id="1731098346-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1731098346-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="1731098346-9">(</span><span class="p" data-group-id="1731098346-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="1731098346-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1731098346-9">)</span><span class="p" data-group-id="1731098346-8">}</span><span class="p" data-group-id="1731098346-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="1731098346-11">(</span><span class="p" data-group-id="1731098346-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1731098346-13">}</span><span class="p" data-group-id="1731098346-12">}</span><span class="p" data-group-id="1731098346-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1731098346-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="1731098346-15">}</span><span class="p" data-group-id="1731098346-14">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1731098346-16">(</span><span class="n">List</span><span class="p" data-group-id="1731098346-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1731098346-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1731098346-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="1731098346-18">(</span><span class="nf">fun</span><span class="p" data-group-id="1731098346-19">(</span><span class="p" data-group-id="1731098346-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="1731098346-21">}</span><span class="p" data-group-id="1731098346-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1731098346-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="1731098346-23">}</span><span class="p" data-group-id="1731098346-22">}</span><span class="p" data-group-id="1731098346-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="1731098346-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="0471073193-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="0471073193-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0471073193-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="0471073193-2">}</span><span class="gp unselectable">
│ │ │ │ +94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0471073193-3">(</span><span class="p" data-group-id="0471073193-4">[</span><span class="p" data-group-id="0471073193-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0471073193-6">}</span><span class="p" data-group-id="0471073193-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0471073193-8">}</span><span class="p" data-group-id="0471073193-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0471073193-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0471073193-10">}</span><span class="p" data-group-id="0471073193-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0471073193-12">}</span><span class="p" data-group-id="0471073193-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0471073193-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0471073193-14">}</span><span class="p" data-group-id="0471073193-13">}</span><span class="p" data-group-id="0471073193-4">]</span><span class="p" data-group-id="0471073193-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0471073193-15">[</span><span class="p" data-group-id="0471073193-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="0471073193-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0471073193-17">}</span><span class="p" data-group-id="0471073193-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0471073193-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="0471073193-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0471073193-19">}</span><span class="p" data-group-id="0471073193-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0471073193-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0471073193-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="0471073193-21">}</span><span class="p" data-group-id="0471073193-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0471073193-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="0471073193-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0471073193-23">}</span><span class="p" data-group-id="0471073193-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0471073193-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="0471073193-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="0471073193-25">}</span><span class="p" data-group-id="0471073193-24">}</span><span class="p" data-group-id="0471073193-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="9283906751-1">(</span><span class="p" data-group-id="9283906751-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9283906751-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="9283906751-3">}</span><span class="p" data-group-id="9283906751-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9283906751-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9283906751-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="9283906751-5">}</span><span class="p" data-group-id="9283906751-4">}</span><span class="p" data-group-id="9283906751-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │ │  shorthand for a variable that gets a value, but the value is ignored. This can
│ │ │ │  be used anywhere suitable, not just in funs. <code class="inline">Temp1 &lt; Temp2</code> returns <code class="inline">true</code> if
│ │ │ │  <code class="inline">Temp1</code> is less than <code class="inline">Temp2</code>.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/robustness.xhtml
│ │ │ │ @@ -33,68 +33,68 @@
│ │ │ │  </h2>
│ │ │ │  <p>Before improving the messenger program, let us look at some general principles,
│ │ │ │  using the ping pong program as an example. Recall that when &quot;ping&quot; finishes, it
│ │ │ │  tells &quot;pong&quot; that it has done so by sending the atom <code class="inline">finished</code> as a message to
│ │ │ │  &quot;pong&quot; so that &quot;pong&quot; can also finish. Another way to let &quot;pong&quot; finish is to
│ │ │ │  make &quot;pong&quot; exit if it does not receive a message from ping within a certain
│ │ │ │  time. This can be done by adding a <em>time-out</em> to <code class="inline">pong</code> as shown in the
│ │ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1739829805-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="1739829805-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4247973458-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="4247973458-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1739829805-2">(</span><span class="p" data-group-id="1739829805-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1739829805-3">]</span><span class="p" data-group-id="1739829805-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4247973458-2">(</span><span class="p" data-group-id="4247973458-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4247973458-3">]</span><span class="p" data-group-id="4247973458-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="1739829805-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739829805-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739829805-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739829805-6">[</span><span class="p" data-group-id="1739829805-6">]</span><span class="p" data-group-id="1739829805-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="4247973458-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4247973458-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4247973458-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247973458-6">[</span><span class="p" data-group-id="4247973458-6">]</span><span class="p" data-group-id="4247973458-5">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="1739829805-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739829805-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1739829805-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739829805-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1739829805-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1739829805-10">(</span><span class="p" data-group-id="1739829805-10">)</span><span class="p" data-group-id="1739829805-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="4247973458-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4247973458-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4247973458-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4247973458-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4247973458-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4247973458-10">(</span><span class="p" data-group-id="4247973458-10">)</span><span class="p" data-group-id="4247973458-9">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739829805-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739829805-12">[</span><span class="p" data-group-id="1739829805-12">]</span><span class="p" data-group-id="1739829805-11">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4247973458-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247973458-12">[</span><span class="p" data-group-id="4247973458-12">]</span><span class="p" data-group-id="4247973458-11">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="1739829805-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739829805-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="4247973458-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4247973458-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="1739829805-14">(</span><span class="p" data-group-id="1739829805-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="4247973458-14">(</span><span class="p" data-group-id="4247973458-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1739829805-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1739829805-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739829805-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739829805-17">[</span><span class="p" data-group-id="1739829805-17">]</span><span class="p" data-group-id="1739829805-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4247973458-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4247973458-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4247973458-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247973458-17">[</span><span class="p" data-group-id="4247973458-17">]</span><span class="p" data-group-id="4247973458-16">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="1739829805-18">(</span><span class="p" data-group-id="1739829805-18">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="4247973458-18">(</span><span class="p" data-group-id="4247973458-18">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739829805-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739829805-20">[</span><span class="p" data-group-id="1739829805-20">]</span><span class="p" data-group-id="1739829805-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4247973458-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247973458-20">[</span><span class="p" data-group-id="4247973458-20">]</span><span class="p" data-group-id="4247973458-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="1739829805-21">(</span><span class="p" data-group-id="1739829805-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1739829805-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1739829805-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739829805-24">[</span><span class="p" data-group-id="1739829805-24">]</span><span class="p" data-group-id="1739829805-23">)</span><span class="p" data-group-id="1739829805-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="4247973458-21">(</span><span class="p" data-group-id="4247973458-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4247973458-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4247973458-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247973458-24">[</span><span class="p" data-group-id="4247973458-24">]</span><span class="p" data-group-id="4247973458-23">)</span><span class="p" data-group-id="4247973458-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="1739829805-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="1739829805-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1739829805-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739829805-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739829805-27">]</span><span class="p" data-group-id="1739829805-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="4247973458-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="4247973458-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4247973458-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247973458-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="4247973458-27">]</span><span class="p" data-group-id="4247973458-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │ │  directories, the following is seen on (pong@kosken):</p><pre><code class="text">(pong@kosken)1&gt; tut19:start_pong().
│ │ │ │  true
│ │ │ │  Pong received ping
│ │ │ │  Pong received ping
│ │ │ │  Pong received ping
│ │ │ │  Pong timed out</code></pre><p>And the following is seen on (ping@gollum):</p><pre><code class="text">(ping@gollum)1&gt; tut19:start_ping(pong@kosken).
│ │ │ │  &lt;0.36.0&gt;
│ │ │ │  Ping received pong
│ │ │ │  Ping received pong
│ │ │ │  Ping received pong
│ │ │ │ -ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="7709881855-1">(</span><span class="p" data-group-id="7709881855-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="9777345883-1">(</span><span class="p" data-group-id="9777345883-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7709881855-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7709881855-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7709881855-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7709881855-4">[</span><span class="p" data-group-id="7709881855-4">]</span><span class="p" data-group-id="7709881855-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9777345883-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9777345883-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9777345883-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9777345883-4">[</span><span class="p" data-group-id="9777345883-4">]</span><span class="p" data-group-id="9777345883-3">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="7709881855-5">(</span><span class="p" data-group-id="7709881855-5">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="9777345883-5">(</span><span class="p" data-group-id="9777345883-5">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7709881855-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7709881855-7">[</span><span class="p" data-group-id="7709881855-7">]</span><span class="p" data-group-id="7709881855-6">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9777345883-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9777345883-7">[</span><span class="p" data-group-id="9777345883-7">]</span><span class="p" data-group-id="9777345883-6">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The time-out (<code class="inline">after 5000</code>) is started when <code class="inline">receive</code> is entered. The time-out
│ │ │ │  is canceled if <code class="inline">{ping,Ping_PID}</code> is received. If <code class="inline">{ping,Ping_PID}</code> is not
│ │ │ │  received, the actions following the time-out are done after 5000 milliseconds.
│ │ │ │  <code class="inline">after</code> must be last in the <code class="inline">receive</code>, that is, preceded by all other message
│ │ │ │  reception specifications in the <code class="inline">receive</code>. It is also possible to call a
│ │ │ │ -function that returned an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="1886598704-1">(</span><span class="p" data-group-id="1886598704-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │ │ +function that returned an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="3181431269-1">(</span><span class="p" data-group-id="3181431269-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │ │  distributed Erlang system. Time-outs are usually appropriate to supervise
│ │ │ │  external events, for example, if you have expected a message from some external
│ │ │ │  system within a specified time. For example, a time-out can be used to log a
│ │ │ │  user out of the messenger system if they have not accessed it for, say, ten
│ │ │ │  minutes.</p><h2 id="error-handling" class="section-heading">
│ │ │ │    <a href="#error-handling" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -114,96 +114,96 @@
│ │ │ │  something called a <em>signal</em> to all the processes it has links to.</p><p>The signal carries information about the pid it was sent from and the exit
│ │ │ │  reason.</p><p>The default behaviour of a process that receives a normal exit is to ignore the
│ │ │ │  signal.</p><p>The default behaviour in the two other cases (that is, abnormal exit) above is
│ │ │ │  to:</p><ul><li>Bypass all messages to the receiving process.</li><li>Kill the receiving process.</li><li>Propagate the same error signal to the links of the killed process.</li></ul><p>In this way you can connect all processes in a transaction together using links.
│ │ │ │  If one of the processes exits abnormally, all the processes in the transaction
│ │ │ │  are killed. As it is often wanted to create a process and link to it at the same
│ │ │ │  time, there is a special BIF, <a href="../../../lib/../erts/doc/html/erlang.html#spawn_link/1">spawn_link</a> that does the
│ │ │ │ -same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7163007563-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="7163007563-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9851649644-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="9851649644-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7163007563-2">(</span><span class="p" data-group-id="7163007563-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7163007563-3">]</span><span class="p" data-group-id="7163007563-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9851649644-2">(</span><span class="p" data-group-id="9851649644-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9851649644-3">]</span><span class="p" data-group-id="9851649644-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7163007563-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7163007563-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="7163007563-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="7163007563-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="7163007563-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7163007563-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="9851649644-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9851649644-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="9851649644-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="9851649644-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="9851649644-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9851649644-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="7163007563-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7163007563-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="7163007563-8">(</span><span class="ss">ping</span><span class="p" data-group-id="7163007563-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="9851649644-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9851649644-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="9851649644-8">(</span><span class="ss">ping</span><span class="p" data-group-id="9851649644-8">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="7163007563-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7163007563-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7163007563-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7163007563-11">(</span><span class="p" data-group-id="7163007563-11">)</span><span class="p" data-group-id="7163007563-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="9851649644-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9851649644-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9851649644-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9851649644-11">(</span><span class="p" data-group-id="9851649644-11">)</span><span class="p" data-group-id="9851649644-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7163007563-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163007563-13">[</span><span class="p" data-group-id="7163007563-13">]</span><span class="p" data-group-id="7163007563-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9851649644-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9851649644-13">[</span><span class="p" data-group-id="9851649644-13">]</span><span class="p" data-group-id="9851649644-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="7163007563-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="7163007563-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="9851649644-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9851649644-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="7163007563-15">(</span><span class="p" data-group-id="7163007563-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="9851649644-15">(</span><span class="p" data-group-id="9851649644-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7163007563-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7163007563-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7163007563-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163007563-18">[</span><span class="p" data-group-id="7163007563-18">]</span><span class="p" data-group-id="7163007563-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9851649644-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9851649644-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9851649644-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9851649644-18">[</span><span class="p" data-group-id="9851649644-18">]</span><span class="p" data-group-id="9851649644-17">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="7163007563-19">(</span><span class="p" data-group-id="7163007563-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="9851649644-19">(</span><span class="p" data-group-id="9851649644-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="7163007563-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="7163007563-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7163007563-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163007563-22">[</span><span class="p" data-group-id="7163007563-22">]</span><span class="p" data-group-id="7163007563-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7163007563-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7163007563-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="7163007563-24">]</span><span class="p" data-group-id="7163007563-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9851649644-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="9851649644-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9851649644-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9851649644-22">[</span><span class="p" data-group-id="9851649644-22">]</span><span class="p" data-group-id="9851649644-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9851649644-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9851649644-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="9851649644-24">]</span><span class="p" data-group-id="9851649644-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │ │  Pong received ping
│ │ │ │  &lt;3820.41.0&gt;
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong</code></pre><p>This is a slight modification of the ping pong program where both processes are
│ │ │ │  spawned from the same <code class="inline">start/1</code> function, and the &quot;ping&quot; process can be spawned
│ │ │ │  on a separate node. Notice the use of the <code class="inline">link</code> BIF. &quot;Ping&quot; calls
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(ping)</code></a> when it finishes and this causes an exit signal to be
│ │ │ │  sent to &quot;pong&quot;, which also terminates.</p><p>It is possible to modify the default behaviour of a process so that it does not
│ │ │ │  get killed when it receives abnormal exit signals. Instead, all signals are
│ │ │ │  turned into normal messages on the format <code class="inline">{'EXIT',FromPID,Reason}</code> and added to
│ │ │ │ -the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="9734932363-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9734932363-1">)</span></code></pre><p>There are several other process flags, see <a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │ │ +the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="6281876063-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6281876063-1">)</span></code></pre><p>There are several other process flags, see <a href="../../../lib/../erts/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │ │  Changing the default behaviour of a process in this way is usually not done in
│ │ │ │  standard user programs, but is left to the supervisory programs in OTP. However,
│ │ │ │ -the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8201743272-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="8201743272-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5365719022-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="5365719022-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8201743272-2">(</span><span class="p" data-group-id="8201743272-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8201743272-3">]</span><span class="p" data-group-id="8201743272-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5365719022-2">(</span><span class="p" data-group-id="5365719022-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5365719022-3">]</span><span class="p" data-group-id="5365719022-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8201743272-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="8201743272-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="8201743272-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="8201743272-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="8201743272-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="8201743272-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="5365719022-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5365719022-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="5365719022-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="5365719022-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="5365719022-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5365719022-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="8201743272-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8201743272-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="8201743272-8">(</span><span class="ss">ping</span><span class="p" data-group-id="8201743272-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="5365719022-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5365719022-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="5365719022-8">(</span><span class="ss">ping</span><span class="p" data-group-id="5365719022-8">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="8201743272-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="8201743272-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8201743272-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8201743272-11">(</span><span class="p" data-group-id="8201743272-11">)</span><span class="p" data-group-id="8201743272-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="5365719022-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5365719022-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5365719022-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5365719022-11">(</span><span class="p" data-group-id="5365719022-11">)</span><span class="p" data-group-id="5365719022-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8201743272-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8201743272-13">[</span><span class="p" data-group-id="8201743272-13">]</span><span class="p" data-group-id="8201743272-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5365719022-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5365719022-13">[</span><span class="p" data-group-id="5365719022-13">]</span><span class="p" data-group-id="5365719022-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="8201743272-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="8201743272-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="5365719022-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5365719022-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="8201743272-15">(</span><span class="p" data-group-id="8201743272-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="8201743272-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8201743272-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">pong1</span><span class="p" data-group-id="8201743272-17">(</span><span class="p" data-group-id="8201743272-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="5365719022-15">(</span><span class="p" data-group-id="5365719022-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="5365719022-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5365719022-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">pong1</span><span class="p" data-group-id="5365719022-17">(</span><span class="p" data-group-id="5365719022-17">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong1</span><span class="p" data-group-id="8201743272-18">(</span><span class="p" data-group-id="8201743272-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong1</span><span class="p" data-group-id="5365719022-18">(</span><span class="p" data-group-id="5365719022-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8201743272-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8201743272-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8201743272-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8201743272-21">[</span><span class="p" data-group-id="8201743272-21">]</span><span class="p" data-group-id="8201743272-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5365719022-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5365719022-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5365719022-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5365719022-21">[</span><span class="p" data-group-id="5365719022-21">]</span><span class="p" data-group-id="5365719022-20">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong1</span><span class="p" data-group-id="8201743272-22">(</span><span class="p" data-group-id="8201743272-22">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8201743272-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8201743272-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8201743272-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8201743272-25">[</span><span class="p" data-group-id="8201743272-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8201743272-26">}</span><span class="p" data-group-id="8201743272-25">]</span><span class="p" data-group-id="8201743272-24">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong1</span><span class="p" data-group-id="5365719022-22">(</span><span class="p" data-group-id="5365719022-22">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5365719022-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5365719022-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5365719022-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5365719022-25">[</span><span class="p" data-group-id="5365719022-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5365719022-26">}</span><span class="p" data-group-id="5365719022-25">]</span><span class="p" data-group-id="5365719022-24">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8201743272-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="8201743272-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8201743272-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8201743272-29">[</span><span class="p" data-group-id="8201743272-29">]</span><span class="p" data-group-id="8201743272-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8201743272-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8201743272-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="8201743272-31">]</span><span class="p" data-group-id="8201743272-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="5365719022-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="5365719022-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5365719022-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5365719022-29">[</span><span class="p" data-group-id="5365719022-29">]</span><span class="p" data-group-id="5365719022-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5365719022-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5365719022-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="5365719022-31">]</span><span class="p" data-group-id="5365719022-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │ │  &lt;3820.39.0&gt;
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │  Pong received ping
│ │ │ │  Ping received pong
│ │ │ │ @@ -256,135 +256,135 @@
│ │ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3445432544-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="3445432544-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3445432544-2">(</span><span class="p" data-group-id="3445432544-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3445432544-3">]</span><span class="p" data-group-id="3445432544-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3539309164-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="3539309164-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3539309164-2">(</span><span class="p" data-group-id="3539309164-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3539309164-3">]</span><span class="p" data-group-id="3539309164-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="3445432544-4">(</span><span class="p" data-group-id="3445432544-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="3539309164-4">(</span><span class="p" data-group-id="3539309164-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]</span><span class="w">
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="3445432544-5">(</span><span class="p" data-group-id="3445432544-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="3445432544-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3445432544-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="3445432544-7">(</span><span class="p" data-group-id="3445432544-8">[</span><span class="p" data-group-id="3445432544-8">]</span><span class="p" data-group-id="3445432544-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3539309164-5">(</span><span class="p" data-group-id="3539309164-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="3539309164-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3539309164-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="3539309164-7">(</span><span class="p" data-group-id="3539309164-8">[</span><span class="p" data-group-id="3539309164-8">]</span><span class="p" data-group-id="3539309164-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="3445432544-9">(</span><span class="n">User_List</span><span class="p" data-group-id="3445432544-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="3539309164-9">(</span><span class="n">User_List</span><span class="p" data-group-id="3539309164-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3445432544-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="3445432544-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="3445432544-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3445432544-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3445432544-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="3445432544-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="3445432544-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3445432544-15">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3445432544-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3445432544-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-19">[</span><span class="n">User_List</span><span class="p" data-group-id="3445432544-19">]</span><span class="p" data-group-id="3445432544-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="3445432544-20">(</span><span class="n">User_List</span><span class="p" data-group-id="3445432544-20">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3539309164-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="3539309164-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3539309164-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3539309164-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3539309164-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="3539309164-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3539309164-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="3539309164-15">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3539309164-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3539309164-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-19">[</span><span class="n">User_List</span><span class="p" data-group-id="3539309164-19">]</span><span class="p" data-group-id="3539309164-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="3539309164-20">(</span><span class="n">User_List</span><span class="p" data-group-id="3539309164-20">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="3445432544-21">(</span><span class="p" data-group-id="3445432544-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="3445432544-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3445432544-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-24">[</span><span class="p" data-group-id="3445432544-24">]</span><span class="p" data-group-id="3445432544-23">)</span><span class="p" data-group-id="3445432544-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="3539309164-21">(</span><span class="p" data-group-id="3539309164-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="3539309164-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3539309164-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-24">[</span><span class="p" data-group-id="3539309164-24">]</span><span class="p" data-group-id="3539309164-23">)</span><span class="p" data-group-id="3539309164-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="3445432544-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="3539309164-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3445432544-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3539309164-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="3445432544-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="3539309164-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="3445432544-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="3445432544-29">(</span><span class="n">From</span><span class="p" data-group-id="3445432544-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="3445432544-30">[</span><span class="p" data-group-id="3445432544-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3445432544-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="3539309164-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="3539309164-29">(</span><span class="n">From</span><span class="p" data-group-id="3539309164-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3539309164-30">[</span><span class="p" data-group-id="3539309164-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3539309164-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="3445432544-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3445432544-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-33">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="3539309164-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3539309164-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-33">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server transfers a message between user</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="3445432544-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3539309164-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="3445432544-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="3539309164-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3445432544-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3445432544-38">}</span><span class="p" data-group-id="3445432544-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3445432544-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-39">)</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3539309164-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3539309164-38">}</span><span class="p" data-group-id="3539309164-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="3539309164-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-39">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="3445432544-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="3539309164-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="3445432544-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3445432544-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="3539309164-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3539309164-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="3445432544-42">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3445432544-44">}</span><span class="p" data-group-id="3445432544-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-45">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-46">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="3445432544-46">}</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="3539309164-42">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="3539309164-44">}</span><span class="p" data-group-id="3539309164-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-45">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-46">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="3539309164-46">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="3445432544-47">(</span><span class="n">Name</span><span class="p" data-group-id="3445432544-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3445432544-48">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3445432544-48">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="3539309164-47">(</span><span class="n">Name</span><span class="p" data-group-id="3539309164-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3539309164-48">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3539309164-48">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="3445432544-49">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="3445432544-50">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-51">[</span><span class="nf">server_node</span><span class="p" data-group-id="3445432544-52">(</span><span class="p" data-group-id="3445432544-52">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3445432544-51">]</span><span class="p" data-group-id="3445432544-50">)</span><span class="p" data-group-id="3445432544-49">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="3539309164-49">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="3539309164-50">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-51">[</span><span class="nf">server_node</span><span class="p" data-group-id="3539309164-52">(</span><span class="p" data-group-id="3539309164-52">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3539309164-51">]</span><span class="p" data-group-id="3539309164-50">)</span><span class="p" data-group-id="3539309164-49">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="3445432544-53">(</span><span class="p" data-group-id="3445432544-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="3539309164-53">(</span><span class="p" data-group-id="3539309164-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="3445432544-54">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-54">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3445432544-55">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3445432544-55">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="3539309164-54">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-54">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3539309164-55">(</span><span class="ss">mess_client</span><span class="p" data-group-id="3539309164-55">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-56">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-56">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-56">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-56">}</span><span class="p">,</span><span class="w">
│ │ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="3445432544-57">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3445432544-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3445432544-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3445432544-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-59">{</span><span class="nf">self</span><span class="p" data-group-id="3445432544-60">(</span><span class="p" data-group-id="3445432544-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3445432544-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="3445432544-61">(</span><span class="p" data-group-id="3445432544-61">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="3445432544-62">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3445432544-62">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3539309164-57">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3539309164-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3539309164-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3539309164-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-59">{</span><span class="nf">self</span><span class="p" data-group-id="3539309164-60">(</span><span class="p" data-group-id="3539309164-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3539309164-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="3539309164-61">(</span><span class="p" data-group-id="3539309164-61">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="3539309164-62">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3539309164-62">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="3445432544-63">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3445432544-63">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="3539309164-63">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3539309164-63">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="3445432544-64">(</span><span class="ss">normal</span><span class="p" data-group-id="3445432544-64">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-65">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-65">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="3445432544-66">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3445432544-66">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3445432544-67">{</span><span class="nf">self</span><span class="p" data-group-id="3445432544-68">(</span><span class="p" data-group-id="3445432544-68">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-67">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="3445432544-69">(</span><span class="p" data-group-id="3445432544-69">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-70">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-70">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3445432544-71">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-72">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3445432544-72">]</span><span class="p" data-group-id="3445432544-71">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3539309164-64">(</span><span class="ss">normal</span><span class="p" data-group-id="3539309164-64">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-65">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-65">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="3539309164-66">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="3539309164-66">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3539309164-67">{</span><span class="nf">self</span><span class="p" data-group-id="3539309164-68">(</span><span class="p" data-group-id="3539309164-68">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-67">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="3539309164-69">(</span><span class="p" data-group-id="3539309164-69">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-70">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-70">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3539309164-71">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-72">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3539309164-72">]</span><span class="p" data-group-id="3539309164-71">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="3445432544-73">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3445432544-73">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="3539309164-73">(</span><span class="n">Server_Node</span><span class="p" data-group-id="3539309164-73">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="3445432544-74">(</span><span class="p" data-group-id="3445432544-74">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="3539309164-74">(</span><span class="p" data-group-id="3539309164-74">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-75">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="3445432544-75">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3445432544-76">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-77">[</span><span class="n">Why</span><span class="p" data-group-id="3445432544-77">]</span><span class="p" data-group-id="3445432544-76">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="3445432544-78">(</span><span class="ss">normal</span><span class="p" data-group-id="3445432544-78">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="3445432544-79">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="3445432544-79">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3445432544-80">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-81">[</span><span class="n">What</span><span class="p" data-group-id="3445432544-81">]</span><span class="p" data-group-id="3445432544-80">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-75">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="3539309164-75">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3539309164-76">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-77">[</span><span class="n">Why</span><span class="p" data-group-id="3539309164-77">]</span><span class="p" data-group-id="3539309164-76">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3539309164-78">(</span><span class="ss">normal</span><span class="p" data-group-id="3539309164-78">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3539309164-79">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="3539309164-79">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3539309164-80">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-81">[</span><span class="n">What</span><span class="p" data-group-id="3539309164-81">]</span><span class="p" data-group-id="3539309164-80">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3445432544-82">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3445432544-83">[</span><span class="p" data-group-id="3445432544-83">]</span><span class="p" data-group-id="3445432544-82">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="3445432544-84">(</span><span class="ss">timeout</span><span class="p" data-group-id="3445432544-84">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3539309164-82">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3539309164-83">[</span><span class="p" data-group-id="3539309164-83">]</span><span class="p" data-group-id="3539309164-82">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="3539309164-84">(</span><span class="ss">timeout</span><span class="p" data-group-id="3539309164-84">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The following changes are added:</p><p>The messenger server traps exits. If it receives an exit signal,
│ │ │ │  <code class="inline">{'EXIT',From,Reason}</code>, this means that a client process has terminated or is
│ │ │ │  unreachable for one of the following reasons:</p><ul><li>The user has logged off (the &quot;logoff&quot; message is removed).</li><li>The network connection to the client is broken.</li><li>The node on which the client process resides has gone down.</li><li>The client processes has done some illegal operation.</li></ul><p>If an exit signal is received as above, the tuple <code class="inline">{From,Name}</code> is deleted from
│ │ │ │  the servers <code class="inline">User_List</code> using the <code class="inline">server_logoff</code> function. If the node on which
│ │ │ │  the server runs goes down, an exit signal (automatically generated by the
│ │ │ │  system) is sent to all of the client processes:
│ │ │ │  <code class="inline">{'EXIT',MessengerPID,noconnection}</code> causing all the client processes to
│ │ │ ├── OEBPS/release_structure.xhtml
│ │ │ │ @@ -41,37 +41,37 @@
│ │ │ │    <a href="#release-resource-file" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Release Resource File</span>
│ │ │ │  </h2>
│ │ │ │  <p>To define a release, create a <em>release resource file</em>, or in short a <code class="inline">.rel</code>
│ │ │ │  file. In the file, specify the name and version of the release, which ERTS
│ │ │ │ -version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2237860629-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2237860629-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="2237860629-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2237860629-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="2237860629-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2237860629-4">[</span><span class="p" data-group-id="2237860629-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="2237860629-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2551179972-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2551179972-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="2551179972-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2551179972-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="2551179972-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2551179972-4">[</span><span class="p" data-group-id="2551179972-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="2551179972-5">}</span><span class="p">,</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2237860629-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="2237860629-6">}</span><span class="p" data-group-id="2237860629-4">]</span><span class="p" data-group-id="2237860629-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │ │ +  </span><span class="p" data-group-id="2551179972-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="2551179972-6">}</span><span class="p" data-group-id="2551179972-4">]</span><span class="p" data-group-id="2551179972-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │ │  included in the release. The minimal release based on Erlang/OTP consists of the
│ │ │ │  Kernel and STDLIB applications, so these applications must be included in the
│ │ │ │  list.</p><p>If the release is to be upgraded, it must also include the SASL application.</p><p><a href="" id="ch_rel"></a></p><p>Here is an example showing the <code class="inline">.app</code> file for a release of <code class="inline">ch_app</code> from
│ │ │ │ -the <a href="applications.xhtml#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3819538993-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3819538993-2">[</span><span class="p" data-group-id="3819538993-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="3819538993-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3819538993-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3819538993-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3819538993-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3819538993-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3819538993-6">]</span><span class="p" data-group-id="3819538993-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3819538993-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3819538993-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="3819538993-8">]</span><span class="p" data-group-id="3819538993-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3819538993-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3819538993-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3819538993-10">]</span><span class="p" data-group-id="3819538993-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="3819538993-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3819538993-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="3819538993-13">[</span><span class="p" data-group-id="3819538993-13">]</span><span class="p" data-group-id="3819538993-12">}</span><span class="p" data-group-id="3819538993-11">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3819538993-2">]</span><span class="p" data-group-id="3819538993-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ │ -applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5910397645-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5910397645-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="5910397645-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5910397645-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="5910397645-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5910397645-4">[</span><span class="p" data-group-id="5910397645-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="5910397645-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5910397645-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="5910397645-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5910397645-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="5910397645-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5910397645-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="5910397645-8">}</span><span class="p" data-group-id="5910397645-4">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5910397645-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │ │ +the <a href="applications.xhtml#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0746960874-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0746960874-2">[</span><span class="p" data-group-id="0746960874-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="0746960874-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0746960874-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0746960874-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0746960874-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0746960874-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0746960874-6">]</span><span class="p" data-group-id="0746960874-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0746960874-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0746960874-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="0746960874-8">]</span><span class="p" data-group-id="0746960874-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0746960874-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0746960874-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="0746960874-10">]</span><span class="p" data-group-id="0746960874-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="0746960874-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0746960874-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="0746960874-13">[</span><span class="p" data-group-id="0746960874-13">]</span><span class="p" data-group-id="0746960874-12">}</span><span class="p" data-group-id="0746960874-11">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0746960874-2">]</span><span class="p" data-group-id="0746960874-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ │ +applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8914646231-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8914646231-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="8914646231-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8914646231-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="8914646231-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8914646231-4">[</span><span class="p" data-group-id="8914646231-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="8914646231-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8914646231-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="8914646231-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8914646231-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="8914646231-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8914646231-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8914646231-8">}</span><span class="p" data-group-id="8914646231-4">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8914646231-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │ │    <a href="#generating-boot-scripts" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Generating Boot Scripts</span>
│ │ │ │  </h2>
│ │ │ │  <p><a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> in the SASL application includes tools to build and check
│ │ │ │  releases. The functions read the <code class="inline">.rel</code> and <code class="inline">.app</code> files and perform
│ │ │ │ @@ -95,17 +95,17 @@
│ │ │ │    <a href="#creating-a-release-package" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating a Release Package</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <a href="../../../lib/sasl/doc/html/systools.html#make_tar/2"><code class="inline">systools:make_tar/1,2</code></a> function takes a
│ │ │ │  <code class="inline">.rel</code> file as input and creates a zipped tar file with the code for
│ │ │ │ -the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="0693895929-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="0693895929-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="9856934353-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="9856934353-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="0693895929-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="0693895929-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="9856934353-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="9856934353-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>The release package by default contains:</p><ul><li>The <code class="inline">.app</code> files</li><li>The <code class="inline">.rel</code> file</li><li>The object code for all applications, structured according to the
│ │ │ │  <a href="applications.xhtml#app_dir">application directory structure</a></li><li>The binary boot script renamed to <code class="inline">start.boot</code></li></ul><pre><code class="text">% tar tf ch_rel-1.tar
│ │ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │ │  ...
│ │ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ │ ├── OEBPS/release_handling.xhtml
│ │ │ │ @@ -128,38 +128,38 @@
│ │ │ │    <span class="text">update</span>
│ │ │ │  </h3>
│ │ │ │  <p>If a more complex change has been made, for example, a change to the format of
│ │ │ │  the internal state of a <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>, simple code replacement is not sufficient.
│ │ │ │  Instead, it is necessary to:</p><ul><li>Suspend the processes using the module (to avoid that they try to handle any
│ │ │ │  requests before the code replacement is completed).</li><li>Ask them to transform the internal state format and switch to the new version
│ │ │ │  of the module.</li><li>Remove the old version.</li><li>Resume the processes.</li></ul><p>This is called <em>synchronized code replacement</em> and for this the following
│ │ │ │ -instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6656291020-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6656291020-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="6656291020-2">}</span><span class="p" data-group-id="6656291020-1">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6656291020-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="6656291020-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │ │ +instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3654065381-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3654065381-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="3654065381-2">}</span><span class="p" data-group-id="3654065381-1">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3654065381-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3654065381-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │ │  state of a behaviour as described above. It causes behaviour processes to call
│ │ │ │  the callback function <code class="inline">code_change/3</code>, passing the term <code class="inline">Extra</code> and some other
│ │ │ │  information as arguments. See the manual pages for the respective behaviours and
│ │ │ │  <a href="appup_cookbook.xhtml#int_state">Appup Cookbook</a>.</p><p><code class="inline">update</code> with argument <code class="inline">supervisor</code> is used when changing the start
│ │ │ │  specification of a supervisor. See <a href="appup_cookbook.xhtml#sup">Appup Cookbook</a>.</p><p>When a module is to be updated, the release handler finds which processes that
│ │ │ │  are <em>using</em> the module by traversing the supervision tree of each running
│ │ │ │ -application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6094157406-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="6094157406-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │ │ +application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3465479373-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="3465479373-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │ │  specification for the process.</p><p>If <code class="inline">Modules=dynamic</code>, which is the case for event managers, the event manager
│ │ │ │  process informs the release handler about the list of currently installed event
│ │ │ │  handlers (<code class="inline">gen_event</code>), and it is checked if the module name is in this list
│ │ │ │  instead.</p><p>The release handler suspends, asks for code change, and resumes processes by
│ │ │ │  calling the functions <code class="inline">sys:suspend/1,2</code>, <code class="inline">sys:change_code/4,5</code>, and
│ │ │ │  <code class="inline">sys:resume/1,2</code>, respectively.</p><h3 id="add_module-and-delete_module" class="section-heading">
│ │ │ │    <a href="#add_module-and-delete_module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">add_module and delete_module</span>
│ │ │ │  </h3>
│ │ │ │ -<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8792220434-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8792220434-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │ │ +<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2731794665-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="2731794665-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │ │  embedded mode it is necessary to use this this instruction. It is not
│ │ │ │  strictly required when running Erlang in interactive mode, since the
│ │ │ │ -code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1868084062-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1868084062-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │ │ +code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7923226863-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="7923226863-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │ │  killed when the instruction is evaluated. Therefore, the user must
│ │ │ │  ensure that all such processes are terminated before deleting module
│ │ │ │  <code class="inline">Module</code> to avoid a situation with failing supervisor restarts.</p><h3 id="application-instructions" class="section-heading">
│ │ │ │    <a href="#application-instructions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Instructions</span>
│ │ │ │ @@ -246,60 +246,60 @@
│ │ │ │  <code class="inline">.app</code> file.</li><li>Each <code class="inline">UpFromVsn</code> is a previous version of the application to upgrade from.</li><li>Each <code class="inline">DownToVsn</code> is a previous version of the application to downgrade to.</li><li>Each <code class="inline">Instructions</code> is a list of release handling instructions.</li></ul><p><code class="inline">UpFromVsn</code> and <code class="inline">DownToVsn</code> can also be specified as regular expressions. For
│ │ │ │  more information about the syntax and contents of the <code class="inline">.appup</code> file, see
│ │ │ │  <a href="../../../lib/sasl/doc/html/appup.xhtml"><code class="inline">appup</code></a> in SASL.</p><p><a href="appup_cookbook.xhtml">Appup Cookbook</a> includes examples of <code class="inline">.appup</code> files for
│ │ │ │  typical upgrade/downgrade cases.</p><p><em>Example:</em> Consider the release <code class="inline">ch_rel-1</code> from
│ │ │ │  <a href="release_structure.xhtml#ch_rel">Releases</a>. Assume you want to add a function
│ │ │ │  <code class="inline">available/0</code> to server <code class="inline">ch3</code>, which returns the number of available channels
│ │ │ │  (when trying out the example, make the change in a copy of the original
│ │ │ │ -directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0108713552-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="0108713552-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0108713552-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="0108713552-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0857677638-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="0857677638-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0857677638-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="0857677638-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0108713552-3">(</span><span class="p" data-group-id="0108713552-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0108713552-4">]</span><span class="p" data-group-id="0108713552-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0108713552-5">(</span><span class="p" data-group-id="0108713552-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0108713552-6">]</span><span class="p" data-group-id="0108713552-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0108713552-7">(</span><span class="p" data-group-id="0108713552-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0108713552-8">]</span><span class="p" data-group-id="0108713552-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0108713552-9">(</span><span class="p" data-group-id="0108713552-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0108713552-10">]</span><span class="p" data-group-id="0108713552-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0857677638-3">(</span><span class="p" data-group-id="0857677638-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0857677638-4">]</span><span class="p" data-group-id="0857677638-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0857677638-5">(</span><span class="p" data-group-id="0857677638-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0857677638-6">]</span><span class="p" data-group-id="0857677638-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0857677638-7">(</span><span class="p" data-group-id="0857677638-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0857677638-8">]</span><span class="p" data-group-id="0857677638-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0857677638-9">(</span><span class="p" data-group-id="0857677638-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0857677638-10">]</span><span class="p" data-group-id="0857677638-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="0108713552-11">(</span><span class="p" data-group-id="0108713552-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0108713552-12">(</span><span class="p" data-group-id="0108713552-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0108713552-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0108713552-14">[</span><span class="p" data-group-id="0108713552-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0108713552-15">[</span><span class="p" data-group-id="0108713552-15">]</span><span class="p" data-group-id="0108713552-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="0857677638-11">(</span><span class="p" data-group-id="0857677638-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="0857677638-12">(</span><span class="p" data-group-id="0857677638-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0857677638-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857677638-14">[</span><span class="p" data-group-id="0857677638-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857677638-15">[</span><span class="p" data-group-id="0857677638-15">]</span><span class="p" data-group-id="0857677638-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="0108713552-16">(</span><span class="p" data-group-id="0108713552-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0108713552-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="0108713552-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="0857677638-16">(</span><span class="p" data-group-id="0857677638-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0857677638-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="0857677638-17">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="0108713552-18">(</span><span class="n">Ch</span><span class="p" data-group-id="0108713552-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0108713552-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0108713552-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0108713552-20">}</span><span class="p" data-group-id="0108713552-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="0857677638-18">(</span><span class="n">Ch</span><span class="p" data-group-id="0857677638-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0857677638-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0857677638-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0857677638-20">}</span><span class="p" data-group-id="0857677638-19">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">available</span><span class="p" data-group-id="0108713552-21">(</span><span class="p" data-group-id="0108713552-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0108713552-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="0108713552-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">available</span><span class="p" data-group-id="0857677638-21">(</span><span class="p" data-group-id="0857677638-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0857677638-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="0857677638-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0108713552-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="0108713552-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0108713552-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="0108713552-25">(</span><span class="p" data-group-id="0108713552-25">)</span><span class="p" data-group-id="0108713552-24">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0857677638-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="0857677638-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0857677638-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="0857677638-25">(</span><span class="p" data-group-id="0857677638-25">)</span><span class="p" data-group-id="0857677638-24">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="0108713552-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0108713552-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0108713552-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0108713552-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="0108713552-28">(</span><span class="n">Chs</span><span class="p" data-group-id="0108713552-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0108713552-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0108713552-29">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="0108713552-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0108713552-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="0108713552-31">(</span><span class="n">Chs</span><span class="p" data-group-id="0108713552-31">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0108713552-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0108713552-32">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="0857677638-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0857677638-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0857677638-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0857677638-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="0857677638-28">(</span><span class="n">Chs</span><span class="p" data-group-id="0857677638-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0857677638-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0857677638-29">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="0857677638-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0857677638-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="0857677638-31">(</span><span class="n">Chs</span><span class="p" data-group-id="0857677638-31">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0857677638-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0857677638-32">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="0108713552-33">(</span><span class="p" data-group-id="0108713552-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0108713552-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0108713552-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="0108713552-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0108713552-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0108713552-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0108713552-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ │ -updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6282686316-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6282686316-2">[</span><span class="p" data-group-id="6282686316-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="6282686316-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6282686316-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="6282686316-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6282686316-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6282686316-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6282686316-6">]</span><span class="p" data-group-id="6282686316-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6282686316-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6282686316-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="6282686316-8">]</span><span class="p" data-group-id="6282686316-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6282686316-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6282686316-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6282686316-10">]</span><span class="p" data-group-id="6282686316-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6282686316-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6282686316-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="6282686316-13">[</span><span class="p" data-group-id="6282686316-13">]</span><span class="p" data-group-id="6282686316-12">}</span><span class="p" data-group-id="6282686316-11">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6282686316-2">]</span><span class="p" data-group-id="6282686316-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="0857677638-33">(</span><span class="p" data-group-id="0857677638-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0857677638-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0857677638-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="0857677638-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0857677638-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0857677638-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0857677638-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ │ +updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4584238802-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4584238802-2">[</span><span class="p" data-group-id="4584238802-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4584238802-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4584238802-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="4584238802-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4584238802-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4584238802-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4584238802-6">]</span><span class="p" data-group-id="4584238802-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4584238802-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4584238802-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4584238802-8">]</span><span class="p" data-group-id="4584238802-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4584238802-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4584238802-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4584238802-10">]</span><span class="p" data-group-id="4584238802-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4584238802-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4584238802-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4584238802-13">[</span><span class="p" data-group-id="4584238802-13">]</span><span class="p" data-group-id="4584238802-12">}</span><span class="p" data-group-id="4584238802-11">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4584238802-2">]</span><span class="p" data-group-id="4584238802-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │ │  you only need to load the new (old) version of the <code class="inline">ch3</code> callback module. Create
│ │ │ │ -the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4946527171-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4946527171-2">[</span><span class="p" data-group-id="4946527171-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4946527171-4">[</span><span class="p" data-group-id="4946527171-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4946527171-5">}</span><span class="p" data-group-id="4946527171-4">]</span><span class="p" data-group-id="4946527171-3">}</span><span class="p" data-group-id="4946527171-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4946527171-6">[</span><span class="p" data-group-id="4946527171-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4946527171-8">[</span><span class="p" data-group-id="4946527171-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4946527171-9">}</span><span class="p" data-group-id="4946527171-8">]</span><span class="p" data-group-id="4946527171-7">}</span><span class="p" data-group-id="4946527171-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4946527171-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │ │ +the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1049686322-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1049686322-2">[</span><span class="p" data-group-id="1049686322-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1049686322-4">[</span><span class="p" data-group-id="1049686322-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1049686322-5">}</span><span class="p" data-group-id="1049686322-4">]</span><span class="p" data-group-id="1049686322-3">}</span><span class="p" data-group-id="1049686322-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1049686322-6">[</span><span class="p" data-group-id="1049686322-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1049686322-8">[</span><span class="p" data-group-id="1049686322-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1049686322-9">}</span><span class="p" data-group-id="1049686322-8">]</span><span class="p" data-group-id="1049686322-7">}</span><span class="p" data-group-id="1049686322-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1049686322-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │ │    <a href="#release-upgrade-file" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Release Upgrade File</span>
│ │ │ │  </h2>
│ │ │ │  <p>To define how to upgrade/downgrade between the new version and previous versions
│ │ │ │  of a release, a <em>release upgrade file</em>, or in short <code class="inline">.relup</code> file, is to be
│ │ │ │ @@ -310,22 +310,22 @@
│ │ │ │  are to be added and deleted, and which applications that must be upgraded and/or
│ │ │ │  downgraded. The instructions for this are fetched from the <code class="inline">.appup</code> files and
│ │ │ │  transformed into a single list of low-level instructions in the right order.</p><p>If the <code class="inline">relup</code> file is relatively simple, it can be created manually. It is only
│ │ │ │  to contain low-level instructions.</p><p>For details about the syntax and contents of the release upgrade file, see
│ │ │ │  <a href="../../../lib/sasl/doc/html/relup.xhtml"><code class="inline">relup</code></a> in SASL.</p><p><em>Example, continued from the previous section:</em> You have a new version &quot;2&quot; of
│ │ │ │  <code class="inline">ch_app</code> and an <code class="inline">.appup</code> file. A new version of the <code class="inline">.rel</code> file is also needed.
│ │ │ │  This time the file is called <code class="inline">ch_rel-2.rel</code> and the release version string is
│ │ │ │ -changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2262339991-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2262339991-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="2262339991-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2262339991-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="2262339991-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2262339991-4">[</span><span class="p" data-group-id="2262339991-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="2262339991-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2262339991-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="2262339991-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2262339991-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="2262339991-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2262339991-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="2262339991-8">}</span><span class="p" data-group-id="2262339991-4">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2262339991-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │ │ +changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7007171720-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7007171720-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="7007171720-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7007171720-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="7007171720-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7007171720-4">[</span><span class="p" data-group-id="7007171720-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="7007171720-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7007171720-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="7007171720-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7007171720-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="7007171720-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="7007171720-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="7007171720-8">}</span><span class="p" data-group-id="7007171720-4">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7007171720-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │ │  ok</code></pre><p>This generates a <code class="inline">relup</code> file with instructions for how to upgrade from version
│ │ │ │  &quot;A&quot; (&quot;ch_rel-1&quot;) to version &quot;B&quot; (&quot;ch_rel-2&quot;) and how to downgrade from version
│ │ │ │  &quot;B&quot; to version &quot;A&quot;.</p><p>Both the old and new versions of the <code class="inline">.app</code> and <code class="inline">.rel</code> files must be in the code
│ │ │ │  path, as well as the <code class="inline">.appup</code> and (new) <code class="inline">.beam</code> files. The code path can be
│ │ │ │  extended by using the option <code class="inline">path</code>:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;],
│ │ │ │  [{path,[&quot;../ch_rel-1&quot;,
│ │ │ │  &quot;../ch_rel-1/lib/ch_app-1/ebin&quot;]}]).
│ │ │ │ @@ -338,25 +338,25 @@
│ │ │ │  <p>When you have made a new version of a release, a release package can be created
│ │ │ │  with this new version and transferred to the target environment.</p><p>To install the new version of the release in runtime, the <em>release
│ │ │ │  handler</em> is used. This is a process belonging to the SASL application,
│ │ │ │  which handles unpacking, installation, and removal of release
│ │ │ │  packages. The <a href="../../../lib/sasl/doc/html/release_handler.html"><code class="inline">release_handler</code></a> module communicates with this process.</p><p>Assuming there is an operational target system with installation root directory
│ │ │ │  <code class="inline">$ROOT</code>, the release package with the new version of the release is to be copied
│ │ │ │  to <code class="inline">$ROOT/releases</code>.</p><p>First, <em>unpack</em> the release package. The files are then extracted from the
│ │ │ │ -package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="6599465481-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="6599465481-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6599465481-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="6599465481-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │ │ +package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="3603298884-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="3603298884-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3603298884-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="3603298884-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │ │  extension.</li><li><code class="inline">Vsn</code> is the version of the unpacked release, as defined in its <code class="inline">.rel</code> file.</li></ul><p>A directory <code class="inline">$ROOT/lib/releases/Vsn</code> is created, where the <code class="inline">.rel</code> file, the boot
│ │ │ │  script <code class="inline">start.boot</code>, the system configuration file <code class="inline">sys.config</code>, and <code class="inline">relup</code> are
│ │ │ │  placed. For applications with new version numbers, the application directories
│ │ │ │  are placed under <code class="inline">$ROOT/lib</code>. Unchanged applications are not affected.</p><p>An unpacked release can be <em>installed</em>. The release handler then evaluates the
│ │ │ │ -instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="1440622197-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="1440622197-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1440622197-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1440622197-3">[</span><span class="p" data-group-id="1440622197-3">]</span><span class="p" data-group-id="1440622197-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │ │ +instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="4450064044-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="4450064044-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4450064044-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4450064044-3">[</span><span class="p" data-group-id="4450064044-3">]</span><span class="p" data-group-id="4450064044-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │ │  version of the release. If installation succeeds, the system is afterwards using
│ │ │ │  the new version of the release, but if anything happens and the system is
│ │ │ │  rebooted, it starts using the previous version again.</p><p>To be made the default version, the newly installed release must be made
│ │ │ │  <em>permanent</em>, which means the previous version becomes <em>old</em>:</p><pre><code class="text">release_handler:make_permanent(Vsn) =&gt; ok</code></pre><p>The system keeps information about which versions are old and permanent in the
│ │ │ │ -files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="0627378425-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="0627378425-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0627378425-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0627378425-3">[</span><span class="p" data-group-id="0627378425-3">]</span><span class="p" data-group-id="0627378425-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │ │ +files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="6967457286-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="6967457286-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6967457286-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6967457286-3">[</span><span class="p" data-group-id="6967457286-3">]</span><span class="p" data-group-id="6967457286-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │ │  release is then deleted from <code class="inline">$ROOT/releases/RELEASES</code> and the release-specific
│ │ │ │  code, that is, the new application directories and the <code class="inline">$ROOT/releases/Vsn</code>
│ │ │ │  directory, are removed.</p><pre><code class="text">release_handler:remove_release(Vsn) =&gt; ok</code></pre><h3 id="example-continued-from-the-previous-sections" class="section-heading">
│ │ │ │    <a href="#example-continued-from-the-previous-sections" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example (continued from the previous sections)</span>
│ │ │ │ @@ -367,17 +367,17 @@
│ │ │ │  is needed, the file is to contain the empty list:</p><pre><code class="text">[].</code></pre><p><em>Step 2)</em> Start the system as a simple target system. In reality, it is to be
│ │ │ │  started as an embedded system. However, using <code class="inline">erl</code> with the correct boot script
│ │ │ │  and config file is enough for illustration purposes:</p><pre><code class="text">% cd $ROOT
│ │ │ │  % bin/erl -boot $ROOT/releases/A/start -config $ROOT/releases/A/sys
│ │ │ │  ...</code></pre><p><code class="inline">$ROOT</code> is the installation directory of the target system.</p><p><em>Step 3)</em> In another Erlang shell, generate start scripts and create a release
│ │ │ │  package for the new version <code class="inline">&quot;B&quot;</code>. Remember to include (a possible updated)
│ │ │ │  <code class="inline">sys.config</code> and the <code class="inline">relup</code> file. For more information, see
│ │ │ │ -<a href="release_handling.xhtml#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="4889405752-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="4889405752-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="release_handling.xhtml#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7554034560-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="7554034560-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="4889405752-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="4889405752-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7554034560-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="7554034560-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>The new release package now also contains version &quot;2&quot; of <code class="inline">ch_app</code> and the
│ │ │ │  <code class="inline">relup</code> file:</p><pre><code class="text">% tar tf ch_rel-2.tar
│ │ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │ │  ...
│ │ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ │ │ @@ -390,31 +390,31 @@
│ │ │ │  lib/ch_app-2/ebin/ch_sup.beam
│ │ │ │  lib/ch_app-2/ebin/ch3.beam
│ │ │ │  releases/B/start.boot
│ │ │ │  releases/B/relup
│ │ │ │  releases/B/sys.config
│ │ │ │  releases/B/ch_rel-2.rel
│ │ │ │  releases/ch_rel-2.rel</code></pre><p><em>Step 4)</em> Copy the release package <code class="inline">ch_rel-2.tar.gz</code> to the <code class="inline">$ROOT/releases</code>
│ │ │ │ -directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="1883673830-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="1883673830-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1883673830-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="1883673830-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │ │ +directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="8805617367-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="8805617367-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8805617367-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="8805617367-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │ │  <code class="inline">ch_app-1</code>. The <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code> directories are not affected, as
│ │ │ │  they have not changed.</p><p>Under <code class="inline">$ROOT/releases</code>, a new directory <code class="inline">B</code> is created, containing
│ │ │ │ -<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="7101796627-1">(</span><span class="p" data-group-id="7101796627-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="6841171432-1">(</span><span class="p" data-group-id="6841171432-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: undefined function ch3:available/0</span></code></pre><p><em>Step 7)</em> Install the new release. The instructions in <code class="inline">$ROOT/releases/B/relup</code>
│ │ │ │  are executed one by one, resulting in the new version of <code class="inline">ch3</code> being loaded. The
│ │ │ │ -function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="2946477482-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="2946477482-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2946477482-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="2946477482-3">[</span><span class="p" data-group-id="2946477482-3">]</span><span class="p" data-group-id="2946477482-2">}</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="2946477482-4">(</span><span class="p" data-group-id="2946477482-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="8711042901-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="8711042901-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8711042901-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="8711042901-3">[</span><span class="p" data-group-id="8711042901-3">]</span><span class="p" data-group-id="8711042901-2">}</span><span class="gp unselectable">
│ │ │ │ +4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="8711042901-4">(</span><span class="p" data-group-id="8711042901-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="2946477482-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="2946477482-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="8711042901-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="8711042901-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;.../lib/ch_app-2/ebin/ch3.beam&quot;</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="2946477482-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="2946477482-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="8711042901-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="8711042901-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;.../lib/ch_app-1/ebin/ch_sup.beam&quot;</span></code></pre><p>Processes in <code class="inline">ch_app</code> for which code have not been updated, for example, the
│ │ │ │  supervisor, are still evaluating code from <code class="inline">ch_app-1</code>.</p><p><em>Step 8)</em> If the target system is now rebooted, it uses version &quot;A&quot; again. The
│ │ │ │ -&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="0057605037-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="0057605037-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="5166983525-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="5166983525-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p><a href="" id="sys"></a></p><h2 id="updating-application-specifications" class="section-heading">
│ │ │ │    <a href="#updating-application-specifications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating Application Specifications</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a new version of a release is installed, the application specifications are
│ │ │ │ @@ -423,14 +423,14 @@
│ │ │ │  boot script is generated from the same <code class="inline">.rel</code> file as is used to build the
│ │ │ │  release package itself.</p></section><p>Specifically, the application configuration parameters are automatically updated
│ │ │ │  according to (in increasing priority order):</p><ul><li>The data in the boot script, fetched from the new application resource file
│ │ │ │  <code class="inline">App.app</code></li><li>The new <code class="inline">sys.config</code></li><li>Command-line arguments <code class="inline">-App Par Val</code></li></ul><p>This means that parameter values set in the other system configuration files and
│ │ │ │  values set using <a href="../../../lib/kernel/doc/html/application.html#set_env/3"><code class="inline">application:set_env/3</code></a> are disregarded.</p><p>When an installed release is made permanent, the system process <code class="inline">init</code> is set to
│ │ │ │  point out the new <code class="inline">sys.config</code>.</p><p>After the installation, the application controller compares the old and new
│ │ │ │  configuration parameters for all running applications and call the callback
│ │ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="0682840818-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="0682840818-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="4053788942-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="4053788942-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │ │  <code class="inline">.app</code> file.</li><li><code class="inline">Changed</code> and <code class="inline">New</code> are lists of <code class="inline">{Par,Val}</code> for all changed and added
│ │ │ │  configuration parameters, respectively.</li><li><code class="inline">Removed</code> is a list of all parameters <code class="inline">Par</code> that have been removed.</li></ul><p>The function is optional and can be omitted when implementing an application
│ │ │ │  callback module.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/ref_man_records.xhtml
│ │ │ │ @@ -28,17 +28,17 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Defining Records</span>
│ │ │ │  </h2>
│ │ │ │  <p>A record definition consists of the name of the record, followed by the field
│ │ │ │  names of the record. Record and field names must be atoms. Each field can be
│ │ │ │  given an optional default value. If no default value is supplied, <code class="inline">undefined</code> is
│ │ │ │ -used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9423083840-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9423083840-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="9423083840-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="9423083840-3">]</span><span class="p">,</span><span class="w">
│ │ │ │ +used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2945699901-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2945699901-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="2945699901-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="2945699901-3">]</span><span class="p">,</span><span class="w">
│ │ │ │                 </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="9423083840-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="9423083840-4">]</span><span class="p" data-group-id="9423083840-2">}</span><span class="p" data-group-id="9423083840-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │ │ +               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="2945699901-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="2945699901-4">]</span><span class="p" data-group-id="2945699901-2">}</span><span class="p" data-group-id="2945699901-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │ │  not use any variables.</p><p>A record definition can be placed anywhere among the attributes and function
│ │ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │ │  record.</p><p>If a record is used in several modules, it is recommended that the record
│ │ │ │  definition is placed in an include file.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, records can be defined in the Erlang shell
│ │ │ │  using the syntax described in this section. In earlier releases, it was
│ │ │ │  necessary to use the <a href="../../../lib/stdlib/doc/html/shell.html"><code class="inline">shell</code></a> built-in function <code class="inline">rd/2</code>.</p></section><h2 id="creating-records" class="section-heading">
│ │ │ │    <a href="#creating-records" class="hover-link">
│ │ │ │ @@ -48,32 +48,32 @@
│ │ │ │  </h2>
│ │ │ │  <p>The following expression creates a new <code class="inline">Name</code> record where the value of each
│ │ │ │  field <code class="inline">FieldI</code> is the value of evaluating the corresponding expression <code class="inline">ExprI</code>:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>The fields can be in any order, not necessarily the same order as in the record
│ │ │ │  definition, and fields can be omitted. Omitted fields get their respective
│ │ │ │  default value instead.</p><p>If several fields are to be assigned the same value, the following construction
│ │ │ │  can be used:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK, _=ExprL}</code></pre><p>Omitted fields then get the value of evaluating <code class="inline">ExprL</code> instead of their default
│ │ │ │  values. This feature is primarily intended to be used to create patterns for ETS
│ │ │ │ -and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9029650629-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9029650629-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="9029650629-2">}</span><span class="p" data-group-id="9029650629-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9547017486-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9547017486-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="9547017486-2">}</span><span class="p" data-group-id="9547017486-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="9029650629-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="9029650629-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="9029650629-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9029650629-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9029650629-5">}</span><span class="p" data-group-id="9029650629-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="9547017486-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="9547017486-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="9547017486-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9547017486-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9547017486-5">}</span><span class="p" data-group-id="9547017486-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │ │    <a href="#accessing-record-fields" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Accessing Record Fields</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="text">Expr#Name.Field</code></pre><p>Returns the value of the specified field. <code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code>
│ │ │ │ -record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1237812105-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1237812105-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1237812105-2">}</span><span class="p" data-group-id="1237812105-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4099159578-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4099159578-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="4099159578-2">}</span><span class="p" data-group-id="4099159578-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">get_person_name</span><span class="p" data-group-id="1237812105-3">(</span><span class="n">Person</span><span class="p" data-group-id="1237812105-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">get_person_name</span><span class="p" data-group-id="4099159578-3">(</span><span class="n">Person</span><span class="p" data-group-id="4099159578-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span></code></pre><p>The following expression returns the position of the specified field in the
│ │ │ │ -tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2691777885-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2691777885-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="2691777885-2">}</span><span class="p" data-group-id="2691777885-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8388177521-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8388177521-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="8388177521-2">}</span><span class="p" data-group-id="8388177521-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="2691777885-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2691777885-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="2691777885-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2691777885-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="8388177521-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8388177521-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="8388177521-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8388177521-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │ │    <a href="#updating-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating Records</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="text">Expr#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p><code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code> record. A copy of this record is returned,
│ │ │ │  with the value of each specified field <code class="inline">FieldI</code> changed to the value of
│ │ │ │ @@ -83,48 +83,48 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Records in Guards</span>
│ │ │ │  </h2>
│ │ │ │  <p>Since record expressions are expanded to tuple expressions, creating
│ │ │ │  records and accessing record fields are allowed in guards. However,
│ │ │ │  all subexpressions (for initializing fields), must be valid guard
│ │ │ │ -expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="0732762638-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0732762638-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="0732762638-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="0732762638-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="6772035805-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6772035805-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="6772035805-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="6772035805-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle</span><span class="p" data-group-id="0732762638-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0732762638-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../../lib/../erts/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="5801405513-1">(</span><span class="n">P</span><span class="p" data-group-id="5801405513-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="5801405513-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="5801405513-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle</span><span class="p" data-group-id="6772035805-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6772035805-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../../lib/../erts/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="3773100039-1">(</span><span class="n">P</span><span class="p" data-group-id="3773100039-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="3773100039-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="3773100039-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">is_person</span><span class="p" data-group-id="5801405513-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="5801405513-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">is_person</span><span class="p" data-group-id="3773100039-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="3773100039-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><h2 id="records-in-patterns" class="section-heading">
│ │ │ │    <a href="#records-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Records in Patterns</span>
│ │ │ │  </h2>
│ │ │ │  <p>A pattern that matches a certain record is created in the same way as a record
│ │ │ │  is created:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>In this case, one or more of <code class="inline">Expr1</code> ... <code class="inline">ExprK</code> can be unbound variables.</p><h2 id="nested-records" class="section-heading">
│ │ │ │    <a href="#nested-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Nested Records</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2291886733-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2291886733-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="2291886733-2">}</span><span class="p" data-group-id="2291886733-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2291886733-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2291886733-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="2291886733-5">{</span><span class="p" data-group-id="2291886733-5">}</span><span class="p" data-group-id="2291886733-4">}</span><span class="p" data-group-id="2291886733-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2291886733-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2291886733-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="2291886733-8">{</span><span class="p" data-group-id="2291886733-8">}</span><span class="p" data-group-id="2291886733-7">}</span><span class="p" data-group-id="2291886733-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8572196306-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8572196306-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="8572196306-2">}</span><span class="p" data-group-id="8572196306-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8572196306-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8572196306-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="8572196306-5">{</span><span class="p" data-group-id="8572196306-5">}</span><span class="p" data-group-id="8572196306-4">}</span><span class="p" data-group-id="8572196306-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8572196306-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8572196306-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="8572196306-8">{</span><span class="p" data-group-id="8572196306-8">}</span><span class="p" data-group-id="8572196306-7">}</span><span class="p" data-group-id="8572196306-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="2291886733-9">{</span><span class="p" data-group-id="2291886733-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │ │ +</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="8572196306-9">{</span><span class="p" data-group-id="8572196306-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │ │      N0n = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = &quot;nested0a&quot;},</code></pre><p>which is equivalent to:</p><pre><code class="text">&quot;nested0&quot; = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0.name,
│ │ │ │  N0n = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0{name = &quot;nested0a&quot;},</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R14, parentheses were necessary when accessing or updating
│ │ │ │  nested records.</p></section><h2 id="internal-representation-of-records" class="section-heading">
│ │ │ │    <a href="#internal-representation-of-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Internal Representation of Records</span>
│ │ │ │  </h2>
│ │ │ │  <p>Record expressions are translated to tuple expressions during compilation. A
│ │ │ │ -record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7314505366-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7314505366-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="7314505366-2">}</span><span class="p" data-group-id="7314505366-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ │ -obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="2686262926-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="2686262926-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2686262926-2">[</span><span class="n">Field</span><span class="p" data-group-id="2686262926-2">]</span><span class="w">
│ │ │ │ -</span><span class="nf">record_info</span><span class="p" data-group-id="2686262926-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="2686262926-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │ │ +record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8687608246-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8687608246-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="8687608246-2">}</span><span class="p" data-group-id="8687608246-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ │ +obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="3118114456-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="3118114456-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3118114456-2">[</span><span class="n">Field</span><span class="p" data-group-id="3118114456-2">]</span><span class="w">
│ │ │ │ +</span><span class="nf">record_info</span><span class="p" data-group-id="3118114456-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="3118114456-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │ │  number of fields.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/ref_man_processes.xhtml
│ │ │ │ @@ -30,18 +30,18 @@
│ │ │ │  (grow and shrink dynamically) with small memory footprint, fast to create and
│ │ │ │  terminate, and the scheduling overhead is low.</p><h2 id="process-creation" class="section-heading">
│ │ │ │    <a href="#process-creation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Process Creation</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A process is created by calling <a href="../../../lib/../erts/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="5634785351-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="5634785351-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="5634785351-2">(</span><span class="p" data-group-id="5634785351-2">)</span><span class="w">
│ │ │ │ -  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="5634785351-3">(</span><span class="p" data-group-id="5634785351-3">)</span><span class="w">
│ │ │ │ -  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5634785351-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="5634785351-4">]</span><span class="w">
│ │ │ │ -    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="5634785351-5">(</span><span class="p" data-group-id="5634785351-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │ │ +<p>A process is created by calling <a href="../../../lib/../erts/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="4471465049-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4471465049-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="4471465049-2">(</span><span class="p" data-group-id="4471465049-2">)</span><span class="w">
│ │ │ │ +  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4471465049-3">(</span><span class="p" data-group-id="4471465049-3">)</span><span class="w">
│ │ │ │ +  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4471465049-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="4471465049-4">]</span><span class="w">
│ │ │ │ +    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4471465049-5">(</span><span class="p" data-group-id="4471465049-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │ │  arguments are the elements of the (possible empty) <code class="inline">Args</code> argument list.</p><p>There exist a number of different <code class="inline">spawn</code> BIFs:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn/4"><code class="inline">spawn/1,2,3,4</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_link/4"><code class="inline">spawn_link/1,2,3,4</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_monitor/4"><code class="inline">spawn_monitor/1,2,3,4</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_opt/5"><code class="inline">spawn_opt/2,3,4,5</code></a></li><li><a href="../../../lib/../erts/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/1,2,3,4,5</code></a></li></ul><h2 id="registered-processes" class="section-heading">
│ │ │ │    <a href="#registered-processes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Registered Processes</span>
│ │ │ │  </h2>
│ │ │ │  <p>Besides addressing a process by using its pid, there are also BIFs for
│ │ │ ├── OEBPS/ref_man_functions.xhtml
│ │ │ │ @@ -25,51 +25,51 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Function Declaration Syntax</span>
│ │ │ │  </h2>
│ │ │ │  <p>A <em>function declaration</em> is a sequence of function clauses separated by
│ │ │ │  semicolons, and terminated by a period (<code class="inline">.</code>).</p><p>A <em>function clause</em> consists of a <em>clause head</em> and a <em>clause body</em>, separated by
│ │ │ │  <code class="inline">-&gt;</code>.</p><p>A clause <em>head</em> consists of the function name, an argument list, and an optional
│ │ │ │ -guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="4871289743-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="4871289743-1">)</span><span class="w"> </span><span class="p" data-group-id="4871289743-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4871289743-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="4869073645-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="4869073645-1">)</span><span class="w"> </span><span class="p" data-group-id="4869073645-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4869073645-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="n">Name</span><span class="p" data-group-id="4871289743-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="4871289743-3">)</span><span class="w"> </span><span class="p" data-group-id="4871289743-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="4871289743-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="n">Name</span><span class="p" data-group-id="4869073645-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="4869073645-3">)</span><span class="w"> </span><span class="p" data-group-id="4869073645-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="4869073645-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">BodyK</span><span class="p">.</span></code></pre><p>The function name is an atom. Each argument is a pattern.</p><p>The number of arguments <code class="inline">N</code> is the <em>arity</em> of the function. A function is
│ │ │ │  uniquely defined by the module name, function name, and arity. That is, two
│ │ │ │  functions with the same name and in the same module, but with different arities
│ │ │ │  are two different functions.</p><p>A function named <code class="inline">f</code> in module <code class="inline">mod</code> and with arity <code class="inline">N</code> is often denoted as
│ │ │ │  <code class="inline">mod:f/N</code>.</p><p>A clause <em>body</em> consists of a sequence of expressions separated by comma (<code class="inline">,</code>):</p><pre><code class="text">Expr1,
│ │ │ │  ...,
│ │ │ │  ExprN</code></pre><p>Valid Erlang expressions and guard sequences are described in
│ │ │ │ -<a href="expressions.xhtml">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="4826454338-1">(</span><span class="n">N</span><span class="p" data-group-id="4826454338-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="4826454338-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4826454338-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │ │ +<a href="expressions.xhtml">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="6307348060-1">(</span><span class="n">N</span><span class="p" data-group-id="6307348060-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="6307348060-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6307348060-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="4826454338-3">(</span><span class="mi">0</span><span class="p" data-group-id="4826454338-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="6307348060-3">(</span><span class="mi">0</span><span class="p" data-group-id="6307348060-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">                 </span><span class="c1">% second clause body</span></code></pre><p><a href="" id="eval"></a></p><h2 id="function-evaluation" class="section-heading">
│ │ │ │    <a href="#function-evaluation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Function Evaluation</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a function <code class="inline">M:F/N</code> is called, first the code for the function is located.
│ │ │ │  If the function cannot be found, an <code class="inline">undef</code> runtime error occurs. Notice that
│ │ │ │  the function must be exported to be visible outside the module it is defined in.</p><p>If the function is found, the function clauses are scanned sequentially until a
│ │ │ │  clause is found that fulfills both of the following two conditions:</p><ol><li>The patterns in the clause head can be successfully matched against the given
│ │ │ │  arguments.</li><li>The guard sequence, if any, is true.</li></ol><p>If such a clause cannot be found, a <code class="inline">function_clause</code> runtime error occurs.</p><p>If such a clause is found, the corresponding clause body is evaluated. That is,
│ │ │ │  the expressions in the body are evaluated sequentially and the value of the last
│ │ │ │ -expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9659613931-1">(</span><span class="ss">mod</span><span class="p" data-group-id="9659613931-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9659613931-2">(</span><span class="p" data-group-id="9659613931-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9659613931-3">]</span><span class="p" data-group-id="9659613931-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7578270109-1">(</span><span class="ss">mod</span><span class="p" data-group-id="7578270109-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7578270109-2">(</span><span class="p" data-group-id="7578270109-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7578270109-3">]</span><span class="p" data-group-id="7578270109-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="9659613931-4">(</span><span class="n">N</span><span class="p" data-group-id="9659613931-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="9659613931-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9659613931-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="9659613931-6">(</span><span class="mi">0</span><span class="p" data-group-id="9659613931-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="7578270109-4">(</span><span class="n">N</span><span class="p" data-group-id="7578270109-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="7578270109-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7578270109-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="7578270109-6">(</span><span class="mi">0</span><span class="p" data-group-id="7578270109-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">.</span></code></pre><p>Assume that you want to calculate the factorial for 1:</p><pre><code class="text">1&gt; mod:fact(1).</code></pre><p>Evaluation starts at the first clause. The pattern <code class="inline">N</code> is matched against
│ │ │ │  argument 1. The matching succeeds and the guard (<code class="inline">N &gt; 0</code>) is true, thus <code class="inline">N</code> is
│ │ │ │ -bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="8255080033-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="8255080033-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8255080033-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8255080033-2">)</span><span class="w">
│ │ │ │ -</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="8255080033-3">(</span><span class="mi">0</span><span class="p" data-group-id="8255080033-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │ │ +bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3769189950-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="3769189950-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3769189950-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3769189950-2">)</span><span class="w">
│ │ │ │ +</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3769189950-3">(</span><span class="mi">0</span><span class="p" data-group-id="3769189950-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │ │  sequentially again. First, the pattern <code class="inline">N</code> is matched against 0. The
│ │ │ │  matching succeeds, but the guard (<code class="inline">N &gt; 0</code>) is false. Second, the
│ │ │ │  pattern <code class="inline">0</code> is matched against the argument <code class="inline">0</code>. The matching succeeds
│ │ │ │  and the body is evaluated:</p><pre><code class="text">1 * fact(0) =&gt;
│ │ │ │  1 * 1 =&gt;
│ │ │ │  1</code></pre><p>Evaluation has succeed and <code class="inline">mod:fact(1)</code> returns 1.</p><p>If <code class="inline">mod:fact/1</code> is called with a negative number as argument, no clause head
│ │ │ │  matches. A <code class="inline">function_clause</code> runtime error occurs.</p><h2 id="tail-recursion" class="section-heading">
│ │ │ │ @@ -78,17 +78,17 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Tail recursion</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the last expression of a function body is a function call, a
│ │ │ │  <em>tail-recursive call</em> is done. This is to ensure that no system
│ │ │ │  resources, for example, call stack, are consumed. This means that an
│ │ │ │  infinite loop using tail-recursive calls will not exhaust the call
│ │ │ │ -stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2962677760-1">(</span><span class="n">N</span><span class="p" data-group-id="2962677760-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2962677760-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2962677760-3">[</span><span class="n">N</span><span class="p" data-group-id="2962677760-3">]</span><span class="p" data-group-id="2962677760-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="2962677760-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2962677760-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │ │ +stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="1002354648-1">(</span><span class="n">N</span><span class="p" data-group-id="1002354648-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1002354648-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1002354648-3">[</span><span class="n">N</span><span class="p" data-group-id="1002354648-3">]</span><span class="p" data-group-id="1002354648-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="1002354648-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="1002354648-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │ │  tail-recursive, since a multiplication is done on the result of the recursive
│ │ │ │  call to <code class="inline">fact(N-1)</code>.</p><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │ │  </h2>
│ │ │ │ @@ -96,14 +96,14 @@
│ │ │ │  system. BIFs do things that are difficult or impossible to implement
│ │ │ │  in Erlang. Most of the BIFs belong to module <a href="../../../lib/../erts/doc/html/erlang.html"><code class="inline">erlang</code></a>, but there
│ │ │ │  are also BIFs belonging to a few other modules, for example <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a>
│ │ │ │  and <a href="../../../lib/stdlib/doc/html/ets.html"><code class="inline">ets</code></a>.</p><p>The most commonly used BIFs belonging to <a href="../../../lib/../erts/doc/html/erlang.html"><code class="inline">erlang</code></a> are <em>auto-imported</em>. They do
│ │ │ │  not need to be prefixed with the module name. Which BIFs that are auto-imported
│ │ │ │  is specified in the <a href="../../../lib/../erts/doc/html/erlang.html"><code class="inline">erlang</code></a> module in ERTS. For example, standard-type
│ │ │ │  conversion BIFs like <code class="inline">atom_to_list</code> and BIFs allowed in guards can be called
│ │ │ │ -without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="2670504856-1">(</span><span class="p" data-group-id="2670504856-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2670504856-2">}</span><span class="p" data-group-id="2670504856-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="1273357240-1">(</span><span class="p" data-group-id="1273357240-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1273357240-2">}</span><span class="p" data-group-id="1273357240-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="2670504856-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="2670504856-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1273357240-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="1273357240-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;Erlang&quot;</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/records_macros.xhtml
│ │ │ │ @@ -29,40 +29,40 @@
│ │ │ │  </h2>
│ │ │ │  <p>To illustrate this, the messenger example from the previous section is divided
│ │ │ │  into the following five files:</p><ul><li><p><code class="inline">mess_config.hrl</code></p><p>Header file for configuration data</p></li><li><p><code class="inline">mess_interface.hrl</code></p><p>Interface definitions between the client and the messenger</p></li><li><p><code class="inline">user_interface.erl</code></p><p>Functions for the user interface</p></li><li><p><code class="inline">mess_client.erl</code></p><p>Functions for the client side of the messenger</p></li><li><p><code class="inline">mess_server.erl</code></p><p>Functions for the server side of the messenger</p></li></ul><p>While doing this, the message passing interface between the shell, the client,
│ │ │ │  and the server is cleaned up and is defined using <em>records</em>. Also, <em>macros</em> are
│ │ │ │  introduced:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_config.hrl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2826633523-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="2826633523-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3505854883-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="3505854883-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_interface.hrl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Message interface between client and server and client shell for</span><span class="w">
│ │ │ │  </span><span class="c1">%%% messenger program</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%Messages from Client to server received in server/1 function.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0819651454-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="0819651454-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="0819651454-2">}</span><span class="p" data-group-id="0819651454-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0819651454-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="0819651454-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="0819651454-4">}</span><span class="p" data-group-id="0819651454-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8923857098-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="8923857098-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="8923857098-2">}</span><span class="p" data-group-id="8923857098-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8923857098-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="8923857098-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8923857098-4">}</span><span class="p" data-group-id="8923857098-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% {&#39;EXIT&#39;, ClientPid, Reason}  (client terminated or unreachable.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Messages from Server to Client, received in await_result/0 function</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0819651454-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="0819651454-6">{</span><span class="ss">message</span><span class="p" data-group-id="0819651454-6">}</span><span class="p" data-group-id="0819651454-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8923857098-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="8923857098-6">{</span><span class="ss">message</span><span class="p" data-group-id="8923857098-6">}</span><span class="p" data-group-id="8923857098-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Messages are: user_exists_at_other_node,</span><span class="w">
│ │ │ │  </span><span class="c1">%%%               you_are_not_logged_on</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0819651454-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="0819651454-8">{</span><span class="ss">message</span><span class="p" data-group-id="0819651454-8">}</span><span class="p" data-group-id="0819651454-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8923857098-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="8923857098-8">{</span><span class="ss">message</span><span class="p" data-group-id="8923857098-8">}</span><span class="p" data-group-id="8923857098-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Messages are: logged_on</span><span class="w">
│ │ │ │  </span><span class="c1">%%%               receiver_not_found</span><span class="w">
│ │ │ │  </span><span class="c1">%%%               sent  (Message has been sent (no guarantee)</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Messages from Server to Client received in client/1 function</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0819651454-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="0819651454-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="0819651454-10">}</span><span class="p" data-group-id="0819651454-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8923857098-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="8923857098-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8923857098-10">}</span><span class="p" data-group-id="8923857098-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Messages from shell to Client received in client/1 function</span><span class="w">
│ │ │ │  </span><span class="c1">%%% spawn(mess_client, client, [server_node(), Name])</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0819651454-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="0819651454-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="0819651454-12">}</span><span class="p" data-group-id="0819651454-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8923857098-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="8923857098-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8923857098-12">}</span><span class="p" data-group-id="8923857098-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% logoff</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE user_interface.erl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% User interface to the messenger program</span><span class="w">
│ │ │ │  </span><span class="c1">%%% login(Name)</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     One user at a time can log in from each Erlang node in the</span><span class="w">
│ │ │ │ @@ -75,177 +75,177 @@
│ │ │ │  </span><span class="c1">%%%     Logs off anybody at that node</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% message(ToName, Message)</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     sends Message to ToName. Error messages if the user of this</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     function is not logged on or if ToName is not logged on at</span><span class="w">
│ │ │ │  </span><span class="c1">%%%     any node.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8355533404-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="8355533404-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8355533404-2">(</span><span class="p" data-group-id="8355533404-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8355533404-3">]</span><span class="p" data-group-id="8355533404-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8355533404-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="8355533404-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8355533404-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="8355533404-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6266280487-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="6266280487-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6266280487-2">(</span><span class="p" data-group-id="6266280487-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6266280487-3">]</span><span class="p" data-group-id="6266280487-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6266280487-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="6266280487-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6266280487-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="6266280487-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="8355533404-6">(</span><span class="n">Name</span><span class="p" data-group-id="8355533404-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8355533404-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8355533404-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="6266280487-6">(</span><span class="n">Name</span><span class="p" data-group-id="6266280487-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="6266280487-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6266280487-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="8355533404-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="8355533404-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8355533404-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8355533404-10">]</span><span class="p" data-group-id="8355533404-9">)</span><span class="p" data-group-id="8355533404-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="6266280487-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="6266280487-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6266280487-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6266280487-10">]</span><span class="p" data-group-id="6266280487-9">)</span><span class="p" data-group-id="6266280487-8">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="8355533404-11">(</span><span class="p" data-group-id="8355533404-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="6266280487-11">(</span><span class="p" data-group-id="6266280487-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="8355533404-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8355533404-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8355533404-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8355533404-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="6266280487-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6266280487-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="6266280487-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6266280487-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="8355533404-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="8355533404-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="6266280487-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6266280487-14">}</span><span class="p">,</span><span class="w">
│ │ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_client.erl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5204550820-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5204550820-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5204550820-2">(</span><span class="p" data-group-id="5204550820-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5204550820-3">]</span><span class="p" data-group-id="5204550820-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5204550820-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="5204550820-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5204550820-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5204550820-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5204550820-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5204550820-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="5204550820-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5204550820-8">(</span><span class="p" data-group-id="5204550820-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="5204550820-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="5204550820-9">(</span><span class="p" data-group-id="5204550820-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5204550820-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5204550820-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9811324896-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9811324896-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9811324896-2">(</span><span class="p" data-group-id="9811324896-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9811324896-3">]</span><span class="p" data-group-id="9811324896-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9811324896-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="9811324896-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9811324896-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9811324896-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9811324896-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9811324896-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="9811324896-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="9811324896-8">(</span><span class="p" data-group-id="9811324896-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="9811324896-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="9811324896-9">(</span><span class="p" data-group-id="9811324896-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9811324896-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9811324896-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5204550820-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5204550820-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9811324896-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9811324896-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5204550820-12">(</span><span class="ss">normal</span><span class="p" data-group-id="5204550820-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5204550820-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5204550820-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="5204550820-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5204550820-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ │ -                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="5204550820-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5204550820-16">(</span><span class="p" data-group-id="5204550820-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5204550820-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="5204550820-17">(</span><span class="p" data-group-id="5204550820-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5204550820-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5204550820-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5204550820-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5204550820-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5204550820-20">]</span><span class="p" data-group-id="5204550820-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9811324896-12">(</span><span class="ss">normal</span><span class="p" data-group-id="9811324896-12">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="9811324896-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="9811324896-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9811324896-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9811324896-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ │ +                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="9811324896-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="9811324896-16">(</span><span class="p" data-group-id="9811324896-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="9811324896-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="9811324896-17">(</span><span class="p" data-group-id="9811324896-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9811324896-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9811324896-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9811324896-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9811324896-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9811324896-20">]</span><span class="p" data-group-id="9811324896-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5204550820-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5204550820-21">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9811324896-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9811324896-21">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="5204550820-22">(</span><span class="p" data-group-id="5204550820-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="9811324896-22">(</span><span class="p" data-group-id="9811324896-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="5204550820-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="5204550820-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5204550820-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5204550820-25">[</span><span class="n">Why</span><span class="p" data-group-id="5204550820-25">]</span><span class="p" data-group-id="5204550820-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5204550820-26">(</span><span class="ss">normal</span><span class="p" data-group-id="5204550820-26">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="5204550820-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="5204550820-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5204550820-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5204550820-29">[</span><span class="n">What</span><span class="p" data-group-id="5204550820-29">]</span><span class="p" data-group-id="5204550820-28">)</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="9811324896-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="9811324896-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9811324896-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9811324896-25">[</span><span class="n">Why</span><span class="p" data-group-id="9811324896-25">]</span><span class="p" data-group-id="9811324896-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9811324896-26">(</span><span class="ss">normal</span><span class="p" data-group-id="9811324896-26">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="9811324896-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="9811324896-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9811324896-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9811324896-29">[</span><span class="n">What</span><span class="p" data-group-id="9811324896-29">]</span><span class="p" data-group-id="9811324896-28">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5204550820-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5204550820-31">[</span><span class="p" data-group-id="5204550820-31">]</span><span class="p" data-group-id="5204550820-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5204550820-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="5204550820-32">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9811324896-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9811324896-31">[</span><span class="p" data-group-id="9811324896-31">]</span><span class="p" data-group-id="9811324896-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9811324896-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="9811324896-32">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE---</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_server.erl----</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% This is the server process of the messenger service</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6988189700-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="6988189700-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6988189700-2">(</span><span class="p" data-group-id="6988189700-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6988189700-3">]</span><span class="p" data-group-id="6988189700-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6988189700-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="6988189700-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="6988189700-5">(</span><span class="p" data-group-id="6988189700-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="6988189700-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6988189700-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="6988189700-7">(</span><span class="p" data-group-id="6988189700-8">[</span><span class="p" data-group-id="6988189700-8">]</span><span class="p" data-group-id="6988189700-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0195472898-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="0195472898-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0195472898-2">(</span><span class="p" data-group-id="0195472898-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0195472898-3">]</span><span class="p" data-group-id="0195472898-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0195472898-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="0195472898-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="0195472898-5">(</span><span class="p" data-group-id="0195472898-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="0195472898-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0195472898-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="0195472898-7">(</span><span class="p" data-group-id="0195472898-8">[</span><span class="p" data-group-id="0195472898-8">]</span><span class="p" data-group-id="0195472898-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]</span><span class="w">
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="6988189700-9">(</span><span class="n">User_List</span><span class="p" data-group-id="6988189700-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6988189700-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988189700-11">[</span><span class="n">User_List</span><span class="p" data-group-id="6988189700-11">]</span><span class="p" data-group-id="6988189700-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="0195472898-9">(</span><span class="n">User_List</span><span class="p" data-group-id="0195472898-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0195472898-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0195472898-11">[</span><span class="n">User_List</span><span class="p" data-group-id="0195472898-11">]</span><span class="p" data-group-id="0195472898-10">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="6988189700-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="6988189700-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="6988189700-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="6988189700-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="6988189700-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6988189700-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="6988189700-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="6988189700-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="6988189700-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="6988189700-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="6988189700-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6988189700-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="6988189700-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="6988189700-20">(</span><span class="n">User_List</span><span class="p" data-group-id="6988189700-20">)</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="0195472898-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="0195472898-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="0195472898-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="0195472898-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="0195472898-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0195472898-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="0195472898-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="0195472898-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="0195472898-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="0195472898-17">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="0195472898-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0195472898-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="0195472898-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="0195472898-20">(</span><span class="n">User_List</span><span class="p" data-group-id="0195472898-20">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="6988189700-21">(</span><span class="p" data-group-id="6988189700-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="6988189700-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6988189700-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988189700-24">[</span><span class="p" data-group-id="6988189700-24">]</span><span class="p" data-group-id="6988189700-23">)</span><span class="p" data-group-id="6988189700-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="0195472898-21">(</span><span class="p" data-group-id="0195472898-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0195472898-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0195472898-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0195472898-24">[</span><span class="p" data-group-id="0195472898-24">]</span><span class="p" data-group-id="0195472898-23">)</span><span class="p" data-group-id="0195472898-22">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="6988189700-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="0195472898-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6988189700-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="0195472898-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="6988189700-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="6988189700-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="0195472898-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="0195472898-27">}</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="6988189700-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="6988189700-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="6988189700-29">(</span><span class="n">From</span><span class="p" data-group-id="6988189700-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="6988189700-30">[</span><span class="p" data-group-id="6988189700-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6988189700-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="0195472898-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="0195472898-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="0195472898-29">(</span><span class="n">From</span><span class="p" data-group-id="0195472898-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0195472898-30">[</span><span class="p" data-group-id="0195472898-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0195472898-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="6988189700-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="6988189700-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-33">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="0195472898-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="0195472898-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-33">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server transfers a message between user</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="6988189700-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="0195472898-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="6988189700-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="0195472898-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="6988189700-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="6988189700-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6988189700-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988189700-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6988189700-38">}</span><span class="p" data-group-id="6988189700-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="6988189700-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-39">)</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="0195472898-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="0195472898-36">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0195472898-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0195472898-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0195472898-38">}</span><span class="p" data-group-id="0195472898-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="0195472898-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-39">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="6988189700-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="0195472898-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="6988189700-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6988189700-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="0195472898-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0195472898-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="6988189700-42">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="6988189700-42">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6988189700-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6988189700-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="6988189700-44">}</span><span class="p" data-group-id="6988189700-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="6988189700-45">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6988189700-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="6988189700-46">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="6988189700-46">}</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="0195472898-42">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="0195472898-42">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0195472898-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0195472898-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="0195472898-44">}</span><span class="p" data-group-id="0195472898-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="0195472898-45">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0195472898-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="0195472898-46">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="0195472898-46">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%%----END FILE---</span></code></pre><h2 id="header-files" class="section-heading">
│ │ │ │    <a href="#header-files" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Header Files</span>
│ │ │ │  </h2>
│ │ │ │  <p>As shown above, some files have extension <code class="inline">.hrl</code>. These are header files that
│ │ │ │ -are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="3505064104-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="3505064104-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1540305001-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="1540305001-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │ │ +are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="3891304133-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="3891304133-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0724120054-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="0724120054-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │ │  files in the messenger example. (<em>manual</em>).</p><p>.hrl files can contain any valid Erlang code but are most often used for record
│ │ │ │  and macro definitions.</p><h2 id="records" class="section-heading">
│ │ │ │    <a href="#records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Records</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2375514169-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="2375514169-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2375514169-2">}</span><span class="p" data-group-id="2375514169-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8501023470-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="8501023470-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8501023470-2">}</span><span class="p" data-group-id="8501023470-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2946900862-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="2946900862-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="2632589838-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p">)</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6541604468-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6541604468-1">}</span></code></pre><p>Notice that you do not have to worry about the order you assign values to the
│ │ │ │ +<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3091248598-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="3091248598-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3091248598-2">}</span><span class="p" data-group-id="3091248598-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8709413300-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="8709413300-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8709413300-2">}</span><span class="p" data-group-id="8709413300-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2755786079-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="2755786079-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5286888794-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p">)</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9002135209-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9002135209-1">}</span></code></pre><p>Notice that you do not have to worry about the order you assign values to the
│ │ │ │  various parts of the records when you create it. The advantage of using records
│ │ │ │  is that by placing their definitions in header files you can conveniently define
│ │ │ │  interfaces that are easy to change. For example, if you want to add a new field
│ │ │ │  to the record, you only have to change the code where the new field is used and
│ │ │ │  not at every place the record is referred to. If you leave out a field when
│ │ │ │  creating a record, it gets the value of the atom <code class="inline">undefined</code>. (<em>manual</em>)</p><p>Pattern matching with records is very similar to creating records. For example,
│ │ │ │ -inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="1319738895-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="1319738895-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3790364056-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="3790364056-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │ │ +inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="9281032399-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="9281032399-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1034840376-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1034840376-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │ │    <a href="#macros" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Macros</span>
│ │ │ │  </h2>
│ │ │ │  <p>Another thing that has been added to the messenger is a macro. The file
│ │ │ │  <code class="inline">mess_config.hrl</code> contains the definition:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6232586399-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="6232586399-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1605167090-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="1605167090-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ │ -<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="0238493491-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0238493491-2">[</span><span class="p" data-group-id="0238493491-2">]</span><span class="p" data-group-id="0238493491-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2893035190-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="2893035190-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5283017220-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="5283017220-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ │ +<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="8914423820-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8914423820-2">[</span><span class="p" data-group-id="8914423820-2">]</span><span class="p" data-group-id="8914423820-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │ │  <code class="inline">?MODULE</code> is always replaced by the name of the current module (that is, the
│ │ │ │  <code class="inline">-module</code> definition near the start of the file). There are more advanced ways
│ │ │ │  of using macros with, for example, <a href="macros.xhtml#defining-and-using-macros">parameters</a>.</p><p>The three Erlang (<code class="inline">.erl</code>) files in the messenger example are individually
│ │ │ │  compiled into object code file (<code class="inline">.beam</code>). The Erlang system loads and links
│ │ │ │  these files into the system when they are referred to during execution of the
│ │ │ │  code. In this case, they are simply put in our current working directory (that
│ │ │ │  is, the place you have done &quot;cd&quot; to). There are ways of putting the <code class="inline">.beam</code>
│ │ │ ├── OEBPS/prog_ex_records.xhtml
│ │ │ │ @@ -27,105 +27,105 @@
│ │ │ │    <span class="text">Records and Tuples</span>
│ │ │ │  </h2>
│ │ │ │  <p>The main advantage of using records rather than tuples is that fields in a
│ │ │ │  record are accessed by name, whereas fields in a tuple are accessed by position.
│ │ │ │  To illustrate these differences, suppose that you want to represent a person
│ │ │ │  with the tuple <code class="inline">{Name, Address, Phone}</code>.</p><p>To write functions that manipulate this data, remember the following:</p><ul><li>The <code class="inline">Name</code> field is the first element of the tuple.</li><li>The <code class="inline">Address</code> field is the second element.</li><li>The <code class="inline">Phone</code> field is the third element.</li></ul><p>For example, to extract data from a variable <code class="inline">P</code> that contains such a tuple, you
│ │ │ │  can write the following code and then use pattern matching to extract the
│ │ │ │ -relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="4698019548-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="4698019548-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="4698019548-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="4698019548-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="6469157770-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="6469157770-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="6469157770-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="6469157770-2">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Such code is difficult to read and understand, and errors occur if the numbering
│ │ │ │  of the elements in the tuple is wrong. If the data representation of the fields
│ │ │ │  is changed, by re-ordering, adding, or removing fields, all references to the
│ │ │ │  person tuple must be checked and possibly modified.</p><p>Records allow references to the fields by name, instead of by position. In the
│ │ │ │ -following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0976982802-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0976982802-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="0976982802-2">}</span><span class="p" data-group-id="0976982802-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │ │ +following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5950047897-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5950047897-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="5950047897-2">}</span><span class="p" data-group-id="5950047897-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │ │  is a variable whose value is a <code class="inline">person</code> record, the following code access the
│ │ │ │  name and address fields of the records:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">address</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8723481140-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="8723481140-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8917657433-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="8917657433-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │ │    <a href="#defining-a-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Defining a Record</span>
│ │ │ │  </h2>
│ │ │ │  <p>This following definition of a <code class="inline">person</code> is used in several examples in this
│ │ │ │  section. Three fields are included, <code class="inline">name</code>, <code class="inline">phone</code>, and <code class="inline">address</code>. The default
│ │ │ │  values for <code class="inline">name</code> and <code class="inline">phone</code> is &quot;&quot; and [], respectively. The default value for
│ │ │ │  <code class="inline">address</code> is the atom <code class="inline">undefined</code>, since no default value is supplied for this
│ │ │ │ -field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1561800588-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1561800588-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1561800588-3">[</span><span class="p" data-group-id="1561800588-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1561800588-2">}</span><span class="p" data-group-id="1561800588-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ │ -the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="4332654076-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4332654076-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4332654076-3">[</span><span class="p" data-group-id="4332654076-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="4332654076-2">}</span><span class="p" data-group-id="4332654076-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8656961221-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8656961221-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8656961221-3">[</span><span class="p" data-group-id="8656961221-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="8656961221-2">}</span><span class="p" data-group-id="8656961221-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ │ +the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="1705965677-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1705965677-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1705965677-3">[</span><span class="p" data-group-id="1705965677-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1705965677-2">}</span><span class="p" data-group-id="1705965677-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">person</span></code></pre><p>This is because record definitions are only available at compile time, not at
│ │ │ │  runtime. For details on records in the shell, see the <a href="../../../lib/stdlib/doc/html/shell.html"><code class="inline">shell</code></a> manual page in
│ │ │ │  STDLIB.</p><h2 id="creating-a-record" class="section-heading">
│ │ │ │    <a href="#creating-a-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating a Record</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1457106046-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="1457106046-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1457106046-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="1457106046-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1457106046-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1457106046-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1457106046-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="1457106046-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ │ -special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9496431738-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9496431738-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9496431738-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9496431738-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │ │ +<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6789189110-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="6789189110-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6789189110-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="6789189110-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6789189110-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6789189110-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6789189110-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="6789189110-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ │ +special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7490418544-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="7490418544-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7490418544-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="7490418544-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │ │  <a href="../../../lib/mnesia/doc/html/mnesia.html#match_object/3"><code class="inline">mnesia:match_object/3</code></a>, to set record fields to the atom <code class="inline">'_'</code>. (This is a
│ │ │ │  wildcard in <a href="../../../lib/stdlib/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>.)</p><h2 id="accessing-a-record-field" class="section-heading">
│ │ │ │    <a href="#accessing-a-record-field" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Accessing a Record Field</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9097498412-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9097498412-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9097498412-2">]</span><span class="p" data-group-id="9097498412-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9097498412-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9097498412-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9097498412-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="9097498412-3">}</span><span class="gp unselectable">
│ │ │ │ +<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5164651965-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5164651965-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5164651965-2">]</span><span class="p" data-group-id="5164651965-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5164651965-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5164651965-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5164651965-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="5164651965-3">}</span><span class="gp unselectable">
│ │ │ │  &gt; </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><h2 id="updating-a-record" class="section-heading">
│ │ │ │    <a href="#updating-a-record" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating a Record</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0920180374-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="0920180374-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0920180374-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="0920180374-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0920180374-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0920180374-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0920180374-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="0920180374-3">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0920180374-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="0920180374-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0920180374-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0920180374-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0920180374-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="0920180374-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │ │ +<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1522425078-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="1522425078-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1522425078-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="1522425078-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1522425078-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1522425078-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1522425078-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="1522425078-3">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1522425078-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="1522425078-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1522425078-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1522425078-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1522425078-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="1522425078-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │ │    <a href="#type-testing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Testing</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following example shows that the guard succeeds if <code class="inline">P</code> is record of type
│ │ │ │ -<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4924610162-1">(</span><span class="n">P</span><span class="p" data-group-id="4924610162-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="4924610162-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="4924610162-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="4924610162-3">(</span><span class="p">_</span><span class="p" data-group-id="4924610162-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │ │ +<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0147866991-1">(</span><span class="n">P</span><span class="p" data-group-id="0147866991-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="0147866991-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="0147866991-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="0147866991-3">(</span><span class="p">_</span><span class="p" data-group-id="0147866991-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │ │    <a href="#pattern-matching" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Pattern Matching</span>
│ │ │ │  </h2>
│ │ │ │  <p>Matching can be used in combination with records, as shown in the following
│ │ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2605593731-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="2605593731-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2605593731-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="2605593731-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2605593731-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2605593731-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2605593731-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="2605593731-3">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2605593731-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2605593731-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2406481501-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="2406481501-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2406481501-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="2406481501-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2406481501-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2406481501-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2406481501-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="2406481501-3">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2406481501-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2406481501-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><p>The following function takes a list of <code class="inline">person</code> records and searches for the
│ │ │ │ -phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="1633857383-1">(</span><span class="p" data-group-id="1633857383-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1633857383-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="1633857383-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1633857383-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1633857383-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1633857383-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="1633857383-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="1633857383-5">(</span><span class="p" data-group-id="1633857383-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1633857383-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1633857383-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">find_phone</span><span class="p" data-group-id="1633857383-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1633857383-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="1633857383-8">(</span><span class="p" data-group-id="1633857383-9">[</span><span class="p" data-group-id="1633857383-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1633857383-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="5435481293-1">(</span><span class="p" data-group-id="5435481293-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5435481293-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="5435481293-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5435481293-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5435481293-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5435481293-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="5435481293-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="5435481293-5">(</span><span class="p" data-group-id="5435481293-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5435481293-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5435481293-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">find_phone</span><span class="p" data-group-id="5435481293-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5435481293-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="5435481293-8">(</span><span class="p" data-group-id="5435481293-9">[</span><span class="p" data-group-id="5435481293-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5435481293-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">not_found</span><span class="p">.</span></code></pre><p>The fields referred to in the pattern can be given in any order.</p><h2 id="nested-records" class="section-heading">
│ │ │ │    <a href="#nested-records" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Nested Records</span>
│ │ │ │  </h2>
│ │ │ │  <p>The value of a field in a record can be an instance of a record. Retrieval of
│ │ │ │  nested data can be done stepwise, or in a single step, as shown in the following
│ │ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0118785450-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0118785450-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="0118785450-2">}</span><span class="p" data-group-id="0118785450-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0118785450-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0118785450-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="0118785450-5">{</span><span class="p" data-group-id="0118785450-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="0118785450-4">}</span><span class="p" data-group-id="0118785450-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4345082819-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4345082819-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="4345082819-2">}</span><span class="p" data-group-id="4345082819-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4345082819-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4345082819-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="4345082819-5">{</span><span class="p" data-group-id="4345082819-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="4345082819-4">}</span><span class="p" data-group-id="4345082819-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">demo</span><span class="p" data-group-id="0118785450-6">(</span><span class="p" data-group-id="0118785450-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0118785450-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="0118785450-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="0118785450-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="0118785450-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0118785450-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="0118785450-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │ │ +</span><span class="nf">demo</span><span class="p" data-group-id="4345082819-6">(</span><span class="p" data-group-id="4345082819-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4345082819-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="4345082819-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="4345082819-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="4345082819-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4345082819-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="4345082819-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │ │    <a href="#a-longer-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">A Longer Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>Comments are embedded in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% File: person.hrl</span><span class="w">
│ │ │ │  
│ │ │ │ @@ -135,44 +135,44 @@
│ │ │ │  </span><span class="c1">%%    name:  A string (default is undefined).</span><span class="w">
│ │ │ │  </span><span class="c1">%%    age:   An integer (default is undefined).</span><span class="w">
│ │ │ │  </span><span class="c1">%%    phone: A list of integers (default is []).</span><span class="w">
│ │ │ │  </span><span class="c1">%%    dict:  A dictionary containing various information</span><span class="w">
│ │ │ │  </span><span class="c1">%%           about the person.</span><span class="w">
│ │ │ │  </span><span class="c1">%%           A {Key, Value} list (default is the empty list).</span><span class="w">
│ │ │ │  </span><span class="c1">%%------------------------------------------------------------</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4789550475-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4789550475-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4789550475-3">[</span><span class="p" data-group-id="4789550475-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4789550475-4">[</span><span class="p" data-group-id="4789550475-4">]</span><span class="p" data-group-id="4789550475-2">}</span><span class="p" data-group-id="4789550475-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1817610791-1">(</span><span class="ss">person</span><span class="p" data-group-id="1817610791-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1817610791-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="1817610791-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="1817610791-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="1817610791-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0659343481-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0659343481-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0659343481-3">[</span><span class="p" data-group-id="0659343481-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0659343481-4">[</span><span class="p" data-group-id="0659343481-4">]</span><span class="p" data-group-id="0659343481-2">}</span><span class="p" data-group-id="0659343481-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4646991870-1">(</span><span class="ss">person</span><span class="p" data-group-id="4646991870-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4646991870-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="4646991870-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="4646991870-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="4646991870-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% This creates an instance of a person.</span><span class="w">
│ │ │ │  </span><span class="c1">%%   Note: The phone number is not supplied so the</span><span class="w">
│ │ │ │  </span><span class="c1">%%         default value [] will be used.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="1817610791-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="1817610791-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1817610791-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1817610791-6">[</span><span class="p" data-group-id="1817610791-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="1817610791-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                   </span><span class="p" data-group-id="1817610791-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="1817610791-8">}</span><span class="p" data-group-id="1817610791-6">]</span><span class="p" data-group-id="1817610791-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="4646991870-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="4646991870-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4646991870-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4646991870-6">[</span><span class="p" data-group-id="4646991870-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="4646991870-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                   </span><span class="p" data-group-id="4646991870-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="4646991870-8">}</span><span class="p" data-group-id="4646991870-6">]</span><span class="p" data-group-id="4646991870-5">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% This demonstrates matching in arguments</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">print</span><span class="p" data-group-id="1817610791-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1817610791-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="1817610791-10">}</span><span class="p" data-group-id="1817610791-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1817610791-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ │ -            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1817610791-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="1817610791-12">]</span><span class="p" data-group-id="1817610791-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">print</span><span class="p" data-group-id="4646991870-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4646991870-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="4646991870-10">}</span><span class="p" data-group-id="4646991870-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4646991870-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ │ +            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4646991870-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="4646991870-12">]</span><span class="p" data-group-id="4646991870-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Demonstrates type testing, selector, updating.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">birthday</span><span class="p" data-group-id="1817610791-13">(</span><span class="n">P</span><span class="p" data-group-id="1817610791-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="1817610791-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="1817610791-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1817610791-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1817610791-15">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">birthday</span><span class="p" data-group-id="4646991870-13">(</span><span class="n">P</span><span class="p" data-group-id="4646991870-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="4646991870-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="4646991870-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4646991870-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4646991870-15">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="1817610791-16">(</span><span class="p" data-group-id="1817610791-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="1817610791-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="1817610791-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="1817610791-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="1817610791-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="4646991870-16">(</span><span class="p" data-group-id="4646991870-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="4646991870-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="4646991870-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="4646991870-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="4646991870-18">)</span><span class="p">,</span><span class="w">
│ │ │ │     </span><span class="c1">% The central_register_server should have</span><span class="w">
│ │ │ │     </span><span class="c1">% an interface function for this.</span><span class="w">
│ │ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1817610791-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="1817610791-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1817610791-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ │ -             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1817610791-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1817610791-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1817610791-22">]</span><span class="p" data-group-id="1817610791-21">}</span><span class="p" data-group-id="1817610791-20">}</span><span class="p">.</span></code></pre>
│ │ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4646991870-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="4646991870-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4646991870-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ │ +             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4646991870-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4646991870-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4646991870-22">]</span><span class="p" data-group-id="4646991870-21">}</span><span class="p" data-group-id="4646991870-20">}</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/patterns.xhtml
│ │ │ │ @@ -33,16 +33,16 @@
│ │ │ │  succeeds, any unbound variables in the pattern become bound. If the matching
│ │ │ │  fails, an exception is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** 1:1: variable &#39;X&#39; is unbound **</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="gp unselectable">
│ │ │ │  3&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="p" data-group-id="6293977611-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6293977611-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6293977611-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6293977611-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="p" data-group-id="2114313205-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2114313205-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2114313205-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2114313205-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value {1,2}</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="p" data-group-id="6293977611-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6293977611-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6293977611-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6293977611-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6293977611-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6293977611-5">}</span><span class="gp unselectable">
│ │ │ │ +5&gt; </span><span class="p" data-group-id="2114313205-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2114313205-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2114313205-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2114313205-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2114313205-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2114313205-5">}</span><span class="gp unselectable">
│ │ │ │  6&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/otp-patch-apply.xhtml
│ │ │ │ @@ -106,13 +106,13 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Sanity check</span>
│ │ │ │  </h2>
│ │ │ │  <p>The application dependencies can be checked using the Erlang shell.
│ │ │ │  Application dependencies are verified among installed applications by
│ │ │ │  <code class="inline">otp_patch_apply</code>, but these are not necessarily those actually loaded.
│ │ │ │  By calling <code class="inline">system_information:sanity_check()</code> one can validate
│ │ │ │ -dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="2057611789-1">(</span><span class="p" data-group-id="2057611789-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="3223563112-1">(</span><span class="p" data-group-id="3223563112-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>Please take a look at the reference of <a href="../../../lib/runtime_tools/doc/html/system_information.html#sanity_check/0" title="">sanity_check()</a> for more
│ │ │ │  information.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/opaques.xhtml
│ │ │ │ @@ -27,24 +27,24 @@
│ │ │ │    <span class="text">Opaque Type Aliases</span>
│ │ │ │  </h2>
│ │ │ │  <p>The main use case for opacity in Erlang is to hide the implementation of a data
│ │ │ │  type, enabling evolving the API while minimizing the risk of breaking consumers.
│ │ │ │  The runtime does not check opacity. Dialyzer provides some opacity-checking, but
│ │ │ │  the rest is up to convention.</p><p>This document explains what Erlang opacity is (and the trade-offs involved) via
│ │ │ │  the example of the <a href="../../../lib/stdlib/doc/html/sets.html#t:set/0"><code class="inline">sets:set()</code></a> data type. This type <em>was</em>
│ │ │ │ -defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="8338042962-1">(</span><span class="n">Element</span><span class="p" data-group-id="8338042962-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="8338042962-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="8338042962-3">(</span><span class="n">Element</span><span class="p" data-group-id="8338042962-3">)</span><span class="p" data-group-id="8338042962-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ │ -<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="6404065042-1">(</span><span class="n">Element</span><span class="p" data-group-id="6404065042-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="6404065042-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="6404065042-3">(</span><span class="n">Element</span><span class="p" data-group-id="6404065042-3">)</span><span class="p" data-group-id="6404065042-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="6404065042-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="6404065042-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │ │ +defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="5507410175-1">(</span><span class="n">Element</span><span class="p" data-group-id="5507410175-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="5507410175-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="5507410175-3">(</span><span class="n">Element</span><span class="p" data-group-id="5507410175-3">)</span><span class="p" data-group-id="5507410175-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ │ +<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="7402837066-1">(</span><span class="n">Element</span><span class="p" data-group-id="7402837066-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="7402837066-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="7402837066-3">(</span><span class="n">Element</span><span class="p" data-group-id="7402837066-3">)</span><span class="p" data-group-id="7402837066-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7402837066-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="7402837066-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │ │  been defined with <code class="inline">-type</code> instead of <code class="inline">-opaque</code>. Here is why: when a module
│ │ │ │  defines an <code class="inline">-opaque</code>, the contract is that only the defining module should rely
│ │ │ │  on the definition of the type: no other modules should rely on the definition.</p><p>This means that code that pattern-matched on <code class="inline">set</code> as a record/tuple technically
│ │ │ │  broke the contract, and opted in to being potentially broken when the definition
│ │ │ │  of <code class="inline">set()</code> changed. Before OTP 24, this code printed <code class="inline">ok</code>. In OTP 24 it may
│ │ │ │ -error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4829970627-1">(</span><span class="p" data-group-id="4829970627-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="4829970627-2">(</span><span class="n">Set</span><span class="p" data-group-id="4829970627-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4829970627-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="4829970627-3">)</span><span class="w">
│ │ │ │ +error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="8826394907-1">(</span><span class="p" data-group-id="8826394907-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="8826394907-2">(</span><span class="n">Set</span><span class="p" data-group-id="8826394907-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8826394907-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="8826394907-3">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p><strong>When working with an opaque defined in another module, here are some
│ │ │ │  recommendations:</strong></p><ul><li>Don't examine the underlying type using pattern-matching, guards, or functions
│ │ │ │  that reveal the type, such as <a href="../../../lib/../erts/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a> .</li><li>Instead, use functions provided by the module for working with the type. For
│ │ │ │  example, <code class="inline">sets</code> module provides <a href="../../../lib/stdlib/doc/html/sets.html#new/0"><code class="inline">sets:new/0</code></a>, <a href="../../../lib/stdlib/doc/html/sets.html#add_element/2"><code class="inline">sets:add_element/2</code></a>,
│ │ │ │  <a href="../../../lib/stdlib/doc/html/sets.html#is_element/2"><code class="inline">sets:is_element/2</code></a>, and so on.</li><li><p><a href="../../../lib/stdlib/doc/html/sets.html#t:set/1"><code class="inline">sets:set(a)</code></a> is a subtype of <code class="inline">sets:set(a | b)</code> and not the
│ │ │ │  other way around. Generally, you can rely on the property that <code class="inline">the_opaque(T)</code>
│ │ │ │  is a subtype of <code class="inline">the_opaque(U)</code> when T is a subtype of U.</p></li></ul><p><strong>When defining your own opaques, here are some recommendations:</strong></p><ul><li>Since consumers are expected to not rely on the definition of the opaque type,
│ │ │ ├── OEBPS/nif.xhtml
│ │ │ │ @@ -38,26 +38,26 @@
│ │ │ │    <span class="text">Erlang Program</span>
│ │ │ │  </h2>
│ │ │ │  <p>Even if all functions of a module are NIFs, an Erlang module is still needed for
│ │ │ │  two reasons:</p><ul><li>The NIF library must be explicitly loaded by Erlang code in the same module.</li><li>All NIFs of a module must have an Erlang implementation as well.</li></ul><p>Normally these are minimal stub implementations that throw an exception. But
│ │ │ │  they can also be used as fallback implementations for functions that do not have
│ │ │ │  native implementations on some architectures.</p><p>NIF libraries are loaded by calling <a href="../../../lib/../erts/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a>, with the name of the
│ │ │ │  shared library as argument. The second argument can be any term that will be
│ │ │ │ -passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6767812859-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="6767812859-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6767812859-2">(</span><span class="p" data-group-id="6767812859-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6767812859-3">]</span><span class="p" data-group-id="6767812859-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="6767812859-4">(</span><span class="p" data-group-id="6767812859-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6767812859-5">]</span><span class="p" data-group-id="6767812859-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="6767812859-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6767812859-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6767812859-7">(</span><span class="p" data-group-id="6767812859-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="6767812859-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6767812859-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="6767812859-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="6767812859-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="6767812859-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="6767812859-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="6767812859-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="6767812859-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="6767812859-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="6767812859-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │ │ +passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9459655708-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="9459655708-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9459655708-2">(</span><span class="p" data-group-id="9459655708-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9459655708-3">]</span><span class="p" data-group-id="9459655708-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="9459655708-4">(</span><span class="p" data-group-id="9459655708-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9459655708-5">]</span><span class="p" data-group-id="9459655708-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="9459655708-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9459655708-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9459655708-7">(</span><span class="p" data-group-id="9459655708-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="9459655708-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9459655708-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="9459655708-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="9459655708-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="9459655708-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="9459655708-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="9459655708-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="9459655708-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="9459655708-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="9459655708-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │ │  called when the module is loaded. If <code class="inline">init</code> returns anything other than <code class="inline">ok</code>,
│ │ │ │  such when the loading of the NIF library fails in this example, the module is
│ │ │ │  unloaded and calls to functions within it, fail.</p><p>Loading the NIF library overrides the stub implementations and cause calls to
│ │ │ │  <code class="inline">foo</code> and <code class="inline">bar</code> to be dispatched to the NIF implementations instead.</p><h2 id="nif-library-code" class="section-heading">
│ │ │ │    <a href="#nif-library-code" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -114,22 +114,22 @@
│ │ │ │    <a href="#running-the-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running the Example</span>
│ │ │ │  </h2>
│ │ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o complex6_nif.so -fpic -shared complex.c complex6_nif.c
│ │ │ │  windows&gt; cl -LD -MD -Fe complex6_nif.dll complex.c complex6_nif.c</code></pre><p><em>Step 2:</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="8642113527-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="8642113527-1">)</span><span class="w"> </span><span class="p" data-group-id="8642113527-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="8642113527-2">]</span><span class="w"> </span><span class="p" data-group-id="8642113527-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8642113527-3">]</span><span class="w"> </span><span class="p" data-group-id="8642113527-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8642113527-4">]</span><span class="w"> </span><span class="p" data-group-id="8642113527-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="8642113527-5">]</span><span class="w"> </span><span class="p" data-group-id="8642113527-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="8642113527-6">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="2188376029-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="2188376029-1">)</span><span class="w"> </span><span class="p" data-group-id="2188376029-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="2188376029-2">]</span><span class="w"> </span><span class="p" data-group-id="2188376029-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="2188376029-3">]</span><span class="w"> </span><span class="p" data-group-id="2188376029-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="2188376029-4">]</span><span class="w"> </span><span class="p" data-group-id="2188376029-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="2188376029-5">]</span><span class="w"> </span><span class="p" data-group-id="2188376029-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="2188376029-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="8642113527-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="8642113527-7">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="8642113527-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="8642113527-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8642113527-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="8642113527-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0586198740-1">(</span><span class="mi">3</span><span class="p" data-group-id="0586198740-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="2188376029-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="2188376029-7">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="2188376029-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="2188376029-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2188376029-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="2188376029-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5237206255-1">(</span><span class="mi">3</span><span class="p" data-group-id="5237206255-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="0586198740-2">(</span><span class="mi">5</span><span class="p" data-group-id="0586198740-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="5237206255-2">(</span><span class="mi">5</span><span class="p" data-group-id="5237206255-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0586198740-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="0586198740-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5237206255-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="5237206255-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: bad argument
│ │ │ │       in function  complex6:foo/1
│ │ │ │          called as comlpex6:foo(&quot;not an integer&quot;)</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/modules.xhtml
│ │ │ │ @@ -23,20 +23,20 @@
│ │ │ │  <h2 id="module-syntax" class="section-heading">
│ │ │ │    <a href="#module-syntax" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Module Syntax</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang code is divided into <em>modules</em>. A module consists of a sequence of
│ │ │ │ -attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2834281573-1">(</span><span class="ss">m</span><span class="p" data-group-id="2834281573-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2834281573-2">(</span><span class="p" data-group-id="2834281573-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2834281573-3">]</span><span class="p" data-group-id="2834281573-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │ +attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9552481501-1">(</span><span class="ss">m</span><span class="p" data-group-id="9552481501-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9552481501-2">(</span><span class="p" data-group-id="9552481501-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9552481501-3">]</span><span class="p" data-group-id="9552481501-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="2834281573-4">(</span><span class="n">N</span><span class="p" data-group-id="2834281573-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="2834281573-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2834281573-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="2834281573-6">(</span><span class="mi">0</span><span class="p" data-group-id="2834281573-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="9552481501-4">(</span><span class="n">N</span><span class="p" data-group-id="9552481501-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="9552481501-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9552481501-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="9552481501-6">(</span><span class="mi">0</span><span class="p" data-group-id="9552481501-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">               </span><span class="c1">% end of function declaration</span></code></pre><p>For a description of function declarations, see
│ │ │ │  <a href="ref_man_functions.xhtml">Function Declaration Syntax</a>.</p><h2 id="module-attributes" class="section-heading">
│ │ │ │    <a href="#module-attributes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Module Attributes</span>
│ │ │ │  </h2>
│ │ │ │ @@ -81,71 +81,71 @@
│ │ │ │  meaning.</p></section></li></ul><h3 id="behaviour-module-attribute" class="section-heading">
│ │ │ │    <a href="#behaviour-module-attribute" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Behaviour Module Attribute</span>
│ │ │ │  </h3>
│ │ │ │  <p>It is possible to specify that the module is the callback module for a
│ │ │ │ -<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8858894061-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="8858894061-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │ │ +<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1328379305-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="1328379305-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │ │  user-defined behaviour or one of the following OTP standard behaviours:</p><ul><li><code class="inline">gen_server</code></li><li><code class="inline">gen_statem</code></li><li><code class="inline">gen_event</code></li><li><code class="inline">supervisor</code></li></ul><p>The spelling <code class="inline">behavior</code> is also accepted.</p><p>The callback functions of the module can be specified either directly by the
│ │ │ │ -exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="8707336843-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="8707336843-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0997238762-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="0997238762-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │ │ +exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="6269929233-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="6269929233-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="4304957548-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="4304957548-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │ │  is to be preferred since the extra type information can be used by tools to
│ │ │ │  produce documentation or find discrepancies.</p><p>Read more about behaviours and callback modules in
│ │ │ │  <a href="../../../lib/../system/doc/html/spec_proc.xhtml#behaviours">OTP Design Principles</a>.</p><h3 id="record-definitions" class="section-heading">
│ │ │ │    <a href="#record-definitions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Record Definitions</span>
│ │ │ │  </h3>
│ │ │ │ -<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2779967059-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="2779967059-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │ │ +<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4560208262-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="4560208262-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │ │  declarations. Read more in <a href="ref_man_records.xhtml">Records</a>.</p><h3 id="preprocessor" class="section-heading">
│ │ │ │    <a href="#preprocessor" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Preprocessor</span>
│ │ │ │  </h3>
│ │ │ │  <p>The same syntax as for module attributes is used by the preprocessor, which
│ │ │ │ -supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1834656443-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="1834656443-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1834656443-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="1834656443-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.xhtml">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │ │ +supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0818500158-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="0818500158-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0818500158-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="0818500158-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.xhtml">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │ │    <a href="#setting-file-and-line" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Setting File and Line</span>
│ │ │ │  </h3>
│ │ │ │  <p>The same syntax as for module attributes is used for changing the pre-defined
│ │ │ │ -macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="4521243197-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="4521243197-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │ │ +macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="1527102534-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="1527102534-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │ │  source program is generated by another tool. It also indicates the
│ │ │ │  correspondence of source files to lines of the original user-written file, from
│ │ │ │  which the source program is produced.</p><h3 id="types-and-function-specifications" class="section-heading">
│ │ │ │    <a href="#types-and-function-specifications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Types and function specifications</span>
│ │ │ │  </h3>
│ │ │ │  <p>A similar syntax as for module attributes is used for specifying types and
│ │ │ │ -function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="8868531901-1">(</span><span class="p" data-group-id="8868531901-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="8868531901-2">(</span><span class="p" data-group-id="8868531901-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8868531901-3">(</span><span class="p" data-group-id="8868531901-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="8868531901-4">(</span><span class="nf">integer</span><span class="p" data-group-id="8868531901-5">(</span><span class="p" data-group-id="8868531901-5">)</span><span class="p" data-group-id="8868531901-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8868531901-6">(</span><span class="p" data-group-id="8868531901-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.xhtml">Types and Function specifications</a>.</p><p>The description is based on
│ │ │ │ +function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="1397404147-1">(</span><span class="p" data-group-id="1397404147-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="1397404147-2">(</span><span class="p" data-group-id="1397404147-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="1397404147-3">(</span><span class="p" data-group-id="1397404147-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="1397404147-4">(</span><span class="nf">integer</span><span class="p" data-group-id="1397404147-5">(</span><span class="p" data-group-id="1397404147-5">)</span><span class="p" data-group-id="1397404147-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="1397404147-6">(</span><span class="p" data-group-id="1397404147-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.xhtml">Types and Function specifications</a>.</p><p>The description is based on
│ │ │ │  <a href="http://www.erlang.org/eeps/eep-0008.html">EEP8 - Types and function specifications</a>,
│ │ │ │  which is not to be further updated.</p><h3 id="documentation-attributes" class="section-heading">
│ │ │ │    <a href="#documentation-attributes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documentation attributes</span>
│ │ │ │  </h3>
│ │ │ │  <p>The module attribute <code class="inline">-doc(Documentation)</code> is used to provide user documentation
│ │ │ │ -for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2737880038-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="2737880038-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="2737880038-2">(</span><span class="p" data-group-id="2737880038-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents.The
│ │ │ │ +for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="4335749380-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="4335749380-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="4335749380-2">(</span><span class="p" data-group-id="4335749380-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents.The
│ │ │ │  parenthesis are optional around <code class="inline">Documentation</code>. The allowed values for
│ │ │ │  <code class="inline">Documentation</code> are:</p><ul><li><p><strong><a href="data_types.xhtml#string">literal string</a> or
│ │ │ │  <a href="expressions.xhtml#unicode-segments">utf-8 encoded binary string</a></strong> - The string
│ │ │ │  documenting the entity. Any literal string is allowed, so both
│ │ │ │  <a href="data_types.xhtml#tqstring">triple quoted strings</a> and
│ │ │ │  <a href="data_types.xhtml#sigil">sigils</a> that translate to literal strings can be used.
│ │ │ │ -The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="0333908945-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="0333908945-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="0333908945-2">(</span><span class="p" data-group-id="0333908945-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="0333908945-3">&gt;&gt;</span><span class="p" data-group-id="0333908945-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="6753351742-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="6753351742-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="6753351742-2">(</span><span class="p" data-group-id="6753351742-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="6753351742-3">&gt;&gt;</span><span class="p" data-group-id="6753351742-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~S/Example &quot;docs&quot;/</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │ │     Example &quot;</span><span class="ss">docs</span><span class="s">&quot;
│ │ │ │     &quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~B|Example &quot;docs&quot;|</span><span class="p">.</span></code></pre><p>For clarity it is recommended to use either normal <code class="inline">&quot;strings&quot;</code> or triple
│ │ │ │  quoted strings for documentation attributes.</p></li><li><p><strong><code class="inline">{file,</code> <a href="../../../lib/kernel/doc/html/file.html#t:name/0"><code class="inline">file:name/0</code></a> <code class="inline">}</code></strong> - Read the contents of filename and use
│ │ │ │  that as the documentation string.</p></li><li><p><strong><code class="inline">false</code></strong> - Set the current entity as hidden, that is, it should not be
│ │ │ │ @@ -158,15 +158,15 @@
│ │ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The feature directive</span>
│ │ │ │  </h2>
│ │ │ │  <p>While not a module attribute, but rather a directive (since it might affect
│ │ │ │  syntax), there is the <code class="inline">-feature(..)</code> directive used for enabling and disabling
│ │ │ │ -<a href="../../../lib/../system/doc/html/features.xhtml#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="4840772206-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="4840772206-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.xhtml#feature-directive">feature directive</a> can only appear
│ │ │ │ +<a href="../../../lib/../system/doc/html/features.xhtml#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="9261422145-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="9261422145-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.xhtml#feature-directive">feature directive</a> can only appear
│ │ │ │  in a prefix of the module.</p><h2 id="comments" class="section-heading">
│ │ │ │    <a href="#comments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Comments</span>
│ │ │ │  </h2>
│ │ │ │  <p>Comments can be placed anywhere in a module except within strings and
│ │ │ ├── OEBPS/maps.xhtml
│ │ │ │ @@ -53,16 +53,16 @@
│ │ │ │  single function that constructs the map using the map syntax and always use
│ │ │ │  it.</p></li><li><p>Always update the map using the <code class="inline">:=</code> operator (that is, requiring that an
│ │ │ │  element with that key already exists). The <code class="inline">:=</code> operator is slightly more
│ │ │ │  efficient, and it helps catching mispellings of keys.</p></li><li><p>Whenever possible, match multiple map elements at once.</p></li><li><p>Whenever possible, update multiple map elements at once.</p></li><li><p>Avoid default values and the <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> function. If there are default
│ │ │ │  values, sharing of keys between different instances of the map will be less
│ │ │ │  effective, and it is not possible to match multiple elements having default
│ │ │ │  values in one go.</p></li><li><p>To avoid having to deal with a map that may lack some keys, <a href="../../../lib/stdlib/doc/html/maps.html#merge/2"><code class="inline">maps:merge/2</code></a> can
│ │ │ │ -efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0457802293-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="0457802293-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="0457802293-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="0457802293-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │ │ +efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1134047696-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="1134047696-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="1134047696-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="1134047696-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │ │    <a href="#using-maps-as-dictionaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using Maps as Dictionaries</span>
│ │ │ │  </h2>
│ │ │ │  <p>Using a map as a dictionary implies the following usage pattern:</p><ul><li>Keys are usually variables not known at compile-time.</li><li>There can be any number of elements in the map.</li><li>Usually, no more than one element is looked up or updated at once.</li></ul><p>Given that usage pattern, the difference in performance between using the map
│ │ │ │  syntax and the maps module is usually small. Therefore, which one to use is
│ │ │ │ @@ -72,18 +72,18 @@
│ │ │ │  choice.</li></ul><h2 id="using-maps-as-sets" class="section-heading">
│ │ │ │    <a href="#using-maps-as-sets" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using Maps as Sets</span>
│ │ │ │  </h2>
│ │ │ │  <p>Starting in OTP 24, the <a href="../../../lib/stdlib/doc/html/sets.html"><code class="inline">sets</code></a> module has an option to represent sets as maps.
│ │ │ │ -Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="5789188795-1">(</span><span class="p" data-group-id="5789188795-2">[</span><span class="p" data-group-id="5789188795-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5789188795-3">}</span><span class="p" data-group-id="5789188795-2">]</span><span class="p" data-group-id="5789188795-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5789188795-4">#{</span><span class="p" data-group-id="5789188795-4">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="5789188795-5">(</span><span class="p" data-group-id="5789188795-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="5789188795-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5789188795-7">[</span><span class="p" data-group-id="5789188795-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5789188795-8">}</span><span class="p" data-group-id="5789188795-7">]</span><span class="p" data-group-id="5789188795-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5789188795-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5789188795-10">[</span><span class="p" data-group-id="5789188795-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5789188795-11">[</span><span class="p" data-group-id="5789188795-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5789188795-12">[</span><span class="p" data-group-id="5789188795-12">]</span><span class="p" data-group-id="5789188795-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │ │ +Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="3783671636-1">(</span><span class="p" data-group-id="3783671636-2">[</span><span class="p" data-group-id="3783671636-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3783671636-3">}</span><span class="p" data-group-id="3783671636-2">]</span><span class="p" data-group-id="3783671636-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3783671636-4">#{</span><span class="p" data-group-id="3783671636-4">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="3783671636-5">(</span><span class="p" data-group-id="3783671636-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3783671636-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3783671636-7">[</span><span class="p" data-group-id="3783671636-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3783671636-8">}</span><span class="p" data-group-id="3783671636-7">]</span><span class="p" data-group-id="3783671636-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3783671636-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3783671636-10">[</span><span class="p" data-group-id="3783671636-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3783671636-11">[</span><span class="p" data-group-id="3783671636-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3783671636-12">[</span><span class="p" data-group-id="3783671636-12">]</span><span class="p" data-group-id="3783671636-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │ │  few possible exceptions:</p><ul><li><a href="../../../lib/stdlib/doc/html/ordsets.html#intersection/2"><code class="inline">ordsets:intersection/2</code></a> can be more efficient than <a href="../../../lib/stdlib/doc/html/sets.html#intersection/2"><code class="inline">sets:intersection/2</code></a>. If
│ │ │ │  the intersection operation is frequently used and operations that operate on a
│ │ │ │  single element in a set (such as <code class="inline">is_element/2</code>) are avoided, <a href="../../../lib/stdlib/doc/html/ordsets.html"><code class="inline">ordsets</code></a> can
│ │ │ │  be a better choice than <a href="../../../lib/stdlib/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the intersection operation is frequently used and operations that operate
│ │ │ │  on a single element in a set (such as <code class="inline">is_element/2</code>) must also be efficient,
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gb_sets.html"><code class="inline">gb_sets</code></a> can potentially be a better choice than <a href="../../../lib/stdlib/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the elements of the set are integers in a fairly compact range, the set can
│ │ │ │  be represented as an integer where each bit represents an element in the set.
│ │ │ │ @@ -108,18 +108,18 @@
│ │ │ │  for the runtime system).</p></li><li><p><strong>N</strong> - The number of elements in the map.</p></li><li><p><strong>Keys</strong> - A tuple with keys of the map: <code class="inline">{Key1,...,KeyN}</code>. The keys are
│ │ │ │  sorted.</p></li><li><p><strong>Value1</strong> - The value corresponding to the first key in the key tuple.</p></li><li><p><strong>ValueN</strong> - The value corresponding to the last key in the key tuple.</p></li></ul><p>As an example, let us look at how the map <code class="inline">#{a =&gt; foo, z =&gt; bar}</code> is
│ │ │ │  represented:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: left;">4</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;"><em>2</em></td><td style="text-align: center;"><code class="inline">{a,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: left;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, z =&gt; bar}</em></p><p>Let us update the map: <code class="inline">M#{q =&gt; baz}</code>. The map now looks like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;"><em>3</em></td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bar}</em></p><p>Finally, change the value of one element: <code class="inline">M#{z := bird}</code>. The map now looks
│ │ │ │  like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;"><em>3</em></td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bird</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bird}</em></p><p>When the value for an existing key is updated, the key tuple is not updated,
│ │ │ │  allowing the key tuple to be shared with other instances of the map that have
│ │ │ │  the same keys. In fact, the key tuple can be shared between all maps with the
│ │ │ │  same keys with some care. To arrange that, define a function that returns a map.
│ │ │ │ -For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="6829992442-1">(</span><span class="p" data-group-id="6829992442-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6829992442-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="6829992442-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │ │ +For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="2819325953-1">(</span><span class="p" data-group-id="2819325953-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2819325953-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="2819325953-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │ │  that the key tuple is shared when creating an instance of the map, always call
│ │ │ │ -<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="0764601431-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0764601431-2">(</span><span class="p" data-group-id="0764601431-2">)</span><span class="p" data-group-id="0764601431-1">)</span><span class="p" data-group-id="0764601431-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="0764601431-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │ │ +<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="8058830345-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="8058830345-2">(</span><span class="p" data-group-id="8058830345-2">)</span><span class="p" data-group-id="8058830345-1">)</span><span class="p" data-group-id="8058830345-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="8058830345-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │ │  keys are known at compile-time, the map is updated in one go, making the time to
│ │ │ │  update a map essentially constant regardless of the number of keys updated. The
│ │ │ │  same goes for matching. (When the keys are variables, one or more of the keys
│ │ │ │  could be identical, so the operations need to be performed sequentially from
│ │ │ │  left to right.)</p><p>The memory size for a small map is the size of all keys and values plus 5 words.
│ │ │ │  See <a href="memory.xhtml">Memory</a> for more information about memory sizes.</p><h3 id="how-large-maps-are-implemented" class="section-heading">
│ │ │ │    <a href="#how-large-maps-are-implemented" class="hover-link">
│ │ │ │ @@ -146,21 +146,21 @@
│ │ │ │    <a href="#using-the-map-syntax" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using the Map Syntax</span>
│ │ │ │  </h2>
│ │ │ │  <p>Using the map syntax is usually slightly more efficient than using the
│ │ │ │  corresponding function in the <a href="../../../lib/stdlib/doc/html/maps.html"><code class="inline">maps</code></a> module.</p><p>The gain in efficiency for the map syntax is more noticeable for the following
│ │ │ │ -operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="2926906626-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="2926906626-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="8055581606-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8055581606-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="8055581606-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="8055581606-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="8055581606-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="8055581606-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ │ -right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="2164808664-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="2164808664-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ │ -left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8628501743-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8628501743-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="8628501743-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8628501743-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="8628501743-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="8628501743-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │ │ +operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="4596084122-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="4596084122-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="0698040217-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="0698040217-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="0698040217-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="0698040217-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="0698040217-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="0698040217-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ │ +right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="9924006467-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="9924006467-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ │ +left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="6112848695-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6112848695-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="6112848695-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6112848695-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="6112848695-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="6112848695-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │ │  efficient than using the <code class="inline">=&gt;</code> operator for a small map.</p><h2 id="using-the-functions-in-the-maps-module" class="section-heading">
│ │ │ │    <a href="#using-the-functions-in-the-maps-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Using the Functions in the maps Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>Here follows some notes about most of the functions in the <code class="inline">maps</code> module. For
│ │ │ │ @@ -211,23 +211,23 @@
│ │ │ │    <a href="#maps-get-3" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">maps:get/3</span>
│ │ │ │  </h3>
│ │ │ │  <p>As an optimization, the compiler will rewrite a call to <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> to Erlang
│ │ │ │  code similar to the following:</p><pre><code class="makeup erlang" translate="no"><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">Map</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="5297072636-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="5297072636-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ │ -             </span><span class="p" data-group-id="5297072636-2">#{</span><span class="p" data-group-id="5297072636-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="1703843888-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1703843888-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ │ +             </span><span class="p" data-group-id="1703843888-2">#{</span><span class="p" data-group-id="1703843888-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │ │           </span><span class="k">end</span></code></pre><p>This is reasonably efficient, but if a small map is used as an alternative to
│ │ │ │  using a record it is often better not to rely on default values as it prevents
│ │ │ │  sharing of keys, which may in the end use more memory than what you save from
│ │ │ │  not storing default values in the map.</p><p>If default values are nevertheless required, instead of calling <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a>
│ │ │ │  multiple times, consider putting the default values in a map and merging that
│ │ │ │ -map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3253082640-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="3253082640-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="3253082640-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="3253082640-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │ │ +map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2057994738-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="2057994738-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="2057994738-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="2057994738-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │ │  to, as long as the default map contains <em>all</em> the keys that will ever be used
│ │ │ │  and not just the ones with default values. Whether this is faster than calling
│ │ │ │  <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> multiple times depends on the size of the map and the number of
│ │ │ │  default values.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before OTP 26.0 <a href="../../../lib/stdlib/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> was implemented by calling the function instead
│ │ │ │  of rewriting it as an Erlang expression. It is now slightly faster but can no
│ │ │ │  longer be traced.</p></section><h3 id="maps-intersect-2-maps-intersect_with-3" class="section-heading">
│ │ │ │    <a href="#maps-intersect-2-maps-intersect_with-3" class="hover-link">
│ │ │ ├── OEBPS/macros.xhtml
│ │ │ │ @@ -22,56 +22,56 @@
│ │ │ │      </h1>
│ │ │ │  <h2 id="file-inclusion" class="section-heading">
│ │ │ │    <a href="#file-inclusion" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">File Inclusion</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4245263917-1">(</span><span class="n">File</span><span class="p" data-group-id="4245263917-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="4245263917-2">(</span><span class="n">File</span><span class="p" data-group-id="4245263917-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │ │ +<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9218339691-1">(</span><span class="n">File</span><span class="p" data-group-id="9218339691-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="9218339691-2">(</span><span class="n">File</span><span class="p" data-group-id="9218339691-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │ │  as is, at the position of the directive.</p><p>Include files are typically used for record and macro definitions that are
│ │ │ │  shared by several modules. It is recommended to use the file name extension
│ │ │ │  <code class="inline">.hrl</code> for include files.</p><p><code class="inline">File</code> can start with a path component <code class="inline">$VAR</code>, for some string <code class="inline">VAR</code>. If that is
│ │ │ │  the case, the value of the environment variable <code class="inline">VAR</code> as returned by
│ │ │ │  <code class="inline">os:getenv(VAR)</code> is substituted for <code class="inline">$VAR</code>. If <code class="inline">os:getenv(VAR)</code> returns <code class="inline">false</code>,
│ │ │ │  <code class="inline">$VAR</code> is left as is.</p><p>If the filename <code class="inline">File</code> is absolute (possibly after variable substitution), the
│ │ │ │  include file with that name is included. Otherwise, the specified file is
│ │ │ │  searched for in the following directories, and in this order:</p><ol><li>The current working directory</li><li>The directory where the module is being compiled</li><li>The directories given by the <code class="inline">include</code> option</li></ol><p>For details, see <a href="../../../lib/../erts/doc/html/erlc_cmd.xhtml">erlc</a> in ERTS and
│ │ │ │ -<a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8244381869-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="8244381869-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8244381869-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="8244381869-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8244381869-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="8244381869-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8244381869-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="8244381869-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │ │ +<a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0412980206-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="0412980206-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0412980206-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="0412980206-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0412980206-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="0412980206-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0412980206-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="0412980206-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │ │  Instead, the first path component (possibly after variable substitution) is
│ │ │ │ -assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="9025159224-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="9025159224-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │ │ +assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="5476688488-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="5476688488-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │ │  (latest) version of Kernel, and then the subdirectory <code class="inline">include</code> is searched for
│ │ │ │  the file <code class="inline">file.hrl</code>.</p><h2 id="defining-and-using-macros" class="section-heading">
│ │ │ │    <a href="#defining-and-using-macros" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Defining and Using Macros</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0870681314-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="0870681314-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0870681314-2">(</span><span class="n">Func</span><span class="p" data-group-id="0870681314-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="0870681314-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="0870681314-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │ │ +<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0098514692-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="0098514692-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0098514692-2">(</span><span class="n">Func</span><span class="p" data-group-id="0098514692-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="0098514692-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="0098514692-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │ │  macro.</p><p>If a macro is used in several modules, it is recommended that the macro
│ │ │ │  definition is placed in an include file.</p><p>A macro is used as follows:</p><pre><code class="text">?Const
│ │ │ │  ?Func(Arg1,...,ArgN)</code></pre><p>Macros are expanded during compilation. A simple macro <code class="inline">?Const</code> is replaced with
│ │ │ │ -<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1315355261-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="1315355261-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1362012467-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="1362012467-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="1315355261-2">(</span><span class="n">Request</span><span class="p" data-group-id="1315355261-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1315355261-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="1315355261-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="0997870076-1">(</span><span class="n">Request</span><span class="p" data-group-id="0997870076-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="0997870076-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="0997870076-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="1362012467-2">(</span><span class="n">Request</span><span class="p" data-group-id="1362012467-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1362012467-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="1362012467-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="3315053869-1">(</span><span class="n">Request</span><span class="p" data-group-id="3315053869-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="3315053869-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="3315053869-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │ │  occurrences of a variable <code class="inline">Var</code> from the macro definition are replaced with the
│ │ │ │ -corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7016954214-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="7016954214-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7016954214-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7016954214-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7016954214-3">}</span><span class="p" data-group-id="7016954214-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7280392464-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="7280392464-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7280392464-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7280392464-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7280392464-3">}</span><span class="p" data-group-id="7280392464-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="7016954214-4">(</span><span class="n">X</span><span class="p" data-group-id="7016954214-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="7016954214-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="7016954214-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="7016954214-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="7016954214-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="1635094242-1">(</span><span class="n">X</span><span class="p" data-group-id="1635094242-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1635094242-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1635094242-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1635094242-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="1635094242-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="7280392464-4">(</span><span class="n">X</span><span class="p" data-group-id="7280392464-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="7280392464-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="7280392464-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="7280392464-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="7280392464-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="6241776415-1">(</span><span class="n">X</span><span class="p" data-group-id="6241776415-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6241776415-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6241776415-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6241776415-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="6241776415-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │ │  definition is a valid Erlang syntactic form.</p><p>To view the result of macro expansion, a module can be compiled with the <code class="inline">'P'</code>
│ │ │ │  option. <code class="inline">compile:file(File, ['P'])</code>. This produces a listing of the parsed code
│ │ │ │  after preprocessing and parse transforms, in the file <code class="inline">File.P</code>.</p><h2 id="predefined-macros" class="section-heading">
│ │ │ │    <a href="#predefined-macros" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Predefined Macros</span>
│ │ │ │ @@ -90,29 +90,29 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Macros Overloading</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is possible to overload macros, except for predefined macros. An overloaded
│ │ │ │  macro has more than one definition, each with a different number of arguments.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Support for overloading of macros was added in Erlang 5.7.5/OTP R13B04.</p></section><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> with a (possibly empty) list of arguments results
│ │ │ │  in an error message if there is at least one definition of <code class="inline">Func</code> with
│ │ │ │ -arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8221001720-1">(</span><span class="n">F0</span><span class="p" data-group-id="8221001720-2">(</span><span class="p" data-group-id="8221001720-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="8221001720-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8221001720-3">(</span><span class="n">F1</span><span class="p" data-group-id="8221001720-4">(</span><span class="n">A</span><span class="p" data-group-id="8221001720-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8221001720-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8221001720-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="8221001720-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="1076065606-1">(</span><span class="p" data-group-id="1076065606-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4953574109-1">(</span><span class="n">F0</span><span class="p" data-group-id="4953574109-2">(</span><span class="p" data-group-id="4953574109-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="4953574109-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4953574109-3">(</span><span class="n">F1</span><span class="p" data-group-id="4953574109-4">(</span><span class="n">A</span><span class="p" data-group-id="4953574109-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="4953574109-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4953574109-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="4953574109-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="2867137078-1">(</span><span class="p" data-group-id="2867137078-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="o">?</span><span class="n">F0</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, an empty list of arguments expected.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f1</span><span class="p" data-group-id="1076065606-2">(</span><span class="n">A</span><span class="p" data-group-id="1076065606-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="1076065606-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="1076065606-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ │ -    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="5687440198-1">(</span><span class="p" data-group-id="5687440198-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="5687440198-2">(</span><span class="p" data-group-id="5687440198-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │ │ +</span><span class="nf">f1</span><span class="p" data-group-id="2867137078-2">(</span><span class="n">A</span><span class="p" data-group-id="2867137078-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="2867137078-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="2867137078-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ │ +    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4438838792-1">(</span><span class="p" data-group-id="4438838792-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="4438838792-2">(</span><span class="p" data-group-id="4438838792-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │ │    <a href="#removing-a-macro-definition" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Removing a macro definition</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A definition of macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="2731954543-1">(</span><span class="n">Macro</span><span class="p" data-group-id="2731954543-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │ │ +<p>A definition of macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="6928712617-1">(</span><span class="n">Macro</span><span class="p" data-group-id="6928712617-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │ │    <a href="#conditional-compilation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Conditional Compilation</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following macro directives support conditional compilation:</p><ul><li><p><strong><code class="inline">-ifdef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is
│ │ │ │  defined.</p></li><li><p><strong><code class="inline">-ifndef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is not
│ │ │ │ @@ -124,43 +124,43 @@
│ │ │ │  true, and the <code class="inline">Condition</code> evaluates to true, the lines following the <code class="inline">elif</code>
│ │ │ │  are evaluated instead.</p></li><li><p><strong><code class="inline">-endif.</code></strong> - Specifies the end of a series of control flow directives.</p></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Macro directives cannot be used inside functions.</p></section><p>Syntactically, the <code class="inline">Condition</code> in <code class="inline">if</code> and <code class="inline">elif</code> must be a
│ │ │ │  <a href="expressions.xhtml#guard-expressions">guard expression</a>. Other constructs (such as
│ │ │ │  a <code class="inline">case</code> expression) result in a compilation error.</p><p>As opposed to the standard guard expressions, an expression in an <code class="inline">if</code> and
│ │ │ │  <code class="inline">elif</code> also supports calling the psuedo-function <code class="inline">defined(Name)</code>, which tests
│ │ │ │  whether the <code class="inline">Name</code> argument is the name of a previously defined macro.
│ │ │ │  <code class="inline">defined(Name)</code> evaluates to <code class="inline">true</code> if the macro is defined and <code class="inline">false</code>
│ │ │ │ -otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9435984925-1">(</span><span class="ss">m</span><span class="p" data-group-id="9435984925-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8586124856-1">(</span><span class="ss">m</span><span class="p" data-group-id="8586124856-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="9435984925-2">(</span><span class="ss">debug</span><span class="p" data-group-id="9435984925-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9435984925-3">(</span><span class="n">LOG</span><span class="p" data-group-id="9435984925-4">(</span><span class="n">X</span><span class="p" data-group-id="9435984925-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9435984925-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9435984925-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="9435984925-6">]</span><span class="p" data-group-id="9435984925-5">)</span><span class="p" data-group-id="9435984925-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="8586124856-2">(</span><span class="ss">debug</span><span class="p" data-group-id="8586124856-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8586124856-3">(</span><span class="n">LOG</span><span class="p" data-group-id="8586124856-4">(</span><span class="n">X</span><span class="p" data-group-id="8586124856-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8586124856-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8586124856-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="8586124856-6">]</span><span class="p" data-group-id="8586124856-5">)</span><span class="p" data-group-id="8586124856-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9435984925-7">(</span><span class="n">LOG</span><span class="p" data-group-id="9435984925-8">(</span><span class="n">X</span><span class="p" data-group-id="9435984925-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9435984925-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8586124856-7">(</span><span class="n">LOG</span><span class="p" data-group-id="8586124856-8">(</span><span class="n">X</span><span class="p" data-group-id="8586124856-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8586124856-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When trace output is desired, <code class="inline">debug</code> is to be defined when the module <code class="inline">m</code> is
│ │ │ │  compiled:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlc -Ddebug m.erl</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="ow">or</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="2082810084-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2082810084-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="2082810084-2">}</span><span class="p" data-group-id="2082810084-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2082810084-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="2082810084-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provide the user
│ │ │ │ -with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9092583370-1">(</span><span class="ss">m</span><span class="p" data-group-id="9092583370-1">)</span><span class="w">
│ │ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="9044779176-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9044779176-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="9044779176-2">}</span><span class="p" data-group-id="9044779176-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9044779176-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="9044779176-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provide the user
│ │ │ │ +with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7613773895-1">(</span><span class="ss">m</span><span class="p" data-group-id="7613773895-1">)</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="9092583370-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="9092583370-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="7613773895-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="7613773895-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Code that will work in OTP 25 or higher</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="9092583370-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="9092583370-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="7613773895-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="7613773895-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Code that will work in OTP 26 or higher</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Code that will work in OTP 24 or lower.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro to conditionally select code depending on
│ │ │ │ -release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3327664726-1">(</span><span class="ss">m</span><span class="p" data-group-id="3327664726-1">)</span><span class="w">
│ │ │ │ +release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5301422172-1">(</span><span class="ss">m</span><span class="p" data-group-id="5301422172-1">)</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="3327664726-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="3327664726-3">(</span><span class="ss">debug</span><span class="p" data-group-id="3327664726-3">)</span><span class="p" data-group-id="3327664726-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="5301422172-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="5301422172-3">(</span><span class="ss">debug</span><span class="p" data-group-id="5301422172-3">)</span><span class="p" data-group-id="5301422172-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Debugging code that requires OTP 26 or later.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% Non-debug code that works in any release.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro and <code class="inline">defined(debug)</code> to compile debug
│ │ │ │  code only for OTP 26 or later.</p><h2 id="the-feature-directive" class="section-heading">
│ │ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │ │ @@ -175,40 +175,40 @@
│ │ │ │  used. In practice this means it should appear before any <code class="inline">-export(..)</code> or record
│ │ │ │  definitions.</p><h2 id="error-and-warning-directives" class="section-heading">
│ │ │ │    <a href="#error-and-warning-directives" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">-error() and -warning() directives</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5016872633-1">(</span><span class="ss">t</span><span class="p" data-group-id="5016872633-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5016872633-2">(</span><span class="p" data-group-id="5016872633-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5016872633-3">]</span><span class="p" data-group-id="5016872633-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6024824050-1">(</span><span class="ss">t</span><span class="p" data-group-id="6024824050-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6024824050-2">(</span><span class="p" data-group-id="6024824050-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6024824050-3">]</span><span class="p" data-group-id="6024824050-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="5016872633-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="5016872633-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="5016872633-5">(</span><span class="p" data-group-id="5016872633-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="6024824050-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="6024824050-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="6024824050-5">(</span><span class="p" data-group-id="6024824050-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="5016872633-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="5016872633-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="5016872633-7">(</span><span class="p" data-group-id="5016872633-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="6024824050-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="6024824050-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="6024824050-7">(</span><span class="p" data-group-id="6024824050-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span></code></pre><p>The error message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ │ -t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3739937682-1">(</span><span class="ss">t</span><span class="p" data-group-id="3739937682-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3739937682-2">(</span><span class="p" data-group-id="3739937682-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3739937682-3">]</span><span class="p" data-group-id="3739937682-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7820486219-1">(</span><span class="ss">t</span><span class="p" data-group-id="7820486219-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7820486219-2">(</span><span class="p" data-group-id="7820486219-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7820486219-3">]</span><span class="p" data-group-id="7820486219-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="3739937682-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="3739937682-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="3739937682-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="3739937682-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3739937682-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="3739937682-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="7820486219-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="7820486219-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="7820486219-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="7820486219-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7820486219-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="7820486219-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="3739937682-7">(</span><span class="p" data-group-id="3739937682-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="7820486219-7">(</span><span class="p" data-group-id="7820486219-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ │  t.erl:5: Warning: -warning(&quot;Macro VERSION not defined -- using default version.&quot;).</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The <code class="inline">-error()</code> and <code class="inline">-warning()</code> directives were added in Erlang/OTP 19.</p></section><h2 id="stringifying-macro-arguments" class="section-heading">
│ │ │ │    <a href="#stringifying-macro-arguments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stringifying Macro Arguments</span>
│ │ │ │  </h2>
│ │ │ │  <p>The construction <code class="inline">??Arg</code>, where <code class="inline">Arg</code> is a macro argument, is expanded to a
│ │ │ │  string containing the tokens of the argument. This is similar to the <code class="inline">#arg</code>
│ │ │ │ -stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4371570850-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="4371570850-2">(</span><span class="n">Call</span><span class="p" data-group-id="4371570850-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4371570850-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4371570850-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="4371570850-4">]</span><span class="p" data-group-id="4371570850-3">)</span><span class="p" data-group-id="4371570850-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1409100463-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="1409100463-2">(</span><span class="n">Call</span><span class="p" data-group-id="1409100463-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1409100463-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1409100463-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="1409100463-4">]</span><span class="p" data-group-id="1409100463-3">)</span><span class="p" data-group-id="1409100463-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="4371570850-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="4371570850-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4371570850-6">)</span><span class="p" data-group-id="4371570850-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="4371570850-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="4371570850-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4371570850-8">)</span><span class="p" data-group-id="4371570850-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7045475181-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7045475181-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="7045475181-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7045475181-3">)</span><span class="p" data-group-id="7045475181-2">]</span><span class="p" data-group-id="7045475181-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7045475181-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7045475181-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="7045475181-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7045475181-6">)</span><span class="p" data-group-id="7045475181-5">]</span><span class="p" data-group-id="7045475181-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="1409100463-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="1409100463-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1409100463-6">)</span><span class="p" data-group-id="1409100463-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="1409100463-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="1409100463-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1409100463-8">)</span><span class="p" data-group-id="1409100463-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7915961985-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7915961985-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="7915961985-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7915961985-3">)</span><span class="p" data-group-id="7915961985-2">]</span><span class="p" data-group-id="7915961985-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7915961985-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7915961985-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="7915961985-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7915961985-6">)</span><span class="p" data-group-id="7915961985-5">]</span><span class="p" data-group-id="7915961985-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/listhandling.xhtml
│ │ │ │ @@ -25,101 +25,101 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating a List</span>
│ │ │ │  </h2>
│ │ │ │  <p>Lists can only be built starting from the end and attaching list elements at the
│ │ │ │  beginning. If you use the <code class="inline">++</code> operator as follows, a new list is created that
│ │ │ │  is a copy of the elements in <code class="inline">List1</code>, followed by <code class="inline">List2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">List1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">List2</span></code></pre><p>Looking at how <a href="../../../lib/stdlib/doc/html/lists.html#append/2"><code class="inline">lists:append/2</code></a> or <code class="inline">++</code> would be implemented in plain Erlang,
│ │ │ │ -clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="9275296400-1">(</span><span class="p" data-group-id="9275296400-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9275296400-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9275296400-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9275296400-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="9275296400-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9275296400-4">)</span><span class="p" data-group-id="9275296400-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">append</span><span class="p" data-group-id="9275296400-5">(</span><span class="p" data-group-id="9275296400-6">[</span><span class="p" data-group-id="9275296400-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9275296400-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="0709612109-1">(</span><span class="p" data-group-id="0709612109-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0709612109-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="0709612109-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0709612109-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="0709612109-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="0709612109-4">)</span><span class="p" data-group-id="0709612109-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">append</span><span class="p" data-group-id="0709612109-5">(</span><span class="p" data-group-id="0709612109-6">[</span><span class="p" data-group-id="0709612109-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="0709612109-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>When recursing and building a list, it is important to ensure that you attach
│ │ │ │  the new elements to the beginning of the list. In this way, you will build <em>one</em>
│ │ │ │ -list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="8845429597-1">(</span><span class="n">N</span><span class="p" data-group-id="8845429597-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="8845429597-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8845429597-3">[</span><span class="p" data-group-id="8845429597-3">]</span><span class="p" data-group-id="8845429597-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="9028442152-1">(</span><span class="n">N</span><span class="p" data-group-id="9028442152-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="9028442152-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9028442152-3">[</span><span class="p" data-group-id="9028442152-3">]</span><span class="p" data-group-id="9028442152-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="8845429597-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="8845429597-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="9028442152-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="9028442152-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Fibs</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="8845429597-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="8845429597-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="8845429597-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8845429597-7">[</span><span class="n">Current</span><span class="p" data-group-id="8845429597-7">]</span><span class="p" data-group-id="8845429597-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="9028442152-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="9028442152-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="9028442152-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9028442152-7">[</span><span class="n">Current</span><span class="p" data-group-id="9028442152-7">]</span><span class="p" data-group-id="9028442152-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │ │  that is one element longer than the new previous list.</p><p>To avoid copying the result in each iteration, build the list in reverse order
│ │ │ │ -and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5646976481-1">(</span><span class="n">N</span><span class="p" data-group-id="5646976481-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5646976481-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5646976481-3">[</span><span class="p" data-group-id="5646976481-3">]</span><span class="p" data-group-id="5646976481-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="2493466676-1">(</span><span class="n">N</span><span class="p" data-group-id="2493466676-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="2493466676-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2493466676-3">[</span><span class="p" data-group-id="2493466676-3">]</span><span class="p" data-group-id="2493466676-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5646976481-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="5646976481-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5646976481-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="5646976481-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5646976481-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="5646976481-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5646976481-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5646976481-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="5646976481-8">]</span><span class="p" data-group-id="5646976481-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="2493466676-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="2493466676-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2493466676-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="2493466676-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="2493466676-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="2493466676-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="2493466676-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2493466676-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="2493466676-8">]</span><span class="p" data-group-id="2493466676-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │ │    <a href="#list-comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">List Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │ -<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3169550403-1">[</span><span class="n">Expr</span><span class="p" data-group-id="3169550403-2">(</span><span class="n">E</span><span class="p" data-group-id="3169550403-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3169550403-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5976451863-1">(</span><span class="p" data-group-id="5976451863-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="5976451863-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="5976451863-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5976451863-3">[</span><span class="n">Expr</span><span class="p" data-group-id="5976451863-4">(</span><span class="n">E</span><span class="p" data-group-id="5976451863-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5976451863-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="5976451863-5">)</span><span class="p" data-group-id="5976451863-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5976451863-6">(</span><span class="p" data-group-id="5976451863-7">[</span><span class="p" data-group-id="5976451863-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="5976451863-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5976451863-8">[</span><span class="p" data-group-id="5976451863-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ │ -will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3320226744-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="3320226744-2">(</span><span class="n">E</span><span class="p" data-group-id="3320226744-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3320226744-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6482367751-1">[</span><span class="n">Expr</span><span class="p" data-group-id="6482367751-2">(</span><span class="n">E</span><span class="p" data-group-id="6482367751-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6482367751-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="9857872562-1">(</span><span class="p" data-group-id="9857872562-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="9857872562-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="9857872562-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9857872562-3">[</span><span class="n">Expr</span><span class="p" data-group-id="9857872562-4">(</span><span class="n">E</span><span class="p" data-group-id="9857872562-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="9857872562-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="9857872562-5">)</span><span class="p" data-group-id="9857872562-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="9857872562-6">(</span><span class="p" data-group-id="9857872562-7">[</span><span class="p" data-group-id="9857872562-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="9857872562-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9857872562-8">[</span><span class="p" data-group-id="9857872562-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ │ +will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6081973156-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="6081973156-2">(</span><span class="n">E</span><span class="p" data-group-id="6081973156-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6081973156-1">]</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>or in this code:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Var</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1430676960-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="1430676960-2">(</span><span class="n">E</span><span class="p" data-group-id="1430676960-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1430676960-1">]</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="3225991783-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="3225991783-2">(</span><span class="n">E</span><span class="p" data-group-id="3225991783-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3225991783-1">]</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="1430676960-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1430676960-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="3225991783-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3225991783-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │ │  returned. This means that there is no need to construct a list and the compiler
│ │ │ │ -will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="3722596728-1">(</span><span class="p" data-group-id="3722596728-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="3722596728-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="3722596728-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Expr</span><span class="p" data-group-id="3722596728-3">(</span><span class="n">E</span><span class="p" data-group-id="3722596728-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="3722596728-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="3722596728-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="3722596728-5">(</span><span class="p" data-group-id="3722596728-6">[</span><span class="p" data-group-id="3722596728-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="3722596728-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3722596728-7">[</span><span class="p" data-group-id="3722596728-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ │ -not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5655169323-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="5655169323-2">(</span><span class="n">E</span><span class="p" data-group-id="5655169323-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5655169323-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0226325159-1">(</span><span class="p" data-group-id="0226325159-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0226325159-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0226325159-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Expr</span><span class="p" data-group-id="0226325159-3">(</span><span class="n">E</span><span class="p" data-group-id="0226325159-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0226325159-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0226325159-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0226325159-5">(</span><span class="p" data-group-id="0226325159-6">[</span><span class="p" data-group-id="0226325159-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="0226325159-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0226325159-7">[</span><span class="p" data-group-id="0226325159-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ │ +not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5673202373-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="5673202373-2">(</span><span class="n">E</span><span class="p" data-group-id="5673202373-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5673202373-1">]</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="deep-and-flat-lists" class="section-heading">
│ │ │ │    <a href="#deep-and-flat-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deep and Flat Lists</span>
│ │ │ │  </h2>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a> builds an entirely new list. It is therefore expensive, and
│ │ │ │  even <em>more</em> expensive than the <code class="inline">++</code> operator (which copies its left argument,
│ │ │ │  but not its right argument).</p><p>In the following situations it is unnecessary to call <a href="../../../lib/stdlib/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a>:</p><ul><li>When sending data to a port. Ports understand deep lists so there is no reason
│ │ │ │  to flatten the list before sending it to the port.</li><li>When calling BIFs that accept deep lists, such as
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a> or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#iolist_to_binary/1"><code class="inline">iolist_to_binary/1</code></a>.</li><li>When you know that your list is only one level deep. Use <a href="../../../lib/stdlib/doc/html/lists.html#append/1"><code class="inline">lists:append/1</code></a>
│ │ │ │ -instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="3537646297-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="3537646297-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="5820542658-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="5820542658-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="5820542658-2">)</span><span class="p" data-group-id="5820542658-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8864844500-1">[</span><span class="mi">0</span><span class="p" data-group-id="8864844500-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="8864844500-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="8864844500-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2588473701-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2588473701-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="2588473701-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="2588473701-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="7154538877-1">(</span><span class="p" data-group-id="7154538877-2">[</span><span class="p" data-group-id="7154538877-3">[</span><span class="mi">1</span><span class="p" data-group-id="7154538877-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7154538877-4">[</span><span class="mi">2</span><span class="p" data-group-id="7154538877-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7154538877-5">[</span><span class="mi">3</span><span class="p" data-group-id="7154538877-5">]</span><span class="p" data-group-id="7154538877-2">]</span><span class="p" data-group-id="7154538877-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7154538877-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7154538877-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="1528843794-1">(</span><span class="p" data-group-id="1528843794-2">[</span><span class="p" data-group-id="1528843794-3">[</span><span class="mi">1</span><span class="p" data-group-id="1528843794-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1528843794-4">[</span><span class="mi">2</span><span class="p" data-group-id="1528843794-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1528843794-5">[</span><span class="mi">3</span><span class="p" data-group-id="1528843794-5">]</span><span class="p" data-group-id="1528843794-2">]</span><span class="p" data-group-id="1528843794-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1528843794-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1528843794-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │ │ +instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="3804329211-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="3804329211-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="4224483751-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="4224483751-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="4224483751-2">)</span><span class="p" data-group-id="4224483751-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3850693371-1">[</span><span class="mi">0</span><span class="p" data-group-id="3850693371-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="3850693371-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="3850693371-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5458257141-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5458257141-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="5458257141-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="5458257141-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="8572988634-1">(</span><span class="p" data-group-id="8572988634-2">[</span><span class="p" data-group-id="8572988634-3">[</span><span class="mi">1</span><span class="p" data-group-id="8572988634-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8572988634-4">[</span><span class="mi">2</span><span class="p" data-group-id="8572988634-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8572988634-5">[</span><span class="mi">3</span><span class="p" data-group-id="8572988634-5">]</span><span class="p" data-group-id="8572988634-2">]</span><span class="p" data-group-id="8572988634-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8572988634-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8572988634-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="9812355607-1">(</span><span class="p" data-group-id="9812355607-2">[</span><span class="p" data-group-id="9812355607-3">[</span><span class="mi">1</span><span class="p" data-group-id="9812355607-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9812355607-4">[</span><span class="mi">2</span><span class="p" data-group-id="9812355607-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9812355607-5">[</span><span class="mi">3</span><span class="p" data-group-id="9812355607-5">]</span><span class="p" data-group-id="9812355607-2">]</span><span class="p" data-group-id="9812355607-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9812355607-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9812355607-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │ │    <a href="#recursive-list-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Recursive List Functions</span>
│ │ │ │  </h2>
│ │ │ │  <p>There are two basic ways to write a function that traverses a list and
│ │ │ │  produces a new list.</p><p>The first way is writing a <em>body-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="5301837770-1">(</span><span class="p" data-group-id="5301837770-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5301837770-2">]</span><span class="p" data-group-id="5301837770-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5301837770-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="5301837770-4">(</span><span class="n">T</span><span class="p" data-group-id="5301837770-4">)</span><span class="p" data-group-id="5301837770-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="5301837770-5">(</span><span class="p" data-group-id="5301837770-6">[</span><span class="p" data-group-id="5301837770-6">]</span><span class="p" data-group-id="5301837770-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5301837770-7">[</span><span class="p" data-group-id="5301837770-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="5556838549-1">(</span><span class="n">List</span><span class="p" data-group-id="5556838549-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="5556838549-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5556838549-3">[</span><span class="p" data-group-id="5556838549-3">]</span><span class="p" data-group-id="5556838549-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="4040736552-1">(</span><span class="p" data-group-id="4040736552-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4040736552-2">]</span><span class="p" data-group-id="4040736552-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4040736552-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="4040736552-4">(</span><span class="n">T</span><span class="p" data-group-id="4040736552-4">)</span><span class="p" data-group-id="4040736552-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="4040736552-5">(</span><span class="p" data-group-id="4040736552-6">[</span><span class="p" data-group-id="4040736552-6">]</span><span class="p" data-group-id="4040736552-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4040736552-7">[</span><span class="p" data-group-id="4040736552-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="0411346681-1">(</span><span class="n">List</span><span class="p" data-group-id="0411346681-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="0411346681-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0411346681-3">[</span><span class="p" data-group-id="0411346681-3">]</span><span class="p" data-group-id="0411346681-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="5556838549-4">(</span><span class="p" data-group-id="5556838549-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5556838549-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5556838549-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="5556838549-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5556838549-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5556838549-7">]</span><span class="p" data-group-id="5556838549-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="5556838549-8">(</span><span class="p" data-group-id="5556838549-9">[</span><span class="p" data-group-id="5556838549-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5556838549-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5556838549-10">(</span><span class="n">Acc</span><span class="p" data-group-id="5556838549-10">)</span><span class="p">.</span></code></pre><p>In early version of Erlang the tail-recursive function would typically
│ │ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="0411346681-4">(</span><span class="p" data-group-id="0411346681-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0411346681-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0411346681-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="0411346681-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0411346681-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0411346681-7">]</span><span class="p" data-group-id="0411346681-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="0411346681-8">(</span><span class="p" data-group-id="0411346681-9">[</span><span class="p" data-group-id="0411346681-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0411346681-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="0411346681-10">(</span><span class="n">Acc</span><span class="p" data-group-id="0411346681-10">)</span><span class="p">.</span></code></pre><p>In early version of Erlang the tail-recursive function would typically
│ │ │ │  be more efficient. In modern versions of Erlang, there is usually not
│ │ │ │  much difference in performance between a body-recursive list function and
│ │ │ │  tail-recursive function that reverses the list at the end. Therefore,
│ │ │ │  concentrate on writing beautiful code and forget about the performance
│ │ │ │  of your list functions. In the time-critical parts of your code,
│ │ │ │  <em>measure</em> before rewriting your code.</p><p>For a thorough discussion about tail and body recursion, see
│ │ │ │  <a href="http://ferd.ca/erlang-s-tail-recursion-is-not-a-silver-bullet.html">Erlang's Tail Recursion is Not a Silver Bullet</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>This section is about list functions that <em>construct</em> lists. A tail-recursive
│ │ │ │  function that does not construct a list runs in constant space, while the
│ │ │ │  corresponding body-recursive function uses stack space proportional to the
│ │ │ │  length of the list.</p></section><p>For example, a function that sums a list of integers, is <em>not</em> to be written as
│ │ │ │ -follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="5185626916-1">(</span><span class="p" data-group-id="5185626916-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5185626916-2">]</span><span class="p" data-group-id="5185626916-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="5185626916-3">(</span><span class="n">T</span><span class="p" data-group-id="5185626916-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">recursive_sum</span><span class="p" data-group-id="5185626916-4">(</span><span class="p" data-group-id="5185626916-5">[</span><span class="p" data-group-id="5185626916-5">]</span><span class="p" data-group-id="5185626916-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="7208582161-1">(</span><span class="n">L</span><span class="p" data-group-id="7208582161-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="7208582161-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7208582161-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="2302004296-1">(</span><span class="p" data-group-id="2302004296-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2302004296-2">]</span><span class="p" data-group-id="2302004296-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="2302004296-3">(</span><span class="n">T</span><span class="p" data-group-id="2302004296-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">recursive_sum</span><span class="p" data-group-id="2302004296-4">(</span><span class="p" data-group-id="2302004296-5">[</span><span class="p" data-group-id="2302004296-5">]</span><span class="p" data-group-id="2302004296-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="7025214686-1">(</span><span class="n">L</span><span class="p" data-group-id="7025214686-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="7025214686-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7025214686-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="7208582161-3">(</span><span class="p" data-group-id="7208582161-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7208582161-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="7208582161-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="7208582161-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="7208582161-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="7208582161-6">(</span><span class="p" data-group-id="7208582161-7">[</span><span class="p" data-group-id="7208582161-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="7208582161-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="7025214686-3">(</span><span class="p" data-group-id="7025214686-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7025214686-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="7025214686-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="7025214686-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="7025214686-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="7025214686-6">(</span><span class="p" data-group-id="7025214686-7">[</span><span class="p" data-group-id="7025214686-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="7025214686-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/list_comprehensions.xhtml
│ │ │ │ @@ -22,33 +22,33 @@
│ │ │ │      </h1>
│ │ │ │  <h2 id="simple-examples" class="section-heading">
│ │ │ │    <a href="#simple-examples" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simple Examples</span>
│ │ │ │  </h2>
│ │ │ │ -<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="4159651259-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="4159651259-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4159651259-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4159651259-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4159651259-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4159651259-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │ │ +<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="6482456613-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="6482456613-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6482456613-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6482456613-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6482456613-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6482456613-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │ │  <code class="inline">[1,2,a,...]</code> and X is greater than 3.</p><p>The notation <code class="inline">X &lt;- [1,2,a,...]</code> is a generator and the expression <code class="inline">X &gt; 3</code> is a
│ │ │ │  filter.</p><p>An additional filter, <a href="../../../lib/../erts/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(X)</code></a>, can be added to
│ │ │ │ -restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7550308946-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7550308946-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7550308946-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7550308946-3">(</span><span class="n">X</span><span class="p" data-group-id="7550308946-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7550308946-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7550308946-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7550308946-4">]</span></code></pre><p>Generators can be combined. For example, the Cartesian product of two lists can
│ │ │ │ -be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7626954952-1">[</span><span class="p" data-group-id="7626954952-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7626954952-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7626954952-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7626954952-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7626954952-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7626954952-4">]</span><span class="p" data-group-id="7626954952-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7626954952-5">[</span><span class="p" data-group-id="7626954952-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7626954952-6">}</span><span class="p">,</span><span class="p" data-group-id="7626954952-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7626954952-7">}</span><span class="p">,</span><span class="p" data-group-id="7626954952-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7626954952-8">}</span><span class="p">,</span><span class="p" data-group-id="7626954952-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7626954952-9">}</span><span class="p">,</span><span class="p" data-group-id="7626954952-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7626954952-10">}</span><span class="p">,</span><span class="p" data-group-id="7626954952-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7626954952-11">}</span><span class="p" data-group-id="7626954952-5">]</span></code></pre><h2 id="quick-sort" class="section-heading">
│ │ │ │ +restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="2187448955-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="2187448955-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2187448955-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="2187448955-3">(</span><span class="n">X</span><span class="p" data-group-id="2187448955-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2187448955-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2187448955-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2187448955-4">]</span></code></pre><p>Generators can be combined. For example, the Cartesian product of two lists can
│ │ │ │ +be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1137919537-1">[</span><span class="p" data-group-id="1137919537-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1137919537-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1137919537-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1137919537-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1137919537-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1137919537-4">]</span><span class="p" data-group-id="1137919537-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1137919537-5">[</span><span class="p" data-group-id="1137919537-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1137919537-6">}</span><span class="p">,</span><span class="p" data-group-id="1137919537-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1137919537-7">}</span><span class="p">,</span><span class="p" data-group-id="1137919537-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1137919537-8">}</span><span class="p">,</span><span class="p" data-group-id="1137919537-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1137919537-9">}</span><span class="p">,</span><span class="p" data-group-id="1137919537-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1137919537-10">}</span><span class="p">,</span><span class="p" data-group-id="1137919537-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1137919537-11">}</span><span class="p" data-group-id="1137919537-5">]</span></code></pre><h2 id="quick-sort" class="section-heading">
│ │ │ │    <a href="#quick-sort" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Quick Sort</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="2771535554-1">(</span><span class="p" data-group-id="2771535554-2">[</span><span class="p" data-group-id="2771535554-2">]</span><span class="p" data-group-id="2771535554-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2771535554-3">[</span><span class="p" data-group-id="2771535554-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="2771535554-4">(</span><span class="p" data-group-id="2771535554-5">[</span><span class="p">_</span><span class="p" data-group-id="2771535554-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2771535554-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="2771535554-6">(</span><span class="p" data-group-id="2771535554-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2771535554-7">]</span><span class="p" data-group-id="2771535554-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="2771535554-8">(</span><span class="p" data-group-id="2771535554-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="2771535554-9">]</span><span class="p" data-group-id="2771535554-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2771535554-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="2771535554-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="2771535554-11">(</span><span class="p" data-group-id="2771535554-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="2771535554-12">]</span><span class="p" data-group-id="2771535554-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │ │ +<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="9744628191-1">(</span><span class="p" data-group-id="9744628191-2">[</span><span class="p" data-group-id="9744628191-2">]</span><span class="p" data-group-id="9744628191-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9744628191-3">[</span><span class="p" data-group-id="9744628191-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="9744628191-4">(</span><span class="p" data-group-id="9744628191-5">[</span><span class="p">_</span><span class="p" data-group-id="9744628191-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="9744628191-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="9744628191-6">(</span><span class="p" data-group-id="9744628191-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9744628191-7">]</span><span class="p" data-group-id="9744628191-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="9744628191-8">(</span><span class="p" data-group-id="9744628191-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="9744628191-9">]</span><span class="p" data-group-id="9744628191-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9744628191-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="9744628191-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="9744628191-11">(</span><span class="p" data-group-id="9744628191-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="9744628191-12">]</span><span class="p" data-group-id="9744628191-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │ │  that are less than <code class="inline">Pivot</code>.</p><p><code class="inline">[X || X &lt;- T, X &gt;= Pivot]</code> is the list of all elements in <code class="inline">T</code> that are greater
│ │ │ │  than or equal to <code class="inline">Pivot</code>.</p><p>With the algorithm above, a list is sorted as follows:</p><ul><li>A list with zero or one element is trivially sorted.</li><li>For lists with more than one element:<ol><li>The first element in the list is isolated as the pivot element.</li><li>The remaining list is partitioned into two sublists, such that:</li></ol><ul><li>The first sublist contains all elements that are smaller than the pivot
│ │ │ │  element.</li><li>The second sublist contains all elements that are greater than or equal to
│ │ │ │  the pivot element.</li></ul><ol><li>The sublists are recursively sorted by the same algorithm and the results
│ │ │ │  are combined, resulting in a list consisting of:</li></ol><ul><li>All elements from the first sublist, that is all elements smaller than the
│ │ │ │  pivot element, in sorted order.</li><li>The pivot element.</li><li>All elements from the second sublist, that is all elements greater than or
│ │ │ │  equal to the pivot element, in sorted order.</li></ul></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>While the sorting algorithm as shown above serves as a nice example to
│ │ │ │ @@ -56,90 +56,90 @@
│ │ │ │  <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a> module contains sorting functions that are implemented in a more
│ │ │ │  efficient way.</p></section><h2 id="permutations" class="section-heading">
│ │ │ │    <a href="#permutations" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Permutations</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="5081582696-1">(</span><span class="p" data-group-id="5081582696-2">[</span><span class="p" data-group-id="5081582696-2">]</span><span class="p" data-group-id="5081582696-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5081582696-3">[</span><span class="p" data-group-id="5081582696-4">[</span><span class="p" data-group-id="5081582696-4">]</span><span class="p" data-group-id="5081582696-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">perms</span><span class="p" data-group-id="5081582696-5">(</span><span class="n">L</span><span class="p" data-group-id="5081582696-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5081582696-6">[</span><span class="p" data-group-id="5081582696-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5081582696-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="5081582696-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="5081582696-9">[</span><span class="n">H</span><span class="p" data-group-id="5081582696-9">]</span><span class="p" data-group-id="5081582696-8">)</span><span class="p" data-group-id="5081582696-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │ │ +<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="9168152761-1">(</span><span class="p" data-group-id="9168152761-2">[</span><span class="p" data-group-id="9168152761-2">]</span><span class="p" data-group-id="9168152761-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9168152761-3">[</span><span class="p" data-group-id="9168152761-4">[</span><span class="p" data-group-id="9168152761-4">]</span><span class="p" data-group-id="9168152761-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">perms</span><span class="p" data-group-id="9168152761-5">(</span><span class="n">L</span><span class="p" data-group-id="9168152761-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9168152761-6">[</span><span class="p" data-group-id="9168152761-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9168152761-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="9168152761-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="9168152761-9">[</span><span class="n">H</span><span class="p" data-group-id="9168152761-9">]</span><span class="p" data-group-id="9168152761-8">)</span><span class="p" data-group-id="9168152761-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │ │  <code class="inline">[H|T]</code>, where <code class="inline">T</code> is the set of all possible permutations of <code class="inline">L</code>, with <code class="inline">H</code>
│ │ │ │ -removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="4765126049-1">(</span><span class="p" data-group-id="4765126049-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="4765126049-2">]</span><span class="p" data-group-id="4765126049-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4765126049-3">[</span><span class="p" data-group-id="4765126049-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="4765126049-4">]</span><span class="p">,</span><span class="p" data-group-id="4765126049-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="4765126049-5">]</span><span class="p">,</span><span class="p" data-group-id="4765126049-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="4765126049-6">]</span><span class="p">,</span><span class="p" data-group-id="4765126049-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4765126049-7">]</span><span class="p">,</span><span class="p" data-group-id="4765126049-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="4765126049-8">]</span><span class="p">,</span><span class="p" data-group-id="4765126049-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4765126049-9">]</span><span class="p" data-group-id="4765126049-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │ │ +removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="5237681288-1">(</span><span class="p" data-group-id="5237681288-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="5237681288-2">]</span><span class="p" data-group-id="5237681288-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5237681288-3">[</span><span class="p" data-group-id="5237681288-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="5237681288-4">]</span><span class="p">,</span><span class="p" data-group-id="5237681288-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="5237681288-5">]</span><span class="p">,</span><span class="p" data-group-id="5237681288-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="5237681288-6">]</span><span class="p">,</span><span class="p" data-group-id="5237681288-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5237681288-7">]</span><span class="p">,</span><span class="p" data-group-id="5237681288-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="5237681288-8">]</span><span class="p">,</span><span class="p" data-group-id="5237681288-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5237681288-9">]</span><span class="p" data-group-id="5237681288-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │ │    <a href="#pythagorean-triplets" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Pythagorean Triplets</span>
│ │ │ │  </h2>
│ │ │ │  <p>Pythagorean triplets are sets of integers <code class="inline">{A,B,C}</code> such that
│ │ │ │  <code class="inline">A**2 + B**2 = C**2</code>.</p><p>The function <code class="inline">pyth(N)</code> generates a list of all integers <code class="inline">{A,B,C}</code> such that
│ │ │ │  <code class="inline">A**2 + B**2 = C**2</code> and where the sum of the sides is equal to, or less than,
│ │ │ │ -<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="7757806891-1">(</span><span class="n">N</span><span class="p" data-group-id="7757806891-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7757806891-2">[</span><span class="w"> </span><span class="p" data-group-id="7757806891-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="7757806891-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ -        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7757806891-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="7757806891-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7757806891-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="7757806891-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7757806891-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="7757806891-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="9110815258-1">(</span><span class="n">N</span><span class="p" data-group-id="9110815258-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9110815258-2">[</span><span class="w"> </span><span class="p" data-group-id="9110815258-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="9110815258-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ +        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9110815258-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="9110815258-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9110815258-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="9110815258-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="9110815258-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="9110815258-6">)</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7757806891-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="1430880011-1">(</span><span class="mi">3</span><span class="p" data-group-id="1430880011-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1430880011-2">[</span><span class="p" data-group-id="1430880011-2">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="1430880011-3">(</span><span class="mi">11</span><span class="p" data-group-id="1430880011-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1430880011-4">[</span><span class="p" data-group-id="1430880011-4">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="1430880011-5">(</span><span class="mi">12</span><span class="p" data-group-id="1430880011-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1430880011-6">[</span><span class="p" data-group-id="1430880011-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1430880011-7">}</span><span class="p">,</span><span class="p" data-group-id="1430880011-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1430880011-8">}</span><span class="p" data-group-id="1430880011-6">]</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="1430880011-9">(</span><span class="mi">50</span><span class="p" data-group-id="1430880011-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1430880011-10">[</span><span class="p" data-group-id="1430880011-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1430880011-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1430880011-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="1430880011-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="1430880011-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="1430880011-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="1430880011-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="1430880011-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="1430880011-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="1430880011-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="1430880011-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="1430880011-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1430880011-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="1430880011-22">}</span><span class="p" data-group-id="1430880011-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="1699702361-1">(</span><span class="n">N</span><span class="p" data-group-id="1699702361-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1699702361-2">[</span><span class="p" data-group-id="1699702361-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="1699702361-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ -       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1699702361-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="1699702361-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1699702361-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="1699702361-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1699702361-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="1699702361-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9110815258-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5262060639-1">(</span><span class="mi">3</span><span class="p" data-group-id="5262060639-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5262060639-2">[</span><span class="p" data-group-id="5262060639-2">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5262060639-3">(</span><span class="mi">11</span><span class="p" data-group-id="5262060639-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5262060639-4">[</span><span class="p" data-group-id="5262060639-4">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5262060639-5">(</span><span class="mi">12</span><span class="p" data-group-id="5262060639-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5262060639-6">[</span><span class="p" data-group-id="5262060639-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5262060639-7">}</span><span class="p">,</span><span class="p" data-group-id="5262060639-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5262060639-8">}</span><span class="p" data-group-id="5262060639-6">]</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="5262060639-9">(</span><span class="mi">50</span><span class="p" data-group-id="5262060639-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5262060639-10">[</span><span class="p" data-group-id="5262060639-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5262060639-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5262060639-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="5262060639-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="5262060639-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="5262060639-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="5262060639-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="5262060639-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="5262060639-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="5262060639-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="5262060639-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="5262060639-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5262060639-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="5262060639-22">}</span><span class="p" data-group-id="5262060639-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="1321945640-1">(</span><span class="n">N</span><span class="p" data-group-id="1321945640-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="1321945640-2">[</span><span class="p" data-group-id="1321945640-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="1321945640-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ │ +       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1321945640-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="1321945640-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1321945640-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="1321945640-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1321945640-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="1321945640-6">)</span><span class="p">,</span><span class="w">
│ │ │ │         </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │ │ -       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="1699702361-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │ │ +       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="1321945640-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │ │    <a href="#simplifications-with-list-comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simplifications With List Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │  <p>As an example, list comprehensions can be used to simplify some of the functions
│ │ │ │ -in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="4853002265-1">(</span><span class="n">L</span><span class="p" data-group-id="4853002265-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="4853002265-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="4853002265-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="4853002265-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4853002265-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4853002265-4">[</span><span class="n">Fun</span><span class="p" data-group-id="4853002265-5">(</span><span class="n">X</span><span class="p" data-group-id="4853002265-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4853002265-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="4853002265-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4853002265-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4853002265-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="4853002265-8">(</span><span class="n">X</span><span class="p" data-group-id="4853002265-8">)</span><span class="p" data-group-id="4853002265-7">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │ │ +in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="0445531103-1">(</span><span class="n">L</span><span class="p" data-group-id="0445531103-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="0445531103-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="0445531103-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="0445531103-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0445531103-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0445531103-4">[</span><span class="n">Fun</span><span class="p" data-group-id="0445531103-5">(</span><span class="n">X</span><span class="p" data-group-id="0445531103-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0445531103-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="0445531103-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0445531103-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0445531103-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0445531103-8">(</span><span class="n">X</span><span class="p" data-group-id="0445531103-8">)</span><span class="p" data-group-id="0445531103-7">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │ │    <a href="#variable-bindings-in-list-comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Variable Bindings in List Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │  <p>The scope rules for variables that occur in list comprehensions are as follows:</p><ul><li>All variables that occur in a generator pattern are assumed to be &quot;fresh&quot;
│ │ │ │  variables.</li><li>Any variables that are defined before the list comprehension, and that are
│ │ │ │  used in filters, have the values they had before the list comprehension.</li><li>Variables cannot be exported from a list comprehension.</li></ul><p>As an example of these rules, suppose you want to write the function <code class="inline">select</code>,
│ │ │ │  which selects certain elements from a list of tuples. Suppose you write
│ │ │ │  <code class="inline">select(X, L) -&gt; [Y || {X, Y} &lt;- L].</code> with the intention of extracting all
│ │ │ │  tuples from <code class="inline">L</code>, where the first item is <code class="inline">X</code>.</p><p>Compiling this gives the following diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'X' shadowed in generate</code></pre><p>This diagnostic warns that the variable <code class="inline">X</code> in the pattern is not the same as
│ │ │ │ -the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="2976933727-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="2976933727-2">[</span><span class="p" data-group-id="2976933727-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2976933727-3">}</span><span class="p">,</span><span class="p" data-group-id="2976933727-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2976933727-4">}</span><span class="p">,</span><span class="p" data-group-id="2976933727-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2976933727-5">}</span><span class="p">,</span><span class="p" data-group-id="2976933727-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2976933727-6">}</span><span class="p" data-group-id="2976933727-2">]</span><span class="p" data-group-id="2976933727-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2976933727-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2976933727-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ │ -written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="6428499422-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6428499422-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="6428499422-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6428499422-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6428499422-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="6428499422-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ │ -the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="3433550508-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="3433550508-2">[</span><span class="p" data-group-id="3433550508-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3433550508-3">}</span><span class="p">,</span><span class="p" data-group-id="3433550508-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3433550508-4">}</span><span class="p">,</span><span class="p" data-group-id="3433550508-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3433550508-5">}</span><span class="p">,</span><span class="p" data-group-id="3433550508-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3433550508-6">}</span><span class="p" data-group-id="3433550508-2">]</span><span class="p" data-group-id="3433550508-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3433550508-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3433550508-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ │ -same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="4670129181-1">[</span><span class="p" data-group-id="4670129181-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="4670129181-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="4670129181-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4670129181-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="4670129181-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4670129181-4">]</span><span class="p" data-group-id="4670129181-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4670129181-5">[</span><span class="p" data-group-id="4670129181-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4670129181-6">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4670129181-7">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4670129181-8">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4670129181-9">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4670129181-10">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4670129181-11">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="4670129181-12">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="4670129181-13">}</span><span class="p">,</span><span class="p" data-group-id="4670129181-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4670129181-14">}</span><span class="p" data-group-id="4670129181-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehensions is
│ │ │ │ +the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="9001290312-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="9001290312-2">[</span><span class="p" data-group-id="9001290312-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9001290312-3">}</span><span class="p">,</span><span class="p" data-group-id="9001290312-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9001290312-4">}</span><span class="p">,</span><span class="p" data-group-id="9001290312-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9001290312-5">}</span><span class="p">,</span><span class="p" data-group-id="9001290312-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9001290312-6">}</span><span class="p" data-group-id="9001290312-2">]</span><span class="p" data-group-id="9001290312-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9001290312-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9001290312-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ │ +written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="4040225842-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4040225842-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="4040225842-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="4040225842-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4040225842-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="4040225842-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ │ +the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="4570613723-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="4570613723-2">[</span><span class="p" data-group-id="4570613723-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4570613723-3">}</span><span class="p">,</span><span class="p" data-group-id="4570613723-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4570613723-4">}</span><span class="p">,</span><span class="p" data-group-id="4570613723-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4570613723-5">}</span><span class="p">,</span><span class="p" data-group-id="4570613723-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4570613723-6">}</span><span class="p" data-group-id="4570613723-2">]</span><span class="p" data-group-id="4570613723-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4570613723-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4570613723-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ │ +same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1754132449-1">[</span><span class="p" data-group-id="1754132449-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="1754132449-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1754132449-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1754132449-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1754132449-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1754132449-4">]</span><span class="p" data-group-id="1754132449-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1754132449-5">[</span><span class="p" data-group-id="1754132449-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1754132449-6">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1754132449-7">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1754132449-8">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1754132449-9">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1754132449-10">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1754132449-11">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1754132449-12">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1754132449-13">}</span><span class="p">,</span><span class="p" data-group-id="1754132449-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1754132449-14">}</span><span class="p" data-group-id="1754132449-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehensions is
│ │ │ │  that certain pattern matching operations must be moved into the filters and
│ │ │ │ -cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="5460470491-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5460470491-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9847840146-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9847840146-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5460470491-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5460470491-2">]</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3112364712-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3112364712-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9847840146-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9847840146-2">]</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3153416313-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3153416313-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3112364712-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3112364712-2">]</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3153416313-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3153416313-2">]</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/install-win32.xhtml
│ │ │ │ @@ -200,15 +200,15 @@
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">cd erts/emulator
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">cd ../etc
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │ │  </span></code></pre><p>and sometimes</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make local_setup
│ │ │ │  </span></code></pre><p>So now when you run <code class="inline">$ERL_TOP/erl.exe</code>, you should have a debug compiled
│ │ │ │ -emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="8614451233-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="8614451233-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │ │ +emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="9977532867-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="9977532867-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │ │  got a debug compiled emulator.</p><p>To hack the erlang libraries, you simply do a <code class="inline">make opt</code> in the
│ │ │ │  specific &quot;applications&quot; directory, like:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │ │  </span></code></pre><p>or even in the source directory...</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib/src
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │ │  </span></code></pre><p>Note that you're expected to have a fresh Erlang in your path when
│ │ │ │  doing this, preferably the plain 27 you have built in the previous
│ │ │ │ @@ -223,19 +223,19 @@
│ │ │ │  </span><span class="">:$ERL_TOP/erts/etc/win32/wsl_tools:$ERL_TOP/bootstrap/bin:$PATH
│ │ │ │  </span></code></pre><p>That should make it possible to rebuild any library without hassle...</p><p>If you want to copy a library (an application) newly built, to a
│ │ │ │  release area, you do like with the emulator:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │ │  </span><span class="gp unselectable">$ </span><span class="">make TESTROOT=/tmp/erlang_release release
│ │ │ │  </span></code></pre><p>Remember that:</p><ul><li><p>  Windows specific C-code goes in the <code class="inline">$ERL_TOP/erts/emulator/sys/win32</code>,
│ │ │ │  <code class="inline">$ERL_TOP/erts/emulator/drivers/win32</code> or <code class="inline">$ERL_TOP/erts/etc/win32</code>.</p></li><li><p>  Windows specific erlang code should be used conditionally and the
│ │ │ │  host OS tested in <em>runtime</em>, the exactly same beam files should be
│ │ │ │ -distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="8705488337-1">(</span><span class="p" data-group-id="8705488337-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8705488337-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8705488337-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="8705488337-3">(</span><span class="p" data-group-id="8705488337-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="1390175741-1">(</span><span class="p" data-group-id="1390175741-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1390175741-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1390175741-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="1390175741-3">(</span><span class="p" data-group-id="1390175741-3">)</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">Other</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="8705488337-4">(</span><span class="p" data-group-id="8705488337-4">)</span><span class="w">
│ │ │ │ +        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="1390175741-4">(</span><span class="p" data-group-id="1390175741-4">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre></li></ul><p>That's basically all you need to get going.</p><h2 id="frequently-asked-questions" class="section-heading">
│ │ │ │    <a href="#frequently-asked-questions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Frequently Asked Questions</span>
│ │ │ │  </h2>
│ │ │ │  <ul><li><p>  Q: So, now I can build Erlang using GCC on Windows?</p><p>A: No, unfortunately not. You'll need Microsoft's Visual C++
│ │ │ ├── OEBPS/included_applications.xhtml
│ │ │ │ @@ -66,72 +66,72 @@
│ │ │ │  belonging to the primary application.</p><h2 id="specifying-included-applications" class="section-heading">
│ │ │ │    <a href="#specifying-included-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Specifying Included Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>Which applications to include is defined by the <code class="inline">included_applications</code> key in
│ │ │ │ -the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2162273593-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2162273593-2">[</span><span class="p" data-group-id="2162273593-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="2162273593-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2162273593-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2162273593-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="2162273593-6">]</span><span class="p" data-group-id="2162273593-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2162273593-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="2162273593-8">]</span><span class="p" data-group-id="2162273593-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2162273593-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="2162273593-10">]</span><span class="p" data-group-id="2162273593-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2162273593-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="2162273593-12">]</span><span class="p" data-group-id="2162273593-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2162273593-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="2162273593-15">[</span><span class="p" data-group-id="2162273593-15">]</span><span class="p" data-group-id="2162273593-14">}</span><span class="p" data-group-id="2162273593-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2162273593-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2162273593-17">[</span><span class="p" data-group-id="2162273593-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="2162273593-18">}</span><span class="p" data-group-id="2162273593-17">]</span><span class="p" data-group-id="2162273593-16">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2162273593-2">]</span><span class="p" data-group-id="2162273593-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │ │ +the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6076778040-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6076778040-2">[</span><span class="p" data-group-id="6076778040-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="6076778040-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6076778040-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6076778040-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="6076778040-6">]</span><span class="p" data-group-id="6076778040-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6076778040-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="6076778040-8">]</span><span class="p" data-group-id="6076778040-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6076778040-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="6076778040-10">]</span><span class="p" data-group-id="6076778040-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6076778040-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6076778040-12">]</span><span class="p" data-group-id="6076778040-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6076778040-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="6076778040-15">[</span><span class="p" data-group-id="6076778040-15">]</span><span class="p" data-group-id="6076778040-14">}</span><span class="p" data-group-id="6076778040-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6076778040-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6076778040-17">[</span><span class="p" data-group-id="6076778040-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6076778040-18">}</span><span class="p" data-group-id="6076778040-17">]</span><span class="p" data-group-id="6076778040-16">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6076778040-2">]</span><span class="p" data-group-id="6076778040-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │ │    <a href="#synchronizing-processes-during-startup" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Synchronizing Processes during Startup</span>
│ │ │ │  </h2>
│ │ │ │  <p>The supervisor tree of an included application is started as part of the
│ │ │ │  supervisor tree of the including application. If there is a need for
│ │ │ │  synchronization between processes in the including and included applications,
│ │ │ │  this can be achieved by using <em>start phases</em>.</p><p>Start phases are defined by the <code class="inline">start_phases</code> key in the <code class="inline">.app</code> file as a list
│ │ │ │  of tuples <code class="inline">{Phase,PhaseArgs}</code>, where <code class="inline">Phase</code> is an atom and <code class="inline">PhaseArgs</code> is a
│ │ │ │  term.</p><p>The value of the <code class="inline">mod</code> key of the including application must be set to
│ │ │ │  <code class="inline">{application_starter,[Module,StartArgs]}</code>, where <code class="inline">Module</code> as usual is the
│ │ │ │  application callback module. <code class="inline">StartArgs</code> is a term provided as argument to the
│ │ │ │ -callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2447131647-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2447131647-2">[</span><span class="p" data-group-id="2447131647-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="2447131647-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2447131647-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="2447131647-6">]</span><span class="p" data-group-id="2447131647-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="2447131647-8">]</span><span class="p" data-group-id="2447131647-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="2447131647-10">]</span><span class="p" data-group-id="2447131647-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-12">[</span><span class="p" data-group-id="2447131647-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="2447131647-14">[</span><span class="p" data-group-id="2447131647-14">]</span><span class="p" data-group-id="2447131647-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="2447131647-16">[</span><span class="p" data-group-id="2447131647-16">]</span><span class="p" data-group-id="2447131647-15">}</span><span class="p" data-group-id="2447131647-12">]</span><span class="p" data-group-id="2447131647-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="2447131647-18">]</span><span class="p" data-group-id="2447131647-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="2447131647-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="2447131647-22">[</span><span class="p" data-group-id="2447131647-22">]</span><span class="p" data-group-id="2447131647-21">]</span><span class="p" data-group-id="2447131647-20">}</span><span class="p" data-group-id="2447131647-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-24">[</span><span class="p" data-group-id="2447131647-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="2447131647-25">}</span><span class="p" data-group-id="2447131647-24">]</span><span class="p" data-group-id="2447131647-23">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2447131647-2">]</span><span class="p" data-group-id="2447131647-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8400062393-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8400062393-2">[</span><span class="p" data-group-id="8400062393-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="8400062393-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8400062393-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="8400062393-6">]</span><span class="p" data-group-id="8400062393-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="8400062393-8">]</span><span class="p" data-group-id="8400062393-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="8400062393-10">]</span><span class="p" data-group-id="8400062393-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-12">[</span><span class="p" data-group-id="8400062393-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="8400062393-14">[</span><span class="p" data-group-id="8400062393-14">]</span><span class="p" data-group-id="8400062393-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="8400062393-16">[</span><span class="p" data-group-id="8400062393-16">]</span><span class="p" data-group-id="8400062393-15">}</span><span class="p" data-group-id="8400062393-12">]</span><span class="p" data-group-id="8400062393-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="8400062393-18">]</span><span class="p" data-group-id="8400062393-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="8400062393-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="8400062393-22">[</span><span class="p" data-group-id="8400062393-22">]</span><span class="p" data-group-id="8400062393-21">]</span><span class="p" data-group-id="8400062393-20">}</span><span class="p" data-group-id="8400062393-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-24">[</span><span class="p" data-group-id="8400062393-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="8400062393-25">}</span><span class="p" data-group-id="8400062393-24">]</span><span class="p" data-group-id="8400062393-23">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8400062393-2">]</span><span class="p" data-group-id="8400062393-1">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="2447131647-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2447131647-27">[</span><span class="p" data-group-id="2447131647-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="2447131647-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2447131647-29">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="2447131647-31">]</span><span class="p" data-group-id="2447131647-30">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-33">[</span><span class="p" data-group-id="2447131647-33">]</span><span class="p" data-group-id="2447131647-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-35">[</span><span class="p" data-group-id="2447131647-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="2447131647-37">[</span><span class="p" data-group-id="2447131647-37">]</span><span class="p" data-group-id="2447131647-36">}</span><span class="p" data-group-id="2447131647-35">]</span><span class="p" data-group-id="2447131647-34">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="2447131647-39">]</span><span class="p" data-group-id="2447131647-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2447131647-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2447131647-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="2447131647-42">[</span><span class="p" data-group-id="2447131647-42">]</span><span class="p" data-group-id="2447131647-41">}</span><span class="p" data-group-id="2447131647-40">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2447131647-27">]</span><span class="p" data-group-id="2447131647-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │ │ +</span><span class="p" data-group-id="8400062393-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8400062393-27">[</span><span class="p" data-group-id="8400062393-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="8400062393-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8400062393-29">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="8400062393-31">]</span><span class="p" data-group-id="8400062393-30">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-33">[</span><span class="p" data-group-id="8400062393-33">]</span><span class="p" data-group-id="8400062393-32">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-35">[</span><span class="p" data-group-id="8400062393-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="8400062393-37">[</span><span class="p" data-group-id="8400062393-37">]</span><span class="p" data-group-id="8400062393-36">}</span><span class="p" data-group-id="8400062393-35">]</span><span class="p" data-group-id="8400062393-34">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="8400062393-39">]</span><span class="p" data-group-id="8400062393-38">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8400062393-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8400062393-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="8400062393-42">[</span><span class="p" data-group-id="8400062393-42">]</span><span class="p" data-group-id="8400062393-41">}</span><span class="p" data-group-id="8400062393-40">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8400062393-27">]</span><span class="p" data-group-id="8400062393-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │ │  application is started the normal way, that is:</p><ul><li>The application controller creates an application master for the application</li><li>The application master calls <code class="inline">Module:start(normal, StartArgs)</code> to start the
│ │ │ │  top supervisor.</li></ul><p>Then, for the primary application and each included application in top-down,
│ │ │ │  left-to-right order, the application master calls
│ │ │ │  <code class="inline">Module:start_phase(Phase, Type, PhaseArgs)</code> for each phase defined for the
│ │ │ │  primary application, in that order. If a phase is not defined for an included
│ │ │ │  application, the function is not called for this phase and application.</p><p>The following requirements apply to the <code class="inline">.app</code> file for an included application:</p><ul><li>The <code class="inline">{mod, {Module,StartArgs}}</code> option must be included. This option is used
│ │ │ │  to find the callback module <code class="inline">Module</code> of the application. <code class="inline">StartArgs</code> is
│ │ │ │  ignored, as <code class="inline">Module:start/2</code> is called only for the primary application.</li><li>If the included application itself contains included applications, instead the
│ │ │ │  <code class="inline">{mod, {application_starter, [Module,StartArgs]}}</code> option must be included.</li><li>The <code class="inline">{start_phases, [{Phase,PhaseArgs}]}</code> option must be included, and the set
│ │ │ │  of specified phases must be a subset of the set of phases specified for the
│ │ │ │  primary application.</li></ul><p>When starting <code class="inline">prim_app</code> as defined above, the application controller calls the
│ │ │ │  following callback functions before <code class="inline">application:start(prim_app)</code> returns a
│ │ │ │ -value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4996234573-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="4996234573-1">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4996234573-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4996234573-3">[</span><span class="p" data-group-id="4996234573-3">]</span><span class="p" data-group-id="4996234573-2">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="4996234573-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4996234573-5">[</span><span class="p" data-group-id="4996234573-5">]</span><span class="p" data-group-id="4996234573-4">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="4996234573-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4996234573-7">[</span><span class="p" data-group-id="4996234573-7">]</span><span class="p" data-group-id="4996234573-6">)</span><span class="w">
│ │ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="4996234573-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4996234573-9">[</span><span class="p" data-group-id="4996234573-9">]</span><span class="p" data-group-id="4996234573-8">)</span><span class="w">
│ │ │ │ +value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7628786307-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="7628786307-1">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7628786307-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7628786307-3">[</span><span class="p" data-group-id="7628786307-3">]</span><span class="p" data-group-id="7628786307-2">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="7628786307-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7628786307-5">[</span><span class="p" data-group-id="7628786307-5">]</span><span class="p" data-group-id="7628786307-4">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="7628786307-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7628786307-7">[</span><span class="p" data-group-id="7628786307-7">]</span><span class="p" data-group-id="7628786307-6">)</span><span class="w">
│ │ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="7628786307-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7628786307-9">[</span><span class="p" data-group-id="7628786307-9">]</span><span class="p" data-group-id="7628786307-8">)</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/gen_server_concepts.xhtml
│ │ │ │ @@ -62,63 +62,63 @@
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>An example of a simple server written in plain Erlang is provided in
│ │ │ │  <a href="design_principles.xhtml#ch1">Overview</a>. The server can be reimplemented using
│ │ │ │ -<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1296366992-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="1296366992-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1296366992-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="1296366992-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2976547487-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="2976547487-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2976547487-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="2976547487-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1296366992-3">(</span><span class="p" data-group-id="1296366992-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1296366992-4">]</span><span class="p" data-group-id="1296366992-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1296366992-5">(</span><span class="p" data-group-id="1296366992-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1296366992-6">]</span><span class="p" data-group-id="1296366992-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1296366992-7">(</span><span class="p" data-group-id="1296366992-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1296366992-8">]</span><span class="p" data-group-id="1296366992-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2976547487-3">(</span><span class="p" data-group-id="2976547487-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2976547487-4">]</span><span class="p" data-group-id="2976547487-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2976547487-5">(</span><span class="p" data-group-id="2976547487-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2976547487-6">]</span><span class="p" data-group-id="2976547487-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2976547487-7">(</span><span class="p" data-group-id="2976547487-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2976547487-8">]</span><span class="p" data-group-id="2976547487-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="1296366992-9">(</span><span class="p" data-group-id="1296366992-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1296366992-10">(</span><span class="p" data-group-id="1296366992-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1296366992-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1296366992-12">[</span><span class="p" data-group-id="1296366992-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1296366992-13">[</span><span class="p" data-group-id="1296366992-13">]</span><span class="p" data-group-id="1296366992-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="2976547487-9">(</span><span class="p" data-group-id="2976547487-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2976547487-10">(</span><span class="p" data-group-id="2976547487-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2976547487-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2976547487-12">[</span><span class="p" data-group-id="2976547487-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2976547487-13">[</span><span class="p" data-group-id="2976547487-13">]</span><span class="p" data-group-id="2976547487-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="1296366992-14">(</span><span class="p" data-group-id="1296366992-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1296366992-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="1296366992-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="2976547487-14">(</span><span class="p" data-group-id="2976547487-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2976547487-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2976547487-15">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="1296366992-16">(</span><span class="n">Ch</span><span class="p" data-group-id="1296366992-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1296366992-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1296366992-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1296366992-18">}</span><span class="p" data-group-id="1296366992-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="2976547487-16">(</span><span class="n">Ch</span><span class="p" data-group-id="2976547487-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2976547487-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2976547487-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2976547487-18">}</span><span class="p" data-group-id="2976547487-17">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1296366992-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1296366992-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1296366992-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1296366992-21">(</span><span class="p" data-group-id="1296366992-21">)</span><span class="p" data-group-id="1296366992-20">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2976547487-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2976547487-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2976547487-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="2976547487-21">(</span><span class="p" data-group-id="2976547487-21">)</span><span class="p" data-group-id="2976547487-20">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="1296366992-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1296366992-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1296366992-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1296366992-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="1296366992-24">(</span><span class="n">Chs</span><span class="p" data-group-id="1296366992-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1296366992-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1296366992-25">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="2976547487-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2976547487-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2976547487-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2976547487-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="2976547487-24">(</span><span class="n">Chs</span><span class="p" data-group-id="2976547487-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2976547487-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2976547487-25">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="1296366992-26">(</span><span class="p" data-group-id="1296366992-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1296366992-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1296366992-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="1296366992-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1296366992-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1296366992-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="1296366992-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="2976547487-26">(</span><span class="p" data-group-id="2976547487-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2976547487-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2976547487-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2976547487-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2976547487-28">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2976547487-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2976547487-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │ │    <a href="#starting-a-gen_server" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting a Gen_Server</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the example in the previous section, <code class="inline">gen_server</code> is started by calling
│ │ │ │ -<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="8864218490-1">(</span><span class="p" data-group-id="8864218490-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8864218490-2">(</span><span class="p" data-group-id="8864218490-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8864218490-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8864218490-4">[</span><span class="p" data-group-id="8864218490-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8864218490-5">[</span><span class="p" data-group-id="8864218490-5">]</span><span class="p" data-group-id="8864218490-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8864218490-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="8864218490-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │ │ +<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="2685714754-1">(</span><span class="p" data-group-id="2685714754-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2685714754-2">(</span><span class="p" data-group-id="2685714754-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2685714754-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2685714754-4">[</span><span class="p" data-group-id="2685714754-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2685714754-5">[</span><span class="p" data-group-id="2685714754-5">]</span><span class="p" data-group-id="2685714754-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2685714754-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2685714754-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │ │  spawns and links to a new process, a <code class="inline">gen_server</code>.</p><ul><li><p>The first argument, <code class="inline">{local, ch3}</code>, specifies the name.
│ │ │ │  The gen_server is then locally registered as <code class="inline">ch3</code>.</p><p>If the name is omitted, the <code class="inline">gen_server</code> is not registered. Instead its pid
│ │ │ │  must be used. The name can also be given as <code class="inline">{global, Name}</code>, in which case
│ │ │ │  the <code class="inline">gen_server</code> is registered using <a href="../../../lib/kernel/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a>.</p></li><li><p>The second argument, <code class="inline">ch3</code>, is the name of the callback module, which is
│ │ │ │  the module where the callback functions are located.</p><p>The interface functions (<code class="inline">start_link/0</code>, <code class="inline">alloc/0</code>, and <code class="inline">free/1</code>) are located
│ │ │ │  in the same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">handle_call/3</code>, and
│ │ │ │  <code class="inline">handle_cast/2</code>). It is usually good programming practice to have the code
│ │ │ │  corresponding to one process contained in a single module.</p></li><li><p>The third argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any indata and ignores the
│ │ │ │  argument.</p></li><li><p>The fourth argument, <code class="inline">[]</code>, is a list of options. See <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ │  for the available options.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_server</code> process calls the callback
│ │ │ │  function <code class="inline">ch3:init([])</code>. <code class="inline">init</code> is expected to return <code class="inline">{ok, State}</code>, where
│ │ │ │  <code class="inline">State</code> is the internal state of the <code class="inline">gen_server</code>. In this case, the state is
│ │ │ │ -the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6955070351-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6955070351-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6955070351-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="6955070351-3">(</span><span class="p" data-group-id="6955070351-3">)</span><span class="p" data-group-id="6955070351-2">}</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │ │ +the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1411496957-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1411496957-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1411496957-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="1411496957-3">(</span><span class="p" data-group-id="1411496957-3">)</span><span class="p" data-group-id="1411496957-2">}</span><span class="p">.</span></code></pre><p><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │ │  <code class="inline">gen_server</code> has been initialized and is ready to receive requests.</p><p><a href="../../../lib/stdlib/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> must be used if the <code class="inline">gen_server</code> is part of
│ │ │ │  a supervision tree, meaning that it was started by a supervisor. There
│ │ │ │  is another function, <a href="../../../lib/stdlib/doc/html/gen_server.html#start/4"><code class="inline">gen_server:start/4</code></a>, to start a standalone
│ │ │ │  <code class="inline">gen_server</code> that is not part of a supervision tree.</p><h2 id="synchronous-requests-call" class="section-heading">
│ │ │ │    <a href="#synchronous-requests-call" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -126,32 +126,32 @@
│ │ │ │  </h2>
│ │ │ │  <p>The synchronous request <code class="inline">alloc()</code> is implemented using <a href="../../../lib/stdlib/doc/html/gen_server.html#call/2"><code class="inline">gen_server:call/2</code></a>:</p><pre><code class="text">alloc() -&gt;
│ │ │ │      gen_server:call(ch3, alloc).</code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code> and must agree with the name
│ │ │ │  used to start it. <code class="inline">alloc</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ │  When the request is received, the <code class="inline">gen_server</code> calls
│ │ │ │  <code class="inline">handle_call(Request, From, State)</code>, which is expected to return
│ │ │ │  a tuple <code class="inline">{reply,Reply,State1}</code>. <code class="inline">Reply</code> is the reply that is to be sent back
│ │ │ │ -to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="7571073428-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7571073428-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7571073428-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7571073428-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="7571073428-3">(</span><span class="n">Chs</span><span class="p" data-group-id="7571073428-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7571073428-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7571073428-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │ │ +to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="9647109304-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9647109304-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9647109304-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9647109304-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9647109304-3">(</span><span class="n">Chs</span><span class="p" data-group-id="9647109304-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9647109304-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9647109304-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │ │  set of remaining available channels <code class="inline">Chs2</code>.</p><p>Thus, the call <code class="inline">ch3:alloc()</code> returns the allocated channel <code class="inline">Ch</code> and the
│ │ │ │  <code class="inline">gen_server</code> then waits for new requests, now with an updated list of
│ │ │ │  available channels.</p><h2 id="asynchronous-requests-cast" class="section-heading">
│ │ │ │    <a href="#asynchronous-requests-cast" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Asynchronous Requests - Cast</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../../lib/stdlib/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="5398975055-1">(</span><span class="n">Ch</span><span class="p" data-group-id="5398975055-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5398975055-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5398975055-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5398975055-3">}</span><span class="p" data-group-id="5398975055-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ │ +<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../../lib/stdlib/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="7778333623-1">(</span><span class="n">Ch</span><span class="p" data-group-id="7778333623-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7778333623-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7778333623-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7778333623-3">}</span><span class="p" data-group-id="7778333623-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ │  <code class="inline">cast</code>, and thus <code class="inline">free</code>, then returns <code class="inline">ok</code>.</p><p>When the request is received, the <code class="inline">gen_server</code> calls
│ │ │ │  <code class="inline">handle_cast(Request, State)</code>, which is expected to return a tuple
│ │ │ │ -<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="7870781954-1">(</span><span class="p" data-group-id="7870781954-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7870781954-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7870781954-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="7870781954-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7870781954-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7870781954-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7870781954-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │ │ +<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="4991835589-1">(</span><span class="p" data-group-id="4991835589-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4991835589-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4991835589-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="4991835589-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4991835589-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4991835589-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4991835589-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │ │  The <code class="inline">gen_server</code> is now ready for new requests.</p><h2 id="stopping" class="section-heading">
│ │ │ │    <a href="#stopping" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stopping</span>
│ │ │ │  </h2>
│ │ │ │  <h3 id="in-a-supervision-tree" class="section-heading">
│ │ │ │ @@ -162,65 +162,65 @@
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_server</code> is part of a supervision tree, no stop function is needed.
│ │ │ │  The <code class="inline">gen_server</code> is automatically terminated by its supervisor.  Exactly how
│ │ │ │  this is done is defined by a <a href="sup_princ.xhtml#shutdown">shutdown strategy</a>
│ │ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │ │  must be a time-out value and the <code class="inline">gen_server</code> must be set to trap exit signals
│ │ │ │  in function <code class="inline">init</code>. When ordered to shutdown, the <code class="inline">gen_server</code> then calls
│ │ │ │ -the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1219465548-1">(</span><span class="n">Args</span><span class="p" data-group-id="1219465548-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8665602156-1">(</span><span class="n">Args</span><span class="p" data-group-id="8665602156-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="1219465548-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1219465548-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="8665602156-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8665602156-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1219465548-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1219465548-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8665602156-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8665602156-3">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="1219465548-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1219465548-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="8665602156-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8665602156-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code for cleaning up here</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_servers" class="section-heading">
│ │ │ │    <a href="#standalone-gen_servers" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standalone Gen_Servers</span>
│ │ │ │  </h3>
│ │ │ │  <p>If the <code class="inline">gen_server</code> is not part of a supervision tree, a stop function
│ │ │ │  can be useful, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">export</span><span class="p" data-group-id="0667283817-1">(</span><span class="p" data-group-id="0667283817-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0667283817-2">]</span><span class="p" data-group-id="0667283817-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">export</span><span class="p" data-group-id="8184955304-1">(</span><span class="p" data-group-id="8184955304-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8184955304-2">]</span><span class="p" data-group-id="8184955304-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0667283817-3">(</span><span class="p" data-group-id="0667283817-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="0667283817-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="0667283817-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="8184955304-3">(</span><span class="p" data-group-id="8184955304-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="8184955304-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="8184955304-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="0667283817-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0667283817-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0667283817-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0667283817-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="0667283817-7">(</span><span class="p" data-group-id="0667283817-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0667283817-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0667283817-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="8184955304-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8184955304-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8184955304-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8184955304-6">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="8184955304-7">(</span><span class="p" data-group-id="8184955304-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="8184955304-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8184955304-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="0667283817-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0667283817-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="8184955304-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8184955304-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback function handling the <code class="inline">stop</code> request returns a tuple
│ │ │ │  <code class="inline">{stop,normal,State1}</code>, where <code class="inline">normal</code> specifies that it is
│ │ │ │  a normal termination and <code class="inline">State1</code> is a new value for the state
│ │ │ │  of the <code class="inline">gen_server</code>.  This causes the <code class="inline">gen_server</code> to call
│ │ │ │  <code class="inline">terminate(normal, State1)</code> and then it terminates gracefully.</p><h2 id="handling-other-messages" class="section-heading">
│ │ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling Other Messages</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the <code class="inline">gen_server</code> is to be able to receive other messages than requests,
│ │ │ │  the callback function <code class="inline">handle_info(Info, State)</code> must be implemented
│ │ │ │  to handle them.  Examples of other messages are exit messages,
│ │ │ │  if the <code class="inline">gen_server</code> is linked to other processes than the supervisor
│ │ │ │ -and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="3218707491-1">(</span><span class="p" data-group-id="3218707491-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3218707491-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3218707491-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="2347653900-1">(</span><span class="p" data-group-id="2347653900-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2347653900-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2347653900-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3218707491-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="3218707491-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="5930163829-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="5930163829-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2347653900-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="2347653900-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="3919746343-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="3919746343-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5930163829-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="5930163829-2">}</span><span class="p">.</span></code></pre>
│ │ │ │ +    </span><span class="p" data-group-id="3919746343-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="3919746343-2">}</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/funs.xhtml
│ │ │ │ @@ -22,399 +22,399 @@
│ │ │ │      </h1>
│ │ │ │  <h2 id="map" class="section-heading">
│ │ │ │    <a href="#map" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">map</span>
│ │ │ │  </h2>
│ │ │ │ -<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="4060800798-1">(</span><span class="p" data-group-id="4060800798-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4060800798-2">]</span><span class="p" data-group-id="4060800798-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4060800798-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="4060800798-4">(</span><span class="n">T</span><span class="p" data-group-id="4060800798-4">)</span><span class="p" data-group-id="4060800798-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="4060800798-5">(</span><span class="p" data-group-id="4060800798-6">[</span><span class="p" data-group-id="4060800798-6">]</span><span class="p" data-group-id="4060800798-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4060800798-7">[</span><span class="p" data-group-id="4060800798-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="8594527394-1">(</span><span class="p" data-group-id="8594527394-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8594527394-2">]</span><span class="p" data-group-id="8594527394-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8594527394-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="8594527394-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="2789847412-1">(</span><span class="p" data-group-id="2789847412-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2789847412-2">]</span><span class="p" data-group-id="2789847412-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2789847412-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="2789847412-4">(</span><span class="n">T</span><span class="p" data-group-id="2789847412-4">)</span><span class="p" data-group-id="2789847412-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="2789847412-5">(</span><span class="p" data-group-id="2789847412-6">[</span><span class="p" data-group-id="2789847412-6">]</span><span class="p" data-group-id="2789847412-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2789847412-7">[</span><span class="p" data-group-id="2789847412-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ │ -by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="9594550799-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9594550799-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9594550799-2">]</span><span class="p" data-group-id="9594550799-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9594550799-3">[</span><span class="n">F</span><span class="p" data-group-id="9594550799-4">(</span><span class="n">H</span><span class="p" data-group-id="9594550799-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="9594550799-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9594550799-5">)</span><span class="p" data-group-id="9594550799-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="9594550799-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9594550799-7">[</span><span class="p" data-group-id="9594550799-7">]</span><span class="p" data-group-id="9594550799-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9594550799-8">[</span><span class="p" data-group-id="9594550799-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ │ -follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="2242497483-1">(</span><span class="n">L</span><span class="p" data-group-id="2242497483-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="2242497483-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2242497483-3">(</span><span class="n">X</span><span class="p" data-group-id="2242497483-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2242497483-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="2242497483-4">(</span><span class="n">L</span><span class="p" data-group-id="2242497483-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="2242497483-5">(</span><span class="nf">fun</span><span class="p" data-group-id="2242497483-6">(</span><span class="n">X</span><span class="p" data-group-id="2242497483-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2242497483-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │ │ +<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="9067929132-1">(</span><span class="p" data-group-id="9067929132-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9067929132-2">]</span><span class="p" data-group-id="9067929132-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9067929132-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="9067929132-4">(</span><span class="n">T</span><span class="p" data-group-id="9067929132-4">)</span><span class="p" data-group-id="9067929132-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="9067929132-5">(</span><span class="p" data-group-id="9067929132-6">[</span><span class="p" data-group-id="9067929132-6">]</span><span class="p" data-group-id="9067929132-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9067929132-7">[</span><span class="p" data-group-id="9067929132-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="6398508682-1">(</span><span class="p" data-group-id="6398508682-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6398508682-2">]</span><span class="p" data-group-id="6398508682-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6398508682-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="6398508682-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="7801524775-1">(</span><span class="p" data-group-id="7801524775-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7801524775-2">]</span><span class="p" data-group-id="7801524775-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7801524775-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="7801524775-4">(</span><span class="n">T</span><span class="p" data-group-id="7801524775-4">)</span><span class="p" data-group-id="7801524775-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="7801524775-5">(</span><span class="p" data-group-id="7801524775-6">[</span><span class="p" data-group-id="7801524775-6">]</span><span class="p" data-group-id="7801524775-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7801524775-7">[</span><span class="p" data-group-id="7801524775-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ │ +by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="4694629423-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4694629423-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4694629423-2">]</span><span class="p" data-group-id="4694629423-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4694629423-3">[</span><span class="n">F</span><span class="p" data-group-id="4694629423-4">(</span><span class="n">H</span><span class="p" data-group-id="4694629423-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="4694629423-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4694629423-5">)</span><span class="p" data-group-id="4694629423-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="4694629423-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4694629423-7">[</span><span class="p" data-group-id="4694629423-7">]</span><span class="p" data-group-id="4694629423-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4694629423-8">[</span><span class="p" data-group-id="4694629423-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ │ +follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="2201194482-1">(</span><span class="n">L</span><span class="p" data-group-id="2201194482-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="2201194482-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2201194482-3">(</span><span class="n">X</span><span class="p" data-group-id="2201194482-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2201194482-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="2201194482-4">(</span><span class="n">L</span><span class="p" data-group-id="2201194482-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="2201194482-5">(</span><span class="nf">fun</span><span class="p" data-group-id="2201194482-6">(</span><span class="n">X</span><span class="p" data-group-id="2201194482-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2201194482-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │ │  arguments and returns a new list, obtained by applying <code class="inline">F</code> to each of the
│ │ │ │  elements in <code class="inline">L</code>.</p><p>The process of abstracting out the common features of a number of different
│ │ │ │  programs is called <em>procedural abstraction</em>. Procedural abstraction can be used
│ │ │ │  to write several different functions that have a similar structure, but differ
│ │ │ │  in some minor detail. This is done as follows:</p><ol><li><em>Step 1.</em> Write one function that represents the common features of these
│ │ │ │  functions.</li><li><em>Step 2.</em> Parameterize the difference in terms of functions that are passed
│ │ │ │  as arguments to the common function.</li></ol><h2 id="foreach" class="section-heading">
│ │ │ │    <a href="#foreach" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">foreach</span>
│ │ │ │  </h2>
│ │ │ │  <p>This section illustrates procedural abstraction. Initially, the following two
│ │ │ │ -examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="9888649452-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9888649452-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9888649452-2">]</span><span class="p" data-group-id="9888649452-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9888649452-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9888649452-4">[</span><span class="n">H</span><span class="p" data-group-id="9888649452-4">]</span><span class="p" data-group-id="9888649452-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">print_list</span><span class="p" data-group-id="9888649452-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9888649452-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">print_list</span><span class="p" data-group-id="9888649452-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9888649452-7">[</span><span class="p" data-group-id="9888649452-7">]</span><span class="p" data-group-id="9888649452-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="5462283831-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5462283831-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="5462283831-2">]</span><span class="p" data-group-id="5462283831-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="7095627266-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7095627266-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7095627266-2">]</span><span class="p" data-group-id="7095627266-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7095627266-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7095627266-4">[</span><span class="n">H</span><span class="p" data-group-id="7095627266-4">]</span><span class="p" data-group-id="7095627266-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">print_list</span><span class="p" data-group-id="7095627266-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7095627266-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">print_list</span><span class="p" data-group-id="7095627266-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7095627266-7">[</span><span class="p" data-group-id="7095627266-7">]</span><span class="p" data-group-id="7095627266-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="0672336612-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0672336612-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="0672336612-2">]</span><span class="p" data-group-id="0672336612-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Msg</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">broadcast</span><span class="p" data-group-id="5462283831-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="5462283831-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">broadcast</span><span class="p" data-group-id="5462283831-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5462283831-5">[</span><span class="p" data-group-id="5462283831-5">]</span><span class="p" data-group-id="5462283831-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">broadcast</span><span class="p" data-group-id="0672336612-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="0672336612-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">broadcast</span><span class="p" data-group-id="0672336612-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0672336612-5">[</span><span class="p" data-group-id="0672336612-5">]</span><span class="p" data-group-id="0672336612-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><p>These two functions have a similar structure. They both iterate over a list and
│ │ │ │  do something to each element in the list. The &quot;something&quot; is passed on as an
│ │ │ │ -extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="2711598340-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2711598340-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2711598340-2">]</span><span class="p" data-group-id="2711598340-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="2711598340-3">(</span><span class="n">H</span><span class="p" data-group-id="2711598340-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="2711598340-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2711598340-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="2711598340-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2711598340-6">[</span><span class="p" data-group-id="2711598340-6">]</span><span class="p" data-group-id="2711598340-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1752086771-1">(</span><span class="nf">fun</span><span class="p" data-group-id="1752086771-2">(</span><span class="n">H</span><span class="p" data-group-id="1752086771-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1752086771-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1752086771-4">[</span><span class="n">H</span><span class="p" data-group-id="1752086771-4">]</span><span class="p" data-group-id="1752086771-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1752086771-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1377170693-1">(</span><span class="nf">fun</span><span class="p" data-group-id="1377170693-2">(</span><span class="n">Pid</span><span class="p" data-group-id="1377170693-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1377170693-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun ,L)</code>
│ │ │ │ +extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="6159633809-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6159633809-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6159633809-2">]</span><span class="p" data-group-id="6159633809-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="6159633809-3">(</span><span class="n">H</span><span class="p" data-group-id="6159633809-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="6159633809-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6159633809-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="6159633809-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6159633809-6">[</span><span class="p" data-group-id="6159633809-6">]</span><span class="p" data-group-id="6159633809-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="5000576794-1">(</span><span class="nf">fun</span><span class="p" data-group-id="5000576794-2">(</span><span class="n">H</span><span class="p" data-group-id="5000576794-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5000576794-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="5000576794-4">[</span><span class="n">H</span><span class="p" data-group-id="5000576794-4">]</span><span class="p" data-group-id="5000576794-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5000576794-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="2704080774-1">(</span><span class="nf">fun</span><span class="p" data-group-id="2704080774-2">(</span><span class="n">Pid</span><span class="p" data-group-id="2704080774-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2704080774-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun ,L)</code>
│ │ │ │  calls <code class="inline">Fun(X)</code> for each element <code class="inline">X</code> in <code class="inline">L</code> and the processing occurs in the
│ │ │ │  order that the elements were defined in <code class="inline">L</code>. <code class="inline">map</code> does not define the order in
│ │ │ │  which its elements are processed.</p><h2 id="syntax-of-funs" class="section-heading">
│ │ │ │    <a href="#syntax-of-funs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Syntax of Funs</span>
│ │ │ │  </h2>
│ │ │ │  <p>Funs are written with the following syntax (see
│ │ │ │ -<a href="../../../lib/../system/doc/html/expressions.xhtml#fun-expressions">Fun Expressions </a>for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1469957960-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="1469957960-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<a href="../../../lib/../system/doc/html/expressions.xhtml#fun-expressions">Fun Expressions </a>for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6142304695-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="6142304695-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │      </span><span class="k">end</span></code></pre><p>This creates an anonymous function of <code class="inline">N</code> arguments and binds it to the variable
│ │ │ │  <code class="inline">F</code>.</p><p>Another function, <code class="inline">FunctionName</code>, written in the same module, can be passed as
│ │ │ │  an argument, using the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>With this form of function reference, the function that is referred to does not
│ │ │ │  need to be exported from the module.</p><p>It is also possible to refer to a function defined in a different module, with
│ │ │ │ -the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5162986536-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="5162986536-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5162986536-2">(</span><span class="p" data-group-id="5162986536-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5162986536-3">]</span><span class="p" data-group-id="5162986536-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="5162986536-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5162986536-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5162986536-5">]</span><span class="p" data-group-id="5162986536-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3417860364-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="3417860364-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3417860364-2">(</span><span class="p" data-group-id="3417860364-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3417860364-3">]</span><span class="p" data-group-id="3417860364-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="3417860364-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3417860364-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3417860364-5">]</span><span class="p" data-group-id="3417860364-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">t1</span><span class="p" data-group-id="5162986536-6">(</span><span class="p" data-group-id="5162986536-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="5162986536-7">(</span><span class="nf">fun</span><span class="p" data-group-id="5162986536-8">(</span><span class="n">X</span><span class="p" data-group-id="5162986536-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5162986536-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5162986536-9">]</span><span class="p" data-group-id="5162986536-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">t1</span><span class="p" data-group-id="3417860364-6">(</span><span class="p" data-group-id="3417860364-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="3417860364-7">(</span><span class="nf">fun</span><span class="p" data-group-id="3417860364-8">(</span><span class="n">X</span><span class="p" data-group-id="3417860364-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3417860364-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3417860364-9">]</span><span class="p" data-group-id="3417860364-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">t2</span><span class="p" data-group-id="5162986536-10">(</span><span class="p" data-group-id="5162986536-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="5162986536-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5162986536-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="5162986536-12">]</span><span class="p" data-group-id="5162986536-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">t2</span><span class="p" data-group-id="3417860364-10">(</span><span class="p" data-group-id="3417860364-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="3417860364-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3417860364-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3417860364-12">]</span><span class="p" data-group-id="3417860364-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="5162986536-13">(</span><span class="n">X</span><span class="p" data-group-id="5162986536-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="3401263486-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="3401263486-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="0487801835-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="0487801835-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="0487801835-2">(</span><span class="n">F</span><span class="p" data-group-id="0487801835-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="nf">apply</span><span class="p" data-group-id="0487801835-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="0487801835-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="0487801835-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="0487801835-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="0487801835-5">(</span><span class="n">N</span><span class="p" data-group-id="0487801835-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="3417860364-13">(</span><span class="n">X</span><span class="p" data-group-id="3417860364-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="0665654777-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="0665654777-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8739625499-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8739625499-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="8739625499-2">(</span><span class="n">F</span><span class="p" data-group-id="8739625499-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="nf">apply</span><span class="p" data-group-id="8739625499-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8739625499-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="8739625499-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8739625499-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8739625499-5">(</span><span class="n">N</span><span class="p" data-group-id="8739625499-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │     </span><span class="n">N</span><span class="p">.</span></code></pre><p>Funs are a distinct type. The BIFs <code class="inline">erlang:fun_info/1,2</code> can be used to retrieve
│ │ │ │  information about a fun, and the BIF <a href="../../../lib/../erts/doc/html/erlang.html#fun_to_list/1"><code class="inline">erlang:fun_to_list/1</code></a> returns a textual
│ │ │ │  representation of a fun. The <a href="../../../lib/../erts/doc/html/erlang.html#check_process_code/2"><code class="inline">check_process_code/2</code></a>
│ │ │ │  BIF returns <code class="inline">true</code> if the process contains funs that depend on the old version
│ │ │ │  of a module.</p><h2 id="variable-bindings-within-a-fun" class="section-heading">
│ │ │ │    <a href="#variable-bindings-within-a-fun" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Variable Bindings Within a Fun</span>
│ │ │ │  </h2>
│ │ │ │  <p>The scope rules for variables that occur in funs are as follows:</p><ul><li>All variables that occur in the head of a fun are assumed to be &quot;fresh&quot;
│ │ │ │  variables.</li><li>Variables that are defined before the fun, and that occur in function calls or
│ │ │ │ -guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="8857304987-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8857304987-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8857304987-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="8857304987-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="8857304987-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="8857304987-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="8857304987-4">(</span><span class="nf">fun</span><span class="p" data-group-id="8857304987-5">(</span><span class="n">X</span><span class="p" data-group-id="8857304987-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8857304987-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="8857304987-7">[</span><span class="n">X</span><span class="p" data-group-id="8857304987-7">]</span><span class="p" data-group-id="8857304987-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8857304987-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="8857304987-8">(</span><span class="n">Stream</span><span class="p" data-group-id="8857304987-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │ │ +guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="1334009486-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1334009486-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1334009486-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="1334009486-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1334009486-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="1334009486-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="1334009486-4">(</span><span class="nf">fun</span><span class="p" data-group-id="1334009486-5">(</span><span class="n">X</span><span class="p" data-group-id="1334009486-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1334009486-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1334009486-7">[</span><span class="n">X</span><span class="p" data-group-id="1334009486-7">]</span><span class="p" data-group-id="1334009486-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1334009486-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1334009486-8">(</span><span class="n">Stream</span><span class="p" data-group-id="1334009486-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │ │  variable <code class="inline">Stream</code>, which is used within the fun, gets its value from the
│ │ │ │  <code class="inline">file:open</code> line.</p><p>As any variable that occurs in the head of a fun is considered a new variable,
│ │ │ │ -it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="6269539091-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6269539091-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6269539091-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="6269539091-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="6269539091-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="6269539091-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="6269539091-4">(</span><span class="nf">fun</span><span class="p" data-group-id="6269539091-5">(</span><span class="n">File</span><span class="p" data-group-id="6269539091-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6269539091-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6269539091-7">[</span><span class="n">File</span><span class="p" data-group-id="6269539091-7">]</span><span class="p" data-group-id="6269539091-6">)</span><span class="w">
│ │ │ │ -            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6269539091-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="6269539091-8">(</span><span class="n">Stream</span><span class="p" data-group-id="6269539091-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │ │ +it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="9817365470-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9817365470-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9817365470-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="9817365470-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9817365470-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="9817365470-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="9817365470-4">(</span><span class="nf">fun</span><span class="p" data-group-id="9817365470-5">(</span><span class="n">File</span><span class="p" data-group-id="9817365470-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9817365470-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9817365470-7">[</span><span class="n">File</span><span class="p" data-group-id="9817365470-7">]</span><span class="p" data-group-id="9817365470-6">)</span><span class="w">
│ │ │ │ +            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9817365470-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9817365470-8">(</span><span class="n">Stream</span><span class="p" data-group-id="9817365470-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │ │  because code in the fun body cannot refer to the variable <code class="inline">File</code>, which is
│ │ │ │  defined outside of the fun. Compiling this example gives the following
│ │ │ │  diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'File'
│ │ │ │        shadowed in 'fun'</code></pre><p>This indicates that the variable <code class="inline">File</code>, which is defined inside the fun,
│ │ │ │  collides with the variable <code class="inline">File</code>, which is defined outside the fun.</p><p>The rules for importing variables into a fun has the consequence that certain
│ │ │ │  pattern matching operations must be moved into guard expressions and cannot be
│ │ │ │  written in the head of the fun. For example, you might write the following code
│ │ │ │  if you intend the first clause of <code class="inline">F</code> to be evaluated when the value of its
│ │ │ │ -argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1612361460-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1612361460-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7015897146-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7015897146-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="1612361460-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1612361460-3">(</span><span class="n">X</span><span class="p" data-group-id="1612361460-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="7015897146-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7015897146-3">(</span><span class="n">X</span><span class="p" data-group-id="7015897146-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">;</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="1612361460-4">(</span><span class="p">_</span><span class="p" data-group-id="1612361460-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="7015897146-4">(</span><span class="p">_</span><span class="p" data-group-id="7015897146-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1612361460-2">)</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7813678107-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7813678107-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7015897146-2">)</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="5169527130-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5169527130-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="7813678107-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7813678107-3">(</span><span class="n">Y</span><span class="p" data-group-id="7813678107-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="5169527130-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5169527130-3">(</span><span class="n">Y</span><span class="p" data-group-id="5169527130-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">;</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="7813678107-4">(</span><span class="p">_</span><span class="p" data-group-id="7813678107-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="5169527130-4">(</span><span class="p">_</span><span class="p" data-group-id="5169527130-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7813678107-2">)</span><span class="w">
│ │ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5169527130-2">)</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="funs-and-module-lists" class="section-heading">
│ │ │ │    <a href="#funs-and-module-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Funs and Module Lists</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following examples show a dialogue with the Erlang shell. All the higher
│ │ │ │  order functions discussed are exported from the module <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a>.</p><h3 id="map-1" class="section-heading">
│ │ │ │    <a href="#map-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">map</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="7475837681-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7475837681-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7475837681-2">]</span><span class="p" data-group-id="7475837681-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7475837681-3">[</span><span class="n">F</span><span class="p" data-group-id="7475837681-4">(</span><span class="n">H</span><span class="p" data-group-id="7475837681-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="7475837681-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7475837681-5">)</span><span class="p" data-group-id="7475837681-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="7475837681-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7475837681-7">[</span><span class="p" data-group-id="7475837681-7">]</span><span class="p" data-group-id="7475837681-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7475837681-8">[</span><span class="p" data-group-id="7475837681-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="3521170853-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3521170853-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3521170853-2">]</span><span class="p" data-group-id="3521170853-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3521170853-3">[</span><span class="n">F</span><span class="p" data-group-id="3521170853-4">(</span><span class="n">H</span><span class="p" data-group-id="3521170853-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="3521170853-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3521170853-5">)</span><span class="p" data-group-id="3521170853-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="3521170853-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3521170853-7">[</span><span class="p" data-group-id="3521170853-7">]</span><span class="p" data-group-id="3521170853-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3521170853-8">[</span><span class="p" data-group-id="3521170853-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │ │  list.</p><p>When a new fun is defined in the shell, the value of the fun is printed as
│ │ │ │ -<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7089041744-1">(</span><span class="n">X</span><span class="p" data-group-id="7089041744-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0851615534-1">(</span><span class="n">X</span><span class="p" data-group-id="0851615534-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7089041744-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7089041744-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7089041744-3">]</span><span class="p" data-group-id="7089041744-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7089041744-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="7089041744-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0851615534-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0851615534-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0851615534-3">]</span><span class="p" data-group-id="0851615534-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0851615534-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="0851615534-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │ │    <a href="#any" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">any</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="3035361708-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3035361708-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3035361708-2">]</span><span class="p" data-group-id="3035361708-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3035361708-3">(</span><span class="n">H</span><span class="p" data-group-id="3035361708-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="0899091981-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0899091981-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0899091981-2">]</span><span class="p" data-group-id="0899091981-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0899091981-3">(</span><span class="n">H</span><span class="p" data-group-id="0899091981-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="3035361708-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3035361708-4">)</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="0899091981-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0899091981-4">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">any</span><span class="p" data-group-id="3035361708-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3035361708-6">[</span><span class="p" data-group-id="3035361708-6">]</span><span class="p" data-group-id="3035361708-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">any</span><span class="p" data-group-id="0899091981-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0899091981-6">[</span><span class="p" data-group-id="0899091981-6">]</span><span class="p" data-group-id="0899091981-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><p>A predicate is a function that returns <code class="inline">true</code> or <code class="inline">false</code>. <code class="inline">any</code> is <code class="inline">true</code> if
│ │ │ │  there is a term <code class="inline">X</code> in the list such that <code class="inline">P(X)</code> is <code class="inline">true</code>.</p><p>A predicate <code class="inline">Big(X)</code> is defined, which is <code class="inline">true</code> if its argument is greater that
│ │ │ │ -10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="8648033636-1">(</span><span class="n">X</span><span class="p" data-group-id="8648033636-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="2490003050-1">(</span><span class="n">X</span><span class="p" data-group-id="2490003050-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="8648033636-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8648033636-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8648033636-3">]</span><span class="p" data-group-id="8648033636-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="2490003050-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2490003050-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2490003050-3">]</span><span class="p" data-group-id="2490003050-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="8648033636-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8648033636-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8648033636-5">]</span><span class="p" data-group-id="8648033636-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="2490003050-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2490003050-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2490003050-5">]</span><span class="p" data-group-id="2490003050-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h3 id="all" class="section-heading">
│ │ │ │    <a href="#all" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">all</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="4400690326-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4400690326-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4400690326-2">]</span><span class="p" data-group-id="4400690326-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="4400690326-3">(</span><span class="n">H</span><span class="p" data-group-id="4400690326-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="4400690326-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4400690326-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="0864446103-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0864446103-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0864446103-2">]</span><span class="p" data-group-id="0864446103-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0864446103-3">(</span><span class="n">H</span><span class="p" data-group-id="0864446103-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="0864446103-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0864446103-4">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">false</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="4400690326-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4400690326-6">[</span><span class="p" data-group-id="4400690326-6">]</span><span class="p" data-group-id="4400690326-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="7395550687-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7395550687-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7395550687-2">]</span><span class="p" data-group-id="7395550687-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="0864446103-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0864446103-6">[</span><span class="p" data-group-id="0864446103-6">]</span><span class="p" data-group-id="0864446103-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="5040700535-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5040700535-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5040700535-2">]</span><span class="p" data-group-id="5040700535-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="7395550687-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7395550687-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="7395550687-4">]</span><span class="p" data-group-id="7395550687-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="5040700535-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5040700535-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="5040700535-4">]</span><span class="p" data-group-id="5040700535-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h3 id="foreach-1" class="section-heading">
│ │ │ │    <a href="#foreach-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">foreach</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="5674201517-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5674201517-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5674201517-2">]</span><span class="p" data-group-id="5674201517-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="5674201517-3">(</span><span class="n">H</span><span class="p" data-group-id="5674201517-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="5674201517-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="5674201517-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="5674201517-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5674201517-6">[</span><span class="p" data-group-id="5674201517-6">]</span><span class="p" data-group-id="5674201517-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="4760364456-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4760364456-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4760364456-2">]</span><span class="p" data-group-id="4760364456-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="4760364456-3">(</span><span class="n">H</span><span class="p" data-group-id="4760364456-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="4760364456-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4760364456-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="4760364456-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4760364456-6">[</span><span class="p" data-group-id="4760364456-6">]</span><span class="p" data-group-id="4760364456-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The function is applied to each argument in the list. <code class="inline">foreach</code> returns <code class="inline">ok</code>. It
│ │ │ │ -is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="4786928779-1">(</span><span class="nf">fun</span><span class="p" data-group-id="4786928779-2">(</span><span class="n">X</span><span class="p" data-group-id="4786928779-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4786928779-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4786928779-4">[</span><span class="n">X</span><span class="p" data-group-id="4786928779-4">]</span><span class="p" data-group-id="4786928779-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4786928779-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4786928779-5">]</span><span class="p" data-group-id="4786928779-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="6513022989-1">(</span><span class="nf">fun</span><span class="p" data-group-id="6513022989-2">(</span><span class="n">X</span><span class="p" data-group-id="6513022989-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6513022989-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6513022989-4">[</span><span class="n">X</span><span class="p" data-group-id="6513022989-4">]</span><span class="p" data-group-id="6513022989-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6513022989-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6513022989-5">]</span><span class="p" data-group-id="6513022989-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="w">
│ │ │ │  </span><span class="mi">2</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><h3 id="foldl" class="section-heading">
│ │ │ │    <a href="#foldl" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">foldl</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="9665402601-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9665402601-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="9665402601-2">]</span><span class="p" data-group-id="9665402601-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">foldl</span><span class="p" data-group-id="9665402601-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="9665402601-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="9665402601-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9665402601-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">foldl</span><span class="p" data-group-id="9665402601-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9665402601-6">[</span><span class="p" data-group-id="9665402601-6">]</span><span class="p" data-group-id="9665402601-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="1751939210-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1751939210-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="1751939210-2">]</span><span class="p" data-group-id="1751939210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">foldl</span><span class="p" data-group-id="1751939210-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1751939210-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="1751939210-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="1751939210-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">foldl</span><span class="p" data-group-id="1751939210-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1751939210-6">[</span><span class="p" data-group-id="1751939210-6">]</span><span class="p" data-group-id="1751939210-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │ │  elements in the list. The second argument is the accumulator. The function must
│ │ │ │  return a new accumulator, which is used the next time the function is called.</p><p>If you have a list of lists <code class="inline">L = [&quot;I&quot;,&quot;like&quot;,&quot;Erlang&quot;]</code>, then you can sum the
│ │ │ │ -lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5831305713-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="5831305713-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5831305713-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="5831305713-2">]</span><span class="gp unselectable">
│ │ │ │ -10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="5831305713-3">(</span><span class="nf">fun</span><span class="p" data-group-id="5831305713-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="5831305713-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5831305713-5">(</span><span class="n">X</span><span class="p" data-group-id="5831305713-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5831305713-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">11</span></code></pre><p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="7118763566-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="7118763566-1">]</span><span class="p">,</span><span class="w">
│ │ │ │ +lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6047760791-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6047760791-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6047760791-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6047760791-2">]</span><span class="gp unselectable">
│ │ │ │ +10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="6047760791-3">(</span><span class="nf">fun</span><span class="p" data-group-id="6047760791-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="6047760791-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6047760791-5">(</span><span class="n">X</span><span class="p" data-group-id="6047760791-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6047760791-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">11</span></code></pre><p><a href="../../../lib/stdlib/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="4986785625-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="4986785625-1">]</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="nf">while</span><span class="p" data-group-id="7118763566-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7118763566-3">[</span><span class="p" data-group-id="7118763566-3">]</span><span class="p" data-group-id="7118763566-2">)</span><span class="p" data-group-id="7118763566-4">{</span><span class="w">
│ │ │ │ -    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7118763566-5">(</span><span class="nf">head</span><span class="p" data-group-id="7118763566-6">(</span><span class="n">L</span><span class="p" data-group-id="7118763566-6">)</span><span class="p" data-group-id="7118763566-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="7118763566-7">(</span><span class="n">L</span><span class="p" data-group-id="7118763566-7">)</span><span class="w">
│ │ │ │ +</span><span class="nf">while</span><span class="p" data-group-id="4986785625-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4986785625-3">[</span><span class="p" data-group-id="4986785625-3">]</span><span class="p" data-group-id="4986785625-2">)</span><span class="p" data-group-id="4986785625-4">{</span><span class="w">
│ │ │ │ +    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="4986785625-5">(</span><span class="nf">head</span><span class="p" data-group-id="4986785625-6">(</span><span class="n">L</span><span class="p" data-group-id="4986785625-6">)</span><span class="p" data-group-id="4986785625-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="4986785625-7">(</span><span class="n">L</span><span class="p" data-group-id="4986785625-7">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><h3 id="mapfoldl" class="section-heading">
│ │ │ │    <a href="#mapfoldl" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">mapfoldl</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="5741720225-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5741720225-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="5741720225-2">]</span><span class="p" data-group-id="5741720225-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5741720225-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="5741720225-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="5741720225-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="5741720225-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5741720225-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="5741720225-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="5741720225-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5741720225-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5741720225-7">{</span><span class="p" data-group-id="5741720225-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="5741720225-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="5741720225-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">mapfoldl</span><span class="p" data-group-id="5741720225-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5741720225-10">[</span><span class="p" data-group-id="5741720225-10">]</span><span class="p" data-group-id="5741720225-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5741720225-11">{</span><span class="p" data-group-id="5741720225-12">[</span><span class="p" data-group-id="5741720225-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="5741720225-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ │ -then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="2688919869-1">(</span><span class="n">X</span><span class="p" data-group-id="2688919869-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2688919869-2">(</span><span class="n">X</span><span class="p" data-group-id="2688919869-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="2189112483-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2189112483-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="2189112483-2">]</span><span class="p" data-group-id="2189112483-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2189112483-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="2189112483-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="2189112483-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="2189112483-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2189112483-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="2189112483-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="2189112483-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="2189112483-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2189112483-7">{</span><span class="p" data-group-id="2189112483-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="2189112483-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="2189112483-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">mapfoldl</span><span class="p" data-group-id="2189112483-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2189112483-10">[</span><span class="p" data-group-id="2189112483-10">]</span><span class="p" data-group-id="2189112483-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2189112483-11">{</span><span class="p" data-group-id="2189112483-12">[</span><span class="p" data-group-id="2189112483-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="2189112483-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ │ +then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="9147831995-1">(</span><span class="n">X</span><span class="p" data-group-id="9147831995-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9147831995-2">(</span><span class="n">X</span><span class="p" data-group-id="9147831995-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │  &gt; </span><span class="n">Upcase_word</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ │ -</span><span class="nf">fun</span><span class="p" data-group-id="2688919869-3">(</span><span class="n">X</span><span class="p" data-group-id="2688919869-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2688919869-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2688919869-4">)</span><span class="w">
│ │ │ │ +</span><span class="nf">fun</span><span class="p" data-group-id="9147831995-3">(</span><span class="n">X</span><span class="p" data-group-id="9147831995-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9147831995-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9147831995-4">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="2688919869-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="2688919869-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="9147831995-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="9147831995-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;ERLANG&quot;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2688919869-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2688919869-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2688919869-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="2688919869-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="7879567710-1">(</span><span class="nf">fun</span><span class="p" data-group-id="7879567710-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="7879567710-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7879567710-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="7879567710-4">(</span><span class="n">Word</span><span class="p" data-group-id="7879567710-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7879567710-5">(</span><span class="n">Word</span><span class="p" data-group-id="7879567710-5">)</span><span class="p" data-group-id="7879567710-3">}</span><span class="w">
│ │ │ │ -</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7879567710-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7879567710-6">{</span><span class="p" data-group-id="7879567710-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="7879567710-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="7879567710-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9147831995-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="9147831995-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9147831995-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="9147831995-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="0214899670-1">(</span><span class="nf">fun</span><span class="p" data-group-id="0214899670-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="0214899670-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0214899670-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="0214899670-4">(</span><span class="n">Word</span><span class="p" data-group-id="0214899670-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="0214899670-5">(</span><span class="n">Word</span><span class="p" data-group-id="0214899670-5">)</span><span class="p" data-group-id="0214899670-3">}</span><span class="w">
│ │ │ │ +</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0214899670-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0214899670-6">{</span><span class="p" data-group-id="0214899670-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="0214899670-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="0214899670-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │ │    <a href="#filter" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">filter</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#filter/2"><code class="inline">lists:filter/2</code></a> takes a predicate of one argument and a list and returns all elements
│ │ │ │ -in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="7474314885-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7474314885-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7474314885-2">]</span><span class="p" data-group-id="7474314885-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7474314885-3">(</span><span class="n">H</span><span class="p" data-group-id="7474314885-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7474314885-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="7474314885-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7474314885-5">)</span><span class="p" data-group-id="7474314885-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="7474314885-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7474314885-6">)</span><span class="w">
│ │ │ │ +in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="7046874298-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7046874298-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7046874298-2">]</span><span class="p" data-group-id="7046874298-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7046874298-3">(</span><span class="n">H</span><span class="p" data-group-id="7046874298-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7046874298-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="7046874298-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7046874298-5">)</span><span class="p" data-group-id="7046874298-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="7046874298-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7046874298-6">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="7474314885-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7474314885-8">[</span><span class="p" data-group-id="7474314885-8">]</span><span class="p" data-group-id="7474314885-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7474314885-9">[</span><span class="p" data-group-id="7474314885-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="3428971578-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3428971578-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3428971578-2">]</span><span class="p" data-group-id="3428971578-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3428971578-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="3428971578-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="7046874298-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7046874298-8">[</span><span class="p" data-group-id="7046874298-8">]</span><span class="p" data-group-id="7046874298-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7046874298-9">[</span><span class="p" data-group-id="7046874298-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="4704646394-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4704646394-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="4704646394-2">]</span><span class="p" data-group-id="4704646394-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4704646394-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="4704646394-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │ │  to define a set difference function <code class="inline">diff(L1, L2)</code> to be the difference between
│ │ │ │ -the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="4014938210-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="4014938210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">filter</span><span class="p" data-group-id="4014938210-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4014938210-3">(</span><span class="n">X</span><span class="p" data-group-id="4014938210-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="4014938210-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="4014938210-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="4014938210-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the list <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="7431270605-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="7431270605-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="7431270605-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7431270605-3">(</span><span class="n">X</span><span class="p" data-group-id="7431270605-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="7431270605-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="7431270605-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="7431270605-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │ │ +the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="4085324665-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="4085324665-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">filter</span><span class="p" data-group-id="4085324665-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4085324665-3">(</span><span class="n">X</span><span class="p" data-group-id="4085324665-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="4085324665-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="4085324665-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="4085324665-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the list <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="4258078717-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="4258078717-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="4258078717-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4258078717-3">(</span><span class="n">X</span><span class="p" data-group-id="4258078717-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="4258078717-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="4258078717-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="4258078717-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │ │    <a href="#takewhile" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">takewhile</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#takewhile/2"><code class="inline">lists:takewhile/2</code></a> takes elements <code class="inline">X</code> from a list <code class="inline">L</code> as long as the predicate
│ │ │ │ -<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="1177333112-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1177333112-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1177333112-2">]</span><span class="p" data-group-id="1177333112-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="1177333112-3">(</span><span class="n">H</span><span class="p" data-group-id="1177333112-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1177333112-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="1177333112-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1177333112-5">)</span><span class="p" data-group-id="1177333112-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1177333112-6">[</span><span class="p" data-group-id="1177333112-6">]</span><span class="w">
│ │ │ │ +<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="2728320391-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2728320391-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2728320391-2">]</span><span class="p" data-group-id="2728320391-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="2728320391-3">(</span><span class="n">H</span><span class="p" data-group-id="2728320391-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2728320391-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="2728320391-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2728320391-5">)</span><span class="p" data-group-id="2728320391-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2728320391-6">[</span><span class="p" data-group-id="2728320391-6">]</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">takewhile</span><span class="p" data-group-id="1177333112-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1177333112-8">[</span><span class="p" data-group-id="1177333112-8">]</span><span class="p" data-group-id="1177333112-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1177333112-9">[</span><span class="p" data-group-id="1177333112-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="5219754309-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5219754309-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="5219754309-2">]</span><span class="p" data-group-id="5219754309-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5219754309-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="5219754309-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │ │ +</span><span class="nf">takewhile</span><span class="p" data-group-id="2728320391-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2728320391-8">[</span><span class="p" data-group-id="2728320391-8">]</span><span class="p" data-group-id="2728320391-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2728320391-9">[</span><span class="p" data-group-id="2728320391-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="0347557380-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0347557380-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0347557380-2">]</span><span class="p" data-group-id="0347557380-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0347557380-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0347557380-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │ │    <a href="#dropwhile" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">dropwhile</span>
│ │ │ │  </h3>
│ │ │ │ -<p><a href="../../../lib/stdlib/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="7812996161-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7812996161-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7812996161-2">]</span><span class="p" data-group-id="7812996161-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="7812996161-3">(</span><span class="n">H</span><span class="p" data-group-id="7812996161-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="7812996161-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7812996161-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7812996161-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7812996161-5">]</span><span class="w">
│ │ │ │ +<p><a href="../../../lib/stdlib/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="9534025279-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9534025279-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9534025279-2">]</span><span class="p" data-group-id="9534025279-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="9534025279-3">(</span><span class="n">H</span><span class="p" data-group-id="9534025279-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="9534025279-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9534025279-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9534025279-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9534025279-5">]</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">dropwhile</span><span class="p" data-group-id="7812996161-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7812996161-7">[</span><span class="p" data-group-id="7812996161-7">]</span><span class="p" data-group-id="7812996161-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7812996161-8">[</span><span class="p" data-group-id="7812996161-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="3902339655-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3902339655-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3902339655-2">]</span><span class="p" data-group-id="3902339655-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3902339655-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3902339655-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │ │ +</span><span class="nf">dropwhile</span><span class="p" data-group-id="9534025279-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9534025279-7">[</span><span class="p" data-group-id="9534025279-7">]</span><span class="p" data-group-id="9534025279-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9534025279-8">[</span><span class="p" data-group-id="9534025279-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="1933469646-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1933469646-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1933469646-2">]</span><span class="p" data-group-id="1933469646-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1933469646-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1933469646-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │ │    <a href="#splitwith" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">splitwith</span>
│ │ │ │  </h3>
│ │ │ │  <p><a href="../../../lib/stdlib/doc/html/lists.html#splitwith/2"><code class="inline">lists:splitwith/2</code></a> splits the list <code class="inline">L</code> into the two sublists <code class="inline">{L1, L2}</code>, where
│ │ │ │ -<code class="inline">L = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="5174763792-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5174763792-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">splitwith</span><span class="p" data-group-id="5174763792-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174763792-3">[</span><span class="p" data-group-id="5174763792-3">]</span><span class="p" data-group-id="5174763792-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">L = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="1476823692-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1476823692-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">splitwith</span><span class="p" data-group-id="1476823692-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1476823692-3">[</span><span class="p" data-group-id="1476823692-3">]</span><span class="p" data-group-id="1476823692-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="5174763792-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174763792-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5174763792-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5174763792-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="5174763792-6">(</span><span class="n">H</span><span class="p" data-group-id="5174763792-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="5174763792-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174763792-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="5174763792-8">]</span><span class="p" data-group-id="5174763792-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5174763792-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="5174763792-10">(</span><span class="n">L</span><span class="p" data-group-id="5174763792-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174763792-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5174763792-11">]</span><span class="p" data-group-id="5174763792-9">}</span><span class="w">
│ │ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="1476823692-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1476823692-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1476823692-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1476823692-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="1476823692-6">(</span><span class="n">H</span><span class="p" data-group-id="1476823692-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="1476823692-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1476823692-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="1476823692-8">]</span><span class="p" data-group-id="1476823692-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1476823692-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="1476823692-10">(</span><span class="n">L</span><span class="p" data-group-id="1476823692-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1476823692-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1476823692-11">]</span><span class="p" data-group-id="1476823692-9">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="5174763792-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174763792-13">[</span><span class="p" data-group-id="5174763792-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5174763792-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5174763792-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="5174763792-15">(</span><span class="n">L</span><span class="p" data-group-id="5174763792-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174763792-16">[</span><span class="p" data-group-id="5174763792-16">]</span><span class="p" data-group-id="5174763792-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="8420741352-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8420741352-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8420741352-2">]</span><span class="p" data-group-id="8420741352-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8420741352-3">{</span><span class="p" data-group-id="8420741352-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="8420741352-4">]</span><span class="p">,</span><span class="p" data-group-id="8420741352-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8420741352-5">]</span><span class="p" data-group-id="8420741352-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="1476823692-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1476823692-13">[</span><span class="p" data-group-id="1476823692-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1476823692-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1476823692-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="1476823692-15">(</span><span class="n">L</span><span class="p" data-group-id="1476823692-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1476823692-16">[</span><span class="p" data-group-id="1476823692-16">]</span><span class="p" data-group-id="1476823692-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="2253487182-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2253487182-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2253487182-2">]</span><span class="p" data-group-id="2253487182-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2253487182-3">{</span><span class="p" data-group-id="2253487182-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="2253487182-4">]</span><span class="p">,</span><span class="p" data-group-id="2253487182-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2253487182-5">]</span><span class="p" data-group-id="2253487182-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │ │    <a href="#funs-returning-funs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Funs Returning Funs</span>
│ │ │ │  </h2>
│ │ │ │  <p>So far, only functions that take funs as arguments have been described. More
│ │ │ │  powerful functions, that themselves return funs, can also be written. The
│ │ │ │  following examples illustrate these type of functions.</p><h3 id="simple-higher-order-functions" class="section-heading">
│ │ │ │    <a href="#simple-higher-order-functions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Simple Higher Order Functions</span>
│ │ │ │  </h3>
│ │ │ │  <p><code class="inline">Adder(X)</code> is a function that given <code class="inline">X</code>, returns a new function <code class="inline">G</code> such that
│ │ │ │ -<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1642345976-1">(</span><span class="n">X</span><span class="p" data-group-id="1642345976-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1642345976-2">(</span><span class="n">Y</span><span class="p" data-group-id="1642345976-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5025882336-1">(</span><span class="n">X</span><span class="p" data-group-id="5025882336-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5025882336-2">(</span><span class="n">Y</span><span class="p" data-group-id="5025882336-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="1642345976-3">(</span><span class="mi">6</span><span class="p" data-group-id="1642345976-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="5025882336-3">(</span><span class="mi">6</span><span class="p" data-group-id="5025882336-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">Add6</span><span class="p" data-group-id="1642345976-4">(</span><span class="mi">10</span><span class="p" data-group-id="1642345976-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="n">Add6</span><span class="p" data-group-id="5025882336-4">(</span><span class="mi">10</span><span class="p" data-group-id="5025882336-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">16</span></code></pre><h3 id="infinite-lists" class="section-heading">
│ │ │ │    <a href="#infinite-lists" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Infinite Lists</span>
│ │ │ │  </h3>
│ │ │ │ -<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7230189184-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="7230189184-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7230189184-2">(</span><span class="p" data-group-id="7230189184-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7230189184-3">]</span><span class="p" data-group-id="7230189184-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">ints_from</span><span class="p" data-group-id="7230189184-4">(</span><span class="n">N</span><span class="p" data-group-id="7230189184-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="p" data-group-id="7230189184-5">(</span><span class="p" data-group-id="7230189184-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7230189184-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="7230189184-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="7230189184-7">)</span><span class="p" data-group-id="7230189184-6">]</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="4007431553-1">(</span><span class="mi">1</span><span class="p" data-group-id="4007431553-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0128920825-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="0128920825-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0128920825-2">(</span><span class="p" data-group-id="0128920825-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0128920825-3">]</span><span class="p" data-group-id="0128920825-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">ints_from</span><span class="p" data-group-id="0128920825-4">(</span><span class="n">N</span><span class="p" data-group-id="0128920825-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="p" data-group-id="0128920825-5">(</span><span class="p" data-group-id="0128920825-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0128920825-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="0128920825-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0128920825-7">)</span><span class="p" data-group-id="0128920825-6">]</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="6212693582-1">(</span><span class="mi">1</span><span class="p" data-group-id="6212693582-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">XX</span><span class="p" data-group-id="4007431553-2">(</span><span class="p" data-group-id="4007431553-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4007431553-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="4007431553-3">]</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nf">hd</span><span class="p" data-group-id="4007431553-4">(</span><span class="n">XX</span><span class="p" data-group-id="4007431553-5">(</span><span class="p" data-group-id="4007431553-5">)</span><span class="p" data-group-id="4007431553-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="n">XX</span><span class="p" data-group-id="6212693582-2">(</span><span class="p" data-group-id="6212693582-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6212693582-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="6212693582-3">]</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nf">hd</span><span class="p" data-group-id="6212693582-4">(</span><span class="n">XX</span><span class="p" data-group-id="6212693582-5">(</span><span class="p" data-group-id="6212693582-5">)</span><span class="p" data-group-id="6212693582-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="4007431553-6">(</span><span class="n">XX</span><span class="p" data-group-id="4007431553-7">(</span><span class="p" data-group-id="4007431553-7">)</span><span class="p" data-group-id="4007431553-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="6212693582-6">(</span><span class="n">XX</span><span class="p" data-group-id="6212693582-7">(</span><span class="p" data-group-id="6212693582-7">)</span><span class="p" data-group-id="6212693582-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nf">hd</span><span class="p" data-group-id="4007431553-8">(</span><span class="n">Y</span><span class="p" data-group-id="4007431553-9">(</span><span class="p" data-group-id="4007431553-9">)</span><span class="p" data-group-id="4007431553-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="nf">hd</span><span class="p" data-group-id="6212693582-8">(</span><span class="n">Y</span><span class="p" data-group-id="6212693582-9">(</span><span class="p" data-group-id="6212693582-9">)</span><span class="p" data-group-id="6212693582-8">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">2</span></code></pre><p>And so on. This is an example of &quot;lazy embedding&quot;.</p><h3 id="parsing" class="section-heading">
│ │ │ │    <a href="#parsing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Parsing</span>
│ │ │ │  </h3>
│ │ │ │ -<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="3299439630-1">(</span><span class="n">Toks</span><span class="p" data-group-id="3299439630-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3299439630-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="3299439630-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │ │ +<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="8141645718-1">(</span><span class="n">Toks</span><span class="p" data-group-id="8141645718-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8141645718-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="8141645718-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │ │  <code class="inline">{ok, Tree, Toks1}</code>.</p><ul><li><code class="inline">Tree</code> is a parse tree.</li><li><code class="inline">Toks1</code> is a tail of <code class="inline">Tree</code> that contains symbols encountered after the
│ │ │ │  structure that was correctly parsed.</li></ul><p>An unsuccessful parse returns <code class="inline">fail</code>.</p><p>The following example illustrates a simple, functional parser that parses the
│ │ │ │  grammar:</p><pre><code class="text">(a | b) &amp; (c | d)</code></pre><p>The following code defines a function <code class="inline">pconst(X)</code> in the module <code class="inline">funparse</code>,
│ │ │ │ -which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="6239339691-1">(</span><span class="n">X</span><span class="p" data-group-id="6239339691-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6239339691-2">(</span><span class="n">T</span><span class="p" data-group-id="6239339691-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="8442901350-1">(</span><span class="n">X</span><span class="p" data-group-id="8442901350-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8442901350-2">(</span><span class="n">T</span><span class="p" data-group-id="8442901350-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │         </span><span class="k">case</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="6239339691-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="6239339691-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6239339691-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6239339691-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6239339691-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6239339691-4">}</span><span class="p">;</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="8442901350-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="8442901350-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8442901350-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8442901350-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8442901350-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8442901350-4">}</span><span class="p">;</span><span class="w">
│ │ │ │             </span><span class="p">_</span><span class="w">      </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">fail</span><span class="w">
│ │ │ │         </span><span class="k">end</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="3622963665-1">(</span><span class="ss">a</span><span class="p" data-group-id="3622963665-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="6593101180-1">(</span><span class="ss">a</span><span class="p" data-group-id="6593101180-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">funparse</span><span class="p">.</span><span class="mf">0.22674075</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">P1</span><span class="p" data-group-id="3622963665-2">(</span><span class="p" data-group-id="3622963665-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3622963665-3">]</span><span class="p" data-group-id="3622963665-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3622963665-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3622963665-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3622963665-5">}</span><span class="p">,</span><span class="p" data-group-id="3622963665-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3622963665-6">]</span><span class="p" data-group-id="3622963665-4">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="n">P1</span><span class="p" data-group-id="3622963665-7">(</span><span class="p" data-group-id="3622963665-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3622963665-8">]</span><span class="p" data-group-id="3622963665-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +&gt; </span><span class="n">P1</span><span class="p" data-group-id="6593101180-2">(</span><span class="p" data-group-id="6593101180-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6593101180-3">]</span><span class="p" data-group-id="6593101180-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6593101180-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6593101180-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6593101180-5">}</span><span class="p">,</span><span class="p" data-group-id="6593101180-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6593101180-6">]</span><span class="p" data-group-id="6593101180-4">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="n">P1</span><span class="p" data-group-id="6593101180-7">(</span><span class="p" data-group-id="6593101180-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6593101180-8">]</span><span class="p" data-group-id="6593101180-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">fail</span></code></pre><p>Next, the two higher order functions <code class="inline">pand</code> and <code class="inline">por</code> are defined. They combine
│ │ │ │ -primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="4084179175-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="4084179175-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4084179175-2">(</span><span class="n">T</span><span class="p" data-group-id="4084179175-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="4084179175-3">(</span><span class="n">T</span><span class="p" data-group-id="4084179175-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="4084179175-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="4084179175-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="4084179175-5">(</span><span class="n">T1</span><span class="p" data-group-id="4084179175-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="4084179175-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="4084179175-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="p" data-group-id="4084179175-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4084179175-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="4084179175-8">}</span><span class="p" data-group-id="4084179175-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="0128233397-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="0128233397-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0128233397-2">(</span><span class="n">T</span><span class="p" data-group-id="0128233397-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="0128233397-3">(</span><span class="n">T</span><span class="p" data-group-id="0128233397-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0128233397-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="0128233397-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="0128233397-5">(</span><span class="n">T1</span><span class="p" data-group-id="0128233397-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="0128233397-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="0128233397-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                        </span><span class="p" data-group-id="0128233397-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0128233397-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="0128233397-8">}</span><span class="p" data-group-id="0128233397-7">}</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │ │                  </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="ss">fail</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Given a parser <code class="inline">P1</code> for grammar <code class="inline">G1</code>, and a parser <code class="inline">P2</code> for grammar <code class="inline">G2</code>,
│ │ │ │  <code class="inline">pand(P1, P2)</code> returns a parser for the grammar, which consists of sequences of
│ │ │ │  tokens that satisfy <code class="inline">G1</code>, followed by sequences of tokens that satisfy <code class="inline">G2</code>.</p><p><code class="inline">por(P1, P2)</code> returns a parser for the language described by the grammar <code class="inline">G1</code> or
│ │ │ │ -<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="1657240267-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="1657240267-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1657240267-2">(</span><span class="n">T</span><span class="p" data-group-id="1657240267-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="1657240267-3">(</span><span class="n">T</span><span class="p" data-group-id="1657240267-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1657240267-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1657240267-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="1657240267-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1657240267-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="1657240267-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1657240267-5">}</span><span class="p">;</span><span class="w">
│ │ │ │ +<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="9111492677-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="9111492677-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9111492677-2">(</span><span class="n">T</span><span class="p" data-group-id="9111492677-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="9111492677-3">(</span><span class="n">T</span><span class="p" data-group-id="9111492677-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9111492677-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="9111492677-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="9111492677-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9111492677-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="9111492677-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="9111492677-5">}</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="1657240267-7">(</span><span class="n">T</span><span class="p" data-group-id="1657240267-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="1657240267-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1657240267-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                        </span><span class="p" data-group-id="1657240267-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1657240267-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="1657240267-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1657240267-9">}</span><span class="p">;</span><span class="w">
│ │ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="9111492677-7">(</span><span class="n">T</span><span class="p" data-group-id="9111492677-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="9111492677-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="9111492677-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                        </span><span class="p" data-group-id="9111492677-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9111492677-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="9111492677-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="9111492677-9">}</span><span class="p">;</span><span class="w">
│ │ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │ │                  </span><span class="k">end</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The original problem was to parse the grammar <code class="inline">(a | b) &amp; (c | d)</code>. The following
│ │ │ │ -code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="0717215125-1">(</span><span class="p" data-group-id="0717215125-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">pand</span><span class="p" data-group-id="0717215125-2">(</span><span class="w">
│ │ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="0717215125-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="0717215125-4">(</span><span class="ss">a</span><span class="p" data-group-id="0717215125-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="0717215125-5">(</span><span class="ss">b</span><span class="p" data-group-id="0717215125-5">)</span><span class="p" data-group-id="0717215125-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="0717215125-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="0717215125-7">(</span><span class="ss">c</span><span class="p" data-group-id="0717215125-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="0717215125-8">(</span><span class="ss">d</span><span class="p" data-group-id="0717215125-8">)</span><span class="p" data-group-id="0717215125-6">)</span><span class="p" data-group-id="0717215125-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="8913405334-1">(</span><span class="n">List</span><span class="p" data-group-id="8913405334-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8913405334-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="8913405334-3">(</span><span class="p" data-group-id="8913405334-3">)</span><span class="p" data-group-id="8913405334-2">)</span><span class="p" data-group-id="8913405334-4">(</span><span class="n">List</span><span class="p" data-group-id="8913405334-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="2150538306-1">(</span><span class="p" data-group-id="2150538306-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2150538306-2">]</span><span class="p" data-group-id="2150538306-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2150538306-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2150538306-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="2150538306-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="2150538306-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="2150538306-6">}</span><span class="p" data-group-id="2150538306-5">}</span><span class="p">,</span><span class="p" data-group-id="2150538306-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="2150538306-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2150538306-8">}</span><span class="p" data-group-id="2150538306-7">}</span><span class="p" data-group-id="2150538306-4">}</span><span class="p" data-group-id="2150538306-3">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="2150538306-9">(</span><span class="p" data-group-id="2150538306-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="2150538306-10">]</span><span class="p" data-group-id="2150538306-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2150538306-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2150538306-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="2150538306-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="2150538306-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="2150538306-14">}</span><span class="p" data-group-id="2150538306-13">}</span><span class="p">,</span><span class="p" data-group-id="2150538306-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="2150538306-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="2150538306-16">}</span><span class="p" data-group-id="2150538306-15">}</span><span class="p" data-group-id="2150538306-12">}</span><span class="p" data-group-id="2150538306-11">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="2150538306-17">(</span><span class="p" data-group-id="2150538306-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2150538306-18">]</span><span class="p" data-group-id="2150538306-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2150538306-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2150538306-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="2150538306-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="2150538306-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="2150538306-22">}</span><span class="p" data-group-id="2150538306-21">}</span><span class="p">,</span><span class="p" data-group-id="2150538306-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="2150538306-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2150538306-24">}</span><span class="p" data-group-id="2150538306-23">}</span><span class="p" data-group-id="2150538306-20">}</span><span class="p" data-group-id="2150538306-19">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="2150538306-25">(</span><span class="p" data-group-id="2150538306-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="2150538306-26">]</span><span class="p" data-group-id="2150538306-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2150538306-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2150538306-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="2150538306-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="2150538306-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="2150538306-30">}</span><span class="p" data-group-id="2150538306-29">}</span><span class="p">,</span><span class="p" data-group-id="2150538306-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="2150538306-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="2150538306-32">}</span><span class="p" data-group-id="2150538306-31">}</span><span class="p" data-group-id="2150538306-28">}</span><span class="p" data-group-id="2150538306-27">}</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="2150538306-33">(</span><span class="p" data-group-id="2150538306-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="2150538306-34">]</span><span class="p" data-group-id="2150538306-33">)</span><span class="p">.</span><span class="w">
│ │ │ │ +code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="6055613071-1">(</span><span class="p" data-group-id="6055613071-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">pand</span><span class="p" data-group-id="6055613071-2">(</span><span class="w">
│ │ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="6055613071-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="6055613071-4">(</span><span class="ss">a</span><span class="p" data-group-id="6055613071-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="6055613071-5">(</span><span class="ss">b</span><span class="p" data-group-id="6055613071-5">)</span><span class="p" data-group-id="6055613071-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="6055613071-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="6055613071-7">(</span><span class="ss">c</span><span class="p" data-group-id="6055613071-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="6055613071-8">(</span><span class="ss">d</span><span class="p" data-group-id="6055613071-8">)</span><span class="p" data-group-id="6055613071-6">)</span><span class="p" data-group-id="6055613071-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="2507878575-1">(</span><span class="n">List</span><span class="p" data-group-id="2507878575-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2507878575-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="2507878575-3">(</span><span class="p" data-group-id="2507878575-3">)</span><span class="p" data-group-id="2507878575-2">)</span><span class="p" data-group-id="2507878575-4">(</span><span class="n">List</span><span class="p" data-group-id="2507878575-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6145183617-1">(</span><span class="p" data-group-id="6145183617-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6145183617-2">]</span><span class="p" data-group-id="6145183617-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6145183617-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6145183617-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6145183617-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6145183617-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6145183617-6">}</span><span class="p" data-group-id="6145183617-5">}</span><span class="p">,</span><span class="p" data-group-id="6145183617-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6145183617-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6145183617-8">}</span><span class="p" data-group-id="6145183617-7">}</span><span class="p" data-group-id="6145183617-4">}</span><span class="p" data-group-id="6145183617-3">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6145183617-9">(</span><span class="p" data-group-id="6145183617-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6145183617-10">]</span><span class="p" data-group-id="6145183617-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6145183617-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6145183617-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6145183617-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6145183617-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6145183617-14">}</span><span class="p" data-group-id="6145183617-13">}</span><span class="p">,</span><span class="p" data-group-id="6145183617-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6145183617-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6145183617-16">}</span><span class="p" data-group-id="6145183617-15">}</span><span class="p" data-group-id="6145183617-12">}</span><span class="p" data-group-id="6145183617-11">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6145183617-17">(</span><span class="p" data-group-id="6145183617-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6145183617-18">]</span><span class="p" data-group-id="6145183617-17">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6145183617-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6145183617-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6145183617-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6145183617-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6145183617-22">}</span><span class="p" data-group-id="6145183617-21">}</span><span class="p">,</span><span class="p" data-group-id="6145183617-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="6145183617-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6145183617-24">}</span><span class="p" data-group-id="6145183617-23">}</span><span class="p" data-group-id="6145183617-20">}</span><span class="p" data-group-id="6145183617-19">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6145183617-25">(</span><span class="p" data-group-id="6145183617-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6145183617-26">]</span><span class="p" data-group-id="6145183617-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6145183617-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6145183617-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="6145183617-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6145183617-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6145183617-30">}</span><span class="p" data-group-id="6145183617-29">}</span><span class="p">,</span><span class="p" data-group-id="6145183617-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6145183617-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="6145183617-32">}</span><span class="p" data-group-id="6145183617-31">}</span><span class="p" data-group-id="6145183617-28">}</span><span class="p" data-group-id="6145183617-27">}</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="6145183617-33">(</span><span class="p" data-group-id="6145183617-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6145183617-34">]</span><span class="p" data-group-id="6145183617-33">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">fail</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/expressions.xhtml
│ │ │ │ @@ -56,81 +56,81 @@
│ │ │ │  </span><span class="n">Phone_number</span><span class="w">
│ │ │ │  </span><span class="p">_</span><span class="w">
│ │ │ │  </span><span class="p">_</span><span class="n">Height</span><span class="w">
│ │ │ │  </span><span class="ss">name@node</span></code></pre><p>Variables are bound to values using <a href="patterns.xhtml">pattern matching</a>. Erlang uses
│ │ │ │  <em>single assignment</em>, that is, a variable can only be bound once.</p><p>The <em>anonymous variable</em> is denoted by underscore (_) and can be used when a
│ │ │ │  variable is required but its value can be ignored.</p><p><em>Example:</em></p><pre><code class="text">[H|_] = [1,2,3]</code></pre><p>Variables starting with underscore (<code class="inline">_</code>), for example, <code class="inline">_Height</code>, are normal
│ │ │ │  variables, not anonymous. However, they are ignored by the compiler in the sense
│ │ │ │ -that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="5392511431-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5392511431-2">[</span><span class="p" data-group-id="5392511431-2">]</span><span class="p" data-group-id="5392511431-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5392511431-3">[</span><span class="p" data-group-id="5392511431-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="6651266246-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6651266246-2">[</span><span class="p" data-group-id="6651266246-2">]</span><span class="p" data-group-id="6651266246-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6651266246-3">[</span><span class="p" data-group-id="6651266246-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ │ -the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="3854146671-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3854146671-2">[</span><span class="p" data-group-id="3854146671-2">]</span><span class="p" data-group-id="3854146671-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3854146671-3">[</span><span class="p" data-group-id="3854146671-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ │ -following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0524216037-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0524216037-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0524216037-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0524216037-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0337590619-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="0337590619-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0337590619-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0337590619-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │ │ +that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="2618205559-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2618205559-2">[</span><span class="p" data-group-id="2618205559-2">]</span><span class="p" data-group-id="2618205559-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2618205559-3">[</span><span class="p" data-group-id="2618205559-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="2494259664-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2494259664-2">[</span><span class="p" data-group-id="2494259664-2">]</span><span class="p" data-group-id="2494259664-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2494259664-3">[</span><span class="p" data-group-id="2494259664-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ │ +the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="1165550356-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1165550356-2">[</span><span class="p" data-group-id="1165550356-2">]</span><span class="p" data-group-id="1165550356-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1165550356-3">[</span><span class="p" data-group-id="1165550356-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ │ +following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7557896137-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7557896137-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7557896137-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7557896137-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1351242139-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="1351242139-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1351242139-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1351242139-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │ │  an <code class="inline">if</code>, <code class="inline">case</code>, or <code class="inline">receive</code> expression must be bound in all branches to have a
│ │ │ │  value outside the expression. Otherwise they are regarded as unsafe outside
│ │ │ │  the expression.</p><p>For the <code class="inline">try</code> expression variable scoping is limited so that variables bound in
│ │ │ │  the expression are always unsafe outside the expression.</p><h2 id="patterns" class="section-heading">
│ │ │ │    <a href="#patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Patterns</span>
│ │ │ │  </h2>
│ │ │ │  <p>A pattern has the same structure as a term but can contain unbound variables.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">Name1</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8075135653-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8075135653-1">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8075135653-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="8075135653-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.xhtml#case">case expressions</a>,
│ │ │ │ +</span><span class="p" data-group-id="9236782542-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9236782542-1">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9236782542-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="9236782542-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.xhtml#case">case expressions</a>,
│ │ │ │  <a href="expressions.xhtml#receive">receive expressions</a>, and
│ │ │ │  <a href="expressions.xhtml#the-match-operator">match expressions</a>.</p><h3 id="the-compound-pattern-operator" class="section-heading">
│ │ │ │    <a href="#the-compound-pattern-operator" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The Compound Pattern Operator</span>
│ │ │ │  </h3>
│ │ │ │  <p>If <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are valid patterns, the following is also a valid
│ │ │ │  pattern:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span></code></pre><p>When matched against a term, both <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are matched against
│ │ │ │ -the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7149437869-1">(</span><span class="p" data-group-id="7149437869-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="7149437869-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7149437869-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7149437869-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="7149437869-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8402787962-1">(</span><span class="p" data-group-id="8402787962-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="8402787962-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8402787962-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8402787962-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="8402787962-3">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="7149437869-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7149437869-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4964811996-1">(</span><span class="p" data-group-id="4964811996-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4964811996-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4964811996-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="8402787962-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="8402787962-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1067790848-1">(</span><span class="p" data-group-id="1067790848-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1067790848-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1067790848-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="4964811996-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4964811996-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="1067790848-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1067790848-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>The compound pattern operator does not imply that its operands are matched in
│ │ │ │  any particular order. That means that it is not legal to bind a variable in
│ │ │ │  <code class="inline">Pattern1</code> and use it in <code class="inline">Pattern2</code>, or vice versa.</p><h3 id="string-prefix-in-patterns" class="section-heading">
│ │ │ │    <a href="#string-prefix-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">String Prefix in Patterns</span>
│ │ │ │  </h3>
│ │ │ │ -<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9195049549-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="9195049549-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7107143444-1">(</span><span class="p" data-group-id="7107143444-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="7107143444-2">]</span><span class="p" data-group-id="7107143444-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │ │ +<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8479420762-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="8479420762-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3680838672-1">(</span><span class="p" data-group-id="3680838672-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="3680838672-2">]</span><span class="p" data-group-id="3680838672-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │ │    <a href="#expressions-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Expressions in Patterns</span>
│ │ │ │  </h3>
│ │ │ │  <p>An arithmetic expression can be used within a pattern if it meets both of the
│ │ │ │ -following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when complied.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="5201372498-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5201372498-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5201372498-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="5201372498-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │ │ +following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when complied.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="6313642662-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="6313642662-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6313642662-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="6313642662-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │ │    <a href="#the-match-operator" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The Match Operator</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following matches <code class="inline">Pattern</code> against <code class="inline">Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>If the matching succeeds, any unbound variable in the pattern becomes bound and
│ │ │ │  the value of <code class="inline">Expr</code> is returned.</p><p>If multiple match operators are applied in sequence, they will be evaluated from
│ │ │ │ -right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7133051828-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7133051828-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7133051828-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7133051828-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7133051828-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7133051828-3">}</span><span class="gp unselectable">
│ │ │ │ +right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8554833358-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8554833358-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8554833358-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="8554833358-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8554833358-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8554833358-3">}</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">answer</span><span class="gp unselectable">
│ │ │ │  3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ │  4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7133051828-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7133051828-4">}</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="p" data-group-id="7133051828-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7133051828-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7133051828-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7133051828-6">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8554833358-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8554833358-4">}</span><span class="gp unselectable">
│ │ │ │ +5&gt; </span><span class="p" data-group-id="8554833358-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="8554833358-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8554833358-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8554833358-6">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right-hand side value [1,2]</span></code></pre><p>Because multiple match operators are evaluated from right to left, it means
│ │ │ │  that:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span></code></pre><p>is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="n">Temporary</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │ │ @@ -144,30 +144,30 @@
│ │ │ │  can safely be skipped on a first reading.</p></section><p>The <code class="inline">=</code> character is used to denote two similar but distinct operators: the
│ │ │ │  match operator and the compound pattern operator. Which one is meant is
│ │ │ │  determined by context.</p><p>The <em>compound pattern operator</em> is used to construct a compound pattern from two
│ │ │ │  patterns. Compound patterns are accepted everywhere a pattern is accepted. A
│ │ │ │  compound pattern matches if all of its constituent patterns match. It is not
│ │ │ │  legal for a pattern that is part of a compound pattern to use variables (as keys
│ │ │ │  in map patterns or sizes in binary patterns) bound in other sub patterns of the
│ │ │ │ -same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="9784092362-1">(</span><span class="p" data-group-id="9784092362-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="9784092362-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9784092362-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9784092362-3">}</span><span class="p" data-group-id="9784092362-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="6113194068-1">(</span><span class="p" data-group-id="6113194068-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="6113194068-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6113194068-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6113194068-3">}</span><span class="p" data-group-id="6113194068-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:7: variable &#39;Key&#39; is unbound</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9784092362-4">(</span><span class="p" data-group-id="9784092362-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="9784092362-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="9784092362-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9784092362-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="9784092362-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="9784092362-7">(</span><span class="p" data-group-id="9784092362-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9784092362-8">}</span><span class="p" data-group-id="9784092362-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9784092362-9">{</span><span class="p" data-group-id="9784092362-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9784092362-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9784092362-9">}</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9784092362-11">(</span><span class="p" data-group-id="9784092362-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9784092362-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9784092362-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9784092362-13">&gt;&gt;</span><span class="p" data-group-id="9784092362-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9784092362-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="9784092362-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="9784092362-15">(</span><span class="p" data-group-id="9784092362-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="9784092362-16">&gt;&gt;</span><span class="p" data-group-id="9784092362-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9784092362-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="9784092362-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │ │ +2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6113194068-4">(</span><span class="p" data-group-id="6113194068-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6113194068-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="6113194068-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6113194068-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6113194068-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="6113194068-7">(</span><span class="p" data-group-id="6113194068-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6113194068-8">}</span><span class="p" data-group-id="6113194068-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6113194068-9">{</span><span class="p" data-group-id="6113194068-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6113194068-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6113194068-9">}</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6113194068-11">(</span><span class="p" data-group-id="6113194068-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6113194068-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6113194068-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="6113194068-13">&gt;&gt;</span><span class="p" data-group-id="6113194068-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6113194068-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="6113194068-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="6113194068-15">(</span><span class="p" data-group-id="6113194068-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="6113194068-16">&gt;&gt;</span><span class="p" data-group-id="6113194068-15">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6113194068-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="6113194068-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │ │  to match the value of an expression to a pattern. If multiple match operators
│ │ │ │ -are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8752373782-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="8752373782-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8752373782-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="8752373782-2">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">f</span><span class="p" data-group-id="8752373782-3">(</span><span class="n">Key</span><span class="p" data-group-id="8752373782-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8752373782-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8752373782-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8752373782-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8752373782-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │ +are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8532619781-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="8532619781-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8532619781-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="8532619781-2">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nf">f</span><span class="p" data-group-id="8532619781-3">(</span><span class="n">Key</span><span class="p" data-group-id="8532619781-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8532619781-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8532619781-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8532619781-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8532619781-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">value</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nf">f</span><span class="p" data-group-id="8752373782-6">(</span><span class="n">Key</span><span class="p" data-group-id="8752373782-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8752373782-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8752373782-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8752373782-8">(</span><span class="p" data-group-id="8752373782-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8752373782-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="8752373782-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nf">f</span><span class="p" data-group-id="8532619781-6">(</span><span class="n">Key</span><span class="p" data-group-id="8532619781-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8532619781-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8532619781-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8532619781-8">(</span><span class="p" data-group-id="8532619781-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8532619781-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="8532619781-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">value</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nf">f</span><span class="p" data-group-id="8752373782-10">(</span><span class="n">Key</span><span class="p" data-group-id="8752373782-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8752373782-11">(</span><span class="p" data-group-id="8752373782-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8752373782-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8752373782-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8752373782-13">}</span><span class="p" data-group-id="8752373782-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nf">f</span><span class="p" data-group-id="8532619781-10">(</span><span class="n">Key</span><span class="p" data-group-id="8532619781-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8532619781-11">(</span><span class="p" data-group-id="8532619781-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="8532619781-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8532619781-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="8532619781-13">}</span><span class="p" data-group-id="8532619781-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:12: variable &#39;Key&#39; is unbound</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="p" data-group-id="8752373782-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="8752373782-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8752373782-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8752373782-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="p" data-group-id="8532619781-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="8532619781-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8532619781-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8532619781-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span></code></pre><p>The expression at prompt <code class="inline">2&gt;</code> first matches the value of variable <code class="inline">M</code> against
│ │ │ │  pattern <code class="inline">#{key := Key}</code>, binding variable <code class="inline">Key</code>. It then matches the value of
│ │ │ │  <code class="inline">M</code> against pattern <code class="inline">#{Key := Value}</code> using variable <code class="inline">Key</code> as the key, binding
│ │ │ │  variable <code class="inline">Value</code>.</p><p>The expression at prompt <code class="inline">3&gt;</code> matches expression <code class="inline">(#{key := Key} = M)</code> against
│ │ │ │  pattern <code class="inline">#{Key := Value}</code>. The expression inside the parentheses is evaluated
│ │ │ │  first. That is, <code class="inline">M</code> is matched against <code class="inline">#{key := Key}</code>, and then the value of
│ │ │ │  <code class="inline">M</code> is matched against pattern <code class="inline">#{Key := Value}</code>. That is the same evaluation
│ │ │ │ @@ -181,30 +181,30 @@
│ │ │ │  binding variable <code class="inline">Y</code> and creating a binary. The binary is then matched against
│ │ │ │  pattern <code class="inline">&lt;&lt;X:Y&gt;&gt;</code> using the value of <code class="inline">Y</code> as the size of the segment.</p><h2 id="function-calls" class="section-heading">
│ │ │ │    <a href="#function-calls" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Function Calls</span>
│ │ │ │  </h2>
│ │ │ │ -<pre><code class="makeup erlang" translate="no"><span class="n">ExprF</span><span class="p" data-group-id="0657937617-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="0657937617-1">)</span><span class="w">
│ │ │ │ -</span><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="0657937617-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="0657937617-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │ │ +<pre><code class="makeup erlang" translate="no"><span class="n">ExprF</span><span class="p" data-group-id="6431906247-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="6431906247-1">)</span><span class="w">
│ │ │ │ +</span><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="6431906247-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="6431906247-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │ │  <code class="inline">ExprM</code> and <code class="inline">ExprF</code> must be an atom or an expression that evaluates to an atom.
│ │ │ │  The function is said to be called by using the <em>fully qualified function name</em>.
│ │ │ │ -This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1576040037-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1576040037-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │ │ +This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="1610245285-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1610245285-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │ │  an atom or evaluate to a fun.</p><p>If <code class="inline">ExprF</code> is an atom, the function is said to be called by using the
│ │ │ │  <em>implicitly qualified function name</em>. If the function <code class="inline">ExprF</code> is locally
│ │ │ │  defined, it is called. Alternatively, if <code class="inline">ExprF</code> is explicitly imported from the
│ │ │ │  <code class="inline">M</code> module, <code class="inline">M:ExprF(Expr1,...,ExprN)</code> is called. If <code class="inline">ExprF</code> is neither declared
│ │ │ │  locally nor explicitly imported, <code class="inline">ExprF</code> must be the name of an automatically
│ │ │ │ -imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="8996988460-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8996988460-1">)</span><span class="w">
│ │ │ │ -</span><span class="nf">spawn</span><span class="p" data-group-id="8996988460-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8996988460-3">[</span><span class="p" data-group-id="8996988460-3">]</span><span class="p" data-group-id="8996988460-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6051670967-1">(</span><span class="n">X</span><span class="p" data-group-id="6051670967-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Fun1</span><span class="p" data-group-id="6051670967-2">(</span><span class="mi">3</span><span class="p" data-group-id="6051670967-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="8952387067-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8952387067-1">)</span><span class="w">
│ │ │ │ +</span><span class="nf">spawn</span><span class="p" data-group-id="8952387067-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8952387067-3">[</span><span class="p" data-group-id="8952387067-3">]</span><span class="p" data-group-id="8952387067-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="5472053278-1">(</span><span class="n">X</span><span class="p" data-group-id="5472053278-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Fun1</span><span class="p" data-group-id="5472053278-2">(</span><span class="mi">3</span><span class="p" data-group-id="5472053278-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6051670967-3">(</span><span class="p" data-group-id="6051670967-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6051670967-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6051670967-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6051670967-5">]</span><span class="p" data-group-id="6051670967-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6051670967-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6051670967-6">]</span><span class="w">
│ │ │ │ +2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5472053278-3">(</span><span class="p" data-group-id="5472053278-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5472053278-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5472053278-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5472053278-5">]</span><span class="p" data-group-id="5472053278-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5472053278-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5472053278-6">]</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="o">&gt;</span></code></pre><p>Notice that when calling a local function, there is a difference between using
│ │ │ │  the implicitly or fully qualified function name. The latter always refers to the
│ │ │ │  latest version of the module. See
│ │ │ │  <a href="code_loading.xhtml">Compilation and Code Loading </a>and
│ │ │ │  <a href="ref_man_functions.xhtml#eval">Function Evaluation</a>.</p><h3 id="local-function-names-clashing-with-auto-imported-bifs" class="section-heading">
│ │ │ │    <a href="#local-function-names-clashing-with-auto-imported-bifs" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -221,40 +221,40 @@
│ │ │ │  called instead. This is to avoid that future additions to the set of
│ │ │ │  auto-imported BIFs do not silently change the behavior of old code.</p></section><p>However, to avoid that old (pre R14) code changed its behavior when compiled
│ │ │ │  with Erlang/OTP version R14A or later, the following restriction applies: If you
│ │ │ │  override the name of a BIF that was auto-imported in OTP versions prior to R14A
│ │ │ │  (ERTS version 5.8) and have an implicitly qualified call to that function in
│ │ │ │  your code, you either need to explicitly remove the auto-import using a compiler
│ │ │ │  directive, or replace the call with a fully qualified function call. Otherwise
│ │ │ │ -you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6753790279-1">(</span><span class="p" data-group-id="6753790279-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6753790279-2">]</span><span class="p" data-group-id="6753790279-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6432884181-1">(</span><span class="p" data-group-id="6432884181-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6432884181-2">]</span><span class="p" data-group-id="6432884181-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6753790279-3">(</span><span class="p" data-group-id="6753790279-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="6753790279-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6753790279-5">]</span><span class="p" data-group-id="6753790279-4">}</span><span class="p" data-group-id="6753790279-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6432884181-3">(</span><span class="p" data-group-id="6432884181-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="6432884181-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6432884181-5">]</span><span class="p" data-group-id="6432884181-4">}</span><span class="p" data-group-id="6432884181-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="6753790279-6">(</span><span class="p" data-group-id="6753790279-7">[</span><span class="p" data-group-id="6753790279-7">]</span><span class="p" data-group-id="6753790279-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="6432884181-6">(</span><span class="p" data-group-id="6432884181-7">[</span><span class="p" data-group-id="6432884181-7">]</span><span class="p" data-group-id="6432884181-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="6753790279-8">(</span><span class="p" data-group-id="6753790279-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6753790279-9">]</span><span class="p" data-group-id="6753790279-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6753790279-10">(</span><span class="n">T</span><span class="p" data-group-id="6753790279-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="6432884181-8">(</span><span class="p" data-group-id="6432884181-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6432884181-9">]</span><span class="p" data-group-id="6432884181-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6432884181-10">(</span><span class="n">T</span><span class="p" data-group-id="6432884181-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="6753790279-11">(</span><span class="n">X</span><span class="p" data-group-id="6753790279-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6753790279-12">(</span><span class="n">X</span><span class="p" data-group-id="6753790279-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="6432884181-11">(</span><span class="n">X</span><span class="p" data-group-id="6432884181-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6432884181-12">(</span><span class="n">X</span><span class="p" data-group-id="6432884181-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │                                    </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │ │      </span><span class="ss">long</span><span class="p">.</span></code></pre><p>The same logic applies to explicitly imported functions from other modules, as
│ │ │ │  to locally defined functions. It is not allowed to both import a function from
│ │ │ │ -another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6826559922-1">(</span><span class="p" data-group-id="6826559922-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6826559922-2">]</span><span class="p" data-group-id="6826559922-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6133996436-1">(</span><span class="p" data-group-id="6133996436-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6133996436-2">]</span><span class="p" data-group-id="6133996436-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6826559922-3">(</span><span class="p" data-group-id="6826559922-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="6826559922-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6826559922-5">]</span><span class="p" data-group-id="6826559922-4">}</span><span class="p" data-group-id="6826559922-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6133996436-3">(</span><span class="p" data-group-id="6133996436-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="6133996436-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6133996436-5">]</span><span class="p" data-group-id="6133996436-4">}</span><span class="p" data-group-id="6133996436-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="6826559922-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="6826559922-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6826559922-7">]</span><span class="p" data-group-id="6826559922-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="6133996436-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="6133996436-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6133996436-7">]</span><span class="p" data-group-id="6133996436-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="6826559922-8">(</span><span class="n">X</span><span class="p" data-group-id="6826559922-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6826559922-9">(</span><span class="n">X</span><span class="p" data-group-id="6826559922-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="6133996436-8">(</span><span class="n">X</span><span class="p" data-group-id="6133996436-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6133996436-9">(</span><span class="n">X</span><span class="p" data-group-id="6133996436-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ │                                     </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6826559922-10">(</span><span class="n">X</span><span class="p" data-group-id="6826559922-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6133996436-10">(</span><span class="n">X</span><span class="p" data-group-id="6133996436-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="6826559922-11">(</span><span class="n">X</span><span class="p" data-group-id="6826559922-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">length</span><span class="p" data-group-id="6826559922-12">(</span><span class="n">X</span><span class="p" data-group-id="6826559922-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="6133996436-11">(</span><span class="n">X</span><span class="p" data-group-id="6133996436-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">length</span><span class="p" data-group-id="6133996436-12">(</span><span class="n">X</span><span class="p" data-group-id="6133996436-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │ │  name with a local function or explicit import is always allowed. However, if the
│ │ │ │  <code class="inline">-compile({no_auto_import,[F/A])</code> directive is not used, the compiler issues a
│ │ │ │  warning whenever the function is called in the module using the implicitly
│ │ │ │  qualified function name.</p><h2 id="if" class="section-heading">
│ │ │ │    <a href="#if" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -266,40 +266,40 @@
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">GuardSeqN</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The branches of an <code class="inline">if</code>-expression are scanned sequentially until a guard
│ │ │ │  sequence <code class="inline">GuardSeq</code> that evaluates to true is found. Then the corresponding
│ │ │ │  <code class="inline">Body</code> (a sequence of expressions separated by <code class="inline">,</code>) is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">if</code> expression.</p><p>If no guard sequence is evaluated as true, an <code class="inline">if_clause</code> run-time error occurs.
│ │ │ │  If necessary, the guard expression <code class="inline">true</code> can be used in the last branch, as
│ │ │ │ -that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="2693070967-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2693070967-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="1490043603-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1490043603-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">if</span><span class="w">
│ │ │ │          </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% works as an &#39;else&#39; branch</span><span class="w">
│ │ │ │              </span><span class="ss">false</span><span class="w">
│ │ │ │      </span><span class="k">end</span></code></pre><h2 id="case" class="section-heading">
│ │ │ │    <a href="#case" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Case</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Expr</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="5066416586-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5066416586-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2146202137-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2146202137-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="5066416586-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="5066416586-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2146202137-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2146202137-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The expression <code class="inline">Expr</code> is evaluated and the patterns <code class="inline">Pattern</code> are sequentially
│ │ │ │  matched against the result. If a match succeeds and the optional guard sequence
│ │ │ │  <code class="inline">GuardSeq</code> is true, the corresponding <code class="inline">Body</code> is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">case</code> expression.</p><p>If there is no matching pattern with a true guard sequence, a <code class="inline">case_clause</code>
│ │ │ │ -run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="5935459539-1">(</span><span class="n">Signal</span><span class="p" data-group-id="5935459539-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="5382100874-1">(</span><span class="n">Signal</span><span class="p" data-group-id="5382100874-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Signal</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5935459539-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5935459539-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5382100874-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5382100874-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5935459539-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5935459539-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5382100874-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5382100874-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="n">Else</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">false</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="maybe" class="section-heading">
│ │ │ │    <a href="#maybe" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -317,57 +317,57 @@
│ │ │ │  the top-level of a <code class="inline">maybe</code> block. It matches the pattern <code class="inline">Expr1</code> against
│ │ │ │  <code class="inline">Expr2</code>. If the matching succeeds, any unbound variable in the pattern becomes
│ │ │ │  bound. If the expression is the last expression in the <code class="inline">maybe</code> block, it also
│ │ │ │  returns the value of <code class="inline">Expr2</code>. If the matching is unsuccessful, the rest of the
│ │ │ │  expressions in the <code class="inline">maybe</code> block are skipped and the return value of the <code class="inline">maybe</code>
│ │ │ │  block is <code class="inline">Expr2</code>.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the code that
│ │ │ │  follows the block.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6955421707-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6955421707-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="6955421707-2">(</span><span class="p" data-group-id="6955421707-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1551261938-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="1551261938-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="1551261938-2">(</span><span class="p" data-group-id="1551261938-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6955421707-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6955421707-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="6955421707-4">(</span><span class="p" data-group-id="6955421707-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1551261938-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1551261938-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="1551261938-4">(</span><span class="p" data-group-id="1551261938-4">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>Let us first assume that <code class="inline">a()</code> returns <code class="inline">{ok,42}</code> and <code class="inline">b()</code> returns <code class="inline">{ok,58}</code>.
│ │ │ │  With those return values, all of the match operators will succeed, and the
│ │ │ │  return value of the <code class="inline">maybe</code> block is <code class="inline">A + B</code>, which is equal to <code class="inline">42 + 58 = 100</code>.</p><p>Now let us assume that <code class="inline">a()</code> returns <code class="inline">error</code>. The conditional match operator in
│ │ │ │  <code class="inline">{ok, A} ?= a()</code> fails to match, and the return value of the <code class="inline">maybe</code> block is
│ │ │ │  the value of the expression that failed to match, namely <code class="inline">error</code>. Similarly, if
│ │ │ │  <code class="inline">b()</code> returns <code class="inline">wrong</code>, the return value of the <code class="inline">maybe</code> block is <code class="inline">wrong</code>.</p><p>Finally, let us assume that <code class="inline">a()</code> returns <code class="inline">{ok,-1}</code>. Because <code class="inline">true = A &gt;= 0</code> uses
│ │ │ │  the match operator <code class="inline">=</code>, a <code class="inline">{badmatch,false}</code> run-time error occurs when the
│ │ │ │ -expression fails to match the pattern.</p><p>The example can be written in a less succient way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="4385584211-1">(</span><span class="p" data-group-id="4385584211-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4385584211-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="4385584211-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +expression fails to match the pattern.</p><p>The example can be written in a less succient way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="0799997483-1">(</span><span class="p" data-group-id="0799997483-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0799997483-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0799997483-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="4385584211-3">(</span><span class="p" data-group-id="4385584211-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="4385584211-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="4385584211-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="0799997483-3">(</span><span class="p" data-group-id="0799997483-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="0799997483-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0799997483-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">;</span><span class="w">
│ │ │ │              </span><span class="n">Other1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                  </span><span class="n">Other1</span><span class="w">
│ │ │ │          </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="n">Other2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Other2</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">maybe</code> block can be augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ │      </span><span class="n">Expr1</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">ExprN</span><span class="w">
│ │ │ │  </span><span class="k">else</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="8404675174-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="8404675174-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4526843654-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4526843654-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="8404675174-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="8404675174-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4526843654-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4526843654-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>If a conditional match operator fails, the failed expression is matched against
│ │ │ │  the patterns in all clauses between the <code class="inline">else</code> and <code class="inline">end</code> keywords. If a match
│ │ │ │  succeeds and the optional guard sequence <code class="inline">GuardSeq</code> is true, the corresponding
│ │ │ │  <code class="inline">Body</code> is evaluated. The value returned from the body is the return value of the
│ │ │ │  <code class="inline">maybe</code> block.</p><p>If there is no matching pattern with a true guard sequence, an <code class="inline">else_clause</code>
│ │ │ │  run-time error occurs.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the <code class="inline">else</code>
│ │ │ │  clauses. None of the variables bound in the <code class="inline">else</code> clauses must be used in the
│ │ │ │  code that follows the <code class="inline">maybe</code> block.</p><p>Here is the previous example augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7905762385-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="7905762385-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="7905762385-2">(</span><span class="p" data-group-id="7905762385-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3949600611-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="3949600611-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="3949600611-2">(</span><span class="p" data-group-id="3949600611-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7905762385-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7905762385-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="7905762385-4">(</span><span class="p" data-group-id="7905762385-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3949600611-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3949600611-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="3949600611-4">(</span><span class="p" data-group-id="3949600611-4">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │ │  </span><span class="k">else</span><span class="w">
│ │ │ │      </span><span class="ss">error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="ss">wrong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">else</code> clauses translate the failing value from the conditional match
│ │ │ │  operators to the value <code class="inline">error</code>. If the failing value is not one of the
│ │ │ │  recognized values, a <code class="inline">else_clause</code> run-time error occurs.</p><h2 id="send" class="section-heading">
│ │ │ │ @@ -386,75 +386,75 @@
│ │ │ │  <code class="inline">{Name,Node}</code> (or a pid located at another node), also never fails.</li></ul><h2 id="receive" class="section-heading">
│ │ │ │    <a href="#receive" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Receive</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="8566290703-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="8566290703-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4859032475-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4859032475-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="8566290703-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="8566290703-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4859032475-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4859032475-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>Fetches a received message present in the message queue of the process. The
│ │ │ │  first message in the message queue is matched sequentially against the patterns
│ │ │ │  from top to bottom. If no match was found, the matching sequence is repeated for
│ │ │ │  the second message in the queue, and so on. Messages are queued in the
│ │ │ │  <a href="ref_man_processes.xhtml#message-queue-order">order they were received</a>. If a match
│ │ │ │  succeeds, that is, if the <code class="inline">Pattern</code> matches and the optional guard sequence
│ │ │ │  <code class="inline">GuardSeq</code> is true, then the message is removed from the message queue and the
│ │ │ │  corresponding <code class="inline">Body</code> is evaluated. All other messages in the message queue
│ │ │ │  remain unchanged.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">receive</code> expression.</p><p><code class="inline">receive</code> never fails. The execution is suspended, possibly indefinitely, until
│ │ │ │  a message arrives that matches one of the patterns and with a true guard
│ │ │ │ -sequence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="7481587841-1">(</span><span class="p" data-group-id="7481587841-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +sequence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0427852811-1">(</span><span class="p" data-group-id="0427852811-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="7481587841-2">(</span><span class="p" data-group-id="7481587841-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="7481587841-3">(</span><span class="p" data-group-id="7481587841-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7481587841-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7481587841-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7481587841-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7481587841-6">(</span><span class="p" data-group-id="7481587841-6">)</span><span class="p" data-group-id="7481587841-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="7481587841-7">(</span><span class="p" data-group-id="7481587841-7">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="0427852811-2">(</span><span class="p" data-group-id="0427852811-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="0427852811-3">(</span><span class="p" data-group-id="0427852811-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0427852811-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0427852811-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0427852811-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0427852811-6">(</span><span class="p" data-group-id="0427852811-6">)</span><span class="p" data-group-id="0427852811-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0427852811-7">(</span><span class="p" data-group-id="0427852811-7">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> expression can be augmented with a timeout:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="8382442767-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="8382442767-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="5648539028-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5648539028-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="8382442767-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="8382442767-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="5648539028-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="5648539028-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">receive...after</code> works exactly as <code class="inline">receive</code>, except that if no matching message
│ │ │ │  has arrived within <code class="inline">ExprT</code> milliseconds, then <code class="inline">BodyT</code> is evaluated instead. The
│ │ │ │  return value of <code class="inline">BodyT</code> then becomes the return value of the <code class="inline">receive...after</code>
│ │ │ │  expression. <code class="inline">ExprT</code> is to evaluate to an integer, or the atom <code class="inline">infinity</code>. The
│ │ │ │  allowed integer range is from 0 to 4294967295, that is, the longest possible
│ │ │ │  timeout is almost 50 days. With a zero value the timeout occurs immediately if
│ │ │ │  there is no matching message in the message queue.</p><p>The atom <code class="inline">infinity</code> will make the process wait indefinitely for a matching
│ │ │ │  message. This is the same as not using a timeout. It can be useful for timeout
│ │ │ │ -values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="5304903430-1">(</span><span class="p" data-group-id="5304903430-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0923101375-1">(</span><span class="p" data-group-id="0923101375-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="5304903430-2">(</span><span class="p" data-group-id="5304903430-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="5304903430-3">(</span><span class="p" data-group-id="5304903430-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5304903430-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5304903430-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5304903430-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5304903430-6">(</span><span class="p" data-group-id="5304903430-6">)</span><span class="p" data-group-id="5304903430-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="5304903430-7">(</span><span class="p" data-group-id="5304903430-7">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="0923101375-2">(</span><span class="p" data-group-id="0923101375-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="0923101375-3">(</span><span class="p" data-group-id="0923101375-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0923101375-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0923101375-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0923101375-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0923101375-6">(</span><span class="p" data-group-id="0923101375-6">)</span><span class="p" data-group-id="0923101375-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0923101375-7">(</span><span class="p" data-group-id="0923101375-7">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w">
│ │ │ │          </span><span class="mi">60000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="5304903430-8">(</span><span class="p" data-group-id="5304903430-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">error</span><span class="p" data-group-id="5304903430-9">(</span><span class="p" data-group-id="5304903430-9">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="0923101375-8">(</span><span class="p" data-group-id="0923101375-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">error</span><span class="p" data-group-id="0923101375-9">(</span><span class="p" data-group-id="0923101375-9">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is legal to use a <code class="inline">receive...after</code> expression with no branches:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>This construction does not consume any messages, only suspends execution in the
│ │ │ │ -process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="7482951022-1">(</span><span class="p" data-group-id="7482951022-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7482951022-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7482951022-3">[</span><span class="nf">self</span><span class="p" data-group-id="7482951022-4">(</span><span class="p" data-group-id="7482951022-4">)</span><span class="p" data-group-id="7482951022-3">]</span><span class="p" data-group-id="7482951022-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="3560838847-1">(</span><span class="p" data-group-id="3560838847-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3560838847-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3560838847-3">[</span><span class="nf">self</span><span class="p" data-group-id="3560838847-4">(</span><span class="p" data-group-id="3560838847-4">)</span><span class="p" data-group-id="3560838847-3">]</span><span class="p" data-group-id="3560838847-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">timer</span><span class="p" data-group-id="7482951022-5">(</span><span class="n">Pid</span><span class="p" data-group-id="7482951022-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">timer</span><span class="p" data-group-id="3560838847-5">(</span><span class="n">Pid</span><span class="p" data-group-id="3560838847-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w">
│ │ │ │          </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">timeout</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>For more information on timers in Erlang in general, see the
│ │ │ │  <a href="../../../lib/../erts/doc/html/time_correction.xhtml#timers"><em>Timers</em></a> section of the
│ │ │ │  <a href="../../../lib/../erts/doc/html/time_correction.xhtml"><em>Time and Time Correction in Erlang</em></a>
│ │ │ │ @@ -496,21 +496,21 @@
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │  4&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">-</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │  5&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">+</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │  6&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="p" data-group-id="6036732610-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6036732610-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="6036732610-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6036732610-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +7&gt; </span><span class="p" data-group-id="0351931992-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0351931992-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="0351931992-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0351931992-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │ -8&gt; </span><span class="p" data-group-id="6036732610-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="6036732610-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="6036732610-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="6036732610-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +8&gt; </span><span class="p" data-group-id="0351931992-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0351931992-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="0351931992-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="0351931992-4">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -9&gt; </span><span class="p" data-group-id="6036732610-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="6036732610-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="6036732610-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="6036732610-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +9&gt; </span><span class="p" data-group-id="0351931992-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="0351931992-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="0351931992-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="0351931992-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -10&gt; </span><span class="p" data-group-id="6036732610-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="6036732610-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="6036732610-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="6036732610-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +10&gt; </span><span class="p" data-group-id="0351931992-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="0351931992-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="0351931992-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="0351931992-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Prior to OTP 27, the term equivalence operators considered <code class="inline">0.0</code>
│ │ │ │  and <code class="inline">-0.0</code> to be the same term.</p><p>This was changed in OTP 27 but legacy code may have expected them to be
│ │ │ │  considered the same. To help users catch errors that may arise from an
│ │ │ │  upgrade, the compiler raises a warning when <code class="inline">0.0</code> is pattern-matched or used
│ │ │ │  in a term equivalence test.</p><p>If you need to match <code class="inline">0.0</code> specifically, the warning can be silenced by
│ │ │ │  writing <code class="inline">+0.0</code> instead, which produces the same term but makes the compiler
│ │ │ │  interpret the match as being done on purpose.</p></section><h2 id="arithmetic-expressions" class="section-heading">
│ │ │ │ @@ -536,15 +536,15 @@
│ │ │ │  </span><span class="mi">0</span><span class="gp unselectable">
│ │ │ │  8&gt; </span><span class="mi">2#10</span><span class="w"> </span><span class="ow">bor</span><span class="w"> </span><span class="mi">2#01</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │  9&gt; </span><span class="ss">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">10</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │ │       in operator  +/2
│ │ │ │          called as a + 10</span><span class="gp unselectable">
│ │ │ │ -10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="8032631975-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="8032631975-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="5342895014-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="5342895014-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: a system limit has been reached
│ │ │ │       in operator  bsl/2
│ │ │ │          called as 1 bsl 18446744073709551616</span></code></pre><h2 id="boolean-expressions" class="section-heading">
│ │ │ │    <a href="#boolean-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Boolean Expressions</span>
│ │ │ │ @@ -563,136 +563,136 @@
│ │ │ │    <a href="#short-circuit-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Short-Circuit Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="ow">orelse</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p><code class="inline">Expr2</code> is evaluated only if necessary. That is, <code class="inline">Expr2</code> is evaluated only if:</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">false</code> in an <code class="inline">orelse</code> expression.</li></ul><p>or</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">true</code> in an <code class="inline">andalso</code> expression.</li></ul><p>Returns either the value of <code class="inline">Expr1</code> (that is, <code class="inline">true</code> or <code class="inline">false</code>) or the value of
│ │ │ │ -<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="3873624613-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3873624613-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../../lib/stdlib/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ │ -never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="3928394764-1">(</span><span class="n">L</span><span class="p" data-group-id="3928394764-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="3928394764-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="3928394764-3">(</span><span class="n">L</span><span class="p" data-group-id="3928394764-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3928394764-4">(</span><span class="n">L</span><span class="p" data-group-id="3928394764-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3928394764-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ │ -<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="9414376466-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9414376466-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="9414376466-2">]</span><span class="p" data-group-id="9414376466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pred</span><span class="p" data-group-id="9414376466-3">(</span><span class="n">Hd</span><span class="p" data-group-id="9414376466-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="9414376466-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9414376466-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="9414376466-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9414376466-6">[</span><span class="p" data-group-id="9414376466-6">]</span><span class="p" data-group-id="9414376466-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="2022032857-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2022032857-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../../lib/stdlib/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ │ +never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="2499505462-1">(</span><span class="n">L</span><span class="p" data-group-id="2499505462-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="2499505462-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="2499505462-3">(</span><span class="n">L</span><span class="p" data-group-id="2499505462-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="2499505462-4">(</span><span class="n">L</span><span class="p" data-group-id="2499505462-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2499505462-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ │ +<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="4963476866-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4963476866-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="4963476866-2">]</span><span class="p" data-group-id="4963476866-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pred</span><span class="p" data-group-id="4963476866-3">(</span><span class="n">Hd</span><span class="p" data-group-id="4963476866-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="4963476866-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="4963476866-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="4963476866-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4963476866-6">[</span><span class="p" data-group-id="4963476866-6">]</span><span class="p" data-group-id="4963476866-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R13A, <code class="inline">Expr2</code> was required to evaluate to a Boolean value,
│ │ │ │  and as consequence, <code class="inline">andalso</code> and <code class="inline">orelse</code> were <strong>not</strong> tail-recursive.</p></section><h2 id="list-operations" class="section-heading">
│ │ │ │    <a href="#list-operations" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">List Operations</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p>The list concatenation operator <code class="inline">++</code> appends its second argument to its first
│ │ │ │  and returns the resulting list.</p><p>The list subtraction operator <code class="inline">--</code> produces a list that is a copy of the first
│ │ │ │  argument. The procedure is as follows: for each element in the second argument,
│ │ │ │ -the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3014789840-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3014789840-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3014789840-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3014789840-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3014789840-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3014789840-3">]</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="3014789840-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3014789840-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="3014789840-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3014789840-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3014789840-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3014789840-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │ │ +the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8519996617-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8519996617-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8519996617-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8519996617-2">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8519996617-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8519996617-3">]</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="8519996617-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8519996617-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="8519996617-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8519996617-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8519996617-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8519996617-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │ │    <a href="#map-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Map Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <h3 id="creating-maps" class="section-heading">
│ │ │ │    <a href="#creating-maps" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating Maps</span>
│ │ │ │  </h3>
│ │ │ │  <p>Constructing a new map is done by letting an expression <code class="inline">K</code> be associated with
│ │ │ │ -another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4603814984-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="4603814984-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ │ -association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0718370235-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="0718370235-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4780956361-1">#{</span><span class="p" data-group-id="4780956361-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │ │ +another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1006957337-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="1006957337-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ │ +association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4100508444-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="4100508444-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2945209144-1">#{</span><span class="p" data-group-id="2945209144-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │ │  then the resulting terms are used as <em>key</em> and <em>value</em> respectively.</p><p>Keys and values are separated by the <code class="inline">=&gt;</code> arrow and associations are separated
│ │ │ │ -by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5658893768-1">#{</span><span class="p" data-group-id="5658893768-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5658893768-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5658893768-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5658893768-3">&gt;&gt;</span><span class="p" data-group-id="5658893768-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5658893768-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5658893768-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5658893768-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5658893768-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="5658893768-6">}</span><span class="p" data-group-id="5658893768-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5658893768-7">#{</span><span class="p" data-group-id="5658893768-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5658893768-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="5658893768-9">(</span><span class="p" data-group-id="5658893768-9">)</span><span class="p" data-group-id="5658893768-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ │ -map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0901634473-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0901634473-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0901634473-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="0901634473-2">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="0901634473-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0901634473-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0901634473-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="0901634473-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │ │ +by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9963187088-1">#{</span><span class="p" data-group-id="9963187088-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9963187088-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9963187088-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9963187088-3">&gt;&gt;</span><span class="p" data-group-id="9963187088-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9963187088-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9963187088-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9963187088-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9963187088-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="9963187088-6">}</span><span class="p" data-group-id="9963187088-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9963187088-7">#{</span><span class="p" data-group-id="9963187088-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9963187088-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="9963187088-9">(</span><span class="p" data-group-id="9963187088-9">)</span><span class="p" data-group-id="9963187088-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ │ +map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7545531559-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="7545531559-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7545531559-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="7545531559-2">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="7545531559-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="7545531559-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7545531559-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="7545531559-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │ │  values) are evaluated is not defined. The syntactic order of the key-value pairs
│ │ │ │  in the construction is of no relevance, except in the recently mentioned case of
│ │ │ │  two matching keys.</p><h3 id="updating-maps" class="section-heading">
│ │ │ │    <a href="#updating-maps" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Updating Maps</span>
│ │ │ │  </h3>
│ │ │ │  <p>Updating a map has a similar syntax as constructing it.</p><p>An expression defining the map to be updated is put in front of the expression
│ │ │ │ -defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="4919275969-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="4919275969-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map and <code class="inline">K</code> and <code class="inline">V</code> are any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │ │ +defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="7489408208-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="7489408208-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map and <code class="inline">K</code> and <code class="inline">V</code> are any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │ │  created from key <code class="inline">K</code> to value <code class="inline">V</code>.</p><p>If key <code class="inline">K</code> matches an existing key in map <code class="inline">M</code>, its associated value is replaced
│ │ │ │  by the new value <code class="inline">V</code>. In both cases, the evaluated map expression returns a new
│ │ │ │ -map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="7987374288-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="7987374288-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression and <code class="inline">K</code> is an expression
│ │ │ │ +map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="1539362824-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="1539362824-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression and <code class="inline">K</code> is an expression
│ │ │ │  that evaluates to an existing key in <code class="inline">M</code>.</p><p>If key <code class="inline">K</code> does not match any existing keys in map <code class="inline">M</code>, an exception of type
│ │ │ │  <code class="inline">badkey</code> is raised at runtime. If a matching key <code class="inline">K</code> is present in map <code class="inline">M</code>,
│ │ │ │  its associated value is replaced by the new value <code class="inline">V</code>, and the evaluated map
│ │ │ │ -expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0860641121-1">#{</span><span class="p" data-group-id="0860641121-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="0860641121-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0860641121-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="0860641121-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0860641121-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="0860641121-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0860641121-5">(</span><span class="p" data-group-id="0860641121-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="0860641121-6">(</span><span class="p" data-group-id="0860641121-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="0860641121-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="0860641121-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0860641121-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; was added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9606443768-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="9606443768-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9606443768-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="9606443768-2">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="n">M</span><span class="p" data-group-id="9606443768-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9606443768-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9606443768-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9606443768-4">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="n">M</span><span class="p" data-group-id="9606443768-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9606443768-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9606443768-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9606443768-6">}</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="n">M</span><span class="p" data-group-id="9606443768-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9606443768-7">}</span><span class="p">.</span><span class="w">
│ │ │ │ +expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7689377349-1">#{</span><span class="p" data-group-id="7689377349-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="7689377349-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7689377349-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="7689377349-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7689377349-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="7689377349-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7689377349-5">(</span><span class="p" data-group-id="7689377349-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="7689377349-6">(</span><span class="p" data-group-id="7689377349-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="7689377349-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="7689377349-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7689377349-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; was added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1675855257-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="1675855257-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1675855257-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="1675855257-2">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="n">M</span><span class="p" data-group-id="1675855257-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1675855257-3">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1675855257-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1675855257-4">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="n">M</span><span class="p" data-group-id="1675855257-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1675855257-5">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1675855257-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1675855257-6">}</span><span class="gp unselectable">
│ │ │ │ +4&gt; </span><span class="n">M</span><span class="p" data-group-id="1675855257-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1675855257-7">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: bad argument</span></code></pre><p>As in construction, the order in which the key and value expressions are
│ │ │ │  evaluated is not defined. The syntactic order of the key-value pairs in the
│ │ │ │  update is of no relevance, except in the case where two keys match. In that
│ │ │ │  case, the latter value is used.</p><h3 id="maps-in-patterns" class="section-heading">
│ │ │ │    <a href="#maps-in-patterns" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Maps in Patterns</span>
│ │ │ │  </h3>
│ │ │ │ -<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7522145616-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="7522145616-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │ │ +<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8498602109-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="8498602109-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │ │  <a href="expressions.xhtml#guard-expressions">guard expression</a>, with all variables already
│ │ │ │  bound. <code class="inline">V</code> can be any pattern with either bound or unbound variables.</p><p>If the variable <code class="inline">V</code> is unbound, it becomes bound to the value associated with
│ │ │ │  the key <code class="inline">K</code>, which must exist in the map <code class="inline">M</code>. If the variable <code class="inline">V</code> is bound, it
│ │ │ │  must match the value associated with <code class="inline">K</code> in <code class="inline">M</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, the expression defining the key <code class="inline">K</code> was restricted to be
│ │ │ │ -either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5342668687-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5342668687-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5342668687-2">}</span><span class="p" data-group-id="5342668687-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5342668687-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5342668687-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5342668687-4">}</span><span class="p" data-group-id="5342668687-3">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="5342668687-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5342668687-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="5342668687-6">}</span><span class="p" data-group-id="5342668687-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5342668687-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5342668687-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5342668687-8">}</span><span class="p" data-group-id="5342668687-7">}</span><span class="gp unselectable">
│ │ │ │ +either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3807295125-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3807295125-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3807295125-2">}</span><span class="p" data-group-id="3807295125-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3807295125-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3807295125-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3807295125-4">}</span><span class="p" data-group-id="3807295125-3">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="3807295125-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3807295125-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="3807295125-6">}</span><span class="p" data-group-id="3807295125-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3807295125-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3807295125-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3807295125-8">}</span><span class="p" data-group-id="3807295125-7">}</span><span class="gp unselectable">
│ │ │ │  3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0340884387-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="0340884387-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │ │ +</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1595190194-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="1595190194-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │ │  variables. If all key expressions evaluate successfully and all keys
│ │ │ │  exist in map <code class="inline">M</code>, all variables in <code class="inline">V1 .. Vn</code> is matched to the
│ │ │ │  associated values of their respective keys.</p><p>If the matching conditions are not met the match fails.</p><p>Note that when matching a map, only the <code class="inline">:=</code> operator (not the <code class="inline">=&gt;</code>) is allowed
│ │ │ │  as a delimiter for the associations.</p><p>The order in which keys are declared in matching has no relevance.</p><p>Duplicate keys are allowed in matching and match each pattern associated to the
│ │ │ │ -keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0016567730-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="0016567730-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6936407518-1">#{</span><span class="p" data-group-id="6936407518-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map, otherwise it
│ │ │ │ -fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2104457168-1">#{</span><span class="p" data-group-id="2104457168-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="2104457168-3">(</span><span class="n">List</span><span class="p" data-group-id="2104457168-3">)</span><span class="p" data-group-id="2104457168-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="2104457168-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys are allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2591374418-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2591374418-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="2591374418-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2591374418-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1063264190-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="1063264190-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4956098527-1">#{</span><span class="p" data-group-id="4956098527-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map, otherwise it
│ │ │ │ +fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7457954361-1">#{</span><span class="p" data-group-id="7457954361-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7457954361-3">(</span><span class="n">List</span><span class="p" data-group-id="7457954361-3">)</span><span class="p" data-group-id="7457954361-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="7457954361-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys are allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="7807125794-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7807125794-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="7807125794-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7807125794-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2591374418-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2591374418-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="2591374418-4">}</span><span class="p" data-group-id="2591374418-3">}</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7807125794-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7807125794-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="7807125794-4">}</span><span class="p" data-group-id="7807125794-3">}</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% only change if started</span><span class="w">
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2591374418-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2591374418-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="2591374418-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2591374418-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="7807125794-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7807125794-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="7807125794-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7807125794-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2591374418-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2591374418-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="2591374418-8">}</span><span class="p" data-group-id="2591374418-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │ │ +    </span><span class="p" data-group-id="7807125794-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7807125794-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="7807125794-8">}</span><span class="p" data-group-id="7807125794-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │ │    <a href="#maps-in-guards" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Maps in Guards</span>
│ │ │ │  </h3>
│ │ │ │  <p>Maps are allowed in guards as long as all subexpressions are valid guard
│ │ │ │  expressions.</p><p>The following guard BIFs handle maps:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#is_map/1">is_map/1</a> in the <code class="inline">erlang</code> module</li><li><a href="../../../lib/../erts/doc/html/erlang.html#is_map_key/2">is_map_key/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../../lib/../erts/doc/html/erlang.html#map_get/2">map_get/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../../lib/../erts/doc/html/erlang.html#map_size/1">map_size/1</a> in the <code class="inline">erlang</code> module</li></ul><h2 id="bit-syntax-expressions" class="section-heading">
│ │ │ │    <a href="#bit-syntax-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Bit Syntax Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <p>The bit syntax operates on <em>bit strings</em>. A bit string is a sequence of bits
│ │ │ │ -ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1760820970-1">&lt;&lt;</span><span class="p" data-group-id="1760820970-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1760820970-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="1760820970-2">&gt;&gt;</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1760820970-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="1760820970-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │ │ +ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1916776501-1">&lt;&lt;</span><span class="p" data-group-id="1916776501-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1916776501-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="1916776501-2">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1916776501-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="1916776501-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │ │  ordered left to right from the most significant bit to the least significant bit
│ │ │ │  of the bit string.</p><p>Each segment specification <code class="inline">Ei</code> is a value, whose default type is <code class="inline">integer</code>,
│ │ │ │  followed by an optional <em>size expression</em> and an optional <em>type specifier list</em>.</p><pre><code class="makeup erlang" translate="no"><span class="n">Ei</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ │       </span><span class="n">Value</span><span class="o">/</span><span class="n">TypeSpecifierList</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="o">/</span><span class="n">TypeSpecifierList</span></code></pre><p>When used in a bit string construction, <code class="inline">Value</code> is an expression that is to
│ │ │ │  evaluate to an integer, float, or bit string. If the expression is not a single
│ │ │ │ @@ -703,34 +703,34 @@
│ │ │ │  <a href="expressions.xhtml#guard-expressions">guard expression</a> that evaluates to an
│ │ │ │  integer. All variables in the guard expression must be already bound.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable
│ │ │ │  bound to an integer.</p></section><p>The value of <code class="inline">Size</code> specifies the size of the segment in units (see below). The
│ │ │ │  default value depends on the type (see below):</p><ul><li>For <code class="inline">integer</code> it is 8.</li><li>For <code class="inline">float</code> it is 64.</li><li>For <code class="inline">binary</code> and <code class="inline">bitstring</code> it is the whole binary or bit string.</li></ul><p>In matching, the default value for a binary or bit string segment is only valid
│ │ │ │  for the last element. All other bit string or binary elements in the matching
│ │ │ │  must have a size specification.</p><p><a href="" id="binaries"></a></p><p><strong>Binaries</strong></p><p>A bit string with a length that is a multiple of 8 bits is known as a <em>binary</em>,
│ │ │ │  which is the most common and useful type of bit string.</p><p>A binary has a canonical representation in memory. Here follows a sequence of
│ │ │ │ -bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3906746664-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="3906746664-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ │ -information about binaries apply just as well for bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4872808951-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4872808951-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4872808951-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4872808951-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3086490095-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="3086490095-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ │ +information about binaries apply just as well for bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5293051513-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5293051513-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5293051513-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="5293051513-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:3: a binary field without size is only allowed at the end of a binary pattern</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="4872808951-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4872808951-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4872808951-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4872808951-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4872808951-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4872808951-5">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="5293051513-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5293051513-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5293051513-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="5293051513-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5293051513-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="5293051513-5">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │  3&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4872808951-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4872808951-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +</span><span class="p" data-group-id="5293051513-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5293051513-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │  4&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4872808951-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="4872808951-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │ │ +</span><span class="p" data-group-id="5293051513-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="5293051513-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │ │  of the segment is implicitly determined by the type and value itself.</p><p><code class="inline">TypeSpecifierList</code> is a list of type specifiers, in any order, separated by
│ │ │ │  hyphens (-). Default values are used for any omitted type specifiers.</p><ul><li><p><strong><code class="inline">Type</code>= <code class="inline">integer</code> | <code class="inline">float</code> | <code class="inline">binary</code> | <code class="inline">bytes</code> | <code class="inline">bitstring</code> | <code class="inline">bits</code> |
│ │ │ │  <code class="inline">utf8</code> | <code class="inline">utf16</code> | <code class="inline">utf32</code></strong> - The default is <code class="inline">integer</code>. <code class="inline">bytes</code> is a
│ │ │ │  shorthand for <code class="inline">binary</code> and <code class="inline">bits</code> is a shorthand for <code class="inline">bitstring</code>. See below
│ │ │ │  for more information about the <code class="inline">utf</code> types.</p></li><li><p><strong><code class="inline">Signedness</code>= <code class="inline">signed</code> | <code class="inline">unsigned</code></strong> - Only matters for matching and when
│ │ │ │  the type is <code class="inline">integer</code>. The default is <code class="inline">unsigned</code>.</p></li><li><p><strong><code class="inline">Endianness</code>= <code class="inline">big</code> | <code class="inline">little</code> | <code class="inline">native</code></strong> - Specifies byte level (octet
│ │ │ │  level) endianness (byte order). Native-endian means that the endianness is
│ │ │ │  resolved at load time to be either big-endian or little-endian, depending on
│ │ │ │  what is native for the CPU that the Erlang machine is run on. Endianness only
│ │ │ │  matters when the <strong>Type</strong> is either <code class="inline">integer</code>, <code class="inline">utf16</code>, <code class="inline">utf32</code>, or <code class="inline">float</code>. The
│ │ │ │ -default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9115542428-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="9115542428-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9115542428-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9115542428-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9115542428-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9115542428-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │ │ +default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2340360528-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="2340360528-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2340360528-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2340360528-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2340360528-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2340360528-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │ │  Defaults to 1 for <code class="inline">integer</code>, <code class="inline">float</code>, and <code class="inline">bitstring</code>, and to 8 for <code class="inline">binary</code>.
│ │ │ │  For types <code class="inline">bitstring</code>, <code class="inline">bits</code>, and <code class="inline">bytes</code>, it is not allowed to specify a
│ │ │ │  unit value different from the default value. No unit specifier must be given
│ │ │ │  for the types <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code>.</p></li></ul><h3 id="integer-segments" class="section-heading">
│ │ │ │    <a href="#integer-segments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -755,41 +755,41 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Binary segments</span>
│ │ │ │  </h3>
│ │ │ │  <p>In this section, the phrase &quot;binary segment&quot; refers to any one of the segment
│ │ │ │  types <code class="inline">binary</code>, <code class="inline">bitstring</code>, <code class="inline">bytes</code>, and <code class="inline">bits</code>.</p><p>See also the paragraphs about <a href="expressions.xhtml#binaries">Binaries</a>.</p><p>When constructing binaries and no size is specified for a binary segment, the
│ │ │ │  entire binary value is interpolated into the binary being constructed. However,
│ │ │ │  the size in bits of the binary being interpolated must be evenly divisible by
│ │ │ │ -the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7752971676-1">&lt;&lt;</span><span class="p" data-group-id="7752971676-2">(</span><span class="p" data-group-id="7752971676-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7752971676-3">&gt;&gt;</span><span class="p" data-group-id="7752971676-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="7752971676-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7752971676-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7752971676-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="7752971676-5">&lt;&lt;</span><span class="p" data-group-id="7752971676-6">(</span><span class="p" data-group-id="7752971676-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7752971676-7">&gt;&gt;</span><span class="p" data-group-id="7752971676-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7752971676-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7752971676-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7752971676-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="p" data-group-id="7752971676-9">&lt;&lt;</span><span class="p" data-group-id="7752971676-10">(</span><span class="p" data-group-id="7752971676-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7752971676-11">&gt;&gt;</span><span class="p" data-group-id="7752971676-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7752971676-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7752971676-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7752971676-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │ │ +the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8983116599-1">&lt;&lt;</span><span class="p" data-group-id="8983116599-2">(</span><span class="p" data-group-id="8983116599-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8983116599-3">&gt;&gt;</span><span class="p" data-group-id="8983116599-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="8983116599-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8983116599-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8983116599-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="8983116599-5">&lt;&lt;</span><span class="p" data-group-id="8983116599-6">(</span><span class="p" data-group-id="8983116599-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8983116599-7">&gt;&gt;</span><span class="p" data-group-id="8983116599-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8983116599-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8983116599-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8983116599-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="p" data-group-id="8983116599-9">&lt;&lt;</span><span class="p" data-group-id="8983116599-10">(</span><span class="p" data-group-id="8983116599-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8983116599-11">&gt;&gt;</span><span class="p" data-group-id="8983116599-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8983116599-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8983116599-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8983116599-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │ │  segment has a unit value of 8.</p><p>Attempting to interpolate a bit string of size 1 into a binary segment with unit
│ │ │ │ -8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2594722766-1">&lt;&lt;</span><span class="p" data-group-id="2594722766-2">(</span><span class="p" data-group-id="2594722766-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2594722766-3">&gt;&gt;</span><span class="p" data-group-id="2594722766-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2594722766-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1004526813-1">&lt;&lt;</span><span class="p" data-group-id="1004526813-2">(</span><span class="p" data-group-id="1004526813-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1004526813-3">&gt;&gt;</span><span class="p" data-group-id="1004526813-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1004526813-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1004526813-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1004526813-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="p" data-group-id="1004526813-5">&lt;&lt;</span><span class="p" data-group-id="1004526813-6">(</span><span class="p" data-group-id="1004526813-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1004526813-7">&gt;&gt;</span><span class="p" data-group-id="1004526813-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1004526813-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1004526813-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1004526813-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │ │ +8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2548116487-1">&lt;&lt;</span><span class="p" data-group-id="2548116487-2">(</span><span class="p" data-group-id="2548116487-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2548116487-3">&gt;&gt;</span><span class="p" data-group-id="2548116487-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2548116487-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="7978988163-1">&lt;&lt;</span><span class="p" data-group-id="7978988163-2">(</span><span class="p" data-group-id="7978988163-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7978988163-3">&gt;&gt;</span><span class="p" data-group-id="7978988163-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="7978988163-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7978988163-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7978988163-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="p" data-group-id="7978988163-5">&lt;&lt;</span><span class="p" data-group-id="7978988163-6">(</span><span class="p" data-group-id="7978988163-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7978988163-7">&gt;&gt;</span><span class="p" data-group-id="7978988163-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7978988163-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7978988163-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7978988163-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │ │  succeeds if and only if the size in bits of the rest of the binary is evenly
│ │ │ │ -divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9006973580-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9006973580-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9006973580-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="9006973580-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9006973580-3">&lt;&lt;</span><span class="p" data-group-id="9006973580-3">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="9006973580-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9006973580-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9006973580-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="9006973580-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5943334968-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5943334968-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5943334968-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="5943334968-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5943334968-3">&lt;&lt;</span><span class="p" data-group-id="5943334968-3">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="5943334968-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5943334968-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5943334968-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="5943334968-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;a&quot;&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="p" data-group-id="9006973580-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9006973580-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9006973580-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="9006973580-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9006973580-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="9006973580-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="p" data-group-id="9006973580-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9006973580-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9006973580-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="9006973580-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="p" data-group-id="5943334968-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5943334968-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5943334968-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="5943334968-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5943334968-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="5943334968-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +4&gt; </span><span class="p" data-group-id="5943334968-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5943334968-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5943334968-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5943334968-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;abc&quot;&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="p" data-group-id="9006973580-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9006973580-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9006973580-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="9006973580-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9006973580-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="9006973580-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │ │ +5&gt; </span><span class="p" data-group-id="5943334968-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5943334968-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5943334968-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="5943334968-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5943334968-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="5943334968-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │ │  bits is the value of <code class="inline">Size</code> multiplied by the default or explicit unit value.</p><p>When constructing binaries, the size of the binary being interpolated into the
│ │ │ │ -constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3724002592-1">&lt;&lt;</span><span class="p" data-group-id="3724002592-2">(</span><span class="p" data-group-id="3724002592-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3724002592-3">&gt;&gt;</span><span class="p" data-group-id="3724002592-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3724002592-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3724002592-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="3724002592-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="3724002592-5">&lt;&lt;</span><span class="p" data-group-id="3724002592-6">(</span><span class="p" data-group-id="3724002592-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="3724002592-7">&gt;&gt;</span><span class="p" data-group-id="3724002592-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3724002592-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8070985794-1">&lt;&lt;</span><span class="p" data-group-id="8070985794-2">(</span><span class="p" data-group-id="8070985794-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8070985794-3">&gt;&gt;</span><span class="p" data-group-id="8070985794-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8070985794-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8070985794-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="8070985794-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="8070985794-5">&lt;&lt;</span><span class="p" data-group-id="8070985794-6">(</span><span class="p" data-group-id="8070985794-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="8070985794-7">&gt;&gt;</span><span class="p" data-group-id="8070985794-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8070985794-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: construction of binary failed
│ │ │ │          *** segment 1 of type &#39;binary&#39;: the value &lt;&lt;&quot;a&quot;&gt;&gt; is shorter than the size of the segment</span></code></pre><h3 id="unicode-segments" class="section-heading">
│ │ │ │    <a href="#unicode-segments" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Unicode segments</span>
│ │ │ │  </h3>
│ │ │ │ @@ -805,78 +805,78 @@
│ │ │ │  range <code class="inline">0</code> through <code class="inline">16#D7FF</code> or <code class="inline">16#E000</code> through <code class="inline">16#10FFFF</code>. The match fails if the
│ │ │ │  returned value falls outside those ranges.</p><p>A segment of type <code class="inline">utf8</code> matches 1-4 bytes in the bit string, if the bit string
│ │ │ │  at the match position contains a valid UTF-8 sequence. (See RFC-3629 or the
│ │ │ │  Unicode standard.)</p><p>A segment of type <code class="inline">utf16</code> can match 2 or 4 bytes in the bit string. The match
│ │ │ │  fails if the bit string at the match position does not contain a legal UTF-16
│ │ │ │  encoding of a Unicode code point. (See RFC-2781 or the Unicode standard.)</p><p>A segment of type <code class="inline">utf32</code> can match 4 bytes in the bit string in the same way as
│ │ │ │  an <code class="inline">integer</code> segment matches 32 bits. The match fails if the resulting integer
│ │ │ │ -is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5236026333-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="5236026333-4">&gt;&gt;</span><span class="w">
│ │ │ │ +is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2391003541-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="2391003541-4">&gt;&gt;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5236026333-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="p" data-group-id="5236026333-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5236026333-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5236026333-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-9">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2391003541-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +4&gt; </span><span class="p" data-group-id="2391003541-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2391003541-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2391003541-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-9">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │  5&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="p" data-group-id="5236026333-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="5236026333-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5236026333-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-12">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +6&gt; </span><span class="p" data-group-id="2391003541-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="2391003541-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2391003541-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-12">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │  7&gt; </span><span class="n">D</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">273</span><span class="gp unselectable">
│ │ │ │  8&gt; </span><span class="n">F</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ │ -9&gt; </span><span class="p" data-group-id="5236026333-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5236026333-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5236026333-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-15">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +9&gt; </span><span class="p" data-group-id="2391003541-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2391003541-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2391003541-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-15">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │  10&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="5236026333-16">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -11&gt; </span><span class="p" data-group-id="5236026333-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="5236026333-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="5236026333-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="5236026333-19">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="2391003541-16">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +11&gt; </span><span class="p" data-group-id="2391003541-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="2391003541-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="2391003541-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="2391003541-19">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │  12&gt; </span><span class="n">J</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="5236026333-20">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="2391003541-20">&gt;&gt;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="5236026333-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="5236026333-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="5236026333-22">&gt;&gt;</span><span class="w">
│ │ │ │ +</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="2391003541-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="2391003541-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="2391003541-22">&gt;&gt;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="5236026333-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="5236026333-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="5236026333-24">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -15&gt; </span><span class="p" data-group-id="5236026333-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="5236026333-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="5236026333-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5236026333-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="5236026333-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5236026333-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="5236026333-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │ │ +</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="2391003541-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="2391003541-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="2391003541-24">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +15&gt; </span><span class="p" data-group-id="2391003541-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="2391003541-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="2391003541-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2391003541-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="2391003541-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2391003541-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="2391003541-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │ │  error. The correct way is to write a space after <code class="inline">=</code>: &quot;<code class="inline">B = &lt;&lt;1&gt;&gt;</code>.</p><p>More examples are provided in <a href="../../../lib/../system/doc/html/bit_syntax.xhtml">Programming Examples</a>.</p><h2 id="fun-expressions" class="section-heading">
│ │ │ │    <a href="#fun-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Fun Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3560810740-1">[</span><span class="n">Name</span><span class="p" data-group-id="3560810740-1">]</span><span class="p" data-group-id="3560810740-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="3560810740-2">)</span><span class="w"> </span><span class="p" data-group-id="3560810740-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="3560810740-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6083491123-1">[</span><span class="n">Name</span><span class="p" data-group-id="6083491123-1">]</span><span class="p" data-group-id="6083491123-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="6083491123-2">)</span><span class="w"> </span><span class="p" data-group-id="6083491123-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="6083491123-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3560810740-4">[</span><span class="n">Name</span><span class="p" data-group-id="3560810740-4">]</span><span class="p" data-group-id="3560810740-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="3560810740-5">)</span><span class="w"> </span><span class="p" data-group-id="3560810740-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="3560810740-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6083491123-4">[</span><span class="n">Name</span><span class="p" data-group-id="6083491123-4">]</span><span class="p" data-group-id="6083491123-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="6083491123-5">)</span><span class="w"> </span><span class="p" data-group-id="6083491123-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="6083491123-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                </span><span class="n">BodyK</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>A fun expression begins with the keyword <code class="inline">fun</code> and ends with the keyword <code class="inline">end</code>.
│ │ │ │  Between them is to be a function declaration, similar to a
│ │ │ │  <a href="ref_man_functions.xhtml#function-declaration-syntax">regular function declaration</a>,
│ │ │ │  except that the function name is optional and is to be a variable, if any.</p><p>Variables in a fun head shadow the function name and both shadow variables in
│ │ │ │  the function clause surrounding the fun expression. Variables bound in a fun
│ │ │ │ -body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2087804153-1">(</span><span class="n">X</span><span class="p" data-group-id="2087804153-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8572690861-1">(</span><span class="n">X</span><span class="p" data-group-id="8572690861-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="2087804153-2">(</span><span class="mi">2</span><span class="p" data-group-id="2087804153-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="8572690861-2">(</span><span class="mi">2</span><span class="p" data-group-id="8572690861-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2087804153-3">(</span><span class="n">X</span><span class="p" data-group-id="2087804153-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="2087804153-4">(</span><span class="n">X</span><span class="p" data-group-id="2087804153-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8572690861-3">(</span><span class="n">X</span><span class="p" data-group-id="8572690861-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="8572690861-4">(</span><span class="n">X</span><span class="p" data-group-id="8572690861-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="2087804153-5">(</span><span class="mi">7</span><span class="p" data-group-id="2087804153-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="8572690861-5">(</span><span class="mi">7</span><span class="p" data-group-id="8572690861-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">gt</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="2087804153-6">(</span><span class="mi">1</span><span class="p" data-group-id="2087804153-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="2087804153-7">(</span><span class="n">X</span><span class="p" data-group-id="2087804153-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="2087804153-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2087804153-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="8572690861-6">(</span><span class="mi">1</span><span class="p" data-group-id="8572690861-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="8572690861-7">(</span><span class="n">X</span><span class="p" data-group-id="8572690861-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="8572690861-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8572690861-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="2087804153-9">(</span><span class="mi">4</span><span class="p" data-group-id="2087804153-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="8572690861-9">(</span><span class="mi">4</span><span class="p" data-group-id="8572690861-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">24</span></code></pre><p>The following fun expressions are also allowed:</p><pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w"> </span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span><span class="w">
│ │ │ │  </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In <code class="inline">Name/Arity</code>, <code class="inline">Name</code> is an atom and <code class="inline">Arity</code> is an integer. <code class="inline">Name/Arity</code> must
│ │ │ │ -specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0548134855-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="0548134855-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0548134855-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="0548134855-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code>, and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │ │ +specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9220058545-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="9220058545-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9220058545-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="9220058545-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code>, and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │ │  integer. <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> can also be variables. A fun defined in
│ │ │ │  this way refers to the function <code class="inline">Name</code> with arity <code class="inline">Arity</code> in the <em>latest</em>
│ │ │ │  version of module <code class="inline">Module</code>. A fun defined in this way is not dependent on the
│ │ │ │  code for the module in which it is defined.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R15, <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> were not allowed to be
│ │ │ │  variables.</p></section><p>More examples are provided in <a href="../../../lib/../system/doc/html/funs.xhtml">Programming Examples</a>.</p><h2 id="catch-and-throw" class="section-heading">
│ │ │ │    <a href="#catch-and-throw" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -886,35 +886,35 @@
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">catch</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>Returns the value of <code class="inline">Expr</code> unless an exception is raised during the evaluation. In
│ │ │ │  that case, the exception is caught. The return value depends on the class of the
│ │ │ │  exception:</p><ul><li><p><strong><code class="inline">error</code></strong> (a run-time error or the code called <a href="../../../lib/../erts/doc/html/erlang.html#error/1"><code class="inline">error(Term)</code></a>) -
│ │ │ │  <code class="inline">{'EXIT',{Reason,Stack}}</code> is returned.</p></li><li><p><strong><code class="inline">exit</code></strong> (the code called <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(Term)</code></a>) - <code class="inline">{'EXIT',Term}</code> is returned.</p></li><li><p><strong><code class="inline">throw</code></strong> (the code called <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw(Term)</code></a>): <code class="inline">Term</code> is returned.</p></li></ul><p><code class="inline">Reason</code> depends on the type of error that occurred, and <code class="inline">Stack</code> is the stack of
│ │ │ │  recent function calls, see <a href="errors.xhtml#exit_reasons">Exit Reasons</a>.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3929596132-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="3929596132-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="3929596132-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3929596132-3">]</span><span class="p" data-group-id="3929596132-2">}</span><span class="p" data-group-id="3929596132-1">}</span></code></pre><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ │ -function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="6618429742-1">(</span><span class="ss">hello</span><span class="p" data-group-id="6618429742-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6129946053-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6129946053-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="6129946053-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6129946053-3">]</span><span class="p" data-group-id="6129946053-2">}</span><span class="p" data-group-id="6129946053-1">}</span></code></pre><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ │ +function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="9903039477-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9903039477-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span></code></pre><p>If <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> is not evaluated within a catch, a <code class="inline">nocatch</code> run-time
│ │ │ │  error occurs.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 24, the <code class="inline">catch</code> operator had the lowest precedence, making
│ │ │ │ -it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4331421477-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="4331421477-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0658076978-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="0658076978-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span></code></pre><p>Starting from Erlang/OTP 24, the parentheses can be omitted:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">42</span></code></pre></section><h2 id="try" class="section-heading">
│ │ │ │    <a href="#try" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Try</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="7664067797-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7664067797-1">]</span><span class="w"> </span><span class="p" data-group-id="7664067797-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="7664067797-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="9457398741-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9457398741-1">]</span><span class="w"> </span><span class="p" data-group-id="9457398741-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="9457398741-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="7664067797-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7664067797-3">]</span><span class="w"> </span><span class="p" data-group-id="7664067797-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="7664067797-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="9457398741-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9457398741-3">]</span><span class="w"> </span><span class="p" data-group-id="9457398741-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="9457398741-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>This is an enhancement of <a href="expressions.xhtml#catch-and-throw">catch</a>. It gives the
│ │ │ │  possibility to:</p><ul><li>Distinguish between different exception classes.</li><li>Choose to handle only the desired ones.</li><li>Passing the others on to an enclosing <code class="inline">try</code> or <code class="inline">catch</code>, or to default error
│ │ │ │  handling.</li></ul><p>Notice that although the keyword <code class="inline">catch</code> is used in the <code class="inline">try</code> expression, there
│ │ │ │  is not a <code class="inline">catch</code> expression within the <code class="inline">try</code> expression.</p><p>It returns the value of <code class="inline">Exprs</code> (a sequence of expressions <code class="inline">Expr1, ..., ExprN</code>)
│ │ │ │  unless an exception occurs during the evaluation. In that case the exception is
│ │ │ │  caught and the patterns <code class="inline">ExceptionPattern</code> with the right exception class
│ │ │ │ @@ -924,47 +924,47 @@
│ │ │ │  stack trace is bound to the variable when the corresponding <code class="inline">ExceptionPattern</code>
│ │ │ │  matches.</p><p>If an exception occurs during evaluation of <code class="inline">Exprs</code> but there is no matching
│ │ │ │  <code class="inline">ExceptionPattern</code> of the right <code class="inline">Class</code> with a true guard sequence, the
│ │ │ │  exception is passed on as if <code class="inline">Exprs</code> had not been enclosed in a <code class="inline">try</code>
│ │ │ │  expression.</p><p>If an exception occurs during evaluation of <code class="inline">ExceptionBody</code>, it is not caught.</p><p>It is allowed to omit <code class="inline">Class</code> and <code class="inline">Stacktrace</code>. An omitted <code class="inline">Class</code> is shorthand
│ │ │ │  for <code class="inline">throw</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="8618265451-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="8618265451-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="3428894489-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="3428894489-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="8618265451-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="8618265451-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="3428894489-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="3428894489-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">try</code> expression can have an <code class="inline">of</code> section:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="8098906545-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="8098906545-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2392636177-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2392636177-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="8098906545-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="8098906545-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2392636177-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2392636177-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="8098906545-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="8098906545-3">]</span><span class="w"> </span><span class="p" data-group-id="8098906545-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="8098906545-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="2392636177-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2392636177-3">]</span><span class="w"> </span><span class="p" data-group-id="2392636177-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="2392636177-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="8098906545-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="8098906545-5">]</span><span class="w"> </span><span class="p" data-group-id="8098906545-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="8098906545-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="2392636177-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2392636177-5">]</span><span class="w"> </span><span class="p" data-group-id="2392636177-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="2392636177-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>If the evaluation of <code class="inline">Exprs</code> succeeds without an exception, the patterns
│ │ │ │  <code class="inline">Pattern</code> are sequentially matched against the result in the same way as for a
│ │ │ │  <a href="expressions.xhtml#case">case</a> expression, except that if the matching fails, a
│ │ │ │  <code class="inline">try_clause</code> run-time error occurs instead of a <code class="inline">case_clause</code>.</p><p>Only exceptions occurring during the evaluation of <code class="inline">Exprs</code> can be caught by the
│ │ │ │  <code class="inline">catch</code> section. Exceptions occurring in a <code class="inline">Body</code> or due to a failed match are
│ │ │ │  not caught.</p><p>The <code class="inline">try</code> expression can also be augmented with an <code class="inline">after</code> section, intended to
│ │ │ │  be used for cleanup with side effects:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="7395589902-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="7395589902-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4888556569-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4888556569-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="7395589902-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="7395589902-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4888556569-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4888556569-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="7395589902-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7395589902-3">]</span><span class="w"> </span><span class="p" data-group-id="7395589902-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="7395589902-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="4888556569-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4888556569-3">]</span><span class="w"> </span><span class="p" data-group-id="4888556569-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="4888556569-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="7395589902-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="7395589902-5">]</span><span class="w"> </span><span class="p" data-group-id="7395589902-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="7395589902-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="4888556569-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4888556569-5">]</span><span class="w"> </span><span class="p" data-group-id="4888556569-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="4888556569-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">AfterBody</code> is evaluated after either <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>, no matter which
│ │ │ │  one. The evaluated value of <code class="inline">AfterBody</code> is lost; the return value of the <code class="inline">try</code>
│ │ │ │  expression is the same with an <code class="inline">after</code> section as without.</p><p>Even if an exception occurs during evaluation of <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>,
│ │ │ │  <code class="inline">AfterBody</code> is evaluated. In this case the exception is passed on after
│ │ │ │ @@ -987,40 +987,40 @@
│ │ │ │          </span><span class="n">ExpressionBody</span><span class="w">
│ │ │ │  </span><span class="k">after</span><span class="w">
│ │ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">AfterBody</span><span class="w"> </span><span class="k">end</span></code></pre><p>Next is an example of using <code class="inline">after</code>. This closes the file, even in the event of
│ │ │ │  exceptions in <a href="../../../lib/kernel/doc/html/file.html#read/2"><code class="inline">file:read/2</code></a> or in <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. The
│ │ │ │ -exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="1074460400-1">(</span><span class="n">Name</span><span class="p" data-group-id="1074460400-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1074460400-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="1074460400-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1074460400-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1074460400-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="1074460400-4">]</span><span class="p" data-group-id="1074460400-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="9850330096-1">(</span><span class="n">Name</span><span class="p" data-group-id="9850330096-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9850330096-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="9850330096-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9850330096-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9850330096-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="9850330096-4">]</span><span class="p" data-group-id="9850330096-3">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">try</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1074460400-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="1074460400-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="1074460400-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="1074460400-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1074460400-7">(</span><span class="n">Bin</span><span class="p" data-group-id="1074460400-7">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9850330096-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="9850330096-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9850330096-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="9850330096-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9850330096-7">(</span><span class="n">Bin</span><span class="p" data-group-id="9850330096-7">)</span><span class="w">
│ │ │ │      </span><span class="k">after</span><span class="w">
│ │ │ │ -        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1074460400-8">(</span><span class="n">F</span><span class="p" data-group-id="1074460400-8">)</span><span class="w">
│ │ │ │ +        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9850330096-8">(</span><span class="n">F</span><span class="p" data-group-id="9850330096-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Next is an example of using <code class="inline">try</code> to emulate <code class="inline">catch Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Expr</span><span class="w">
│ │ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ │      </span><span class="nc">throw</span><span class="p">:</span><span class="n">Term</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Term</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8457225195-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="8457225195-1">}</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8457225195-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="8457225195-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="8457225195-3">}</span><span class="p" data-group-id="8457225195-2">}</span><span class="w">
│ │ │ │ +    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2701810312-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="2701810312-1">}</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2701810312-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="2701810312-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="2701810312-3">}</span><span class="p" data-group-id="2701810312-2">}</span><span class="w">
│ │ │ │  </span><span class="k">end</span></code></pre><p>Variables bound in the various parts of these expressions have different scopes.
│ │ │ │  Variables bound just after the <code class="inline">try</code> keyword are:</p><ul><li>bound in the <code class="inline">of</code> section</li><li>unsafe in both the <code class="inline">catch</code> and <code class="inline">after</code> sections, as well as after the whole
│ │ │ │  construct</li></ul><p>Variables bound in <code class="inline">of</code> section are:</p><ul><li>unbound in the <code class="inline">catch</code> section</li><li>unsafe in both the <code class="inline">after</code> section, as well as after the whole construct</li></ul><p>Variables bound in the <code class="inline">catch</code> section are unsafe in the <code class="inline">after</code> section, as
│ │ │ │  well as after the whole construct.</p><p>Variables bound in the <code class="inline">after</code> section are unsafe after the whole construct.</p><h2 id="parenthesized-expressions" class="section-heading">
│ │ │ │    <a href="#parenthesized-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Parenthesized Expressions</span>
│ │ │ │  </h2>
│ │ │ │ -<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7628687234-1">(</span><span class="n">Expr</span><span class="p" data-group-id="7628687234-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │ │ +<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9500452104-1">(</span><span class="n">Expr</span><span class="p" data-group-id="9500452104-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │ │  <a href="expressions.xhtml#prec">operator precedences</a>, for example, in arithmetic
│ │ │ │  expressions:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">7</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="1362589814-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1362589814-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="8443374229-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8443374229-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">9</span></code></pre><h2 id="block-expressions" class="section-heading">
│ │ │ │    <a href="#block-expressions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Block Expressions</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">begin</span><span class="w">
│ │ │ │ @@ -1032,71 +1032,71 @@
│ │ │ │    <a href="#comprehensions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Comprehensions</span>
│ │ │ │  </h2>
│ │ │ │  <p>Comprehensions provide a succinct notation for iterating over one or more terms
│ │ │ │  and constructing a new term. Comprehensions come in three different flavors,
│ │ │ │ -depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6995299293-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="6995299293-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │ │ +depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5228532666-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="5228532666-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │ │  <strong>generator</strong> or a <strong>filter</strong>.</p><p>Bit string comprehensions construct bit strings or binaries. They have the
│ │ │ │ -following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8668043592-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="8668043592-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │ │ +following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2038181169-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="2038181169-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │ │  <code class="inline">BitStringExpr</code> is a function call, it must be enclosed in parentheses. Each
│ │ │ │ -<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8248000010-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="8248000010-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │ │ +<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7500427719-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="7500427719-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │ │  is either a <strong>generator</strong> or a <strong>filter</strong>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Map comprehensions and map generators were introduced in Erlang/OTP 26.</p></section><p>There are three kinds of generators.</p><p>A <em>list generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListExpr</span></code></pre><p>where <code class="inline">ListExpr</code> is an expression that evaluates to a list of terms.</p><p>A <em>bit string generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">BitstringPattern</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">BitStringExpr</span></code></pre><p>where <code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string.</p><p>A <em>map generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">KeyPattern</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">ValuePattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">MapExpression</span></code></pre><p>where <code class="inline">MapExpr</code> is an expression that evaluates to a map, or a map iterator
│ │ │ │  obtained by calling <a href="../../../lib/stdlib/doc/html/maps.html#iterator/1"><code class="inline">maps:iterator/1</code></a> or <a href="../../../lib/stdlib/doc/html/maps.html#iterator/2"><code class="inline">maps:iterator/2</code></a>.</p><p>A <em>filter</em> is an expression that evaluates to <code class="inline">true</code> or <code class="inline">false</code>.</p><p>The variables in the generator patterns shadow previously bound variables,
│ │ │ │  including variables bound in a previous generator pattern.</p><p>Variables bound in a generator expression are not visible outside the
│ │ │ │ -expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0380169614-1">[</span><span class="p" data-group-id="0380169614-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="0380169614-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="0380169614-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0380169614-3">]</span><span class="p" data-group-id="0380169614-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6874910685-1">[</span><span class="p" data-group-id="6874910685-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="6874910685-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="6874910685-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6874910685-3">]</span><span class="p" data-group-id="6874910685-1">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">* 1:5: variable &#39;L&#39; is unbound</span></code></pre><p>A <strong>list comprehension</strong> returns a list, where the list elements are the result
│ │ │ │  of evaluating <code class="inline">Expr</code> for each combination of generator elements for which all
│ │ │ │  filters are true.</p><p>A <strong>bit string comprehension</strong> returns a bit string, which is created by
│ │ │ │  concatenating the results of evaluating <code class="inline">BitStringExpr</code> for each combination of
│ │ │ │  bit string generator elements for which all filters are true.</p><p>A <strong>map comprehension</strong> returns a map, where the map elements are the result of
│ │ │ │  evaluating <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> for each combination of generator elements
│ │ │ │  for which all filters are true. If the key expressions are not unique, the last
│ │ │ │ -occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3670201774-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="3670201774-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3670201774-2">]</span><span class="p" data-group-id="3670201774-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3670201774-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3670201774-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8341226561-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="8341226561-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="8341226561-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="8341226561-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8341226561-3">&gt;&gt;</span><span class="p" data-group-id="8341226561-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8341226561-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8341226561-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7536276529-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="7536276529-2">&lt;&lt;</span><span class="p" data-group-id="7536276529-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="7536276529-3">)</span><span class="p" data-group-id="7536276529-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7536276529-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="7536276529-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="7536276529-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7536276529-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="7536276529-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7536276529-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7536276529-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6889798332-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="6889798332-2">&lt;&lt;</span><span class="p" data-group-id="6889798332-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="6889798332-3">)</span><span class="p" data-group-id="6889798332-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="6889798332-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6889798332-4">]</span><span class="w"> </span><span class="p" data-group-id="6889798332-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6889798332-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6889798332-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7202874831-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7202874831-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7202874831-2">]</span><span class="p" data-group-id="7202874831-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7202874831-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7202874831-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3755039693-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="3755039693-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3755039693-2">}</span><span class="p" data-group-id="3755039693-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3755039693-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="3755039693-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2497905973-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="2497905973-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2497905973-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2497905973-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2497905973-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2497905973-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5623055839-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="5623055839-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5623055839-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5623055839-3">[</span><span class="p" data-group-id="5623055839-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5623055839-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5623055839-5">[</span><span class="ss">a</span><span class="p" data-group-id="5623055839-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5623055839-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="5623055839-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5623055839-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5623055839-7">}</span><span class="p" data-group-id="5623055839-3">]</span><span class="p" data-group-id="5623055839-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5623055839-8">[</span><span class="p" data-group-id="5623055839-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5623055839-9">}</span><span class="p">,</span><span class="p" data-group-id="5623055839-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5623055839-10">}</span><span class="p" data-group-id="5623055839-8">]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8470057194-1">[</span><span class="p" data-group-id="8470057194-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="8470057194-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="8470057194-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8470057194-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="8470057194-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8470057194-4">]</span><span class="p" data-group-id="8470057194-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8470057194-5">[</span><span class="p" data-group-id="8470057194-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8470057194-6">}</span><span class="p">,</span><span class="p" data-group-id="8470057194-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8470057194-7">}</span><span class="p">,</span><span class="p" data-group-id="8470057194-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8470057194-8">}</span><span class="p">,</span><span class="p" data-group-id="8470057194-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8470057194-9">}</span><span class="p">,</span><span class="p" data-group-id="8470057194-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8470057194-10">}</span><span class="p">,</span><span class="p" data-group-id="8470057194-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8470057194-11">}</span><span class="p" data-group-id="8470057194-5">]</span></code></pre><p>More examples are provided in
│ │ │ │ +occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8884193087-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="8884193087-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8884193087-2">]</span><span class="p" data-group-id="8884193087-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8884193087-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8884193087-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9573539684-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9573539684-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="9573539684-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="9573539684-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9573539684-3">&gt;&gt;</span><span class="p" data-group-id="9573539684-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9573539684-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9573539684-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9821406233-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="9821406233-2">&lt;&lt;</span><span class="p" data-group-id="9821406233-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="9821406233-3">)</span><span class="p" data-group-id="9821406233-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9821406233-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="9821406233-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="9821406233-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9821406233-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="9821406233-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9821406233-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9821406233-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0345700341-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="0345700341-2">&lt;&lt;</span><span class="p" data-group-id="0345700341-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="0345700341-3">)</span><span class="p" data-group-id="0345700341-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0345700341-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0345700341-4">]</span><span class="w"> </span><span class="p" data-group-id="0345700341-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0345700341-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0345700341-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1443676901-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1443676901-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1443676901-2">]</span><span class="p" data-group-id="1443676901-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1443676901-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1443676901-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0284558053-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0284558053-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0284558053-2">}</span><span class="p" data-group-id="0284558053-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0284558053-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="0284558053-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7731146910-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7731146910-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7731146910-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7731146910-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7731146910-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7731146910-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9666310988-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9666310988-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9666310988-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9666310988-3">[</span><span class="p" data-group-id="9666310988-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9666310988-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9666310988-5">[</span><span class="ss">a</span><span class="p" data-group-id="9666310988-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9666310988-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9666310988-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9666310988-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9666310988-7">}</span><span class="p" data-group-id="9666310988-3">]</span><span class="p" data-group-id="9666310988-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9666310988-8">[</span><span class="p" data-group-id="9666310988-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9666310988-9">}</span><span class="p">,</span><span class="p" data-group-id="9666310988-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9666310988-10">}</span><span class="p" data-group-id="9666310988-8">]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8818940171-1">[</span><span class="p" data-group-id="8818940171-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="8818940171-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="8818940171-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8818940171-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="8818940171-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8818940171-4">]</span><span class="p" data-group-id="8818940171-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8818940171-5">[</span><span class="p" data-group-id="8818940171-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8818940171-6">}</span><span class="p">,</span><span class="p" data-group-id="8818940171-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8818940171-7">}</span><span class="p">,</span><span class="p" data-group-id="8818940171-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8818940171-8">}</span><span class="p">,</span><span class="p" data-group-id="8818940171-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8818940171-9">}</span><span class="p">,</span><span class="p" data-group-id="8818940171-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8818940171-10">}</span><span class="p">,</span><span class="p" data-group-id="8818940171-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8818940171-11">}</span><span class="p" data-group-id="8818940171-5">]</span></code></pre><p>More examples are provided in
│ │ │ │  <a href="../../../lib/../system/doc/html/list_comprehensions.xhtml">Programming Examples.</a></p><p>When there are no generators, a comprehension returns either a term constructed
│ │ │ │  from a single element (the result of evaluating <code class="inline">Expr</code>) if all filters are true,
│ │ │ │  or a term constructed from no elements (that is, <code class="inline">[]</code> for list comprehension,
│ │ │ │ -<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4163873377-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4163873377-2">(</span><span class="mi">2</span><span class="p" data-group-id="4163873377-2">)</span><span class="p" data-group-id="4163873377-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4163873377-3">[</span><span class="mi">2</span><span class="p" data-group-id="4163873377-3">]</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="4163873377-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4163873377-5">(</span><span class="ss">x</span><span class="p" data-group-id="4163873377-5">)</span><span class="p" data-group-id="4163873377-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4163873377-6">[</span><span class="p" data-group-id="4163873377-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │ │ +<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5582602024-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="5582602024-2">(</span><span class="mi">2</span><span class="p" data-group-id="5582602024-2">)</span><span class="p" data-group-id="5582602024-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5582602024-3">[</span><span class="mi">2</span><span class="p" data-group-id="5582602024-3">]</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="5582602024-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="5582602024-5">(</span><span class="ss">x</span><span class="p" data-group-id="5582602024-5">)</span><span class="p" data-group-id="5582602024-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5582602024-6">[</span><span class="p" data-group-id="5582602024-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │ │  depends on the expression:</p><ul><li>If the expression is a <a href="expressions.xhtml#guard-expressions">guard expression</a>,
│ │ │ │  failure to evaluate or evaluating to a non-boolean value is equivalent to
│ │ │ │  evaluating to <code class="inline">false</code>.</li><li>If the expression is not a guard expression and evaluates to a non-Boolean
│ │ │ │  value <code class="inline">Val</code>, an exception <code class="inline">{bad_filter, Val}</code> is triggered at runtime. If the
│ │ │ │  evaluation of the expression raises an exception, it is not caught by the
│ │ │ │ -comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5883559360-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5883559360-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5883559360-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5883559360-2">]</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="5883559360-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5883559360-3">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5883559360-4">[</span><span class="p" data-group-id="5883559360-4">]</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="p" data-group-id="5883559360-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5883559360-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5883559360-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5883559360-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3756085040-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3756085040-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3756085040-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3756085040-2">]</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3756085040-3">(</span><span class="n">E</span><span class="p" data-group-id="3756085040-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7369486274-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7369486274-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7369486274-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7369486274-2">]</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="7369486274-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7369486274-3">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7369486274-4">[</span><span class="p" data-group-id="7369486274-4">]</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="p" data-group-id="7369486274-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7369486274-5">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7369486274-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7369486274-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7291917391-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7291917391-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7291917391-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7291917391-2">]</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7291917391-3">(</span><span class="n">E</span><span class="p" data-group-id="7291917391-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="p" data-group-id="3756085040-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="3756085040-5">(</span><span class="n">E</span><span class="p" data-group-id="3756085040-5">)</span><span class="p" data-group-id="3756085040-4">]</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="p" data-group-id="7291917391-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="7291917391-5">(</span><span class="n">E</span><span class="p" data-group-id="7291917391-5">)</span><span class="p" data-group-id="7291917391-4">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: bad filter 1</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3756085040-6">(</span><span class="n">E</span><span class="p" data-group-id="3756085040-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="7291917391-6">(</span><span class="n">E</span><span class="p" data-group-id="7291917391-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="p" data-group-id="3756085040-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="3756085040-8">(</span><span class="n">E</span><span class="p" data-group-id="3756085040-8">)</span><span class="p" data-group-id="3756085040-7">]</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="p" data-group-id="7291917391-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="7291917391-8">(</span><span class="n">E</span><span class="p" data-group-id="7291917391-8">)</span><span class="p" data-group-id="7291917391-7">]</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │ │       in operator  rem/2
│ │ │ │          called as a rem 2</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="p" data-group-id="3756085040-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="3756085040-10">(</span><span class="n">E</span><span class="p" data-group-id="3756085040-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="3756085040-11">(</span><span class="n">E</span><span class="p" data-group-id="3756085040-11">)</span><span class="p" data-group-id="3756085040-9">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3756085040-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3756085040-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │ │ +6&gt; </span><span class="p" data-group-id="7291917391-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7291917391-10">(</span><span class="n">E</span><span class="p" data-group-id="7291917391-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="7291917391-11">(</span><span class="n">E</span><span class="p" data-group-id="7291917391-11">)</span><span class="p" data-group-id="7291917391-9">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7291917391-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7291917391-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │ │    <a href="#guard-sequences" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Guard Sequences</span>
│ │ │ │  </h2>
│ │ │ │  <p>A <em>guard sequence</em> is a sequence of guards, separated by semicolon (<code class="inline">;</code>). The
│ │ │ │  guard sequence is true if at least one of the guards is true. (The remaining
│ │ │ ├── OEBPS/example.xhtml
│ │ │ │ @@ -36,14 +36,14 @@
│ │ │ │  
│ │ │ │  int bar(int y) {
│ │ │ │    return y*2;
│ │ │ │  }</code></pre><p>The functions are deliberately kept as simple as possible, for readability
│ │ │ │  reasons.</p><p>From an Erlang perspective, it is preferable to be able to call <code class="inline">foo</code> and <code class="inline">bar</code>
│ │ │ │  without having to bother about that they are C functions:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% Erlang code</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="2476812664-1">(</span><span class="n">X</span><span class="p" data-group-id="2476812664-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1041587162-1">(</span><span class="n">X</span><span class="p" data-group-id="1041587162-1">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Here, the communication with C is hidden in the implementation of <code class="inline">complex.erl</code>.
│ │ │ │  In the following sections, it is shown how this module can be implemented using
│ │ │ │  the different interoperability mechanisms.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/events.xhtml
│ │ │ │ @@ -40,43 +40,43 @@
│ │ │ │  event handler.</p><h2 id="example" class="section-heading">
│ │ │ │    <a href="#example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Example</span>
│ │ │ │  </h2>
│ │ │ │  <p>The callback module for the event handler writing error messages to the terminal
│ │ │ │ -can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3829887445-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="3829887445-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3829887445-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="3829887445-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7753846957-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="7753846957-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7753846957-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="7753846957-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3829887445-3">(</span><span class="p" data-group-id="3829887445-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3829887445-4">]</span><span class="p" data-group-id="3829887445-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7753846957-3">(</span><span class="p" data-group-id="7753846957-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7753846957-4">]</span><span class="p" data-group-id="7753846957-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3829887445-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="3829887445-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3829887445-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3829887445-7">[</span><span class="p" data-group-id="3829887445-7">]</span><span class="p" data-group-id="3829887445-6">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7753846957-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7753846957-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7753846957-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7753846957-7">[</span><span class="p" data-group-id="7753846957-7">]</span><span class="p" data-group-id="7753846957-6">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="3829887445-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3829887445-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3829887445-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3829887445-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="3829887445-10">]</span><span class="p" data-group-id="3829887445-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3829887445-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3829887445-11">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="7753846957-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7753846957-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7753846957-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7753846957-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="7753846957-10">]</span><span class="p" data-group-id="7753846957-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7753846957-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7753846957-11">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="3829887445-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="3829887445-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="7753846957-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="7753846957-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback module for the event handler writing error messages to a file can
│ │ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8480751627-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="8480751627-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8480751627-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="8480751627-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7875308412-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="7875308412-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7875308412-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="7875308412-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8480751627-3">(</span><span class="p" data-group-id="8480751627-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8480751627-4">]</span><span class="p" data-group-id="8480751627-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7875308412-3">(</span><span class="p" data-group-id="7875308412-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7875308412-4">]</span><span class="p" data-group-id="7875308412-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8480751627-5">(</span><span class="n">File</span><span class="p" data-group-id="8480751627-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8480751627-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8480751627-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="8480751627-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="8480751627-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8480751627-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8480751627-8">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="8480751627-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8480751627-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8480751627-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8480751627-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="8480751627-11">]</span><span class="p" data-group-id="8480751627-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8480751627-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8480751627-12">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7875308412-5">(</span><span class="n">File</span><span class="p" data-group-id="7875308412-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7875308412-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7875308412-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7875308412-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="7875308412-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7875308412-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7875308412-8">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="7875308412-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7875308412-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7875308412-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7875308412-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="7875308412-11">]</span><span class="p" data-group-id="7875308412-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7875308412-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7875308412-12">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="8480751627-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8480751627-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="8480751627-14">(</span><span class="n">Fd</span><span class="p" data-group-id="8480751627-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="7875308412-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7875308412-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7875308412-14">(</span><span class="n">Fd</span><span class="p" data-group-id="7875308412-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │ │    <a href="#starting-an-event-manager" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting an Event Manager</span>
│ │ │ │  </h2>
│ │ │ │  <p>To start an event manager for handling errors, as described in the previous
│ │ │ │  example, call the following function:</p><pre><code class="text">gen_event:start_link({local, error_man})</code></pre><p><a href="../../../lib/stdlib/doc/html/gen_event.html#start_link/1"><code class="inline">gen_event:start_link/1</code></a> spawns and links to a new event manager process.</p><p>The argument, <code class="inline">{local, error_man}</code>, specifies the name under which the
│ │ │ │ @@ -89,57 +89,57 @@
│ │ │ │  manager that is not part of a supervision tree.</p><h2 id="adding-an-event-handler" class="section-heading">
│ │ │ │    <a href="#adding-an-event-handler" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding an Event Handler</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following example shows how to start an event manager and add an event
│ │ │ │ -handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3490918899-1">(</span><span class="p" data-group-id="3490918899-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="3490918899-2">}</span><span class="p" data-group-id="3490918899-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3490918899-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3490918899-3">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="3490918899-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3490918899-5">[</span><span class="p" data-group-id="3490918899-5">]</span><span class="p" data-group-id="3490918899-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2809101278-1">(</span><span class="p" data-group-id="2809101278-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="2809101278-2">}</span><span class="p" data-group-id="2809101278-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2809101278-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="2809101278-3">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="2809101278-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2809101278-5">[</span><span class="p" data-group-id="2809101278-5">]</span><span class="p" data-group-id="2809101278-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │ │  telling it to add the event handler <code class="inline">terminal_logger</code>. The event manager calls
│ │ │ │  the callback function <code class="inline">terminal_logger:init([])</code>, where the argument <code class="inline">[]</code> is the
│ │ │ │  third argument to <code class="inline">add_handler</code>. <code class="inline">init/1</code> is expected to return <code class="inline">{ok, State}</code>,
│ │ │ │ -where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5849543104-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="5849543104-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5849543104-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5849543104-3">[</span><span class="p" data-group-id="5849543104-3">]</span><span class="p" data-group-id="5849543104-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │ │ +where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2514866579-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2514866579-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2514866579-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2514866579-3">[</span><span class="p" data-group-id="2514866579-3">]</span><span class="p" data-group-id="2514866579-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │ │  <code class="inline">terminal_logger</code>, the internal state is not used. For <code class="inline">file_logger</code>, the
│ │ │ │ -internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5187385239-1">(</span><span class="n">File</span><span class="p" data-group-id="5187385239-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5187385239-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5187385239-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5187385239-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="5187385239-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5187385239-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5187385239-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │ │ +internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4639849157-1">(</span><span class="n">File</span><span class="p" data-group-id="4639849157-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4639849157-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4639849157-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4639849157-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="4639849157-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4639849157-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4639849157-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │ │    <a href="#notifying-about-events" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Notifying about Events</span>
│ │ │ │  </h2>
│ │ │ │  <pre><code class="text">3&gt; gen_event:notify(error_man, no_reply).
│ │ │ │  ***Error*** no_reply
│ │ │ │  ok</code></pre><p><code class="inline">error_man</code> is the name of the event manager and <code class="inline">no_reply</code> is the event.</p><p>The event is made into a message and sent to the event manager. When the event
│ │ │ │  is received, the event manager calls <code class="inline">handle_event(Event, State)</code> for each
│ │ │ │  installed event handler, in the same order as they were added. The function is
│ │ │ │  expected to return a tuple <code class="inline">{ok,State1}</code>, where <code class="inline">State1</code> is a new value for the
│ │ │ │ -state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="5174639561-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5174639561-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5174639561-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5174639561-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="5174639561-3">]</span><span class="p" data-group-id="5174639561-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5174639561-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5174639561-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="7987328542-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7987328542-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7987328542-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7987328542-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="7987328542-3">]</span><span class="p" data-group-id="7987328542-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7987328542-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7987328542-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │ │ +state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="0299841284-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0299841284-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0299841284-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0299841284-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="0299841284-3">]</span><span class="p" data-group-id="0299841284-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0299841284-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0299841284-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="7601240474-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7601240474-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7601240474-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7601240474-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="7601240474-3">]</span><span class="p" data-group-id="7601240474-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7601240474-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7601240474-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │ │    <a href="#deleting-an-event-handler" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Deleting an Event Handler</span>
│ │ │ │  </h2>
│ │ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="3348300735-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3348300735-2">[</span><span class="p" data-group-id="3348300735-2">]</span><span class="p" data-group-id="3348300735-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="3042989992-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3042989992-2">[</span><span class="p" data-group-id="3042989992-2">]</span><span class="p" data-group-id="3042989992-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │ │  telling it to delete the event handler <code class="inline">terminal_logger</code>. The event manager
│ │ │ │  calls the callback function <code class="inline">terminal_logger:terminate([], State)</code>, where the
│ │ │ │  argument <code class="inline">[]</code> is the third argument to <code class="inline">delete_handler</code>. <code class="inline">terminate/2</code> is to be
│ │ │ │  the opposite of <code class="inline">init/1</code> and do any necessary cleaning up. Its return value is
│ │ │ │ -ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="5817077804-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="5817077804-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="0788111722-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0788111722-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="0788111722-2">(</span><span class="n">Fd</span><span class="p" data-group-id="0788111722-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ │ +ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="4507723330-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="4507723330-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="7478394615-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7478394615-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7478394615-2">(</span><span class="n">Fd</span><span class="p" data-group-id="7478394615-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ │    <a href="#stopping" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Stopping</span>
│ │ │ │  </h2>
│ │ │ │  <p>When an event manager is stopped, it gives each of the installed event handlers
│ │ │ │  the chance to clean up by calling <code class="inline">terminate/2</code>, the same way as when deleting a
│ │ │ │ @@ -154,29 +154,29 @@
│ │ │ │  this is done is defined by a <a href="sup_princ.xhtml#shutdown">shutdown strategy</a> set in
│ │ │ │  the supervisor.</p><h3 id="standalone-event-managers" class="section-heading">
│ │ │ │    <a href="#standalone-event-managers" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Standalone Event Managers</span>
│ │ │ │  </h3>
│ │ │ │ -<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6153537318-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="6153537318-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3772810835-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="3772810835-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span></code></pre><h2 id="handling-other-messages" class="section-heading">
│ │ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Handling Other Messages</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the <code class="inline">gen_event</code> process is to be able to receive other messages
│ │ │ │  than events, the callback function <code class="inline">handle_info(Info, State)</code> must be
│ │ │ │  implemented to handle them. Examples of other messages are exit
│ │ │ │  messages if the event manager is linked to other processes than the
│ │ │ │  supervisor (for example via <a href="../../../lib/stdlib/doc/html/gen_event.html#add_sup_handler/3"><code class="inline">gen_event:add_sup_handler/3</code></a>) and is
│ │ │ │ -trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="9435663471-1">(</span><span class="p" data-group-id="9435663471-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9435663471-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9435663471-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="4263457007-1">(</span><span class="p" data-group-id="4263457007-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4263457007-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4263457007-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9435663471-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="9435663471-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="7974415663-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="7974415663-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4263457007-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="4263457007-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="4725292437-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4725292437-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7974415663-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="7974415663-2">}</span><span class="p">.</span></code></pre>
│ │ │ │ +    </span><span class="p" data-group-id="4725292437-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="4725292437-2">}</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/errors.xhtml
│ │ │ │ @@ -56,22 +56,22 @@
│ │ │ │  classes, with different origins. The <a href="expressions.xhtml#try">try</a> expression can
│ │ │ │  distinguish between the different classes, whereas the
│ │ │ │  <a href="expressions.xhtml#catch-and-throw">catch</a> expression cannot. <code class="inline">try</code> and <code class="inline">catch</code> are described
│ │ │ │  in <a href="expressions.xhtml">Expressions</a>.</p><table><thead><tr><th style="text-align: left;"><em>Class</em></th><th style="text-align: left;"><em>Origin</em></th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">error</code></td><td style="text-align: left;">Run-time error, for example, <code class="inline">1+a</code>, or the process called <a href="../../../lib/../erts/doc/html/erlang.html#error/1"><code class="inline">error/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">exit</code></td><td style="text-align: left;">The process called <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">throw</code></td><td style="text-align: left;">The process called <a href="../../../lib/../erts/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a></td></tr></tbody></table><p><em>Table: Exception Classes.</em></p><p>All of the above exceptions can also be generated by calling <a href="../../../lib/../erts/doc/html/erlang.html#raise/3"><code class="inline">erlang:raise/3</code></a>.</p><p>An exception consists of its class, an exit reason (see
│ │ │ │  <a href="errors.xhtml#exit_reasons">Exit Reason</a>), and a stack trace (which aids in finding
│ │ │ │  the code location of the exception).</p><p>The stack trace can be bound to a variable from within a <code class="inline">try</code> expression for
│ │ │ │  any exception class, or as part of the exit reason when a run-time error is
│ │ │ │ -caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="8066228624-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="8066228624-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="8066228624-2">}</span><span class="p" data-group-id="8066228624-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8066228624-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="8066228624-4">(</span><span class="ss">test</span><span class="p" data-group-id="8066228624-4">)</span><span class="p" data-group-id="8066228624-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8066228624-5">[</span><span class="p" data-group-id="8066228624-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="8066228624-7">[</span><span class="p" data-group-id="8066228624-7">]</span><span class="p" data-group-id="8066228624-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8066228624-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="8066228624-9">[</span><span class="p" data-group-id="8066228624-9">]</span><span class="p" data-group-id="8066228624-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8066228624-5">]</span><span class="gp unselectable">
│ │ │ │ -&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="8066228624-10">(</span><span class="ss">test</span><span class="p" data-group-id="8066228624-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8066228624-11">[</span><span class="p" data-group-id="8066228624-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="8066228624-13">[</span><span class="p" data-group-id="8066228624-13">]</span><span class="p" data-group-id="8066228624-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8066228624-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="8066228624-15">[</span><span class="p" data-group-id="8066228624-15">]</span><span class="p" data-group-id="8066228624-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8066228624-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-back-trace-stacktrace" class="section-heading">
│ │ │ │ +caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5332037795-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="5332037795-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="5332037795-2">}</span><span class="p" data-group-id="5332037795-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5332037795-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="5332037795-4">(</span><span class="ss">test</span><span class="p" data-group-id="5332037795-4">)</span><span class="p" data-group-id="5332037795-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5332037795-5">[</span><span class="p" data-group-id="5332037795-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="5332037795-7">[</span><span class="p" data-group-id="5332037795-7">]</span><span class="p" data-group-id="5332037795-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5332037795-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="5332037795-9">[</span><span class="p" data-group-id="5332037795-9">]</span><span class="p" data-group-id="5332037795-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5332037795-5">]</span><span class="gp unselectable">
│ │ │ │ +&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="5332037795-10">(</span><span class="ss">test</span><span class="p" data-group-id="5332037795-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5332037795-11">[</span><span class="p" data-group-id="5332037795-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="5332037795-13">[</span><span class="p" data-group-id="5332037795-13">]</span><span class="p" data-group-id="5332037795-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5332037795-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="5332037795-15">[</span><span class="p" data-group-id="5332037795-15">]</span><span class="p" data-group-id="5332037795-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5332037795-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-back-trace-stacktrace" class="section-heading">
│ │ │ │    <a href="#the-call-stack-back-trace-stacktrace" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">The call-stack back trace (stacktrace)</span>
│ │ │ │  </h3>
│ │ │ │  <p>The stack back-trace (<a href="../../../lib/../erts/doc/html/erlang.html#t:stacktrace/0"><em>stacktrace</em></a>) is a list that
│ │ │ │  contains <code class="inline">{Module, Function, Arity, ExtraInfo}</code> and/or <code class="inline">{Fun, Arity, ExtraInfo}</code>
│ │ │ ├── OEBPS/error_logging.xhtml
│ │ │ │ @@ -48,36 +48,36 @@
│ │ │ │  reports and other error and information reports are by default logged through
│ │ │ │  the log handler which is set up when the Kernel application is started.</p><p>Prior to Erlang/OTP 21.0, supervisor, crash, and progress reports were only
│ │ │ │  logged when the SASL application was running. This behaviour can, for backwards
│ │ │ │  compatibility, be enabled by setting the Kernel configuration parameter
│ │ │ │  <a href="../../../lib/kernel/doc/html/kernel_app.xhtml#logger_sasl_compatible"><code class="inline">logger_sasl_compatible</code></a> to
│ │ │ │  <code class="inline">true</code>. For more information, see
│ │ │ │  <a href="../../../lib/sasl/doc/html/error_logging.xhtml">SASL Error Logging</a> in the SASL User's Guide.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -kernel logger_level info</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">21</span><span class="w"> </span><span class="p" data-group-id="1331720553-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">10.0</span><span class="p" data-group-id="1331720553-1">]</span><span class="w"> </span><span class="p" data-group-id="1331720553-2">[</span><span class="ss">source</span><span class="o">-</span><span class="mi">13</span><span class="ss">c50db</span><span class="p" data-group-id="1331720553-2">]</span><span class="w"> </span><span class="p" data-group-id="1331720553-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="1331720553-3">]</span><span class="w"> </span><span class="p" data-group-id="1331720553-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1331720553-4">]</span><span class="w"> </span><span class="p" data-group-id="1331720553-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="1331720553-5">]</span><span class="w"> </span><span class="p" data-group-id="1331720553-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1331720553-6">]</span><span class="w"> </span><span class="p" data-group-id="1331720553-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="1331720553-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">21</span><span class="w"> </span><span class="p" data-group-id="0712868610-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">10.0</span><span class="p" data-group-id="0712868610-1">]</span><span class="w"> </span><span class="p" data-group-id="0712868610-2">[</span><span class="ss">source</span><span class="o">-</span><span class="mi">13</span><span class="ss">c50db</span><span class="p" data-group-id="0712868610-2">]</span><span class="w"> </span><span class="p" data-group-id="0712868610-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0712868610-3">]</span><span class="w"> </span><span class="p" data-group-id="0712868610-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="0712868610-4">]</span><span class="w"> </span><span class="p" data-group-id="0712868610-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0712868610-5">]</span><span class="w"> </span><span class="p" data-group-id="0712868610-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0712868610-6">]</span><span class="w"> </span><span class="p" data-group-id="0712868610-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="0712868610-7">]</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.916404</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │ │      </span><span class="nc">application</span><span class="p">:</span><span class="w"> </span><span class="ss">kernel</span><span class="w">
│ │ │ │      </span><span class="nc">started_at</span><span class="p">:</span><span class="w"> </span><span class="ss">nonode@nohost</span><span class="w">
│ │ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.922908</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │ │      </span><span class="nc">application</span><span class="p">:</span><span class="w"> </span><span class="ss">stdlib</span><span class="w">
│ │ │ │      </span><span class="nc">started_at</span><span class="p">:</span><span class="w"> </span><span class="ss">nonode@nohost</span><span class="w">
│ │ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.925755</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1331720553-8">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="1331720553-8">}</span><span class="w">
│ │ │ │ -    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1331720553-9">[</span><span class="p" data-group-id="1331720553-10">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.74</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1331720553-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-11">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_sup</span><span class="p" data-group-id="1331720553-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-12">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="1331720553-13">{</span><span class="ss">disk_log_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="1331720553-14">[</span><span class="p" data-group-id="1331720553-14">]</span><span class="p" data-group-id="1331720553-13">}</span><span class="p" data-group-id="1331720553-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-15">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="1331720553-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-16">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">1000</span><span class="p" data-group-id="1331720553-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-17">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">supervisor</span><span class="p" data-group-id="1331720553-17">}</span><span class="p" data-group-id="1331720553-9">]</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0712868610-8">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="0712868610-8">}</span><span class="w">
│ │ │ │ +    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0712868610-9">[</span><span class="p" data-group-id="0712868610-10">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.74</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0712868610-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-11">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_sup</span><span class="p" data-group-id="0712868610-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-12">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="0712868610-13">{</span><span class="ss">disk_log_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="0712868610-14">[</span><span class="p" data-group-id="0712868610-14">]</span><span class="p" data-group-id="0712868610-13">}</span><span class="p" data-group-id="0712868610-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-15">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="0712868610-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-16">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">1000</span><span class="p" data-group-id="0712868610-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-17">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">supervisor</span><span class="p" data-group-id="0712868610-17">}</span><span class="p" data-group-id="0712868610-9">]</span><span class="w">
│ │ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.926056</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1331720553-18">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="1331720553-18">}</span><span class="w">
│ │ │ │ -    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1331720553-19">[</span><span class="p" data-group-id="1331720553-20">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.75</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1331720553-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-21">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_server</span><span class="p" data-group-id="1331720553-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-22">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="1331720553-23">{</span><span class="ss">disk_log_server</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="1331720553-24">[</span><span class="p" data-group-id="1331720553-24">]</span><span class="p" data-group-id="1331720553-23">}</span><span class="p" data-group-id="1331720553-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-25">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="1331720553-25">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-26">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">2000</span><span class="p" data-group-id="1331720553-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="1331720553-27">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">worker</span><span class="p" data-group-id="1331720553-27">}</span><span class="p" data-group-id="1331720553-19">]</span><span class="w">
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V10</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="1331720553-28">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="1331720553-28">)</span><span class="w">
│ │ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0712868610-18">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="0712868610-18">}</span><span class="w">
│ │ │ │ +    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0712868610-19">[</span><span class="p" data-group-id="0712868610-20">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.75</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0712868610-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-21">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_server</span><span class="p" data-group-id="0712868610-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-22">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="0712868610-23">{</span><span class="ss">disk_log_server</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="0712868610-24">[</span><span class="p" data-group-id="0712868610-24">]</span><span class="p" data-group-id="0712868610-23">}</span><span class="p" data-group-id="0712868610-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-25">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="0712868610-25">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-26">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">2000</span><span class="p" data-group-id="0712868610-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="0712868610-27">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">worker</span><span class="p" data-group-id="0712868610-27">}</span><span class="p" data-group-id="0712868610-19">]</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V10</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="0712868610-28">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="0712868610-28">)</span><span class="w">
│ │ │ │  </span><span class="mi">1</span><span class="o">&gt;</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/erl_interface.xhtml
│ │ │ │ @@ -25,119 +25,119 @@
│ │ │ │  to read the port example in <a href="c_port.xhtml">Ports</a> before reading this section.</p><h2 id="erlang-program" class="section-heading">
│ │ │ │    <a href="#erlang-program" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Erlang Program</span>
│ │ │ │  </h2>
│ │ │ │  <p>The following example shows an Erlang program communicating with a C program
│ │ │ │ -over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3389901442-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="3389901442-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3389901442-2">(</span><span class="p" data-group-id="3389901442-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3389901442-3">]</span><span class="p" data-group-id="3389901442-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3389901442-4">(</span><span class="p" data-group-id="3389901442-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3389901442-5">]</span><span class="p" data-group-id="3389901442-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="3389901442-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="3389901442-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3389901442-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3389901442-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="3389901442-8">]</span><span class="p" data-group-id="3389901442-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="3389901442-9">(</span><span class="p" data-group-id="3389901442-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4850475939-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="4850475939-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4850475939-2">(</span><span class="p" data-group-id="4850475939-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4850475939-3">]</span><span class="p" data-group-id="4850475939-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4850475939-4">(</span><span class="p" data-group-id="4850475939-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4850475939-5">]</span><span class="p" data-group-id="4850475939-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4850475939-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4850475939-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4850475939-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4850475939-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="4850475939-8">]</span><span class="p" data-group-id="4850475939-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="4850475939-9">(</span><span class="p" data-group-id="4850475939-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3389901442-10">(</span><span class="n">X</span><span class="p" data-group-id="3389901442-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="3389901442-11">(</span><span class="p" data-group-id="3389901442-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3389901442-12">}</span><span class="p" data-group-id="3389901442-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="3389901442-13">(</span><span class="n">Y</span><span class="p" data-group-id="3389901442-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="3389901442-14">(</span><span class="p" data-group-id="3389901442-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3389901442-15">}</span><span class="p" data-group-id="3389901442-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="4850475939-10">(</span><span class="n">X</span><span class="p" data-group-id="4850475939-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4850475939-11">(</span><span class="p" data-group-id="4850475939-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4850475939-12">}</span><span class="p" data-group-id="4850475939-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="4850475939-13">(</span><span class="n">Y</span><span class="p" data-group-id="4850475939-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4850475939-14">(</span><span class="p" data-group-id="4850475939-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4850475939-15">}</span><span class="p" data-group-id="4850475939-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="3389901442-16">(</span><span class="n">Msg</span><span class="p" data-group-id="3389901442-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3389901442-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3389901442-18">(</span><span class="p" data-group-id="3389901442-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3389901442-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="4850475939-16">(</span><span class="n">Msg</span><span class="p" data-group-id="4850475939-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4850475939-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4850475939-18">(</span><span class="p" data-group-id="4850475939-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4850475939-17">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="3389901442-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3389901442-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4850475939-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4850475939-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3389901442-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="3389901442-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="3389901442-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3389901442-22">(</span><span class="p" data-group-id="3389901442-22">)</span><span class="p" data-group-id="3389901442-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="3389901442-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3389901442-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="3389901442-24">(</span><span class="p" data-group-id="3389901442-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="3389901442-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3389901442-26">[</span><span class="p" data-group-id="3389901442-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3389901442-27">}</span><span class="p" data-group-id="3389901442-26">]</span><span class="p" data-group-id="3389901442-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3389901442-28">(</span><span class="n">Port</span><span class="p" data-group-id="3389901442-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4850475939-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4850475939-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4850475939-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4850475939-22">(</span><span class="p" data-group-id="4850475939-22">)</span><span class="p" data-group-id="4850475939-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="4850475939-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4850475939-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4850475939-24">(</span><span class="p" data-group-id="4850475939-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4850475939-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4850475939-26">[</span><span class="p" data-group-id="4850475939-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4850475939-27">}</span><span class="p" data-group-id="4850475939-26">]</span><span class="p" data-group-id="4850475939-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4850475939-28">(</span><span class="n">Port</span><span class="p" data-group-id="4850475939-28">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="3389901442-29">(</span><span class="n">Port</span><span class="p" data-group-id="3389901442-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="4850475939-29">(</span><span class="n">Port</span><span class="p" data-group-id="4850475939-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="3389901442-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3389901442-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3389901442-31">{</span><span class="nf">self</span><span class="p" data-group-id="3389901442-32">(</span><span class="p" data-group-id="3389901442-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3389901442-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="3389901442-34">(</span><span class="n">Msg</span><span class="p" data-group-id="3389901442-34">)</span><span class="p" data-group-id="3389901442-33">}</span><span class="p" data-group-id="3389901442-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4850475939-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4850475939-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4850475939-31">{</span><span class="nf">self</span><span class="p" data-group-id="4850475939-32">(</span><span class="p" data-group-id="4850475939-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4850475939-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4850475939-34">(</span><span class="n">Msg</span><span class="p" data-group-id="4850475939-34">)</span><span class="p" data-group-id="4850475939-33">}</span><span class="p" data-group-id="4850475939-31">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="3389901442-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3389901442-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3389901442-36">}</span><span class="p" data-group-id="3389901442-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3389901442-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="3389901442-38">(</span><span class="n">Data</span><span class="p" data-group-id="3389901442-38">)</span><span class="p" data-group-id="3389901442-37">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="4850475939-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4850475939-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4850475939-36">}</span><span class="p" data-group-id="4850475939-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4850475939-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4850475939-38">(</span><span class="n">Data</span><span class="p" data-group-id="4850475939-38">)</span><span class="p" data-group-id="4850475939-37">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="3389901442-39">(</span><span class="n">Port</span><span class="p" data-group-id="3389901442-39">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="4850475939-39">(</span><span class="n">Port</span><span class="p" data-group-id="4850475939-39">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3389901442-40">{</span><span class="nf">self</span><span class="p" data-group-id="3389901442-41">(</span><span class="p" data-group-id="3389901442-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="3389901442-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4850475939-40">{</span><span class="nf">self</span><span class="p" data-group-id="4850475939-41">(</span><span class="p" data-group-id="4850475939-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4850475939-40">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="3389901442-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="3389901442-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="3389901442-43">(</span><span class="ss">normal</span><span class="p" data-group-id="3389901442-43">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="4850475939-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4850475939-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="4850475939-43">(</span><span class="ss">normal</span><span class="p" data-group-id="4850475939-43">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="3389901442-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3389901442-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="3389901442-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="3389901442-45">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4850475939-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4850475939-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="4850475939-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4850475939-45">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="3389901442-46">(</span><span class="p" data-group-id="3389901442-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3389901442-47">}</span><span class="p" data-group-id="3389901442-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3389901442-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="3389901442-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="3389901442-49">(</span><span class="p" data-group-id="3389901442-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3389901442-50">}</span><span class="p" data-group-id="3389901442-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3389901442-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3389901442-51">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4850475939-46">(</span><span class="p" data-group-id="4850475939-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4850475939-47">}</span><span class="p" data-group-id="4850475939-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4850475939-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4850475939-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4850475939-49">(</span><span class="p" data-group-id="4850475939-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4850475939-50">}</span><span class="p" data-group-id="4850475939-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4850475939-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4850475939-51">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="3389901442-52">(</span><span class="p" data-group-id="3389901442-53">[</span><span class="n">Int</span><span class="p" data-group-id="3389901442-53">]</span><span class="p" data-group-id="3389901442-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="4850475939-52">(</span><span class="p" data-group-id="4850475939-53">[</span><span class="n">Int</span><span class="p" data-group-id="4850475939-53">]</span><span class="p" data-group-id="4850475939-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │ │  example in <a href="c_port.xhtml">Ports</a>, using only the plain port:</p><ul><li>As Erl_Interface operates on the Erlang external term format, the port must be
│ │ │ │  set to use binaries.</li><li>Instead of inventing an encoding/decoding scheme, the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#term_to_binary/1"><code class="inline">term_to_binary/1</code></a> and
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="7215568348-1">(</span><span class="p" data-group-id="7215568348-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="7215568348-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7215568348-3">[</span><span class="p" data-group-id="7215568348-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7215568348-4">}</span><span class="p" data-group-id="7215568348-3">]</span><span class="p" data-group-id="7215568348-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="0477808112-1">(</span><span class="p" data-group-id="0477808112-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0477808112-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0477808112-3">[</span><span class="p" data-group-id="0477808112-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0477808112-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="0477808112-3">]</span><span class="p" data-group-id="0477808112-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6995426189-1">{</span><span class="nf">self</span><span class="p" data-group-id="6995426189-2">(</span><span class="p" data-group-id="6995426189-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6995426189-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="6995426189-4">(</span><span class="n">Msg</span><span class="p" data-group-id="6995426189-4">)</span><span class="p" data-group-id="6995426189-3">}</span><span class="p" data-group-id="6995426189-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="2153913318-1">(</span><span class="p" data-group-id="2153913318-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="2153913318-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2153913318-3">[</span><span class="p" data-group-id="2153913318-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2153913318-4">}</span><span class="p" data-group-id="2153913318-3">]</span><span class="p" data-group-id="2153913318-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="0450820441-1">(</span><span class="p" data-group-id="0450820441-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0450820441-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0450820441-3">[</span><span class="p" data-group-id="0450820441-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0450820441-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="0450820441-3">]</span><span class="p" data-group-id="0450820441-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3623121551-1">{</span><span class="nf">self</span><span class="p" data-group-id="3623121551-2">(</span><span class="p" data-group-id="3623121551-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3623121551-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="3623121551-4">(</span><span class="n">Msg</span><span class="p" data-group-id="3623121551-4">)</span><span class="p" data-group-id="3623121551-3">}</span><span class="p" data-group-id="3623121551-1">}</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="6995426189-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6995426189-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6995426189-6">}</span><span class="p" data-group-id="6995426189-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6995426189-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="6995426189-8">(</span><span class="n">Data</span><span class="p" data-group-id="6995426189-8">)</span><span class="p" data-group-id="6995426189-7">}</span><span class="w">
│ │ │ │ -</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1605991923-1">{</span><span class="nf">self</span><span class="p" data-group-id="1605991923-2">(</span><span class="p" data-group-id="1605991923-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1605991923-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1605991923-4">(</span><span class="n">Msg</span><span class="p" data-group-id="1605991923-4">)</span><span class="p" data-group-id="1605991923-3">}</span><span class="p" data-group-id="1605991923-1">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="3623121551-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3623121551-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3623121551-6">}</span><span class="p" data-group-id="3623121551-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3623121551-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="3623121551-8">(</span><span class="n">Data</span><span class="p" data-group-id="3623121551-8">)</span><span class="p" data-group-id="3623121551-7">}</span><span class="w">
│ │ │ │ +</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2166754816-1">{</span><span class="nf">self</span><span class="p" data-group-id="2166754816-2">(</span><span class="p" data-group-id="2166754816-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2166754816-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="2166754816-4">(</span><span class="n">Msg</span><span class="p" data-group-id="2166754816-4">)</span><span class="p" data-group-id="2166754816-3">}</span><span class="p" data-group-id="2166754816-1">}</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1605991923-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1605991923-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1605991923-6">}</span><span class="p" data-group-id="1605991923-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1605991923-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1605991923-8">(</span><span class="n">Data</span><span class="p" data-group-id="1605991923-8">)</span><span class="p" data-group-id="1605991923-7">}</span><span class="w">
│ │ │ │ -</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0731951023-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="0731951023-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0731951023-2">(</span><span class="p" data-group-id="0731951023-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0731951023-3">]</span><span class="p" data-group-id="0731951023-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0731951023-4">(</span><span class="p" data-group-id="0731951023-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0731951023-5">]</span><span class="p" data-group-id="0731951023-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0731951023-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0731951023-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="0731951023-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0731951023-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="0731951023-8">]</span><span class="p" data-group-id="0731951023-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0731951023-9">(</span><span class="p" data-group-id="0731951023-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2166754816-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2166754816-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2166754816-6">}</span><span class="p" data-group-id="2166754816-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2166754816-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2166754816-8">(</span><span class="n">Data</span><span class="p" data-group-id="2166754816-8">)</span><span class="p" data-group-id="2166754816-7">}</span><span class="w">
│ │ │ │ +</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0630610212-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="0630610212-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0630610212-2">(</span><span class="p" data-group-id="0630610212-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0630610212-3">]</span><span class="p" data-group-id="0630610212-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0630610212-4">(</span><span class="p" data-group-id="0630610212-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0630610212-5">]</span><span class="p" data-group-id="0630610212-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0630610212-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0630610212-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0630610212-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0630610212-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="0630610212-8">]</span><span class="p" data-group-id="0630610212-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="0630610212-9">(</span><span class="p" data-group-id="0630610212-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0731951023-10">(</span><span class="n">X</span><span class="p" data-group-id="0731951023-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0731951023-11">(</span><span class="p" data-group-id="0731951023-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0731951023-12">}</span><span class="p" data-group-id="0731951023-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="0731951023-13">(</span><span class="n">Y</span><span class="p" data-group-id="0731951023-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0731951023-14">(</span><span class="p" data-group-id="0731951023-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0731951023-15">}</span><span class="p" data-group-id="0731951023-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="0630610212-10">(</span><span class="n">X</span><span class="p" data-group-id="0630610212-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0630610212-11">(</span><span class="p" data-group-id="0630610212-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0630610212-12">}</span><span class="p" data-group-id="0630610212-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="0630610212-13">(</span><span class="n">Y</span><span class="p" data-group-id="0630610212-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="0630610212-14">(</span><span class="p" data-group-id="0630610212-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0630610212-15">}</span><span class="p" data-group-id="0630610212-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="0731951023-16">(</span><span class="n">Msg</span><span class="p" data-group-id="0731951023-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0731951023-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0731951023-18">(</span><span class="p" data-group-id="0731951023-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0731951023-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="0630610212-16">(</span><span class="n">Msg</span><span class="p" data-group-id="0630610212-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0630610212-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0630610212-18">(</span><span class="p" data-group-id="0630610212-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0630610212-17">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0731951023-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0731951023-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0630610212-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0630610212-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0731951023-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0731951023-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="0731951023-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0731951023-22">(</span><span class="p" data-group-id="0731951023-22">)</span><span class="p" data-group-id="0731951023-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="0731951023-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0731951023-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0731951023-24">(</span><span class="p" data-group-id="0731951023-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0731951023-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0731951023-26">[</span><span class="p" data-group-id="0731951023-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0731951023-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="0731951023-26">]</span><span class="p" data-group-id="0731951023-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="0731951023-28">(</span><span class="n">Port</span><span class="p" data-group-id="0731951023-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0630610212-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0630610212-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0630610212-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0630610212-22">(</span><span class="p" data-group-id="0630610212-22">)</span><span class="p" data-group-id="0630610212-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="0630610212-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0630610212-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0630610212-24">(</span><span class="p" data-group-id="0630610212-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0630610212-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0630610212-26">[</span><span class="p" data-group-id="0630610212-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0630610212-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="0630610212-26">]</span><span class="p" data-group-id="0630610212-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="0630610212-28">(</span><span class="n">Port</span><span class="p" data-group-id="0630610212-28">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="0731951023-29">(</span><span class="n">Port</span><span class="p" data-group-id="0731951023-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="0630610212-29">(</span><span class="n">Port</span><span class="p" data-group-id="0630610212-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0731951023-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0731951023-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0731951023-31">{</span><span class="nf">self</span><span class="p" data-group-id="0731951023-32">(</span><span class="p" data-group-id="0731951023-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0731951023-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="0731951023-34">(</span><span class="n">Msg</span><span class="p" data-group-id="0731951023-34">)</span><span class="p" data-group-id="0731951023-33">}</span><span class="p" data-group-id="0731951023-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0630610212-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0630610212-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0630610212-31">{</span><span class="nf">self</span><span class="p" data-group-id="0630610212-32">(</span><span class="p" data-group-id="0630610212-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0630610212-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="0630610212-34">(</span><span class="n">Msg</span><span class="p" data-group-id="0630610212-34">)</span><span class="p" data-group-id="0630610212-33">}</span><span class="p" data-group-id="0630610212-31">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="0731951023-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0731951023-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0731951023-36">}</span><span class="p" data-group-id="0731951023-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0731951023-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="0731951023-38">(</span><span class="n">Data</span><span class="p" data-group-id="0731951023-38">)</span><span class="p" data-group-id="0731951023-37">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="0630610212-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0630610212-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0630610212-36">}</span><span class="p" data-group-id="0630610212-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0630610212-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="0630610212-38">(</span><span class="n">Data</span><span class="p" data-group-id="0630610212-38">)</span><span class="p" data-group-id="0630610212-37">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="0731951023-39">(</span><span class="n">Port</span><span class="p" data-group-id="0731951023-39">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="0630610212-39">(</span><span class="n">Port</span><span class="p" data-group-id="0630610212-39">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0731951023-40">{</span><span class="nf">self</span><span class="p" data-group-id="0731951023-41">(</span><span class="p" data-group-id="0731951023-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="0731951023-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0630610212-40">{</span><span class="nf">self</span><span class="p" data-group-id="0630610212-41">(</span><span class="p" data-group-id="0630610212-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="0630610212-40">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="0731951023-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="0731951023-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="0731951023-43">(</span><span class="ss">normal</span><span class="p" data-group-id="0731951023-43">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="0630610212-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="0630610212-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="0630610212-43">(</span><span class="ss">normal</span><span class="p" data-group-id="0630610212-43">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0731951023-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0731951023-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="0731951023-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="0731951023-45">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="0630610212-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0630610212-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="0630610212-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="0630610212-45">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Notice that calling <code class="inline">complex2:foo/1</code> and <code class="inline">complex2:bar/1</code> results in the tuple
│ │ │ │  <code class="inline">{foo,X}</code> or <code class="inline">{bar,Y}</code> being sent to the <code class="inline">complex</code> process, which codes them as
│ │ │ │  binaries and sends them to the port. This means that the C program must be able
│ │ │ │  to handle these two tuples.</p><h2 id="c-program" class="section-heading">
│ │ │ │    <a href="#c-program" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │ @@ -267,24 +267,24 @@
│ │ │ │      -L/usr/local/otp/lib/erl_interface-3.9.2/lib \
│ │ │ │      complex.c erl_comm.c ei.c -lei -lpthread</code></pre><p>In Erlang/OTP R5B and later versions of OTP, the <code class="inline">include</code> and <code class="inline">lib</code> directories
│ │ │ │  are situated under <code class="inline">$OTPROOT/lib/erl_interface-VSN</code>, where <code class="inline">$OTPROOT</code> is the
│ │ │ │  root directory of the OTP installation (<code class="inline">/usr/local/otp</code> in the recent example)
│ │ │ │  and <code class="inline">VSN</code> is the version of the Erl_interface application (3.2.1 in the recent
│ │ │ │  example).</p><p>In R4B and earlier versions of OTP, <code class="inline">include</code> and <code class="inline">lib</code> are situated under
│ │ │ │  <code class="inline">$OTPROOT/usr</code>.</p><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="4670074646-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="4670074646-1">]</span><span class="w"> </span><span class="p" data-group-id="4670074646-2">[</span><span class="ss">source</span><span class="p" data-group-id="4670074646-2">]</span><span class="w"> </span><span class="p" data-group-id="4670074646-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4670074646-3">]</span><span class="w"> </span><span class="p" data-group-id="4670074646-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4670074646-4">]</span><span class="w"> </span><span class="p" data-group-id="4670074646-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4670074646-5">]</span><span class="w"> </span><span class="p" data-group-id="4670074646-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4670074646-6">]</span><span class="w"> </span><span class="p" data-group-id="4670074646-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="4670074646-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="2967145870-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="2967145870-1">]</span><span class="w"> </span><span class="p" data-group-id="2967145870-2">[</span><span class="ss">source</span><span class="p" data-group-id="2967145870-2">]</span><span class="w"> </span><span class="p" data-group-id="2967145870-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="2967145870-3">]</span><span class="w"> </span><span class="p" data-group-id="2967145870-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2967145870-4">]</span><span class="w"> </span><span class="p" data-group-id="2967145870-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="2967145870-5">]</span><span class="w"> </span><span class="p" data-group-id="2967145870-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2967145870-6">]</span><span class="w"> </span><span class="p" data-group-id="2967145870-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="2967145870-7">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="4670074646-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4670074646-9">(</span><span class="p" data-group-id="4670074646-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4670074646-8">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4670074646-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="4670074646-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4670074646-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="4670074646-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3747653757-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="3747653757-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="2967145870-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="2967145870-9">(</span><span class="p" data-group-id="2967145870-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="2967145870-8">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="2967145870-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="2967145870-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2967145870-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="2967145870-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0138978593-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="0138978593-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="3747653757-2">(</span><span class="mi">3</span><span class="p" data-group-id="3747653757-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0138978593-2">(</span><span class="mi">3</span><span class="p" data-group-id="0138978593-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="3747653757-3">(</span><span class="mi">5</span><span class="p" data-group-id="3747653757-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="0138978593-3">(</span><span class="mi">5</span><span class="p" data-group-id="0138978593-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="3747653757-4">(</span><span class="mi">352</span><span class="p" data-group-id="3747653757-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="0138978593-4">(</span><span class="mi">352</span><span class="p" data-group-id="0138978593-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">704</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3747653757-5">(</span><span class="p" data-group-id="3747653757-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0138978593-5">(</span><span class="p" data-group-id="0138978593-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/eff_guide_processes.xhtml
│ │ │ │ @@ -24,45 +24,45 @@
│ │ │ │    <a href="#creating-an-erlang-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating an Erlang Process</span>
│ │ │ │  </h2>
│ │ │ │  <p>An Erlang process is lightweight compared to threads and processes in operating
│ │ │ │  systems.</p><p>A newly spawned Erlang process uses 327 words of memory. The size can be found
│ │ │ │ -as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="0079087301-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="0079087301-1">]</span><span class="w"> </span><span class="p" data-group-id="0079087301-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0079087301-2">]</span><span class="w"> </span><span class="p" data-group-id="0079087301-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0079087301-3">]</span><span class="w"> </span><span class="p" data-group-id="0079087301-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0079087301-4">]</span><span class="w"> </span><span class="p" data-group-id="0079087301-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0079087301-5">]</span><span class="w"> </span><span class="p" data-group-id="0079087301-6">[</span><span class="ss">jit</span><span class="p" data-group-id="0079087301-6">]</span><span class="w">
│ │ │ │ +as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="6172802553-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="6172802553-1">]</span><span class="w"> </span><span class="p" data-group-id="6172802553-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="6172802553-2">]</span><span class="w"> </span><span class="p" data-group-id="6172802553-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6172802553-3">]</span><span class="w"> </span><span class="p" data-group-id="6172802553-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="6172802553-4">]</span><span class="w"> </span><span class="p" data-group-id="6172802553-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="6172802553-5">]</span><span class="w"> </span><span class="p" data-group-id="6172802553-6">[</span><span class="ss">jit</span><span class="p" data-group-id="6172802553-6">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="0079087301-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="0079087301-8">(</span><span class="p" data-group-id="0079087301-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="0079087301-7">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0079087301-9">(</span><span class="p" data-group-id="0079087301-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="6172802553-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="6172802553-8">(</span><span class="p" data-group-id="6172802553-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="6172802553-7">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6172802553-9">(</span><span class="p" data-group-id="6172802553-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.39164016</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="0079087301-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="0079087301-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="0079087301-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="0079087301-12">(</span><span class="n">Fun</span><span class="p" data-group-id="0079087301-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="0079087301-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0079087301-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="0079087301-13">}</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="0079087301-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="0079087301-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="6172802553-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="6172802553-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="6172802553-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="6172802553-12">(</span><span class="n">Fun</span><span class="p" data-group-id="6172802553-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="6172802553-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6172802553-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="6172802553-13">}</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="6172802553-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="6172802553-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">327</span></code></pre><p>The size includes 233 words for the heap area (which includes the stack). The
│ │ │ │  garbage collector increases the heap as needed.</p><p>The main (outer) loop for a process <em>must</em> be tail-recursive. Otherwise, the
│ │ │ │ -stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="7993494965-1">(</span><span class="p" data-group-id="7993494965-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4462363465-1">(</span><span class="p" data-group-id="4462363465-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7993494965-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7993494965-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="7993494965-3">(</span><span class="n">Msg</span><span class="p" data-group-id="7993494965-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="7993494965-4">(</span><span class="p" data-group-id="7993494965-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7993494965-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7993494965-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7993494965-6">(</span><span class="n">Msg</span><span class="p" data-group-id="7993494965-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4462363465-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4462363465-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="4462363465-3">(</span><span class="n">Msg</span><span class="p" data-group-id="4462363465-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="4462363465-4">(</span><span class="p" data-group-id="4462363465-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="4462363465-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4462363465-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4462363465-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4462363465-6">)</span><span class="p">,</span><span class="w">
│ │ │ │            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="nf">loop</span><span class="p" data-group-id="7993494965-7">(</span><span class="p" data-group-id="7993494965-7">)</span><span class="w">
│ │ │ │ +          </span><span class="nf">loop</span><span class="p" data-group-id="4462363465-7">(</span><span class="p" data-group-id="4462363465-7">)</span><span class="w">
│ │ │ │    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7993494965-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7993494965-9">[</span><span class="p" data-group-id="7993494965-9">]</span><span class="p" data-group-id="7993494965-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4462363465-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4462363465-9">[</span><span class="p" data-group-id="4462363465-9">]</span><span class="p" data-group-id="4462363465-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │ │  still be pushed to the stack each time <code class="inline">loop/0</code> is called recursively. The
│ │ │ │ -correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2149166822-1">(</span><span class="p" data-group-id="2149166822-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3554688535-1">(</span><span class="p" data-group-id="3554688535-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │     </span><span class="k">receive</span><span class="w">
│ │ │ │ -      </span><span class="p" data-group-id="2149166822-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2149166822-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="2149166822-3">(</span><span class="n">Msg</span><span class="p" data-group-id="2149166822-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="2149166822-4">(</span><span class="p" data-group-id="2149166822-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ -      </span><span class="p" data-group-id="2149166822-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2149166822-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2149166822-6">(</span><span class="n">Msg</span><span class="p" data-group-id="2149166822-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +      </span><span class="p" data-group-id="3554688535-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3554688535-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="3554688535-3">(</span><span class="n">Msg</span><span class="p" data-group-id="3554688535-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="3554688535-4">(</span><span class="p" data-group-id="3554688535-4">)</span><span class="p">;</span><span class="w">
│ │ │ │ +      </span><span class="p" data-group-id="3554688535-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3554688535-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3554688535-6">(</span><span class="n">Msg</span><span class="p" data-group-id="3554688535-6">)</span><span class="p">,</span><span class="w">
│ │ │ │           </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="2149166822-7">(</span><span class="p" data-group-id="2149166822-7">)</span><span class="w">
│ │ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="3554688535-7">(</span><span class="p" data-group-id="3554688535-7">)</span><span class="w">
│ │ │ │   </span><span class="k">end</span><span class="p">.</span></code></pre><h3 id="initial-heap-size" class="section-heading">
│ │ │ │    <a href="#initial-heap-size" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Initial Heap Size</span>
│ │ │ │  </h3>
│ │ │ │  <p>The default initial heap size of 233 words is quite conservative to support
│ │ │ │ @@ -94,30 +94,30 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Receiving messages</span>
│ │ │ │  </h2>
│ │ │ │  <p>The cost of receiving messages depends on how complicated the <code class="inline">receive</code>
│ │ │ │  expression is. A simple expression that matches any message is very cheap
│ │ │ │  because it retrieves the first message in the message queue:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="3790929028-1">(</span><span class="n">Message</span><span class="p" data-group-id="3790929028-1">)</span><span class="w">
│ │ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="5131566961-1">(</span><span class="n">Message</span><span class="p" data-group-id="5131566961-1">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>However, this is not always convenient: we can receive a message that we do not
│ │ │ │  know how to handle at this point, so it is common to only match the messages we
│ │ │ │  expect:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4899479255-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="4899479255-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4899479255-2">(</span><span class="n">Message</span><span class="p" data-group-id="4899479255-2">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5459999386-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5459999386-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="5459999386-2">(</span><span class="n">Message</span><span class="p" data-group-id="5459999386-2">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>While this is convenient it means that the entire message queue must be searched
│ │ │ │  until it finds a matching message. This is very expensive for processes with
│ │ │ │  long message queues, so there is an optimization for the common case of
│ │ │ │ -sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="3023546397-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="3023546397-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3023546397-2">{</span><span class="nf">self</span><span class="p" data-group-id="3023546397-3">(</span><span class="p" data-group-id="3023546397-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3023546397-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="9439138483-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="9439138483-1">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9439138483-2">{</span><span class="nf">self</span><span class="p" data-group-id="9439138483-3">(</span><span class="p" data-group-id="9439138483-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9439138483-2">}</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3023546397-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="3023546397-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="3023546397-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3023546397-6">[</span><span class="ss">flush</span><span class="p" data-group-id="3023546397-6">]</span><span class="p" data-group-id="3023546397-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="3023546397-7">(</span><span class="n">Reply</span><span class="p" data-group-id="3023546397-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="3023546397-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3023546397-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nf">handle_error</span><span class="p" data-group-id="3023546397-9">(</span><span class="n">Reason</span><span class="p" data-group-id="3023546397-9">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9439138483-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="9439138483-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="9439138483-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9439138483-6">[</span><span class="ss">flush</span><span class="p" data-group-id="9439138483-6">]</span><span class="p" data-group-id="9439138483-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="9439138483-7">(</span><span class="n">Reply</span><span class="p" data-group-id="9439138483-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9439138483-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9439138483-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nf">handle_error</span><span class="p" data-group-id="9439138483-9">(</span><span class="n">Reason</span><span class="p" data-group-id="9439138483-9">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Since the compiler knows that the reference created by
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a> cannot exist before the call (since it is a globally
│ │ │ │  unique identifier), and that the <code class="inline">receive</code> only matches messages that contain
│ │ │ │  said reference, it will tell the emulator to search only the messages that
│ │ │ │  arrived after the call to <a href="../../../lib/../erts/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a>.</p><p>The above is a simple example where one is but guaranteed that the optimization
│ │ │ │  will take, but what about more complicated code?</p><p><a href="" id="recv_opt_info"></a></p><h3 id="option-recv_opt_info" class="section-heading">
│ │ │ │    <a href="#option-recv_opt_info" class="hover-link">
│ │ │ │ @@ -133,101 +133,101 @@
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">200</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">do</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">suitable</span><span class="w"> </span><span class="ss">reference</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">mark</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">message</span><span class="w"> </span><span class="ss">queue</span><span class="w"> </span><span class="ss">position</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">208</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="nb">monitor</span><span class="p">/</span><span class="mi">2</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">219</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">INFO</span><span class="p">:</span><span class="w"> </span><span class="ss">passing</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="ss">make_ref</span><span class="p">/</span><span class="mi">0</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">218</span><span class="w">
│ │ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">222</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">parameter</span><span class="w"> </span><span class="mi">1</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │ │  example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">simple_receive</span><span class="p" data-group-id="9031123265-1">(</span><span class="p" data-group-id="9031123265-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">simple_receive</span><span class="p" data-group-id="8826651400-1">(</span><span class="p" data-group-id="8826651400-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% efficiency_guide.erl:194: Warning: INFO: not a selective receive, this is always fast</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9031123265-2">(</span><span class="n">Message</span><span class="p" data-group-id="9031123265-2">)</span><span class="w">
│ │ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="8826651400-2">(</span><span class="n">Message</span><span class="p" data-group-id="8826651400-2">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO NOT, unless Tag is known to be a suitable reference: see</span><span class="w">
│ │ │ │  </span><span class="c1">%% cross_function_receive/0 further down.</span><span class="w">
│ │ │ │ -</span><span class="nf">selective_receive</span><span class="p" data-group-id="9031123265-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9031123265-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">selective_receive</span><span class="p" data-group-id="8826651400-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8826651400-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% efficiency_guide.erl:200: Warning: NOT OPTIMIZED: all clauses do not match a suitable reference</span><span class="w">
│ │ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9031123265-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9031123265-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9031123265-5">(</span><span class="n">Message</span><span class="p" data-group-id="9031123265-5">)</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8826651400-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8826651400-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="8826651400-5">(</span><span class="n">Message</span><span class="p" data-group-id="8826651400-5">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">optimized_receive</span><span class="p" data-group-id="9031123265-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9031123265-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">optimized_receive</span><span class="p" data-group-id="8826651400-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="8826651400-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% efficiency_guide.erl:206: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ │ -    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="9031123265-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="9031123265-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9031123265-8">{</span><span class="nf">self</span><span class="p" data-group-id="9031123265-9">(</span><span class="p" data-group-id="9031123265-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9031123265-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="8826651400-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="8826651400-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8826651400-8">{</span><span class="nf">self</span><span class="p" data-group-id="8826651400-9">(</span><span class="p" data-group-id="8826651400-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="8826651400-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:208: Warning: OPTIMIZED: matches reference created by monitor/2 at efficiency_guide.erl:206</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9031123265-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="9031123265-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="9031123265-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9031123265-12">[</span><span class="ss">flush</span><span class="p" data-group-id="9031123265-12">]</span><span class="p" data-group-id="9031123265-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="9031123265-13">(</span><span class="n">Reply</span><span class="p" data-group-id="9031123265-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9031123265-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9031123265-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">handle_error</span><span class="p" data-group-id="9031123265-15">(</span><span class="n">Reason</span><span class="p" data-group-id="9031123265-15">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8826651400-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="8826651400-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="8826651400-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8826651400-12">[</span><span class="ss">flush</span><span class="p" data-group-id="8826651400-12">]</span><span class="p" data-group-id="8826651400-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="8826651400-13">(</span><span class="n">Reply</span><span class="p" data-group-id="8826651400-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8826651400-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8826651400-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">handle_error</span><span class="p" data-group-id="8826651400-15">(</span><span class="n">Reason</span><span class="p" data-group-id="8826651400-15">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9031123265-16">(</span><span class="p" data-group-id="9031123265-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="8826651400-16">(</span><span class="p" data-group-id="8826651400-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:218: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ │ -    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="9031123265-17">(</span><span class="p" data-group-id="9031123265-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="8826651400-17">(</span><span class="p" data-group-id="8826651400-17">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:219: Warning: INFO: passing reference created by make_ref/0 at efficiency_guide.erl:218</span><span class="w">
│ │ │ │ -    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9031123265-18">(</span><span class="n">Ref</span><span class="p" data-group-id="9031123265-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="8826651400-18">(</span><span class="n">Ref</span><span class="p" data-group-id="8826651400-18">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9031123265-19">(</span><span class="n">Ref</span><span class="p" data-group-id="9031123265-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="8826651400-19">(</span><span class="n">Ref</span><span class="p" data-group-id="8826651400-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% efficiency_guide.erl:222: Warning: OPTIMIZED: all clauses match reference in function parameter 1</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9031123265-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9031123265-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9031123265-21">(</span><span class="n">Message</span><span class="p" data-group-id="9031123265-21">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8826651400-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8826651400-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="8826651400-21">(</span><span class="n">Message</span><span class="p" data-group-id="8826651400-21">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="literal-pool" class="section-heading">
│ │ │ │    <a href="#literal-pool" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Literal Pool</span>
│ │ │ │  </h2>
│ │ │ │  <p>Constant Erlang terms (hereafter called <em>literals</em>) are kept in <em>literal pools</em>;
│ │ │ │  each loaded module has its own pool. The following function does not build the
│ │ │ │  tuple every time it is called (only to have it discarded the next time the
│ │ │ │  garbage collector was run), but the tuple is located in the module's literal
│ │ │ │ -pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="6634323358-1">(</span><span class="n">M</span><span class="p" data-group-id="6634323358-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="6634323358-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6634323358-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="6634323358-3">}</span><span class="p" data-group-id="6634323358-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │ │ +pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="2829331076-1">(</span><span class="n">M</span><span class="p" data-group-id="2829331076-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="2829331076-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2829331076-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="2829331076-3">}</span><span class="p" data-group-id="2829331076-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │ │  it is <em>copied</em>. The reason is that the module containing the literal can be
│ │ │ │  unloaded in the future.</p><p>When a literal is sent to another process, it is <em>not</em> copied. When a module
│ │ │ │  holding a literal is unloaded, the literal will be copied to the heap of all
│ │ │ │  processes that hold references to that literal.</p><p>There also exists a global literal pool that is managed by the
│ │ │ │  <a href="../../../lib/../erts/doc/html/persistent_term.html"><code class="inline">persistent_term</code></a> module.</p><p>By default, 1 GB of virtual address space is reserved for all literal pools (in
│ │ │ │  BEAM code and persistent terms). The amount of virtual address space reserved
│ │ │ │  for literals can be changed by using the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erts_alloc.xhtml#MIscs"><code class="inline">+MIscs option</code></a> when starting the emulator.</p><p>Here is an example how the reserved virtual address space for literals can be
│ │ │ │  raised to 2 GB (2048 MB):</p><pre><code class="text">erl +MIscs 2048</code></pre><h2 id="loss-of-sharing" class="section-heading">
│ │ │ │    <a href="#loss-of-sharing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Loss of Sharing</span>
│ │ │ │  </h2>
│ │ │ │ -<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2982397650-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="2982397650-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ │ -subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="7463805863-1">(</span><span class="p" data-group-id="7463805863-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="7463805863-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7463805863-3">[</span><span class="mi">42</span><span class="p" data-group-id="7463805863-3">]</span><span class="p" data-group-id="7463805863-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9754325825-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="9754325825-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ │ +subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="2229647080-1">(</span><span class="p" data-group-id="2229647080-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="2229647080-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2229647080-3">[</span><span class="mi">42</span><span class="p" data-group-id="2229647080-3">]</span><span class="p" data-group-id="2229647080-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="7463805863-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7463805863-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="2229647080-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2229647080-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="7463805863-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7463805863-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="7463805863-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7463805863-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="7463805863-7">]</span><span class="p" data-group-id="7463805863-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../../lib/../erts/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="2229647080-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2229647080-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="2229647080-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2229647080-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2229647080-7">]</span><span class="p" data-group-id="2229647080-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../../lib/../erts/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │ │  is called, the deep list can be converted to a binary of 1024 bytes:</p><pre><code class="text">1&gt; byte_size(list_to_binary(efficiency_guide:kilo_byte())).
│ │ │ │  1024</code></pre><p>Using the <code class="inline">erts_debug:size/1</code> BIF, it can be seen that the deep list only
│ │ │ │ -requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="7433883718-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="7433883718-2">(</span><span class="p" data-group-id="7433883718-2">)</span><span class="p" data-group-id="7433883718-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="6189068320-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="6189068320-2">(</span><span class="p" data-group-id="6189068320-2">)</span><span class="p" data-group-id="6189068320-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">22</span></code></pre><p>Using the <code class="inline">erts_debug:flat_size/1</code> BIF, the size of the deep list can be
│ │ │ │  calculated if sharing is ignored. It becomes the size of the list when it has
│ │ │ │ -been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="6268999050-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="6268999050-2">(</span><span class="p" data-group-id="6268999050-2">)</span><span class="p" data-group-id="6268999050-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="9235681879-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9235681879-2">(</span><span class="p" data-group-id="9235681879-2">)</span><span class="p" data-group-id="9235681879-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4094</span></code></pre><p>It can be verified that sharing will be lost if the data is inserted into an Ets
│ │ │ │ -table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="3903862303-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3903862303-2">[</span><span class="p" data-group-id="3903862303-2">]</span><span class="p" data-group-id="3903862303-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4350510842-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4350510842-2">[</span><span class="p" data-group-id="4350510842-2">]</span><span class="p" data-group-id="4350510842-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.1662103692</span><span class="p">.</span><span class="mf">2407923716.214181</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="3903862303-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3903862303-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="3903862303-5">(</span><span class="p" data-group-id="3903862303-5">)</span><span class="p" data-group-id="3903862303-4">}</span><span class="p" data-group-id="3903862303-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="4350510842-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4350510842-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="4350510842-5">(</span><span class="p" data-group-id="4350510842-5">)</span><span class="p" data-group-id="4350510842-4">}</span><span class="p" data-group-id="4350510842-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="3903862303-6">(</span><span class="nf">element</span><span class="p" data-group-id="3903862303-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="3903862303-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3903862303-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="3903862303-9">)</span><span class="p" data-group-id="3903862303-8">)</span><span class="p" data-group-id="3903862303-7">)</span><span class="p" data-group-id="3903862303-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="4350510842-6">(</span><span class="nf">element</span><span class="p" data-group-id="4350510842-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="4350510842-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="4350510842-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="4350510842-9">)</span><span class="p" data-group-id="4350510842-8">)</span><span class="p" data-group-id="4350510842-7">)</span><span class="p" data-group-id="4350510842-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4094</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="3903862303-10">(</span><span class="nf">element</span><span class="p" data-group-id="3903862303-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="3903862303-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3903862303-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="3903862303-13">)</span><span class="p" data-group-id="3903862303-12">)</span><span class="p" data-group-id="3903862303-11">)</span><span class="p" data-group-id="3903862303-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="4350510842-10">(</span><span class="nf">element</span><span class="p" data-group-id="4350510842-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="4350510842-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="4350510842-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="4350510842-13">)</span><span class="p" data-group-id="4350510842-12">)</span><span class="p" data-group-id="4350510842-11">)</span><span class="p" data-group-id="4350510842-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4094</span></code></pre><p>When the data has passed through an Ets table, <code class="inline">erts_debug:size/1</code> and
│ │ │ │  <code class="inline">erts_debug:flat_size/1</code> return the same value. Sharing has been lost.</p><p>It is possible to build an <em>experimental</em> variant of the runtime system that
│ │ │ │  will preserve sharing when copying terms by giving the
│ │ │ │  <code class="inline">--enable-sharing-preserving</code> option to the <code class="inline">configure</code> script.</p><h2 id="smp-run-time-system" class="section-heading">
│ │ │ │    <a href="#smp-run-time-system" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ ├── OEBPS/eff_guide_functions.xhtml
│ │ │ │ @@ -27,67 +27,67 @@
│ │ │ │    <span class="text">Pattern Matching</span>
│ │ │ │  </h2>
│ │ │ │  <p>Pattern matching in function head as well as in <code class="inline">case</code> and <code class="inline">receive</code> clauses are
│ │ │ │  optimized by the compiler. With a few exceptions, there is nothing to gain by
│ │ │ │  rearranging clauses.</p><p>One exception is pattern matching of binaries. The compiler does not rearrange
│ │ │ │  clauses that match binaries. Placing the clause that matches against the empty
│ │ │ │  binary <em>last</em> is usually slightly faster than placing it <em>first</em>.</p><p>The following is a rather unnatural example to show another exception where
│ │ │ │ -rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-1">(</span><span class="ss">one</span><span class="p" data-group-id="6879938112-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-2">(</span><span class="ss">two</span><span class="p" data-group-id="6879938112-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-3">(</span><span class="ss">three</span><span class="p" data-group-id="6879938112-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-4">(</span><span class="n">Int</span><span class="p" data-group-id="6879938112-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="6879938112-5">(</span><span class="n">Int</span><span class="p" data-group-id="6879938112-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-6">(</span><span class="ss">four</span><span class="p" data-group-id="6879938112-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-7">(</span><span class="ss">five</span><span class="p" data-group-id="6879938112-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="6879938112-8">(</span><span class="ss">six</span><span class="p" data-group-id="6879938112-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │ │ +rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-1">(</span><span class="ss">one</span><span class="p" data-group-id="8959019489-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-2">(</span><span class="ss">two</span><span class="p" data-group-id="8959019489-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-3">(</span><span class="ss">three</span><span class="p" data-group-id="8959019489-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-4">(</span><span class="n">Int</span><span class="p" data-group-id="8959019489-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8959019489-5">(</span><span class="n">Int</span><span class="p" data-group-id="8959019489-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-6">(</span><span class="ss">four</span><span class="p" data-group-id="8959019489-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-7">(</span><span class="ss">five</span><span class="p" data-group-id="8959019489-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8959019489-8">(</span><span class="ss">six</span><span class="p" data-group-id="8959019489-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │ │  anything, including the atoms <code class="inline">four</code>, <code class="inline">five</code>, and <code class="inline">six</code>, which the following
│ │ │ │  clauses also match, the compiler must generate suboptimal code that executes as
│ │ │ │  follows:</p><ul><li>First, the input value is compared to <code class="inline">one</code>, <code class="inline">two</code>, and <code class="inline">three</code> (using a
│ │ │ │  single instruction that does a binary search; thus, quite efficient even if
│ │ │ │  there are many values) to select which one of the first three clauses to
│ │ │ │  execute (if any).</li><li>If none of the first three clauses match, the fourth clause match as a
│ │ │ │  variable always matches.</li><li>If the guard test <a href="../../../lib/../erts/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(Int)</code></a> succeeds, the fourth
│ │ │ │  clause is executed.</li><li>If the guard test fails, the input value is compared to <code class="inline">four</code>, <code class="inline">five</code>, and
│ │ │ │  <code class="inline">six</code>, and the appropriate clause is selected. (There is a <code class="inline">function_clause</code>
│ │ │ │ -exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-1">(</span><span class="ss">one</span><span class="p" data-group-id="6812954214-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-2">(</span><span class="ss">two</span><span class="p" data-group-id="6812954214-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-3">(</span><span class="ss">three</span><span class="p" data-group-id="6812954214-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-4">(</span><span class="ss">four</span><span class="p" data-group-id="6812954214-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-5">(</span><span class="ss">five</span><span class="p" data-group-id="6812954214-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-6">(</span><span class="ss">six</span><span class="p" data-group-id="6812954214-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="6812954214-7">(</span><span class="n">Int</span><span class="p" data-group-id="6812954214-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="6812954214-8">(</span><span class="n">Int</span><span class="p" data-group-id="6812954214-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-1">(</span><span class="n">Int</span><span class="p" data-group-id="6784489100-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="6784489100-2">(</span><span class="n">Int</span><span class="p" data-group-id="6784489100-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-3">(</span><span class="ss">one</span><span class="p" data-group-id="6784489100-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-4">(</span><span class="ss">two</span><span class="p" data-group-id="6784489100-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-5">(</span><span class="ss">three</span><span class="p" data-group-id="6784489100-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-6">(</span><span class="ss">four</span><span class="p" data-group-id="6784489100-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-7">(</span><span class="ss">five</span><span class="p" data-group-id="6784489100-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="6784489100-8">(</span><span class="ss">six</span><span class="p" data-group-id="6784489100-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="6023723900-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6023723900-2">[</span><span class="p" data-group-id="6023723900-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="6023723900-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-1">(</span><span class="ss">one</span><span class="p" data-group-id="4821524466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-2">(</span><span class="ss">two</span><span class="p" data-group-id="4821524466-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-3">(</span><span class="ss">three</span><span class="p" data-group-id="4821524466-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-4">(</span><span class="ss">four</span><span class="p" data-group-id="4821524466-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-5">(</span><span class="ss">five</span><span class="p" data-group-id="4821524466-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-6">(</span><span class="ss">six</span><span class="p" data-group-id="4821524466-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="4821524466-7">(</span><span class="n">Int</span><span class="p" data-group-id="4821524466-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4821524466-8">(</span><span class="n">Int</span><span class="p" data-group-id="4821524466-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-1">(</span><span class="n">Int</span><span class="p" data-group-id="0221583461-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="0221583461-2">(</span><span class="n">Int</span><span class="p" data-group-id="0221583461-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-3">(</span><span class="ss">one</span><span class="p" data-group-id="0221583461-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-4">(</span><span class="ss">two</span><span class="p" data-group-id="0221583461-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-5">(</span><span class="ss">three</span><span class="p" data-group-id="0221583461-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-6">(</span><span class="ss">four</span><span class="p" data-group-id="0221583461-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-7">(</span><span class="ss">five</span><span class="p" data-group-id="0221583461-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="0221583461-8">(</span><span class="ss">six</span><span class="p" data-group-id="0221583461-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="1900636666-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1900636666-2">[</span><span class="p" data-group-id="1900636666-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1900636666-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="6023723900-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6023723900-4">[</span><span class="p" data-group-id="6023723900-4">]</span><span class="p" data-group-id="6023723900-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="1900636666-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1900636666-4">[</span><span class="p" data-group-id="1900636666-4">]</span><span class="p" data-group-id="1900636666-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="6023723900-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6023723900-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="6023723900-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6023723900-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="6023723900-7">]</span><span class="p" data-group-id="6023723900-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6023723900-8">[</span><span class="n">Map</span><span class="p" data-group-id="6023723900-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6023723900-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="6023723900-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="6023723900-10">)</span><span class="p" data-group-id="6023723900-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="1900636666-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1900636666-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="1900636666-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1900636666-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="1900636666-7">]</span><span class="p" data-group-id="1900636666-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1900636666-8">[</span><span class="n">Map</span><span class="p" data-group-id="1900636666-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1900636666-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="1900636666-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1900636666-10">)</span><span class="p" data-group-id="1900636666-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │ │  all clauses. The problem is the variable in the second argument, <code class="inline">Xs</code>, in the
│ │ │ │  middle clause. Because the variable can match anything, the compiler is not
│ │ │ │  allowed to rearrange the clauses, but must generate code that matches them in
│ │ │ │  the order written.</p><p>If the function is rewritten as follows, the compiler is free to rearrange the
│ │ │ │ -clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="1338628891-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1338628891-2">[</span><span class="p" data-group-id="1338628891-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1338628891-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="9346566743-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9346566743-2">[</span><span class="p" data-group-id="9346566743-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="9346566743-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="1338628891-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1338628891-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="1338628891-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1338628891-5">[</span><span class="p" data-group-id="1338628891-5">]</span><span class="w"> </span><span class="p" data-group-id="1338628891-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="9346566743-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9346566743-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="9346566743-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9346566743-5">[</span><span class="p" data-group-id="9346566743-5">]</span><span class="w"> </span><span class="p" data-group-id="9346566743-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="1338628891-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1338628891-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="1338628891-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1338628891-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="1338628891-8">]</span><span class="p" data-group-id="1338628891-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1338628891-9">[</span><span class="n">Map</span><span class="p" data-group-id="1338628891-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1338628891-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="1338628891-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="1338628891-11">)</span><span class="p" data-group-id="1338628891-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="3118807201-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="3118807201-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="9346566743-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9346566743-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="9346566743-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9346566743-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="9346566743-8">]</span><span class="p" data-group-id="9346566743-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9346566743-9">[</span><span class="n">Map</span><span class="p" data-group-id="9346566743-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9346566743-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="9346566743-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="9346566743-11">)</span><span class="p" data-group-id="9346566743-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="9904672274-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="9904672274-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Xs0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="3118807201-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="3118807201-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="9904672274-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="9904672274-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="k">case</span><span class="w"> </span><span class="n">Ys0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="3118807201-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="3118807201-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="p" data-group-id="3118807201-4">[</span><span class="n">Map</span><span class="p" data-group-id="3118807201-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3118807201-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="3118807201-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="3118807201-6">)</span><span class="p" data-group-id="3118807201-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="3118807201-7">[</span><span class="p" data-group-id="3118807201-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="9904672274-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="9904672274-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="p" data-group-id="9904672274-4">[</span><span class="n">Map</span><span class="p" data-group-id="9904672274-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9904672274-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="9904672274-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="9904672274-6">)</span><span class="p" data-group-id="9904672274-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="9904672274-7">[</span><span class="p" data-group-id="9904672274-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  		    </span><span class="n">Xs0</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="3118807201-8">[</span><span class="p" data-group-id="3118807201-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="9904672274-8">[</span><span class="p" data-group-id="9904672274-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Ys0</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>This is slightly faster for probably the most common case that the input lists
│ │ │ │  are not empty or very short. (Another advantage is that Dialyzer can deduce a
│ │ │ │  better type for the <code class="inline">Xs</code> variable.)</p><h2 id="function-calls" class="section-heading">
│ │ │ │    <a href="#function-calls" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ ├── OEBPS/drivers.xhtml
│ │ │ │ @@ -27,23 +27,23 @@
│ │ │ │    <span class="text">Drivers and Concurrency</span>
│ │ │ │  </h2>
│ │ │ │  <p>The runtime system always takes a lock before running any code in a driver.</p><p>By default, that lock is at the driver level, that is, if several ports have
│ │ │ │  been opened to the same driver, only code for one port at the same time can be
│ │ │ │  running.</p><p>A driver can be configured to have one lock for each port instead.</p><p>If a driver is used in a functional way (that is, holds no state, but only does
│ │ │ │  some heavy calculation and returns a result), several ports with registered
│ │ │ │  names can be opened beforehand, and the port to be used can be chosen based on
│ │ │ │ -the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6033648107-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="6033648107-2">(</span><span class="p" data-group-id="6033648107-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="6033648107-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │ │ +the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1898547093-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="1898547093-2">(</span><span class="p" data-group-id="1898547093-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="1898547093-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │ │  	 </span><span class="ss">some_driver_05</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_06</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_07</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_08</span><span class="p">,</span><span class="w">
│ │ │ │  	 </span><span class="ss">some_driver_09</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_10</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_11</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_12</span><span class="p">,</span><span class="w">
│ │ │ │ -	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="6033648107-3">}</span><span class="p" data-group-id="6033648107-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="1898547093-3">}</span><span class="p" data-group-id="1898547093-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client_port</span><span class="p" data-group-id="6033648107-4">(</span><span class="p" data-group-id="6033648107-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="6033648107-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="6033648107-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="6033648107-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="6033648107-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="6033648107-8">(</span><span class="p" data-group-id="6033648107-8">)</span><span class="p" data-group-id="6033648107-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="6033648107-9">(</span><span class="p" data-group-id="6033648107-9">)</span><span class="p" data-group-id="6033648107-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │ │ +</span><span class="nf">client_port</span><span class="p" data-group-id="1898547093-4">(</span><span class="p" data-group-id="1898547093-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="1898547093-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="1898547093-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="1898547093-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="1898547093-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="1898547093-8">(</span><span class="p" data-group-id="1898547093-8">)</span><span class="p" data-group-id="1898547093-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="1898547093-9">(</span><span class="p" data-group-id="1898547093-9">)</span><span class="p" data-group-id="1898547093-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │ │  contention on the port lock for the driver.</p><h2 id="avoiding-copying-binaries-when-calling-a-driver" class="section-heading">
│ │ │ │    <a href="#avoiding-copying-binaries-when-calling-a-driver" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Avoiding Copying Binaries When Calling a Driver</span>
│ │ │ │  </h2>
│ │ │ │  <p>There are basically two ways to avoid copying a binary that is sent to a driver:</p><ul><li><p>If the <code class="inline">Data</code> argument for <a href="../../../lib/../erts/doc/html/erlang.html#port_control/3"><code class="inline">port_control/3</code></a> is a
│ │ │ ├── OEBPS/documentation.xhtml
│ │ │ │ @@ -17,23 +17,23 @@
│ │ │ │    </head>
│ │ │ │    <body class="content-inner">
│ │ │ │  
│ │ │ │      <h1 id="content">
│ │ │ │  Documentation
│ │ │ │      </h1>
│ │ │ │  <p>Documentation in Erlang is done through the <code class="inline">-moduledoc</code> and <code class="inline">-doc</code>
│ │ │ │ -<a href="modules.xhtml#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7568539378-1">(</span><span class="ss">arith</span><span class="p" data-group-id="7568539378-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="modules.xhtml#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2831681269-1">(</span><span class="ss">arith</span><span class="p" data-group-id="2831681269-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  A module for basic arithmetic.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7568539378-2">(</span><span class="p" data-group-id="7568539378-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7568539378-3">]</span><span class="p" data-group-id="7568539378-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2831681269-2">(</span><span class="p" data-group-id="2831681269-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2831681269-3">]</span><span class="p" data-group-id="2831681269-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="7568539378-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7568539378-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="2831681269-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2831681269-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │ │  or function declaration. It documents the overall purpose of the module.</p><p>The <code class="inline">-doc</code> attribute always precedes the <a href="ref_man_functions.xhtml">function</a> or
│ │ │ │  <a href="modules.xhtml#module-attributes">attribute</a> it documents. The
│ │ │ │  attributes that can be documented are
│ │ │ │  <a href="typespec.xhtml#type-declarations-of-user-defined-types">user-defined types</a>
│ │ │ │  (<code class="inline">-type</code> and <code class="inline">-opaque</code>) and
│ │ │ │  <a href="modules.xhtml#behaviour-module-attribute">behaviour module attributes</a>
│ │ │ │  (<code class="inline">-callback</code>).</p><p>By default the format used for documentation attributes is
│ │ │ │ @@ -45,55 +45,55 @@
│ │ │ │  <a href="modules.xhtml#documentation-attributes">Documentation Attributes</a>.</p><p><code class="inline">-doc</code> attributes have been available since Erlang/OTP 27.</p><h2 id="documentation-metadata" class="section-heading">
│ │ │ │    <a href="#documentation-metadata" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documentation metadata</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is possible to add metadata to the documentation entry. You do this by adding
│ │ │ │ -a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8623600361-1">(</span><span class="ss">arith</span><span class="p" data-group-id="8623600361-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0071176119-1">(</span><span class="ss">arith</span><span class="p" data-group-id="0071176119-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  A module for basic arithmetic.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="8623600361-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="8623600361-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="0071176119-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="0071176119-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8623600361-3">(</span><span class="p" data-group-id="8623600361-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8623600361-4">]</span><span class="p" data-group-id="8623600361-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0071176119-3">(</span><span class="p" data-group-id="0071176119-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0071176119-4">]</span><span class="p" data-group-id="0071176119-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="8623600361-5">(</span><span class="p" data-group-id="8623600361-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="8623600361-6">}</span><span class="p" data-group-id="8623600361-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="8623600361-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="8623600361-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="0071176119-5">(</span><span class="p" data-group-id="0071176119-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="0071176119-6">}</span><span class="p" data-group-id="0071176119-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="0071176119-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="0071176119-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │ │  user. There can be multiple metadata documentation entries, in which case the
│ │ │ │  maps will be merged with the latest taking precedence if there are duplicate
│ │ │ │  keys. Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="8983234320-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="8983234320-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="8983234320-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="8983234320-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="8983234320-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="8983234320-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="8377454019-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="8377454019-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="8377454019-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="8377454019-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="8377454019-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="8377454019-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │ │  that only <a href="data_types.xhtml#atom">atoms</a> are used for keys and
│ │ │ │  <a href="data_types.xhtml#string">strings</a> for the values.</p><h2 id="external-documentation-files" class="section-heading">
│ │ │ │    <a href="#external-documentation-files" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">External documentation files</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">-moduledoc</code> and <code class="inline">-doc</code> can also be placed in external files. To do so use
│ │ │ │  <code class="inline">-doc {file, &quot;path/to/doc.md&quot;}</code> to point to the documentation. The path used is
│ │ │ │  relative to the file where the <code class="inline">-doc</code> attribute is located. For example:</p><pre><code class="markdown">%% doc/add.md
│ │ │ │  Adds two numbers.</code></pre><p>and</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% src/arith.erl</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="9183778257-1">(</span><span class="p" data-group-id="9183778257-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="9183778257-2">}</span><span class="p" data-group-id="9183778257-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="9183778257-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9183778257-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="5355210387-1">(</span><span class="p" data-group-id="5355210387-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="5355210387-2">}</span><span class="p" data-group-id="5355210387-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="5355210387-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5355210387-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │ │    <a href="#documenting-a-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documenting a module</span>
│ │ │ │  </h2>
│ │ │ │  <p>The module description should include details on how to use the API and examples
│ │ │ │  of the different functions working together. Here is a good place to use images
│ │ │ │  and other diagrams to better show the usage of the module. Instead of writing a
│ │ │ │  long text in the <code class="inline">moduledoc</code> attribute, it could be better to break it out into
│ │ │ │  an external page.</p><p>The <code class="inline">moduledoc</code> attribute should start with a short paragraph describing the
│ │ │ │ -module and then go into greater details. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1032502732-1">(</span><span class="ss">arith</span><span class="p" data-group-id="1032502732-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +module and then go into greater details. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5660541260-1">(</span><span class="ss">arith</span><span class="p" data-group-id="5660541260-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │ │     A module for basic arithmetic.
│ │ │ │  
│ │ │ │     This module can be used to add and subtract values. For example:
│ │ │ │  
│ │ │ │     ```erlang
│ │ │ │     1&gt; arith:substract(arith:add(2, 3), 1).
│ │ │ │ @@ -108,94 +108,94 @@
│ │ │ │  <p>There are three reserved metadata keys for <code class="inline">-moduledoc</code>:</p><ul><li><code class="inline">since</code> - Shows in which version of the application the module was added.
│ │ │ │  If this is added, all functions, types, and callbacks within will also receive
│ │ │ │  the same <code class="inline">since</code> value unless specified in the metadata of the function, type
│ │ │ │  or callback.</li><li><code class="inline">deprecated</code> - Shows a text in the documentation explaining that it is
│ │ │ │  deprecated and what to use instead.</li><li><code class="inline">format</code> - The format to use for all documentation in this module. The
│ │ │ │  default is <code class="inline">text/markdown</code>. It should be written using the
│ │ │ │  <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types">mime type</a>
│ │ │ │ -of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="4171955021-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="4171955021-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="4171955021-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="4171955021-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="4171955021-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="4171955021-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │ │ +of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="1581499708-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="1581499708-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="1581499708-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="1581499708-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="1581499708-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="1581499708-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │ │    <a href="#documenting-functions-user-defined-types-and-callbacks" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Documenting functions, user-defined types, and callbacks</span>
│ │ │ │  </h2>
│ │ │ │  <p>Functions, types, and callbacks can be documented using the <code class="inline">-doc</code> attribute.
│ │ │ │  Each entry should start with a short paragraph describing the purpose of entity,
│ │ │ │  and then go into greater detail in needed.</p><p>It is not recommended to include images or diagrams in this documentation as it
│ │ │ │  is used by IDEs and <a href="../../../lib/stdlib/doc/html/c.html#h/1"><code class="inline">c:h/1</code></a> to show the documentation to the user.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  A number that can be used by the arith module.
│ │ │ │  
│ │ │ │  We use a special number here so that we know
│ │ │ │  that this number comes from this module.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7572595791-1">(</span><span class="p" data-group-id="7572595791-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7572595791-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="7572595791-3">(</span><span class="p" data-group-id="7572595791-3">)</span><span class="p" data-group-id="7572595791-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9834286500-1">(</span><span class="p" data-group-id="9834286500-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9834286500-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="9834286500-3">(</span><span class="p" data-group-id="9834286500-3">)</span><span class="p" data-group-id="9834286500-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  Adds two numbers.
│ │ │ │  
│ │ │ │  ### Example:
│ │ │ │  
│ │ │ │  ```
│ │ │ │  1&gt; arith:add(arith:number(1), arith:number(2)). {number, 3}
│ │ │ │  ```
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7572595791-4">(</span><span class="nf">number</span><span class="p" data-group-id="7572595791-5">(</span><span class="p" data-group-id="7572595791-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7572595791-6">(</span><span class="p" data-group-id="7572595791-6">)</span><span class="p" data-group-id="7572595791-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7572595791-7">(</span><span class="p" data-group-id="7572595791-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="7572595791-8">(</span><span class="p" data-group-id="7572595791-9">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="7572595791-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7572595791-10">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7572595791-10">}</span><span class="p" data-group-id="7572595791-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7572595791-11">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7572595791-11">}</span><span class="p">.</span></code></pre><h3 id="doc-metadata" class="section-heading">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9834286500-4">(</span><span class="nf">number</span><span class="p" data-group-id="9834286500-5">(</span><span class="p" data-group-id="9834286500-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9834286500-6">(</span><span class="p" data-group-id="9834286500-6">)</span><span class="p" data-group-id="9834286500-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9834286500-7">(</span><span class="p" data-group-id="9834286500-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9834286500-8">(</span><span class="p" data-group-id="9834286500-9">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="9834286500-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9834286500-10">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9834286500-10">}</span><span class="p" data-group-id="9834286500-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9834286500-11">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9834286500-11">}</span><span class="p">.</span></code></pre><h3 id="doc-metadata" class="section-heading">
│ │ │ │    <a href="#doc-metadata" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Doc metadata</span>
│ │ │ │  </h3>
│ │ │ │  <p>There are four reserved metadata keys for <code class="inline">-doc</code>:</p><ul><li><p><code class="inline">since =&gt; unicode:chardata()</code> - Shows which version of the application the
│ │ │ │  module was added.</p></li><li><p><code class="inline">deprecated =&gt; unicode:chardata()</code> - Shows a text in the documentation
│ │ │ │  explaining that it is deprecated and what to use instead. The compiler will
│ │ │ │  automatically insert this key if there is a <code class="inline">-deprecated</code> attribute marking a
│ │ │ │  function as deprecated.</p></li><li><p><code class="inline">equiv =&gt; unicode:chardata() | F/A | F(...)</code> - Notes that this function is equivalent to
│ │ │ │  another function in this module. The equivalence can be described using either
│ │ │ │ -<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../../lib/stdlib/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="6699849460-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6699849460-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="6699849460-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="6699849460-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="6699849460-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6699849460-4">[</span><span class="p" data-group-id="6699849460-4">]</span><span class="p" data-group-id="6699849460-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="6699849460-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="6699849460-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="7137974352-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7137974352-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7137974352-3">[</span><span class="p" data-group-id="7137974352-3">]</span><span class="p" data-group-id="7137974352-2">)</span><span class="p" data-group-id="7137974352-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7137974352-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7137974352-5">(</span><span class="p" data-group-id="7137974352-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7137974352-6">(</span><span class="p" data-group-id="7137974352-6">)</span><span class="p" data-group-id="7137974352-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7137974352-7">(</span><span class="p" data-group-id="7137974352-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="7137974352-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7137974352-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7137974352-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7137974352-10">[</span><span class="p" data-group-id="7137974352-10">]</span><span class="p" data-group-id="7137974352-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="7137974352-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="7137974352-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../../lib/kernel/doc/html/eep48_chapter.xhtml">EEP-48</a> doc chunk metadata is
│ │ │ │ +<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../../lib/stdlib/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="1112202340-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="1112202340-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="1112202340-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="1112202340-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="1112202340-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1112202340-4">[</span><span class="p" data-group-id="1112202340-4">]</span><span class="p" data-group-id="1112202340-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="1112202340-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="1112202340-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="7772880728-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7772880728-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7772880728-3">[</span><span class="p" data-group-id="7772880728-3">]</span><span class="p" data-group-id="7772880728-2">)</span><span class="p" data-group-id="7772880728-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7772880728-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7772880728-5">(</span><span class="p" data-group-id="7772880728-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7772880728-6">(</span><span class="p" data-group-id="7772880728-6">)</span><span class="p" data-group-id="7772880728-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="7772880728-7">(</span><span class="p" data-group-id="7772880728-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7772880728-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7772880728-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7772880728-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7772880728-10">[</span><span class="p" data-group-id="7772880728-10">]</span><span class="p" data-group-id="7772880728-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7772880728-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="7772880728-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../../lib/kernel/doc/html/eep48_chapter.xhtml">EEP-48</a> doc chunk metadata is
│ │ │ │  the value converted to a string.</p></li><li><p><code class="inline">exported =&gt; boolean()</code> - A <a href="../../../lib/../erts/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a> signifying if the entry is <code class="inline">exported</code>
│ │ │ │  or not. This value is automatically set by the compiler and should not be set
│ │ │ │  by the user.</p></li></ul><h3 id="doc-signatures" class="section-heading">
│ │ │ │    <a href="#doc-signatures" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Doc signatures</span>
│ │ │ │  </h3>
│ │ │ │  <p>The doc signature is a short text shown to describe the function and its arguments.
│ │ │ │  By default it is determined by looking at the names of the arguments in the
│ │ │ │ -<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="2082147905-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2082147905-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="5231610345-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5231610345-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="2082147905-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2082147905-3">(</span><span class="p" data-group-id="2082147905-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2082147905-4">(</span><span class="p" data-group-id="2082147905-4">)</span><span class="p" data-group-id="2082147905-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2082147905-5">(</span><span class="p" data-group-id="2082147905-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">sub</span><span class="p" data-group-id="2082147905-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2082147905-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ │ -specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0402675856-1">(</span><span class="n">Value</span><span class="p" data-group-id="0402675856-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0402675856-2">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0402675856-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="5231610345-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5231610345-3">(</span><span class="p" data-group-id="5231610345-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5231610345-4">(</span><span class="p" data-group-id="5231610345-4">)</span><span class="p" data-group-id="5231610345-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5231610345-5">(</span><span class="p" data-group-id="5231610345-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">sub</span><span class="p" data-group-id="5231610345-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5231610345-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ │ +specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="4285382605-1">(</span><span class="n">Value</span><span class="p" data-group-id="4285382605-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="4285382605-2">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="4285382605-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `number(Value)`</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0402675856-3">(</span><span class="p" data-group-id="0402675856-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0402675856-4">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0402675856-5">(</span><span class="p" data-group-id="0402675856-5">)</span><span class="p" data-group-id="0402675856-4">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="4285382605-3">(</span><span class="p" data-group-id="4285382605-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="4285382605-4">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="4285382605-5">(</span><span class="p" data-group-id="4285382605-5">)</span><span class="p" data-group-id="4285382605-4">}</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `number()`</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="0402675856-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0402675856-7">(</span><span class="p" data-group-id="0402675856-7">)</span><span class="p" data-group-id="0402675856-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="4285382605-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="4285382605-7">(</span><span class="p" data-group-id="4285382605-7">)</span><span class="p" data-group-id="4285382605-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `increment(In)`</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="0402675856-8">(</span><span class="n">In</span><span class="p" data-group-id="0402675856-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0402675856-9">(</span><span class="p" data-group-id="0402675856-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="4285382605-8">(</span><span class="n">In</span><span class="p" data-group-id="4285382605-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="4285382605-9">(</span><span class="p" data-group-id="4285382605-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%% signature will be `increment(In)`</span></code></pre><p>If it is not possible to &quot;easily&quot; figure out a nice signature from the code, the
│ │ │ │  MFA syntax is used instead. For example: <code class="inline">add/2</code>, <code class="inline">number/1</code>, <code class="inline">increment/1</code></p><p>It is possible to supply a custom signature by placing it as the first line of the
│ │ │ │  <code class="inline">-doc</code> attribute. The provided signature must be in the form of a function
│ │ │ │  declaration up until the <code class="inline">-&gt;</code>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │ │  add(One, Two)
│ │ │ │  
│ │ │ │  Adds two numbers.
│ │ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="2052501445-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2052501445-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>Will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="3426121206-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3426121206-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>Will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │ │  documentation string, so in the example above only the text <code class="inline">&quot;Adds two numbers&quot;</code>
│ │ │ │  will be part of the documentation. This works for functions, types, and
│ │ │ │  callbacks.</p><h2 id="links-in-markdown" class="section-heading">
│ │ │ │    <a href="#links-in-markdown" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Links in Markdown</span>
│ │ │ │ @@ -233,28 +233,28 @@
│ │ │ │  modules. That is, modules that should be used by other applications and modules
│ │ │ │  that should not. By default all modules in an application are visible, but by
│ │ │ │  setting <code class="inline">-moduledoc false.</code> specific modules can be hidden from being listed as
│ │ │ │  part of the available API.</p><p>An Erlang <a href="modules.xhtml">module</a> consists of public and private functions and type
│ │ │ │  attributes. By default, all exported functions, exported types and callbacks are
│ │ │ │  considered visible and part of the modules public API. In addition, any
│ │ │ │  non-exported type that is referred to by any other visible type attribute is
│ │ │ │ -also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2020756152-1">(</span><span class="p" data-group-id="2020756152-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2020756152-2">]</span><span class="p" data-group-id="2020756152-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9563974186-1">(</span><span class="p" data-group-id="9563974186-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9563974186-2">]</span><span class="p" data-group-id="9563974186-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="2020756152-3">(</span><span class="p" data-group-id="2020756152-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="2020756152-4">(</span><span class="p" data-group-id="2020756152-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="2020756152-5">(</span><span class="p" data-group-id="2020756152-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="2020756152-6">(</span><span class="p" data-group-id="2020756152-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>in the above code, the function <code class="inline">example/0</code> is exported and it referenced the
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="9563974186-3">(</span><span class="p" data-group-id="9563974186-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="9563974186-4">(</span><span class="p" data-group-id="9563974186-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="9563974186-5">(</span><span class="p" data-group-id="9563974186-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="9563974186-6">(</span><span class="p" data-group-id="9563974186-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>in the above code, the function <code class="inline">example/0</code> is exported and it referenced the
│ │ │ │  un-exported type <code class="inline">private/0</code>. Therefore both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be
│ │ │ │  marked as visible. The <code class="inline">private/0</code> type will have the metadata field <code class="inline">exported</code>
│ │ │ │  set to <code class="inline">false</code> to show that it is not part of the public API.</p><p>If you want to make a visible entity hidden you need to set the <code class="inline">-doc</code> attribute
│ │ │ │ -to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0948794120-1">(</span><span class="p" data-group-id="0948794120-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0948794120-2">]</span><span class="p" data-group-id="0948794120-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7461409038-1">(</span><span class="p" data-group-id="7461409038-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7461409038-2">]</span><span class="p" data-group-id="7461409038-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="0948794120-3">(</span><span class="p" data-group-id="0948794120-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="0948794120-4">(</span><span class="p" data-group-id="0948794120-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="0948794120-5">(</span><span class="p" data-group-id="0948794120-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="7461409038-3">(</span><span class="p" data-group-id="7461409038-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="7461409038-4">(</span><span class="p" data-group-id="7461409038-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="7461409038-5">(</span><span class="p" data-group-id="7461409038-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="0948794120-6">(</span><span class="p" data-group-id="0948794120-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="7461409038-6">(</span><span class="p" data-group-id="7461409038-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │ │  both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be hidden.</p><p>Any documentation added to an automatically hidden entity (non-exported function
│ │ │ │  or type) is ignored and will generate a warning. Such functions can be
│ │ │ │  documented using comments.</p><h2 id="compiling-and-getting-documentation" class="section-heading">
│ │ │ │    <a href="#compiling-and-getting-documentation" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Compiling and getting documentation</span>
│ │ │ │ @@ -280,21 +280,21 @@
│ │ │ │    <span class="text">Using ExDoc to generate HTML/ePub documentation</span>
│ │ │ │  </h2>
│ │ │ │  <p><a href="https://hexdocs.pm/ex_doc/">ExDoc</a> has built-in support to generate
│ │ │ │  documentation from Markdown. The simplest way is by using the
│ │ │ │  <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> plugin. To set up a
│ │ │ │  rebar3 project to use <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate
│ │ │ │  documentation add the following to your <code class="inline">rebar3.config</code>.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Enable the plugin</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2529772611-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2529772611-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="2529772611-2">]</span><span class="p" data-group-id="2529772611-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8857957312-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8857957312-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="8857957312-2">]</span><span class="p" data-group-id="8857957312-1">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="2529772611-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2529772611-4">[</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2529772611-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2529772611-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="2529772611-6">]</span><span class="p" data-group-id="2529772611-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2529772611-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="2529772611-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2529772611-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="2529772611-8">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2529772611-4">]</span><span class="p" data-group-id="2529772611-3">}</span><span class="p">.</span></code></pre><p>When configured you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │ │ +</span><span class="p" data-group-id="8857957312-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8857957312-4">[</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8857957312-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8857957312-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="8857957312-6">]</span><span class="p" data-group-id="8857957312-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8857957312-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="8857957312-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="8857957312-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="8857957312-8">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8857957312-4">]</span><span class="p" data-group-id="8857957312-3">}</span><span class="p">.</span></code></pre><p>When configured you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │ │  documentation to <code class="inline">doc/index.html</code>. For more details and options see
│ │ │ │  the <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> documentation.</p><p>You can also download the
│ │ │ │  <a href="https://github.com/elixir/ex_doc/releases/latest">release escript bundle</a> from
│ │ │ │  github and run it from the command line. The documentation for using the escript
│ │ │ │  is found by running <code class="inline">ex_doc --help</code>.</p><p>If you are writing documentation that will be using
│ │ │ │  <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate HTML/ePub it is highly
│ │ │ │  recommended to read its documentation.</p>
│ │ │ ├── OEBPS/distributed_applications.xhtml
│ │ │ │ @@ -55,36 +55,36 @@
│ │ │ │  (within the time-out specified by <code class="inline">sync_nodes_timeout</code>).</li><li><p><code class="inline">sync_nodes_timeout = integer() | infinity</code> - Specifies how many milliseconds
│ │ │ │  to wait for the other nodes to start.</p></li></ul><p>When started, the node waits for all nodes specified by <code class="inline">sync_nodes_mandatory</code>
│ │ │ │  and <code class="inline">sync_nodes_optional</code> to come up. When all nodes are up, or when all
│ │ │ │  mandatory nodes are up and the time specified by <code class="inline">sync_nodes_timeout</code> has
│ │ │ │  elapsed, all applications start. If not all mandatory nodes are up, the node
│ │ │ │  terminates.</p><p><em>Example:</em></p><p>An application <code class="inline">myapp</code> is to run at the node <code class="inline">cp1@cave</code>. If this node goes down,
│ │ │ │  <code class="inline">myapp</code> is to be restarted at <code class="inline">cp2@cave</code> or <code class="inline">cp3@cave</code>. A system configuration
│ │ │ │ -file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5243847754-1">[</span><span class="p" data-group-id="5243847754-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5243847754-3">[</span><span class="p" data-group-id="5243847754-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5243847754-5">[</span><span class="p" data-group-id="5243847754-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5243847754-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5243847754-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="5243847754-8">}</span><span class="p" data-group-id="5243847754-7">]</span><span class="p" data-group-id="5243847754-6">}</span><span class="p" data-group-id="5243847754-5">]</span><span class="p" data-group-id="5243847754-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="5243847754-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5243847754-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="5243847754-10">]</span><span class="p" data-group-id="5243847754-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="5243847754-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="5243847754-11">}</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5243847754-3">]</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5243847754-2">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="5243847754-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │ │ +file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1004063864-1">[</span><span class="p" data-group-id="1004063864-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1004063864-3">[</span><span class="p" data-group-id="1004063864-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004063864-5">[</span><span class="p" data-group-id="1004063864-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004063864-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004063864-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="1004063864-8">}</span><span class="p" data-group-id="1004063864-7">]</span><span class="p" data-group-id="1004063864-6">}</span><span class="p" data-group-id="1004063864-5">]</span><span class="p" data-group-id="1004063864-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="1004063864-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1004063864-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="1004063864-10">]</span><span class="p" data-group-id="1004063864-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="1004063864-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="1004063864-11">}</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1004063864-3">]</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1004063864-2">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1004063864-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │ │  except for the list of mandatory nodes, which is to be <code class="inline">[cp1@cave, cp3@cave]</code>
│ │ │ │  for <code class="inline">cp2@cave</code> and <code class="inline">[cp1@cave, cp2@cave]</code> for <code class="inline">cp3@cave</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>All involved nodes must have the same value for <code class="inline">distributed</code> and
│ │ │ │  <code class="inline">sync_nodes_timeout</code>. Otherwise the system behavior is undefined.</p></section><h2 id="starting-and-stopping-distributed-applications" class="section-heading">
│ │ │ │    <a href="#starting-and-stopping-distributed-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting and Stopping Distributed Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>When all involved (mandatory) nodes have been started, the distributed
│ │ │ │  application can be started by calling <code class="inline">application:start(Application)</code> at <em>all
│ │ │ │  of these nodes.</em></p><p>A boot script (see <a href="release_structure.xhtml">Releases</a>) can be used that
│ │ │ │  automatically starts the application.</p><p>The application is started at the first operational node that is listed in the
│ │ │ │  list of nodes in the <code class="inline">distributed</code> configuration parameter. The application is
│ │ │ │  started as usual. That is, an application master is created and calls the
│ │ │ │ -application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0267718748-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="0267718748-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │ │ +application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2923475335-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="2923475335-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │ │  specifying the system configuration file:</p><pre><code class="text">&gt; erl -sname cp1 -config cp1
│ │ │ │  &gt; erl -sname cp2 -config cp2
│ │ │ │  &gt; erl -sname cp3 -config cp3</code></pre><p>When all nodes are operational, <code class="inline">myapp</code> can be started. This is achieved by
│ │ │ │  calling <code class="inline">application:start(myapp)</code> at all three nodes. It is then started at
│ │ │ │  <code class="inline">cp1</code>, as shown in the following figure:</p><p><a href="" id="dist1"></a></p><p><img src="assets/dist1.gif" alt="Application myapp - Situation 1" title="Application myapp - Situation 1"/></p><p>Similarly, the application must be stopped by calling
│ │ │ │  <code class="inline">application:stop(Application)</code> at all involved nodes.</p><h2 id="failover" class="section-heading">
│ │ │ │    <a href="#failover" class="hover-link">
│ │ │ │ @@ -92,30 +92,30 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Failover</span>
│ │ │ │  </h2>
│ │ │ │  <p>If the node where the application is running goes down, the application is
│ │ │ │  restarted (after the specified time-out) at the first operational node that is
│ │ │ │  listed in the list of nodes in the <code class="inline">distributed</code> configuration parameter. This
│ │ │ │  is called a <em>failover</em>.</p><p>The application is started the normal way at the new node, that is, by the
│ │ │ │ -application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3872354310-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="3872354310-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │ │ +application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9442330334-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="9442330334-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │ │  <a href="included_applications.xhtml">Included Applications</a>). The application is then
│ │ │ │ -instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7762803486-1">(</span><span class="p" data-group-id="7762803486-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="7762803486-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="7762803486-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │ │ +instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6995404650-1">(</span><span class="p" data-group-id="6995404650-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="6995404650-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="6995404650-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │ │  <code class="inline">cp3</code>, has the least number of running applications, but waits for 5 seconds for
│ │ │ │  <code class="inline">cp1</code> to restart. If <code class="inline">cp1</code> does not restart and <code class="inline">cp2</code> runs fewer applications
│ │ │ │  than <code class="inline">cp3</code>, <code class="inline">myapp</code> is restarted on <code class="inline">cp2</code>.</p><p><a href="" id="dist2"></a></p><p><img src="assets/dist2.gif" alt="Application myapp - Situation 2" title="Application myapp - Situation 2"/></p><p>Suppose now that <code class="inline">cp2</code> goes also down and does not restart within 5 seconds.
│ │ │ │  <code class="inline">myapp</code> is now restarted on <code class="inline">cp3</code>.</p><p><a href="" id="dist3"></a></p><p><img src="assets/dist3.gif" alt="Application myapp - Situation 3" title="Application myapp - Situation 3"/></p><h2 id="takeover" class="section-heading">
│ │ │ │    <a href="#takeover" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Takeover</span>
│ │ │ │  </h2>
│ │ │ │  <p>If a node is started, which has higher priority according to <code class="inline">distributed</code> than
│ │ │ │  the node where a distributed application is running, the application is
│ │ │ │  restarted at the new node and stopped at the old node. This is called a
│ │ │ │ -<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4523478048-1">(</span><span class="p" data-group-id="4523478048-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="4523478048-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="4523478048-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │ │ +<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1149622851-1">(</span><span class="p" data-group-id="1149622851-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="1149622851-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="1149622851-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │ │  <code class="inline">myapp</code>, as the order between the <code class="inline">cp2</code> and <code class="inline">cp3</code> nodes is undefined.</p><p><a href="" id="dist4"></a></p><p><img src="assets/dist4.gif" alt="Application myapp - Situation 4" title="Application myapp - Situation 4"/></p><p>However, if <code class="inline">cp1</code> also restarts, the function <a href="../../../lib/kernel/doc/html/application.html#takeover/2"><code class="inline">application:takeover/2</code></a> moves
│ │ │ │  <code class="inline">myapp</code> to <code class="inline">cp1</code>, as <code class="inline">cp1</code> has a higher priority than <code class="inline">cp3</code> for this
│ │ │ │  application. In this case, <code class="inline">Module:start({takeover, cp3@cave}, StartArgs)</code> is
│ │ │ │  executed at <code class="inline">cp1</code> to start the application.</p><p><a href="" id="dist5"></a></p><p><img src="assets/dist5.gif" alt="Application myapp - Situation 5" title="Application myapp - Situation 5"/></p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/distributed.xhtml
│ │ │ │ @@ -47,25 +47,25 @@
│ │ │ │  </h2>
│ │ │ │  <p>A <em>node</em> is an executing Erlang runtime system that has been given a name, using
│ │ │ │  the command-line flag <a href="../../../lib/../erts/doc/html/erl_cmd.xhtml#name"><code class="inline">-name</code></a> (long names) or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erl_cmd.xhtml#sname"><code class="inline">-sname</code></a> (short names).</p><p>The format of the node name is an atom <code class="inline">name@host</code>. <code class="inline">name</code> is the name given by
│ │ │ │  the user. <code class="inline">host</code> is the full host name if long names are used, or the first part
│ │ │ │  of the host name if short names are used. Function <a href="../../../lib/../erts/doc/html/erlang.html#node/0"><code class="inline">node()</code></a>
│ │ │ │  returns the name of the node.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -name dilbert</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6156136294-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="6156136294-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="6156136294-2">(</span><span class="p" data-group-id="6156136294-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9923793370-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="9923793370-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="9923793370-2">(</span><span class="p" data-group-id="9923793370-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">&#39;dilbert@uab.ericsson.se&#39;</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">% erl -sname dilbert</span><span class="gp unselectable">
│ │ │ │ -(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="6156136294-3">(</span><span class="p" data-group-id="6156136294-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="9923793370-3">(</span><span class="p" data-group-id="9923793370-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">dilbert@uab</span></code></pre><p>The node name can also be given in runtime by calling <a href="../../../lib/kernel/doc/html/net_kernel.html#start/1"><code class="inline">net_kernel:start/1</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nf">node</span><span class="p" data-group-id="0025749375-1">(</span><span class="p" data-group-id="0025749375-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +1&gt; </span><span class="nf">node</span><span class="p" data-group-id="2435603579-1">(</span><span class="p" data-group-id="2435603579-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">nonode@nohost</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0025749375-2">(</span><span class="p" data-group-id="0025749375-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="0025749375-3">]</span><span class="p" data-group-id="0025749375-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0025749375-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0025749375-4">}</span><span class="gp unselectable">
│ │ │ │ -(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="0025749375-5">(</span><span class="p" data-group-id="0025749375-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2435603579-2">(</span><span class="p" data-group-id="2435603579-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="2435603579-3">]</span><span class="p" data-group-id="2435603579-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2435603579-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="2435603579-4">}</span><span class="gp unselectable">
│ │ │ │ +(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="2435603579-5">(</span><span class="p" data-group-id="2435603579-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">dilbert@uab</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>A node with a long node name cannot communicate with a node with a short node
│ │ │ │  name.</p></section><h2 id="node-connections" class="section-heading">
│ │ │ │    <a href="#node-connections" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Node Connections</span>
│ │ │ │  </h2>
│ │ │ ├── OEBPS/design_principles.xhtml
│ │ │ │ @@ -57,135 +57,135 @@
│ │ │ │  the code for a process in a generic part (a behaviour module) and a specific
│ │ │ │  part (a <em>callback module</em>).</p><p>The behaviour module is part of Erlang/OTP. To implement a process such as a
│ │ │ │  supervisor, the user only needs to implement the callback module, which is to
│ │ │ │  export a pre-defined set of functions, the <em>callback functions</em>.</p><p>The following example illustrate how code can be divided into a generic and a
│ │ │ │  specific part. Consider the following code (written in plain Erlang) for a
│ │ │ │  simple server, which keeps track of a number of &quot;channels&quot;. Other processes can
│ │ │ │  allocate and free the channels by calling the functions <code class="inline">alloc/0</code> and <code class="inline">free/1</code>,
│ │ │ │ -respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9602166539-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="9602166539-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9602166539-2">(</span><span class="p" data-group-id="9602166539-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9602166539-3">]</span><span class="p" data-group-id="9602166539-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9602166539-4">(</span><span class="p" data-group-id="9602166539-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9602166539-5">]</span><span class="p" data-group-id="9602166539-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9602166539-6">(</span><span class="p" data-group-id="9602166539-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9602166539-7">]</span><span class="p" data-group-id="9602166539-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9223559759-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="9223559759-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9223559759-2">(</span><span class="p" data-group-id="9223559759-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9223559759-3">]</span><span class="p" data-group-id="9223559759-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9223559759-4">(</span><span class="p" data-group-id="9223559759-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9223559759-5">]</span><span class="p" data-group-id="9223559759-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9223559759-6">(</span><span class="p" data-group-id="9223559759-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9223559759-7">]</span><span class="p" data-group-id="9223559759-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="9602166539-8">(</span><span class="p" data-group-id="9602166539-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="9602166539-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9602166539-10">[</span><span class="p" data-group-id="9602166539-10">]</span><span class="p" data-group-id="9602166539-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9223559759-8">(</span><span class="p" data-group-id="9223559759-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9223559759-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9223559759-10">[</span><span class="p" data-group-id="9223559759-10">]</span><span class="p" data-group-id="9223559759-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="9602166539-11">(</span><span class="p" data-group-id="9602166539-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9602166539-12">{</span><span class="nf">self</span><span class="p" data-group-id="9602166539-13">(</span><span class="p" data-group-id="9602166539-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9602166539-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="9223559759-11">(</span><span class="p" data-group-id="9223559759-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9223559759-12">{</span><span class="nf">self</span><span class="p" data-group-id="9223559759-13">(</span><span class="p" data-group-id="9223559759-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9223559759-12">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9602166539-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="9602166539-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9223559759-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="9223559759-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Res</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="9602166539-15">(</span><span class="n">Ch</span><span class="p" data-group-id="9602166539-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9602166539-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9602166539-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="9223559759-15">(</span><span class="n">Ch</span><span class="p" data-group-id="9223559759-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9223559759-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9223559759-16">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9602166539-17">(</span><span class="p" data-group-id="9602166539-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="9602166539-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9602166539-19">(</span><span class="p" data-group-id="9602166539-19">)</span><span class="p" data-group-id="9602166539-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9602166539-20">(</span><span class="p" data-group-id="9602166539-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="9602166539-21">(</span><span class="n">Chs</span><span class="p" data-group-id="9602166539-21">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9223559759-17">(</span><span class="p" data-group-id="9223559759-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9223559759-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9223559759-19">(</span><span class="p" data-group-id="9223559759-19">)</span><span class="p" data-group-id="9223559759-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9223559759-20">(</span><span class="p" data-group-id="9223559759-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="9223559759-21">(</span><span class="n">Chs</span><span class="p" data-group-id="9223559759-21">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="9602166539-22">(</span><span class="n">Chs</span><span class="p" data-group-id="9602166539-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="9223559759-22">(</span><span class="n">Chs</span><span class="p" data-group-id="9223559759-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9602166539-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9602166539-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="9602166539-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9602166539-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9602166539-25">(</span><span class="n">Chs</span><span class="p" data-group-id="9602166539-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9602166539-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9602166539-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9602166539-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="9602166539-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="9602166539-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9602166539-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9602166539-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9602166539-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9602166539-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="9602166539-30">)</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4167629697-1">(</span><span class="ss">server</span><span class="p" data-group-id="4167629697-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4167629697-2">(</span><span class="p" data-group-id="4167629697-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4167629697-3">]</span><span class="p" data-group-id="4167629697-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4167629697-4">(</span><span class="p" data-group-id="4167629697-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4167629697-5">]</span><span class="p" data-group-id="4167629697-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4167629697-6">(</span><span class="p" data-group-id="4167629697-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4167629697-7">]</span><span class="p" data-group-id="4167629697-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9223559759-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9223559759-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9223559759-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9223559759-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9223559759-25">(</span><span class="n">Chs</span><span class="p" data-group-id="9223559759-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9223559759-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9223559759-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="9223559759-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="9223559759-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9223559759-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9223559759-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9223559759-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9223559759-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="9223559759-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="9223559759-30">)</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2402171500-1">(</span><span class="ss">server</span><span class="p" data-group-id="2402171500-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2402171500-2">(</span><span class="p" data-group-id="2402171500-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2402171500-3">]</span><span class="p" data-group-id="2402171500-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2402171500-4">(</span><span class="p" data-group-id="2402171500-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2402171500-5">]</span><span class="p" data-group-id="2402171500-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2402171500-6">(</span><span class="p" data-group-id="2402171500-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2402171500-7">]</span><span class="p" data-group-id="2402171500-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4167629697-8">(</span><span class="n">Mod</span><span class="p" data-group-id="4167629697-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4167629697-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4167629697-10">[</span><span class="n">Mod</span><span class="p" data-group-id="4167629697-10">]</span><span class="p" data-group-id="4167629697-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2402171500-8">(</span><span class="n">Mod</span><span class="p" data-group-id="2402171500-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2402171500-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2402171500-10">[</span><span class="n">Mod</span><span class="p" data-group-id="2402171500-10">]</span><span class="p" data-group-id="2402171500-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="4167629697-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4167629697-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4167629697-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4167629697-13">(</span><span class="p" data-group-id="4167629697-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4167629697-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="2402171500-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2402171500-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2402171500-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2402171500-13">(</span><span class="p" data-group-id="2402171500-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2402171500-12">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4167629697-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="4167629697-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2402171500-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2402171500-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Res</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">cast</span><span class="p" data-group-id="4167629697-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4167629697-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4167629697-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4167629697-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">cast</span><span class="p" data-group-id="2402171500-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2402171500-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2402171500-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2402171500-16">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4167629697-17">(</span><span class="n">Mod</span><span class="p" data-group-id="4167629697-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4167629697-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4167629697-19">(</span><span class="p" data-group-id="4167629697-19">)</span><span class="p" data-group-id="4167629697-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="4167629697-20">(</span><span class="p" data-group-id="4167629697-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4167629697-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4167629697-21">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2402171500-17">(</span><span class="n">Mod</span><span class="p" data-group-id="2402171500-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="2402171500-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2402171500-19">(</span><span class="p" data-group-id="2402171500-19">)</span><span class="p" data-group-id="2402171500-18">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="2402171500-20">(</span><span class="p" data-group-id="2402171500-20">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2402171500-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2402171500-21">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4167629697-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4167629697-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="2402171500-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2402171500-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4167629697-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4167629697-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="4167629697-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="4167629697-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="4167629697-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4167629697-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4167629697-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="4167629697-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="4167629697-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="4167629697-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4167629697-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="4167629697-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="4167629697-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4167629697-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="4167629697-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="4167629697-30">)</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5533678596-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="5533678596-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5533678596-2">(</span><span class="p" data-group-id="5533678596-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5533678596-3">]</span><span class="p" data-group-id="5533678596-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5533678596-4">(</span><span class="p" data-group-id="5533678596-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5533678596-5">]</span><span class="p" data-group-id="5533678596-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5533678596-6">(</span><span class="p" data-group-id="5533678596-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5533678596-7">]</span><span class="p" data-group-id="5533678596-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="5533678596-8">(</span><span class="p" data-group-id="5533678596-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5533678596-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="5533678596-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="5533678596-10">(</span><span class="p" data-group-id="5533678596-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="5533678596-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="5533678596-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="5533678596-12">(</span><span class="n">Ch</span><span class="p" data-group-id="5533678596-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5533678596-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5533678596-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5533678596-14">}</span><span class="p" data-group-id="5533678596-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2402171500-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2402171500-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="2402171500-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2402171500-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="2402171500-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2402171500-25">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2402171500-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2402171500-26">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2402171500-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2402171500-27">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2402171500-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2402171500-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="2402171500-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2402171500-29">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2402171500-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2402171500-30">)</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4549924642-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="4549924642-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4549924642-2">(</span><span class="p" data-group-id="4549924642-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4549924642-3">]</span><span class="p" data-group-id="4549924642-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4549924642-4">(</span><span class="p" data-group-id="4549924642-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4549924642-5">]</span><span class="p" data-group-id="4549924642-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4549924642-6">(</span><span class="p" data-group-id="4549924642-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4549924642-7">]</span><span class="p" data-group-id="4549924642-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4549924642-8">(</span><span class="p" data-group-id="4549924642-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4549924642-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="4549924642-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="4549924642-10">(</span><span class="p" data-group-id="4549924642-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4549924642-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="4549924642-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="4549924642-12">(</span><span class="n">Ch</span><span class="p" data-group-id="4549924642-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4549924642-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4549924642-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4549924642-14">}</span><span class="p" data-group-id="4549924642-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5533678596-15">(</span><span class="p" data-group-id="5533678596-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">channels</span><span class="p" data-group-id="5533678596-16">(</span><span class="p" data-group-id="5533678596-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4549924642-15">(</span><span class="p" data-group-id="4549924642-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">channels</span><span class="p" data-group-id="4549924642-16">(</span><span class="p" data-group-id="4549924642-16">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="5533678596-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5533678596-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">alloc</span><span class="p" data-group-id="5533678596-18">(</span><span class="n">Chs</span><span class="p" data-group-id="5533678596-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="4549924642-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4549924642-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">alloc</span><span class="p" data-group-id="4549924642-18">(</span><span class="n">Chs</span><span class="p" data-group-id="4549924642-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="5533678596-19">(</span><span class="p" data-group-id="5533678596-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5533678596-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5533678596-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">free</span><span class="p" data-group-id="5533678596-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5533678596-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="4549924642-19">(</span><span class="p" data-group-id="4549924642-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4549924642-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4549924642-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">free</span><span class="p" data-group-id="4549924642-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4549924642-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │ │  the client functions. This means that the name can be changed without
│ │ │ │  affecting them.</li><li>The protocol (messages sent to and received from the server) is also hidden.
│ │ │ │  This is good programming practice and allows one to change the protocol
│ │ │ │  without changing the code using the interface functions.</li><li>The functionality of <code class="inline">server</code> can be extended without having to change <code class="inline">ch2</code>
│ │ │ │  or any other callback module.</li></ul><p>In <code class="inline">ch1.erl</code> and <code class="inline">ch2.erl</code> above, the implementation of <code class="inline">channels/0</code>, <code class="inline">alloc/1</code>,
│ │ │ │  and <code class="inline">free/2</code> has been intentionally left out, as it is not relevant to the
│ │ │ │  example. For completeness, one way to write these functions is given below. This
│ │ │ │  is an example only, a realistic implementation must be able to handle situations
│ │ │ │ -like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="0358386752-1">(</span><span class="p" data-group-id="0358386752-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="0358386752-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0358386752-3">[</span><span class="p" data-group-id="0358386752-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="0358386752-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="0358386752-4">)</span><span class="p" data-group-id="0358386752-2">}</span><span class="p">.</span><span class="w">
│ │ │ │ +like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="0110847131-1">(</span><span class="p" data-group-id="0110847131-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="0110847131-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0110847131-3">[</span><span class="p" data-group-id="0110847131-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="0110847131-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="0110847131-4">)</span><span class="p" data-group-id="0110847131-2">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="0358386752-5">(</span><span class="p" data-group-id="0358386752-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358386752-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0358386752-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="0358386752-6">}</span><span class="p" data-group-id="0358386752-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="0358386752-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358386752-9">{</span><span class="p" data-group-id="0358386752-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="0358386752-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0358386752-9">}</span><span class="p" data-group-id="0358386752-8">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="0110847131-5">(</span><span class="p" data-group-id="0110847131-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0110847131-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0110847131-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="0110847131-6">}</span><span class="p" data-group-id="0110847131-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="0110847131-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0110847131-9">{</span><span class="p" data-group-id="0110847131-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="0110847131-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0110847131-9">}</span><span class="p" data-group-id="0110847131-8">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="0358386752-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358386752-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="0358386752-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="0358386752-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="0358386752-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0358386752-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="0110847131-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0110847131-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="0110847131-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="0110847131-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="0110847131-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0110847131-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │        </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -         </span><span class="p" data-group-id="0358386752-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="0358386752-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0358386752-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0358386752-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="0358386752-16">]</span><span class="p" data-group-id="0358386752-14">}</span><span class="p">;</span><span class="w">
│ │ │ │ +         </span><span class="p" data-group-id="0110847131-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="0110847131-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0110847131-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0110847131-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="0110847131-16">]</span><span class="p" data-group-id="0110847131-14">}</span><span class="p">;</span><span class="w">
│ │ │ │        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │           </span><span class="n">Channels</span><span class="w">
│ │ │ │     </span><span class="k">end</span><span class="p">.</span></code></pre><p>Code written without using behaviours can be more efficient, but the increased
│ │ │ │  efficiency is at the expense of generality. The ability to manage all
│ │ │ │  applications in the system in a consistent manner is important.</p><p>Using behaviours also makes it easier to read and understand code written by
│ │ │ │  other programmers. Improvised programming structures, while possibly more
│ │ │ │  efficient, are always more difficult to understand.</p><p>The <code class="inline">server</code> module corresponds, greatly simplified, to the Erlang/OTP behaviour
│ │ │ │  <code class="inline">gen_server</code>.</p><p>The standard Erlang/OTP behaviours are:</p><ul><li><p><a href="gen_server_concepts.xhtml">gen_server</a></p><p>For implementing the server of a client-server relation</p></li><li><p><a href="statem.xhtml">gen_statem</a></p><p>For implementing state machines</p></li><li><p><a href="events.xhtml">gen_event</a></p><p>For implementing event handling functionality</p></li><li><p><a href="sup_princ.xhtml">supervisor</a></p><p>For implementing a supervisor in a supervision tree</p></li></ul><p>The compiler understands the module attribute <code class="inline">-behaviour(Behaviour)</code> and issues
│ │ │ │ -warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7223231578-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="7223231578-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7223231578-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="7223231578-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6726878439-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="6726878439-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6726878439-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="6726878439-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="7223231578-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="7223231578-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="6726878439-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="6726878439-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">chs3</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">10</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">undefined</span><span class="w"> </span><span class="ss">call</span><span class="o">-</span><span class="ss">back</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7223231578-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="7223231578-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │ │ +</span><span class="p" data-group-id="6726878439-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="6726878439-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │ │    <a href="#applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang/OTP comes with a number of components, each implementing some specific
│ │ │ │  functionality. Components are with Erlang/OTP terminology called <em>applications</em>.
│ │ │ ├── OEBPS/data_types.xhtml
│ │ │ │ @@ -97,18 +97,18 @@
│ │ │ │    </a>
│ │ │ │    <span class="text">Representation of Floating Point Numbers</span>
│ │ │ │  </h3>
│ │ │ │  <p>When working with floats you may not see what you expect when printing or doing
│ │ │ │  arithmetic operations. This is because floats are represented by a fixed number
│ │ │ │  of bits in a base-2 system while printed floats are represented with a base-10
│ │ │ │  system. Erlang uses 64-bit floats. Here are examples of this phenomenon:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8980227413-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="8980227413-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8980227413-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="8980227413-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │ │ +</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1524204961-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="1524204961-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1524204961-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="1524204961-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │ │  Erlang's pretty printer rounds <code class="inline">36028797018963968.0</code> to <code class="inline">3.602879701896397e16</code>
│ │ │ │  (<code class="inline">=36028797018963970.0</code>) as all values in the range
│ │ │ │  <code class="inline">[36028797018963966.0, 36028797018963972.0]</code> are represented by
│ │ │ │  <code class="inline">36028797018963968.0</code>.</p><p>For more information about floats and issues with them see:</p><ul><li><a href="https://floating-point-gui.de/">What Every Programmer Should Know About Floating-Point Arithmetic</a></li><li><a href="https://0.30000000000000004.com/">0.30000000000000004.com/</a></li><li><a href="https://docs.python.org/3/tutorial/floatingpoint.html">Floating Point Arithmetic: Issues and Limitations</a></li></ul><p>If you need to work with exact decimal fractions, for instance to represent
│ │ │ │  money, it is recommended to use a library that handles that, or work in
│ │ │ │  cents instead of dollars or euros so that decimal fractions are not needed.</p><p>Also note that Erlang's floats do not exactly match IEEE 754 floats,
│ │ │ │  in that neither <em>Inf</em> nor <em>NaN</em> are supported in Erlang. Any
│ │ │ │ @@ -142,52 +142,52 @@
│ │ │ │  by eight are called <em>binaries</em>.</p><p><em>Examples:</em></p><pre><code class="text">1&gt; &lt;&lt;10,20&gt;&gt;.
│ │ │ │  &lt;&lt;10,20&gt;&gt;
│ │ │ │  2&gt; &lt;&lt;&quot;ABC&quot;&gt;&gt;.
│ │ │ │  &lt;&lt;&quot;ABC&quot;&gt;&gt;
│ │ │ │  3&gt; &lt;&lt;1:1,0:1&gt;&gt;.
│ │ │ │  &lt;&lt;2:2&gt;&gt;</code></pre><p>The <a href="../../../lib/../erts/doc/html/erlang.html#is_bitstring/1"><code class="inline">is_bitstring/1</code></a> BIF tests whether a
│ │ │ │  term is a bit string, and the <a href="../../../lib/../erts/doc/html/erlang.html#is_binary/1"><code class="inline">is_binary/1</code></a>
│ │ │ │ -BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="5524294285-1">(</span><span class="p" data-group-id="5524294285-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5524294285-2">&gt;&gt;</span><span class="p" data-group-id="5524294285-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="4203097254-1">(</span><span class="p" data-group-id="4203097254-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4203097254-2">&gt;&gt;</span><span class="p" data-group-id="4203097254-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="5524294285-3">(</span><span class="p" data-group-id="5524294285-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5524294285-4">&gt;&gt;</span><span class="p" data-group-id="5524294285-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="4203097254-3">(</span><span class="p" data-group-id="4203097254-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4203097254-4">&gt;&gt;</span><span class="p" data-group-id="4203097254-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="5524294285-5">(</span><span class="p" data-group-id="5524294285-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="5524294285-6">&gt;&gt;</span><span class="p" data-group-id="5524294285-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="4203097254-5">(</span><span class="p" data-group-id="4203097254-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="4203097254-6">&gt;&gt;</span><span class="p" data-group-id="4203097254-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │  </span></code></pre><p>For more examples, see <a href="../../../lib/../system/doc/html/bit_syntax.xhtml">Programming Examples</a>.</p><h2 id="reference" class="section-heading">
│ │ │ │    <a href="#reference" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Reference</span>
│ │ │ │  </h2>
│ │ │ │  <p>A term that is <a href="../../../lib/../system/doc/html/system_limits.xhtml#unique_references">unique</a>
│ │ │ │  among connected nodes. A reference is created by calling the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#make_ref/0"><code class="inline">make_ref/0</code></a> BIF. The
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#is_reference/1"><code class="inline">is_reference/1</code></a> BIF tests whether a term
│ │ │ │ -is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="2613581490-1">(</span><span class="p" data-group-id="2613581490-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="4841323286-1">(</span><span class="p" data-group-id="4841323286-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.76482849</span><span class="p">.</span><span class="mf">3801088007.198204</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="2613581490-2">(</span><span class="n">Ref</span><span class="p" data-group-id="2613581490-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="4841323286-2">(</span><span class="n">Ref</span><span class="p" data-group-id="4841323286-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h2 id="fun" class="section-heading">
│ │ │ │    <a href="#fun" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Fun</span>
│ │ │ │  </h2>
│ │ │ │  <p>A fun is a functional object. Funs make it possible to create an anonymous
│ │ │ │  function and pass the function itself — not its name — as argument to other
│ │ │ │ -functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9135774471-1">(</span><span class="n">X</span><span class="p" data-group-id="9135774471-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0330513967-1">(</span><span class="n">X</span><span class="p" data-group-id="0330513967-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="9135774471-2">(</span><span class="mi">2</span><span class="p" data-group-id="9135774471-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="0330513967-2">(</span><span class="mi">2</span><span class="p" data-group-id="0330513967-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span></code></pre><p>The <a href="../../../lib/../erts/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> and <a href="../../../lib/../erts/doc/html/erlang.html#is_function/2"><code class="inline">is_function/2</code></a>
│ │ │ │ -BIFs tests whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2631667701-1">(</span><span class="p" data-group-id="2631667701-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │ +BIFs tests whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2667504475-1">(</span><span class="p" data-group-id="2667504475-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.105768164</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2631667701-2">(</span><span class="n">F</span><span class="p" data-group-id="2631667701-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2667504475-2">(</span><span class="n">F</span><span class="p" data-group-id="2667504475-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2631667701-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2631667701-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2667504475-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2667504475-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2631667701-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2631667701-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="2667504475-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2667504475-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><p>Read more about funs in <a href="expressions.xhtml#fun-expressions">Fun Expressions</a>. For more
│ │ │ │  examples, see <a href="../../../lib/../system/doc/html/funs.xhtml">Programming Examples</a>.</p><h2 id="port-identifier" class="section-heading">
│ │ │ │    <a href="#port-identifier" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Port Identifier</span>
│ │ │ │  </h2>
│ │ │ │ @@ -205,94 +205,94 @@
│ │ │ │  for a new process after a while.</p><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the Pid of the calling process. When
│ │ │ │  <a href="ref_man_processes.xhtml#process-creation">creating a new process</a>, the parent
│ │ │ │  process will be able to get the Pid of the child process either via the return
│ │ │ │  value, as is the case when calling the <a href="../../../lib/../erts/doc/html/erlang.html#spawn/3"><code class="inline">spawn/3</code></a> BIF, or via
│ │ │ │  a message, which is the case when calling the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/5</code></a> BIF. A Pid is typically used when
│ │ │ │  when sending a process a <a href="ref_man_processes.xhtml#signals">signal</a>. The
│ │ │ │ -<a href="../../../lib/../erts/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1779467557-1">(</span><span class="ss">m</span><span class="p" data-group-id="1779467557-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1779467557-2">(</span><span class="p" data-group-id="1779467557-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1779467557-3">]</span><span class="p" data-group-id="1779467557-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<a href="../../../lib/../erts/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9790306980-1">(</span><span class="ss">m</span><span class="p" data-group-id="9790306980-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9790306980-2">(</span><span class="p" data-group-id="9790306980-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9790306980-3">]</span><span class="p" data-group-id="9790306980-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="1779467557-4">(</span><span class="p" data-group-id="1779467557-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="9790306980-4">(</span><span class="p" data-group-id="9790306980-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">who_are_you</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1779467557-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1779467557-6">[</span><span class="nf">self</span><span class="p" data-group-id="1779467557-7">(</span><span class="p" data-group-id="1779467557-7">)</span><span class="p" data-group-id="1779467557-6">]</span><span class="p" data-group-id="1779467557-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="1779467557-8">(</span><span class="p" data-group-id="1779467557-8">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9790306980-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9790306980-6">[</span><span class="nf">self</span><span class="p" data-group-id="9790306980-7">(</span><span class="p" data-group-id="9790306980-7">)</span><span class="p" data-group-id="9790306980-6">]</span><span class="p" data-group-id="9790306980-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="9790306980-8">(</span><span class="p" data-group-id="9790306980-8">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1779467557-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1779467557-10">[</span><span class="p" data-group-id="1779467557-10">]</span><span class="p" data-group-id="1779467557-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9790306980-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9790306980-10">[</span><span class="p" data-group-id="9790306980-10">]</span><span class="p" data-group-id="9790306980-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">who_are_you</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="n">I</span><span class="w"> </span><span class="ss">am</span><span class="w"> </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="ss">who_are_you</span></code></pre><p>Read more about processes in <a href="ref_man_processes.xhtml">Processes</a>.</p><h2 id="tuple" class="section-heading">
│ │ │ │    <a href="#tuple" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Tuple</span>
│ │ │ │  </h2>
│ │ │ │  <p>A tuple is a compound data type with a fixed number of terms:</p><pre><code class="text">{Term1,...,TermN}</code></pre><p>Each term <code class="inline">Term</code> in the tuple is called an <em>element</em>. The number of elements is
│ │ │ │ -said to be the <em>size</em> of the tuple.</p><p>There exists a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8923792115-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="8923792115-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="8923792115-2">}</span><span class="p" data-group-id="8923792115-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8923792115-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="8923792115-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="8923792115-4">}</span><span class="p" data-group-id="8923792115-3">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">element</span><span class="p" data-group-id="8923792115-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="8923792115-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +said to be the <em>size</em> of the tuple.</p><p>There exists a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5817852639-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="5817852639-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5817852639-2">}</span><span class="p" data-group-id="5817852639-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5817852639-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="5817852639-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5817852639-4">}</span><span class="p" data-group-id="5817852639-3">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nf">element</span><span class="p" data-group-id="5817852639-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="5817852639-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">adam</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nf">element</span><span class="p" data-group-id="8923792115-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="8923792115-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8923792115-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="8923792115-7">}</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="8923792115-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="8923792115-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8923792115-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="8923792115-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="8923792115-10">}</span><span class="p" data-group-id="8923792115-9">}</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="8923792115-11">(</span><span class="n">P</span><span class="p" data-group-id="8923792115-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nf">element</span><span class="p" data-group-id="5817852639-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="5817852639-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5817852639-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5817852639-7">}</span><span class="gp unselectable">
│ │ │ │ +4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="5817852639-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="5817852639-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5817852639-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="5817852639-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5817852639-10">}</span><span class="p" data-group-id="5817852639-9">}</span><span class="gp unselectable">
│ │ │ │ +5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="5817852639-11">(</span><span class="n">P</span><span class="p" data-group-id="5817852639-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="8923792115-12">(</span><span class="p" data-group-id="8923792115-13">{</span><span class="p" data-group-id="8923792115-13">}</span><span class="p" data-group-id="8923792115-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="5817852639-12">(</span><span class="p" data-group-id="5817852639-13">{</span><span class="p" data-group-id="5817852639-13">}</span><span class="p" data-group-id="5817852639-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">0</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="8923792115-14">(</span><span class="p" data-group-id="8923792115-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8923792115-15">}</span><span class="p" data-group-id="8923792115-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="5817852639-14">(</span><span class="p" data-group-id="5817852639-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5817852639-15">}</span><span class="p" data-group-id="5817852639-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><h2 id="map" class="section-heading">
│ │ │ │    <a href="#map" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Map</span>
│ │ │ │  </h2>
│ │ │ │  <p>A map is a compound data type with a variable number of key-value associations:</p><pre><code class="text">#{Key1 =&gt; Value1, ..., KeyN =&gt; ValueN}</code></pre><p>Each key-value association in the map is called an <em>association pair</em>. The key
│ │ │ │  and value parts of the pair are called <em>elements</em>. The number of association
│ │ │ │ -pairs is said to be the <em>size</em> of the map.</p><p>There exists a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6760032488-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6760032488-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6760032488-2">}</span><span class="p" data-group-id="6760032488-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6760032488-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6760032488-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6760032488-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="6760032488-3">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="6760032488-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="6760032488-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +pairs is said to be the <em>size</em> of the map.</p><p>There exists a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1074287872-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1074287872-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1074287872-2">}</span><span class="p" data-group-id="1074287872-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1074287872-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1074287872-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1074287872-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="1074287872-3">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="1074287872-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="1074287872-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">adam</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="6760032488-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="6760032488-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6760032488-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6760032488-7">}</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="6760032488-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="6760032488-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6760032488-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6760032488-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6760032488-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="6760032488-9">}</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="6760032488-11">(</span><span class="n">M</span><span class="p" data-group-id="6760032488-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="1074287872-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="1074287872-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1074287872-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1074287872-7">}</span><span class="gp unselectable">
│ │ │ │ +4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="1074287872-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="1074287872-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1074287872-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1074287872-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="1074287872-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="1074287872-9">}</span><span class="gp unselectable">
│ │ │ │ +5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="1074287872-11">(</span><span class="n">M</span><span class="p" data-group-id="1074287872-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="6760032488-12">(</span><span class="p" data-group-id="6760032488-13">#{</span><span class="p" data-group-id="6760032488-13">}</span><span class="p" data-group-id="6760032488-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="1074287872-12">(</span><span class="p" data-group-id="1074287872-13">#{</span><span class="p" data-group-id="1074287872-13">}</span><span class="p" data-group-id="1074287872-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">0</span></code></pre><p>A collection of maps processing functions are found in module <a href="../../../lib/stdlib/doc/html/maps.html"><code class="inline">maps</code></a>
│ │ │ │  in STDLIB.</p><p>Read more about maps in <a href="expressions.xhtml#map-expressions">Map Expressions</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Maps were introduced as an experimental feature in Erlang/OTP R17. Their
│ │ │ │  functionality was extended and became fully supported in Erlang/OTP 18.</p></section><h2 id="list" class="section-heading">
│ │ │ │    <a href="#list" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">List</span>
│ │ │ │  </h2>
│ │ │ │  <p>A list is a compound data type with a variable number of terms.</p><pre><code class="text">[Term1,...,TermN]</code></pre><p>Each term <code class="inline">Term</code> in the list is called an <em>element</em>. The number of elements is
│ │ │ │  said to be the <em>length</em> of the list.</p><p>Formally, a list is either the empty list <code class="inline">[]</code> or consists of a <em>head</em> (first
│ │ │ │  element) and a <em>tail</em> (remainder of the list). The <em>tail</em> is also a list. The
│ │ │ │  latter can be expressed as <code class="inline">[H|T]</code>. The notation <code class="inline">[Term1,...,TermN]</code> above is
│ │ │ │  equivalent with the list <code class="inline">[Term1|[...|[TermN|[]]]]</code>.</p><p><em>Example:</em></p><p><code class="inline">[]</code> is a list, thus<br/><code class="inline">[c|[]]</code> is a list, thus<br/><code class="inline">[b|[c|[]]]</code> is a list, thus<br/><code class="inline">[a|[b|[c|[]]]]</code> is a list, or in short <code class="inline">[a,b,c]</code></p><p>A list where the tail is a list is sometimes called a <em>proper list</em>. It is
│ │ │ │  allowed to have a list where the tail is not a list, for example, <code class="inline">[a|b]</code>.
│ │ │ │ -However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6616174458-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6616174458-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6616174458-2">}</span><span class="p" data-group-id="6616174458-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6616174458-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6616174458-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6616174458-4">}</span><span class="p" data-group-id="6616174458-3">]</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="p" data-group-id="6616174458-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6616174458-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6616174458-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6616174458-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6616174458-7">}</span><span class="p" data-group-id="6616174458-6">]</span><span class="gp unselectable">
│ │ │ │ +However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9999479328-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9999479328-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9999479328-2">}</span><span class="p" data-group-id="9999479328-1">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9999479328-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9999479328-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9999479328-4">}</span><span class="p" data-group-id="9999479328-3">]</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="p" data-group-id="9999479328-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9999479328-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9999479328-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9999479328-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9999479328-7">}</span><span class="p" data-group-id="9999479328-6">]</span><span class="gp unselectable">
│ │ │ │  3&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">a</span><span class="gp unselectable">
│ │ │ │  4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6616174458-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6616174458-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6616174458-9">}</span><span class="p" data-group-id="6616174458-8">]</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6616174458-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6616174458-10">]</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6616174458-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="6616174458-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6616174458-12">}</span><span class="p" data-group-id="6616174458-11">]</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nf">length</span><span class="p" data-group-id="6616174458-13">(</span><span class="n">L1</span><span class="p" data-group-id="6616174458-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9999479328-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9999479328-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9999479328-9">}</span><span class="p" data-group-id="9999479328-8">]</span><span class="gp unselectable">
│ │ │ │ +5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9999479328-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9999479328-10">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9999479328-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9999479328-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9999479328-12">}</span><span class="p" data-group-id="9999479328-11">]</span><span class="gp unselectable">
│ │ │ │ +6&gt; </span><span class="nf">length</span><span class="p" data-group-id="9999479328-13">(</span><span class="n">L1</span><span class="p" data-group-id="9999479328-13">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="nf">length</span><span class="p" data-group-id="6616174458-14">(</span><span class="p" data-group-id="6616174458-15">[</span><span class="p" data-group-id="6616174458-15">]</span><span class="p" data-group-id="6616174458-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +7&gt; </span><span class="nf">length</span><span class="p" data-group-id="9999479328-14">(</span><span class="p" data-group-id="9999479328-15">[</span><span class="p" data-group-id="9999479328-15">]</span><span class="p" data-group-id="9999479328-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">0</span></code></pre><p>A collection of list processing functions are found in module
│ │ │ │  <a href="../../../lib/stdlib/doc/html/lists.html"><code class="inline">lists</code></a> in STDLIB.</p><h2 id="string" class="section-heading">
│ │ │ │    <a href="#string" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">String</span>
│ │ │ │  </h2>
│ │ │ │ @@ -412,41 +412,41 @@
│ │ │ │    <span class="text">Record</span>
│ │ │ │  </h2>
│ │ │ │  <p>A record is a data structure for storing a fixed number of elements. It has
│ │ │ │  named fields and is similar to a struct in C. However, a record is not a true
│ │ │ │  data type. Instead, record expressions are translated to tuple expressions
│ │ │ │  during compilation. Therefore, record expressions are not understood by the
│ │ │ │  shell unless special actions are taken. For details, see module <a href="../../../lib/stdlib/doc/html/shell.html"><code class="inline">shell</code></a>
│ │ │ │ -in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2399810551-1">(</span><span class="ss">person</span><span class="p" data-group-id="2399810551-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2399810551-2">(</span><span class="p" data-group-id="2399810551-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2399810551-3">]</span><span class="p" data-group-id="2399810551-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8930542786-1">(</span><span class="ss">person</span><span class="p" data-group-id="8930542786-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8930542786-2">(</span><span class="p" data-group-id="8930542786-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8930542786-3">]</span><span class="p" data-group-id="8930542786-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2399810551-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2399810551-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="2399810551-5">}</span><span class="p" data-group-id="2399810551-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8930542786-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8930542786-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="8930542786-5">}</span><span class="p" data-group-id="8930542786-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="2399810551-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="2399810551-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2399810551-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="2399810551-7">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="8930542786-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="8930542786-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8930542786-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="8930542786-7">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="2399810551-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="2399810551-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2399810551-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="2399810551-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.xhtml">Records</a>. More examples are
│ │ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="8930542786-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="8930542786-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8930542786-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="8930542786-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.xhtml">Records</a>. More examples are
│ │ │ │  found in <a href="../../../lib/../system/doc/html/prog_ex_records.xhtml">Programming Examples</a>.</p><h2 id="boolean" class="section-heading">
│ │ │ │    <a href="#boolean" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Boolean</span>
│ │ │ │  </h2>
│ │ │ │  <p>There is no Boolean data type in Erlang. Instead the atoms <code class="inline">true</code> and <code class="inline">false</code>
│ │ │ │  are used to denote Boolean values. The <a href="../../../lib/../erts/doc/html/erlang.html#is_boolean/1"><code class="inline">is_boolean/1</code></a>
│ │ │ │  BIF tests whether a term is a boolean.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">2</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │  2&gt; </span><span class="ss">true</span><span class="w"> </span><span class="ow">or</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="5856789098-1">(</span><span class="ss">true</span><span class="p" data-group-id="5856789098-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="4542957291-1">(</span><span class="ss">true</span><span class="p" data-group-id="4542957291-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="5856789098-2">(</span><span class="ss">false</span><span class="p" data-group-id="5856789098-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="4542957291-2">(</span><span class="ss">false</span><span class="p" data-group-id="4542957291-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="5856789098-3">(</span><span class="ss">ok</span><span class="p" data-group-id="5856789098-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="4542957291-3">(</span><span class="ss">ok</span><span class="p" data-group-id="4542957291-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><h2 id="escape-sequences" class="section-heading">
│ │ │ │    <a href="#escape-sequences" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Escape Sequences</span>
│ │ │ │  </h2>
│ │ │ │  <p>Within strings (<code class="inline">&quot;</code>-delimited), quoted atoms, and the content of
│ │ │ │ @@ -464,44 +464,44 @@
│ │ │ │  <a href="data_types.xhtml#sigil"><code class="inline">~b</code> or <code class="inline">~s</code> sigils </a>the escape sequences for normal
│ │ │ │  strings, above, are used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Triple-quoted strings and sigils were introduced in Erlang/OTP 27.</p></section><h2 id="type-conversions" class="section-heading">
│ │ │ │    <a href="#type-conversions" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Type Conversions</span>
│ │ │ │  </h2>
│ │ │ │ -<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1326748648-1">(</span><span class="ss">hello</span><span class="p" data-group-id="1326748648-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="4045881007-1">(</span><span class="ss">hello</span><span class="p" data-group-id="4045881007-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="1326748648-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1326748648-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="4045881007-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4045881007-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1326748648-3">(</span><span class="p" data-group-id="1326748648-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1326748648-4">&gt;&gt;</span><span class="p" data-group-id="1326748648-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="4045881007-3">(</span><span class="p" data-group-id="4045881007-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4045881007-4">&gt;&gt;</span><span class="p" data-group-id="4045881007-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1326748648-5">(</span><span class="p" data-group-id="1326748648-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1326748648-6">&gt;&gt;</span><span class="p" data-group-id="1326748648-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="4045881007-5">(</span><span class="p" data-group-id="4045881007-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="4045881007-6">&gt;&gt;</span><span class="p" data-group-id="4045881007-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="1326748648-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1326748648-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1326748648-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1326748648-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="1326748648-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="4045881007-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4045881007-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="4045881007-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="4045881007-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="4045881007-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="gp unselectable">
│ │ │ │ -7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="1326748648-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="1326748648-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="4045881007-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="4045881007-10">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">7.0</span><span class="gp unselectable">
│ │ │ │ -8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="1326748648-11">(</span><span class="mi">77</span><span class="p" data-group-id="1326748648-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="4045881007-11">(</span><span class="mi">77</span><span class="p" data-group-id="4045881007-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="s">&quot;77&quot;</span><span class="gp unselectable">
│ │ │ │ -9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1326748648-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1326748648-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="4045881007-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="4045881007-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">77</span><span class="gp unselectable">
│ │ │ │ -10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="1326748648-13">(</span><span class="p" data-group-id="1326748648-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1326748648-14">}</span><span class="p" data-group-id="1326748648-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1326748648-15">]</span><span class="gp unselectable">
│ │ │ │ -11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="1326748648-16">(</span><span class="p" data-group-id="1326748648-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1326748648-17">]</span><span class="p" data-group-id="1326748648-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1326748648-18">}</span><span class="gp unselectable">
│ │ │ │ -12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1326748648-19">(</span><span class="p" data-group-id="1326748648-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1326748648-20">}</span><span class="p" data-group-id="1326748648-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1326748648-21">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1326748648-22">(</span><span class="p" data-group-id="1326748648-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1326748648-23">&gt;&gt;</span><span class="p" data-group-id="1326748648-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1326748648-24">}</span><span class="gp unselectable">
│ │ │ │ -14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="1326748648-25">(</span><span class="p" data-group-id="1326748648-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1326748648-26">&gt;&gt;</span><span class="p" data-group-id="1326748648-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ +10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="4045881007-13">(</span><span class="p" data-group-id="4045881007-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4045881007-14">}</span><span class="p" data-group-id="4045881007-13">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4045881007-15">]</span><span class="gp unselectable">
│ │ │ │ +11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="4045881007-16">(</span><span class="p" data-group-id="4045881007-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4045881007-17">]</span><span class="p" data-group-id="4045881007-16">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4045881007-18">}</span><span class="gp unselectable">
│ │ │ │ +12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="4045881007-19">(</span><span class="p" data-group-id="4045881007-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4045881007-20">}</span><span class="p" data-group-id="4045881007-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="4045881007-21">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="4045881007-22">(</span><span class="p" data-group-id="4045881007-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="4045881007-23">&gt;&gt;</span><span class="p" data-group-id="4045881007-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="4045881007-24">}</span><span class="gp unselectable">
│ │ │ │ +14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="4045881007-25">(</span><span class="p" data-group-id="4045881007-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="4045881007-26">&gt;&gt;</span><span class="p" data-group-id="4045881007-25">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">77</span><span class="gp unselectable">
│ │ │ │ -15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="1326748648-27">(</span><span class="mi">77</span><span class="p" data-group-id="1326748648-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1326748648-28">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="1326748648-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="1326748648-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1326748648-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="1326748648-30">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ -17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="1326748648-31">(</span><span class="p" data-group-id="1326748648-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="1326748648-32">&gt;&gt;</span><span class="p" data-group-id="1326748648-31">)</span><span class="p">.</span><span class="w">
│ │ │ │ +15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="4045881007-27">(</span><span class="mi">77</span><span class="p" data-group-id="4045881007-27">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="4045881007-28">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="4045881007-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="4045881007-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4045881007-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="4045881007-30">&gt;&gt;</span><span class="gp unselectable">
│ │ │ │ +17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="4045881007-31">(</span><span class="p" data-group-id="4045881007-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="4045881007-32">&gt;&gt;</span><span class="p" data-group-id="4045881007-31">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mf">7.0</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/create_target.xhtml
│ │ │ │ @@ -43,21 +43,21 @@
│ │ │ │    <span class="text">Creating a Target System</span>
│ │ │ │  </h2>
│ │ │ │  <p>It is assumed that you have a working Erlang/OTP system structured according to
│ │ │ │  the OTP design principles.</p><p><em>Step 1.</em> Create a <code class="inline">.rel</code> file (see the <a href="../../../lib/sasl/doc/html/rel.xhtml">rel(4)</a> manual page in
│ │ │ │  SASL), which specifies the ERTS version and lists all applications that are to
│ │ │ │  be included in the new basic target system. An example is the following
│ │ │ │  <code class="inline">mysystem.rel</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem.rel</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9951414329-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9951414329-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="9951414329-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9951414329-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="9951414329-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9951414329-4">[</span><span class="p" data-group-id="9951414329-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="9951414329-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9951414329-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="9951414329-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9951414329-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="9951414329-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="9951414329-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="9951414329-8">}</span><span class="p" data-group-id="9951414329-4">]</span><span class="p" data-group-id="9951414329-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │ │ +</span><span class="p" data-group-id="6627298594-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6627298594-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="6627298594-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6627298594-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="6627298594-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6627298594-4">[</span><span class="p" data-group-id="6627298594-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="6627298594-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6627298594-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="6627298594-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6627298594-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="6627298594-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="6627298594-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="6627298594-8">}</span><span class="p" data-group-id="6627298594-4">]</span><span class="p" data-group-id="6627298594-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │ │  possibly also new applications that you have written (here exemplified by the
│ │ │ │  application Pea (<code class="inline">pea</code>)).</p><p><em>Step 2.</em> Start Erlang/OTP from the directory where the <code class="inline">mysystem.rel</code> file
│ │ │ │  resides:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-1.0/ebin</code></pre><p>The <code class="inline">-pa</code> argument prepends the path to the <code class="inline">ebin</code> directory for
│ │ │ │  the Pea application to the code path.</p><p><em>Step 3.</em> Create the target system:</p><pre><code class="text">1&gt; target_system:create(&quot;mysystem&quot;).</code></pre><p>The function <code class="inline">target_system:create/1</code> performs the following:</p><ol><li><p>Reads the file <code class="inline">mysystem.rel</code> and creates a new file <code class="inline">plain.rel</code>.
│ │ │ │  The new file is identical to the original, except that it only
│ │ │ │  lists the Kernel and STDLIB applications.</p></li><li><p>From the files <code class="inline">mysystem.rel</code> and <code class="inline">plain.rel</code> creates the files
│ │ │ │  <code class="inline">mysystem.script</code>, <code class="inline">mysystem.boot</code>, <code class="inline">plain.script</code>, and <code class="inline">plain.boot</code>
│ │ │ │ @@ -147,25 +147,25 @@
│ │ │ │    <a href="#creating-the-next-version" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Creating the Next Version</span>
│ │ │ │  </h2>
│ │ │ │  <p>In this example the Pea application has been changed, and so are the
│ │ │ │  applications ERTS, Kernel, STDLIB and SASL.</p><p><em>Step 1.</em> Create the file <code class="inline">.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem2.rel</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2650378368-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2650378368-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="2650378368-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2650378368-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="2650378368-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2650378368-4">[</span><span class="p" data-group-id="2650378368-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="2650378368-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2650378368-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="2650378368-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2650378368-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="2650378368-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="2650378368-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="2650378368-8">}</span><span class="p" data-group-id="2650378368-4">]</span><span class="p" data-group-id="2650378368-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │ │ +</span><span class="p" data-group-id="9653998769-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9653998769-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="9653998769-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9653998769-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="9653998769-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9653998769-4">[</span><span class="p" data-group-id="9653998769-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="9653998769-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9653998769-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="9653998769-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9653998769-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="9653998769-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9653998769-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="9653998769-8">}</span><span class="p" data-group-id="9653998769-4">]</span><span class="p" data-group-id="9653998769-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │ │  <a href="../../../lib/sasl/doc/html/appup.xhtml">appup</a> in SASL) for Pea, for example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% pea.appup</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8545014950-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8545014950-2">[</span><span class="p" data-group-id="8545014950-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="8545014950-4">[</span><span class="p" data-group-id="8545014950-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="8545014950-5">}</span><span class="p" data-group-id="8545014950-4">]</span><span class="p" data-group-id="8545014950-3">}</span><span class="p" data-group-id="8545014950-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8545014950-6">[</span><span class="p" data-group-id="8545014950-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="8545014950-8">[</span><span class="p" data-group-id="8545014950-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="8545014950-9">}</span><span class="p" data-group-id="8545014950-8">]</span><span class="p" data-group-id="8545014950-7">}</span><span class="p" data-group-id="8545014950-6">]</span><span class="p" data-group-id="8545014950-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │ │ +</span><span class="p" data-group-id="7391136435-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7391136435-2">[</span><span class="p" data-group-id="7391136435-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7391136435-4">[</span><span class="p" data-group-id="7391136435-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7391136435-5">}</span><span class="p" data-group-id="7391136435-4">]</span><span class="p" data-group-id="7391136435-3">}</span><span class="p" data-group-id="7391136435-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7391136435-6">[</span><span class="p" data-group-id="7391136435-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7391136435-8">[</span><span class="p" data-group-id="7391136435-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7391136435-9">}</span><span class="p" data-group-id="7391136435-8">]</span><span class="p" data-group-id="7391136435-7">}</span><span class="p" data-group-id="7391136435-6">]</span><span class="p" data-group-id="7391136435-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │ │  Erlang/OTP system, giving the path to the new version of Pea:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-2.0/ebin</code></pre><p><em>Step 4.</em> Create the release upgrade file (see <a href="../../../lib/sasl/doc/html/relup.xhtml">relup</a>
│ │ │ │  in SASL):</p><pre><code class="text">1&gt; systools:make_relup(&quot;mysystem2&quot;,[&quot;mysystem&quot;],[&quot;mysystem&quot;],
│ │ │ │      [{path,[&quot;/home/user/target_system/myapps/pea-1.0/ebin&quot;,
│ │ │ │      &quot;/my/old/erlang/lib/*/ebin&quot;]}]).</code></pre><p>Here <code class="inline">&quot;mysystem&quot;</code> is the base release and <code class="inline">&quot;mysystem2&quot;</code> is the release to
│ │ │ │  upgrade to.</p><p>The <code class="inline">path</code> option is used for pointing out the old version of all applications.
│ │ │ │  (The new versions are already in the code path - assuming of course that the
│ │ │ │  Erlang node on which this is executed is running the correct version of
│ │ │ │ @@ -197,21 +197,21 @@
│ │ │ │  {continue_after_restart,&quot;FIRST&quot;,[]}
│ │ │ │  heart: Tue Apr  1 12:15:10 2014: Erlang has closed.
│ │ │ │  heart: Tue Apr  1 12:15:11 2014: Executed &quot;/usr/local/erl-target/bin/start /usr/local/erl-target/releases/new_start_erl.data&quot; -&gt; 0. Terminating.
│ │ │ │  [End]</code></pre><p>The above return value and output after the call to
│ │ │ │  <a href="../../../lib/sasl/doc/html/release_handler.html#install_release/1"><code class="inline">release_handler:install_release/1</code></a> means that the <code class="inline">release_handler</code> has
│ │ │ │  restarted the node by using <code class="inline">heart</code>. This is always done when the upgrade
│ │ │ │  involves a change of the applications ERTS, Kernel, STDLIB, or SASL. For more
│ │ │ │ -information, see <a href="upgrade.xhtml">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="7490443150-1">(</span><span class="p" data-group-id="7490443150-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7490443150-2">[</span><span class="p" data-group-id="7490443150-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7490443150-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="7490443150-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">current</span><span class="p" data-group-id="7490443150-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7490443150-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="7490443150-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="7490443150-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="ss">permanent</span><span class="p" data-group-id="7490443150-5">}</span><span class="p" data-group-id="7490443150-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │ │ +information, see <a href="upgrade.xhtml">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="9010465972-1">(</span><span class="p" data-group-id="9010465972-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9010465972-2">[</span><span class="p" data-group-id="9010465972-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9010465972-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="9010465972-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">current</span><span class="p" data-group-id="9010465972-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9010465972-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="9010465972-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="9010465972-6">]</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="ss">permanent</span><span class="p" data-group-id="9010465972-5">}</span><span class="p" data-group-id="9010465972-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │ │  our &quot;FIRST&quot; release is still permanent. This means that if the node would be
│ │ │ │  restarted now, it would come up running the &quot;FIRST&quot; release again.</p><p><em>Step 3.</em> Make the new release permanent:</p><pre><code class="text">2&gt; release_handler:make_permanent(&quot;SECOND&quot;).</code></pre><p>Check the releases again:</p><pre><code class="c">3&gt; release_handler:which_releases().
│ │ │ │  [{&quot;MYSYSTEM&quot;,&quot;SECOND&quot;,
│ │ │ │    [&quot;kernel-3.0&quot;,&quot;stdlib-2.0&quot;,&quot;sasl-2.4&quot;,&quot;pea-2.0&quot;],
│ │ │ │    permanent},
│ │ │ │   {&quot;MYSYSTEM&quot;,&quot;FIRST&quot;,
│ │ │ │    [&quot;kernel-2.16.4&quot;,&quot;stdlib-1.19.4&quot;,&quot;sasl-2.3.4&quot;,&quot;pea-1.0&quot;],
│ │ │ │ @@ -220,264 +220,264 @@
│ │ │ │    <a href="#listing-of-target_system-erl" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Listing of target_system.erl</span>
│ │ │ │  </h2>
│ │ │ │  <p>This module can also be found in the <code class="inline">examples</code> directory of the SASL
│ │ │ │  application.</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7015677254-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="7015677254-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7015677254-2">(</span><span class="p" data-group-id="7015677254-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7015677254-3">]</span><span class="p" data-group-id="7015677254-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1715123072-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="1715123072-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1715123072-2">(</span><span class="p" data-group-id="1715123072-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1715123072-3">]</span><span class="p" data-group-id="1715123072-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% Note: RelFileName below is the *stem* without trailing .rel,</span><span class="w">
│ │ │ │  </span><span class="c1">%% .script etc.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% create(RelFileName)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="7015677254-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">create</span><span class="p" data-group-id="7015677254-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="7015677254-6">[</span><span class="p" data-group-id="7015677254-6">]</span><span class="p" data-group-id="7015677254-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="1715123072-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">create</span><span class="p" data-group-id="1715123072-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="1715123072-6">[</span><span class="p" data-group-id="1715123072-6">]</span><span class="p" data-group-id="1715123072-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="7015677254-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7015677254-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="1715123072-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="1715123072-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">RelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7015677254-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="7015677254-9">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="1715123072-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="1715123072-9">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">PlainRelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="7015677254-11">]</span><span class="p" data-group-id="7015677254-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="7015677254-13">]</span><span class="p" data-group-id="7015677254-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="7015677254-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="7015677254-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7015677254-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="7015677254-16">]</span><span class="p" data-group-id="7015677254-15">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7015677254-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7015677254-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="p" data-group-id="7015677254-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="7015677254-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -     </span><span class="n">AppVsns</span><span class="p" data-group-id="7015677254-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7015677254-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="7015677254-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7015677254-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="p" data-group-id="7015677254-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="7015677254-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ -                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="7015677254-23">(</span><span class="nf">fun</span><span class="p" data-group-id="7015677254-24">(</span><span class="p" data-group-id="7015677254-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7015677254-25">}</span><span class="p" data-group-id="7015677254-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="1715123072-11">]</span><span class="p" data-group-id="1715123072-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="1715123072-13">]</span><span class="p" data-group-id="1715123072-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="1715123072-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="1715123072-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="1715123072-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="1715123072-16">]</span><span class="p" data-group-id="1715123072-15">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="1715123072-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="1715123072-18">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="p" data-group-id="1715123072-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="1715123072-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +     </span><span class="n">AppVsns</span><span class="p" data-group-id="1715123072-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1715123072-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="1715123072-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="1715123072-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="p" data-group-id="1715123072-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="1715123072-22">}</span><span class="p">,</span><span class="w">
│ │ │ │ +                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="1715123072-23">(</span><span class="nf">fun</span><span class="p" data-group-id="1715123072-24">(</span><span class="p" data-group-id="1715123072-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1715123072-25">}</span><span class="p" data-group-id="1715123072-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="7015677254-26">(</span><span class="p" data-group-id="7015677254-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7015677254-27">}</span><span class="p" data-group-id="7015677254-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="1715123072-26">(</span><span class="p" data-group-id="1715123072-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1715123072-27">}</span><span class="p" data-group-id="1715123072-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ │ -                                    </span><span class="p" data-group-id="7015677254-28">(</span><span class="p">_</span><span class="p" data-group-id="7015677254-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                                    </span><span class="p" data-group-id="1715123072-28">(</span><span class="p">_</span><span class="p" data-group-id="1715123072-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │                                           </span><span class="ss">false</span><span class="w">
│ │ │ │ -                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="7015677254-23">)</span><span class="w">
│ │ │ │ -                   </span><span class="p" data-group-id="7015677254-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7015677254-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7015677254-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-31">[</span><span class="ss">write</span><span class="p" data-group-id="7015677254-31">]</span><span class="p" data-group-id="7015677254-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="7015677254-33">]</span><span class="p" data-group-id="7015677254-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7015677254-34">(</span><span class="n">Fd</span><span class="p" data-group-id="7015677254-34">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="p" data-group-id="7015677254-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="7015677254-36">]</span><span class="p" data-group-id="7015677254-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="7015677254-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7015677254-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7015677254-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-39">]</span><span class="p" data-group-id="7015677254-38">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="7015677254-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7015677254-40">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="1715123072-23">)</span><span class="w">
│ │ │ │ +                   </span><span class="p" data-group-id="1715123072-20">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1715123072-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1715123072-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-31">[</span><span class="ss">write</span><span class="p" data-group-id="1715123072-31">]</span><span class="p" data-group-id="1715123072-30">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="1715123072-33">]</span><span class="p" data-group-id="1715123072-32">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1715123072-34">(</span><span class="n">Fd</span><span class="p" data-group-id="1715123072-34">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="p" data-group-id="1715123072-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="1715123072-36">]</span><span class="p" data-group-id="1715123072-35">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="1715123072-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="1715123072-37">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="1715123072-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-39">]</span><span class="p" data-group-id="1715123072-38">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="1715123072-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="1715123072-40">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │      </span><span class="n">TarFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="7015677254-42">]</span><span class="p" data-group-id="7015677254-41">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">make_tar</span><span class="p" data-group-id="7015677254-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7015677254-43">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="1715123072-42">]</span><span class="p" data-group-id="1715123072-41">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">make_tar</span><span class="p" data-group-id="1715123072-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="1715123072-43">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="7015677254-44">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7015677254-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-46">]</span><span class="p" data-group-id="7015677254-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7015677254-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-49">]</span><span class="p" data-group-id="7015677254-48">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="7015677254-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-50">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-51">(</span><span class="p" data-group-id="7015677254-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7015677254-52">]</span><span class="p" data-group-id="7015677254-51">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-53">(</span><span class="p" data-group-id="7015677254-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7015677254-54">]</span><span class="p" data-group-id="7015677254-53">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7015677254-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="7015677254-56">]</span><span class="p" data-group-id="7015677254-55">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7015677254-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-58">(</span><span class="p" data-group-id="7015677254-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="7015677254-59">]</span><span class="p" data-group-id="7015677254-58">)</span><span class="p" data-group-id="7015677254-57">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7015677254-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-61">(</span><span class="p" data-group-id="7015677254-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="7015677254-62">]</span><span class="p" data-group-id="7015677254-61">)</span><span class="p" data-group-id="7015677254-60">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="7015677254-64">]</span><span class="p" data-group-id="7015677254-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7015677254-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="7015677254-65">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7015677254-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-68">(</span><span class="p" data-group-id="7015677254-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="7015677254-69">]</span><span class="p" data-group-id="7015677254-68">)</span><span class="p" data-group-id="7015677254-67">]</span><span class="p" data-group-id="7015677254-66">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-71">(</span><span class="p" data-group-id="7015677254-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="7015677254-72">]</span><span class="p" data-group-id="7015677254-71">)</span><span class="p" data-group-id="7015677254-70">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="1715123072-44">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1715123072-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-46">]</span><span class="p" data-group-id="1715123072-45">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="1715123072-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-49">]</span><span class="p" data-group-id="1715123072-48">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="1715123072-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-50">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-51">(</span><span class="p" data-group-id="1715123072-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="1715123072-52">]</span><span class="p" data-group-id="1715123072-51">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-53">(</span><span class="p" data-group-id="1715123072-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="1715123072-54">]</span><span class="p" data-group-id="1715123072-53">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="1715123072-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="1715123072-56">]</span><span class="p" data-group-id="1715123072-55">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="1715123072-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-58">(</span><span class="p" data-group-id="1715123072-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="1715123072-59">]</span><span class="p" data-group-id="1715123072-58">)</span><span class="p" data-group-id="1715123072-57">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="1715123072-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-61">(</span><span class="p" data-group-id="1715123072-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="1715123072-62">]</span><span class="p" data-group-id="1715123072-61">)</span><span class="p" data-group-id="1715123072-60">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="1715123072-64">]</span><span class="p" data-group-id="1715123072-63">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="1715123072-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="1715123072-65">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="1715123072-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-68">(</span><span class="p" data-group-id="1715123072-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="1715123072-69">]</span><span class="p" data-group-id="1715123072-68">)</span><span class="p" data-group-id="1715123072-67">]</span><span class="p" data-group-id="1715123072-66">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-71">(</span><span class="p" data-group-id="1715123072-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="1715123072-72">]</span><span class="p" data-group-id="1715123072-71">)</span><span class="p" data-group-id="1715123072-70">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │ │                </span><span class="s">&quot;~ts to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="p" data-group-id="7015677254-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="7015677254-74">]</span><span class="p" data-group-id="7015677254-73">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-76">(</span><span class="p" data-group-id="7015677254-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="7015677254-77">]</span><span class="p" data-group-id="7015677254-76">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-78">(</span><span class="p" data-group-id="7015677254-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="7015677254-79">]</span><span class="p" data-group-id="7015677254-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="7015677254-80">]</span><span class="p" data-group-id="7015677254-75">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-82">(</span><span class="p" data-group-id="7015677254-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="7015677254-83">]</span><span class="p" data-group-id="7015677254-82">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-84">(</span><span class="p" data-group-id="7015677254-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="7015677254-85">]</span><span class="p" data-group-id="7015677254-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="7015677254-86">]</span><span class="p" data-group-id="7015677254-81">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-88">(</span><span class="p" data-group-id="7015677254-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="7015677254-89">]</span><span class="p" data-group-id="7015677254-88">)</span><span class="p">,</span><span class="w">
│ │ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-90">(</span><span class="p" data-group-id="7015677254-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="7015677254-91">]</span><span class="p" data-group-id="7015677254-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="7015677254-92">]</span><span class="p" data-group-id="7015677254-87">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="p" data-group-id="1715123072-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="1715123072-74">]</span><span class="p" data-group-id="1715123072-73">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-76">(</span><span class="p" data-group-id="1715123072-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="1715123072-77">]</span><span class="p" data-group-id="1715123072-76">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-78">(</span><span class="p" data-group-id="1715123072-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="1715123072-79">]</span><span class="p" data-group-id="1715123072-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="1715123072-80">]</span><span class="p" data-group-id="1715123072-75">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-82">(</span><span class="p" data-group-id="1715123072-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="1715123072-83">]</span><span class="p" data-group-id="1715123072-82">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-84">(</span><span class="p" data-group-id="1715123072-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="1715123072-85">]</span><span class="p" data-group-id="1715123072-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="1715123072-86">]</span><span class="p" data-group-id="1715123072-81">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-88">(</span><span class="p" data-group-id="1715123072-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="1715123072-89">]</span><span class="p" data-group-id="1715123072-88">)</span><span class="p">,</span><span class="w">
│ │ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-90">(</span><span class="p" data-group-id="1715123072-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="1715123072-91">]</span><span class="p" data-group-id="1715123072-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="1715123072-92">]</span><span class="p" data-group-id="1715123072-87">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │      </span><span class="c1">%% This is needed if &#39;start&#39; script created from &#39;start.src&#39; shall</span><span class="w">
│ │ │ │      </span><span class="c1">%% be used as it points out this directory as log dir for &#39;run_erl&#39;</span><span class="w">
│ │ │ │ -    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-93">(</span><span class="p" data-group-id="7015677254-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="7015677254-94">]</span><span class="p" data-group-id="7015677254-93">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="7015677254-96">]</span><span class="p" data-group-id="7015677254-95">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7015677254-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="7015677254-97">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-98">(</span><span class="p" data-group-id="7015677254-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="7015677254-99">]</span><span class="p" data-group-id="7015677254-98">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="7015677254-101">]</span><span class="p" data-group-id="7015677254-100">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7015677254-103">]</span><span class="p" data-group-id="7015677254-102">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="7015677254-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="7015677254-104">)</span><span class="p">,</span><span class="w">
│ │ │ │ -
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -	      </span><span class="p" data-group-id="7015677254-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-106">]</span><span class="p" data-group-id="7015677254-105">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="7015677254-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7015677254-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="7015677254-109">]</span><span class="p" data-group-id="7015677254-108">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-93">(</span><span class="p" data-group-id="1715123072-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="1715123072-94">]</span><span class="p" data-group-id="1715123072-93">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="1715123072-96">]</span><span class="p" data-group-id="1715123072-95">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="1715123072-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="1715123072-97">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-98">(</span><span class="p" data-group-id="1715123072-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="1715123072-99">]</span><span class="p" data-group-id="1715123072-98">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="1715123072-101">]</span><span class="p" data-group-id="1715123072-100">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="1715123072-103">]</span><span class="p" data-group-id="1715123072-102">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="1715123072-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="1715123072-104">)</span><span class="p">,</span><span class="w">
│ │ │ │ +
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +	      </span><span class="p" data-group-id="1715123072-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-106">]</span><span class="p" data-group-id="1715123072-105">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="1715123072-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1715123072-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="1715123072-109">]</span><span class="p" data-group-id="1715123072-108">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% {ok, Cwd} = file:get_cwd(),</span><span class="w">
│ │ │ │      </span><span class="c1">%% file:set_cwd(&quot;tmp&quot;),</span><span class="w">
│ │ │ │      </span><span class="n">ErtsDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="o">++</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7015677254-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7015677254-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-112">[</span><span class="p" data-group-id="7015677254-112">]</span><span class="p" data-group-id="7015677254-110">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7015677254-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="7015677254-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-115">[</span><span class="p" data-group-id="7015677254-115">]</span><span class="p" data-group-id="7015677254-113">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7015677254-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="7015677254-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-118">[</span><span class="p" data-group-id="7015677254-118">]</span><span class="p" data-group-id="7015677254-116">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7015677254-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="7015677254-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-121">[</span><span class="p" data-group-id="7015677254-121">]</span><span class="p" data-group-id="7015677254-119">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7015677254-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="7015677254-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-124">[</span><span class="p" data-group-id="7015677254-124">]</span><span class="p" data-group-id="7015677254-122">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7015677254-125">(</span><span class="n">Tar</span><span class="p" data-group-id="7015677254-125">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="1715123072-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="1715123072-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-112">[</span><span class="p" data-group-id="1715123072-112">]</span><span class="p" data-group-id="1715123072-110">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="1715123072-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="1715123072-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-115">[</span><span class="p" data-group-id="1715123072-115">]</span><span class="p" data-group-id="1715123072-113">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="1715123072-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="1715123072-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-118">[</span><span class="p" data-group-id="1715123072-118">]</span><span class="p" data-group-id="1715123072-116">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="1715123072-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="1715123072-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-121">[</span><span class="p" data-group-id="1715123072-121">]</span><span class="p" data-group-id="1715123072-119">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="1715123072-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="1715123072-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-124">[</span><span class="p" data-group-id="1715123072-124">]</span><span class="p" data-group-id="1715123072-122">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1715123072-125">(</span><span class="n">Tar</span><span class="p" data-group-id="1715123072-125">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%% file:set_cwd(Cwd),</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7015677254-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-127">]</span><span class="p" data-group-id="7015677254-126">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="7015677254-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="7015677254-128">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1715123072-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-127">]</span><span class="p" data-group-id="1715123072-126">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="1715123072-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="1715123072-128">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │ -</span><span class="nf">install</span><span class="p" data-group-id="7015677254-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7015677254-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">install</span><span class="p" data-group-id="1715123072-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="1715123072-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">TarFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="7015677254-131">]</span><span class="p" data-group-id="7015677254-130">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="7015677254-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7015677254-132">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-133">(</span><span class="p" data-group-id="7015677254-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="7015677254-134">]</span><span class="p" data-group-id="7015677254-133">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="7015677254-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="7015677254-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="7015677254-136">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7015677254-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="7015677254-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="7015677254-138">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-139">(</span><span class="p" data-group-id="7015677254-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7015677254-140">]</span><span class="p" data-group-id="7015677254-139">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-141">(</span><span class="p" data-group-id="7015677254-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7015677254-142">]</span><span class="p" data-group-id="7015677254-141">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ │ -              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="7015677254-143">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="7015677254-144">(</span><span class="p" data-group-id="7015677254-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="7015677254-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ │ -                      </span><span class="p" data-group-id="7015677254-146">[</span><span class="p" data-group-id="7015677254-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7015677254-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="7015677254-148">}</span><span class="p" data-group-id="7015677254-146">]</span><span class="p">,</span><span class="w">
│ │ │ │ -                      </span><span class="p" data-group-id="7015677254-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="7015677254-149">]</span><span class="p" data-group-id="7015677254-144">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="1715123072-131">]</span><span class="p" data-group-id="1715123072-130">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="1715123072-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="1715123072-132">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-133">(</span><span class="p" data-group-id="1715123072-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="1715123072-134">]</span><span class="p" data-group-id="1715123072-133">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="1715123072-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="1715123072-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="1715123072-136">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1715123072-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="1715123072-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="1715123072-138">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-139">(</span><span class="p" data-group-id="1715123072-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="1715123072-140">]</span><span class="p" data-group-id="1715123072-139">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-141">(</span><span class="p" data-group-id="1715123072-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="1715123072-142">]</span><span class="p" data-group-id="1715123072-141">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ │ +              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="1715123072-143">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="1715123072-144">(</span><span class="p" data-group-id="1715123072-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="1715123072-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ │ +                      </span><span class="p" data-group-id="1715123072-146">[</span><span class="p" data-group-id="1715123072-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="1715123072-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="1715123072-148">}</span><span class="p" data-group-id="1715123072-146">]</span><span class="p">,</span><span class="w">
│ │ │ │ +                      </span><span class="p" data-group-id="1715123072-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="1715123072-149">]</span><span class="p" data-group-id="1715123072-144">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="c1">%%! Workaround for pre OTP 17.0: start.src and start_erl.src did</span><span class="w">
│ │ │ │      </span><span class="c1">%%! not have correct permissions, so the above &#39;preserve&#39; option did not help</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="7015677254-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="7015677254-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="7015677254-150">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="7015677254-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="7015677254-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="7015677254-152">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="1715123072-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="1715123072-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="1715123072-150">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="1715123072-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="1715123072-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="1715123072-152">)</span><span class="p">,</span><span class="w">
│ │ │ │  
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7015677254-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="7015677254-154">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7015677254-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-156">(</span><span class="p" data-group-id="7015677254-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="7015677254-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-158">)</span><span class="p" data-group-id="7015677254-157">]</span><span class="p" data-group-id="7015677254-156">)</span><span class="p" data-group-id="7015677254-155">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="1715123072-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="1715123072-154">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="1715123072-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-156">(</span><span class="p" data-group-id="1715123072-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="1715123072-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-158">)</span><span class="p" data-group-id="1715123072-157">]</span><span class="p" data-group-id="1715123072-156">)</span><span class="p" data-group-id="1715123072-155">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% LOCALS</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% make_script(RelFileName,Opts)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">make_script</span><span class="p" data-group-id="7015677254-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="7015677254-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7015677254-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ │ -				       </span><span class="p" data-group-id="7015677254-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7015677254-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-163">)</span><span class="p" data-group-id="7015677254-162">}</span><span class="w">
│ │ │ │ -				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="7015677254-161">]</span><span class="p" data-group-id="7015677254-160">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">make_script</span><span class="p" data-group-id="1715123072-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="1715123072-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="1715123072-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ │ +				       </span><span class="p" data-group-id="1715123072-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="1715123072-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-163">)</span><span class="p" data-group-id="1715123072-162">}</span><span class="w">
│ │ │ │ +				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="1715123072-161">]</span><span class="p" data-group-id="1715123072-160">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% make_tar(RelFileName,Opts)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">make_tar</span><span class="p" data-group-id="7015677254-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="7015677254-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="7015677254-165">(</span><span class="p" data-group-id="7015677254-165">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7015677254-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-167">[</span><span class="p" data-group-id="7015677254-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7015677254-168">}</span><span class="p">,</span><span class="w">
│ │ │ │ -				    </span><span class="p" data-group-id="7015677254-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7015677254-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-170">)</span><span class="p" data-group-id="7015677254-169">}</span><span class="w">
│ │ │ │ -				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="7015677254-167">]</span><span class="p" data-group-id="7015677254-166">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">make_tar</span><span class="p" data-group-id="1715123072-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="1715123072-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="1715123072-165">(</span><span class="p" data-group-id="1715123072-165">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="1715123072-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-167">[</span><span class="p" data-group-id="1715123072-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="1715123072-168">}</span><span class="p">,</span><span class="w">
│ │ │ │ +				    </span><span class="p" data-group-id="1715123072-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="1715123072-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-170">)</span><span class="p" data-group-id="1715123072-169">}</span><span class="w">
│ │ │ │ +				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="1715123072-167">]</span><span class="p" data-group-id="1715123072-166">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% extract_tar(TarFile, DestDir)</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">extract_tar</span><span class="p" data-group-id="7015677254-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="7015677254-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="7015677254-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-173">[</span><span class="p" data-group-id="7015677254-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="7015677254-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="7015677254-173">]</span><span class="p" data-group-id="7015677254-172">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">extract_tar</span><span class="p" data-group-id="1715123072-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="1715123072-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="1715123072-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-173">[</span><span class="p" data-group-id="1715123072-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="1715123072-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="1715123072-173">]</span><span class="p" data-group-id="1715123072-172">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7015677254-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="7015677254-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7015677254-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="7015677254-176">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="1715123072-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="1715123072-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="1715123072-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="1715123072-176">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="7015677254-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7015677254-178">(</span><span class="nf">fun</span><span class="p" data-group-id="7015677254-179">(</span><span class="n">Script</span><span class="p" data-group-id="7015677254-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="7015677254-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ │ -                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-180">)</span><span class="w">
│ │ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="7015677254-178">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">subst_src_script</span><span class="p" data-group-id="7015677254-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_file</span><span class="p" data-group-id="7015677254-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-183">(</span><span class="p" data-group-id="7015677254-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="7015677254-184">]</span><span class="p" data-group-id="7015677254-183">)</span><span class="p">,</span><span class="w">
│ │ │ │ -               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-185">(</span><span class="p" data-group-id="7015677254-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="7015677254-186">]</span><span class="p" data-group-id="7015677254-185">)</span><span class="p">,</span><span class="w">
│ │ │ │ -               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-182">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">subst_file</span><span class="p" data-group-id="7015677254-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="7015677254-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="7015677254-189">(</span><span class="n">Src</span><span class="p" data-group-id="7015677254-189">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="7015677254-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7015677254-190">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="7015677254-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="7015677254-191">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="7015677254-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="1715123072-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="1715123072-178">(</span><span class="nf">fun</span><span class="p" data-group-id="1715123072-179">(</span><span class="n">Script</span><span class="p" data-group-id="1715123072-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="1715123072-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ │ +                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-180">)</span><span class="w">
│ │ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="1715123072-178">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">subst_src_script</span><span class="p" data-group-id="1715123072-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_file</span><span class="p" data-group-id="1715123072-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-183">(</span><span class="p" data-group-id="1715123072-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="1715123072-184">]</span><span class="p" data-group-id="1715123072-183">)</span><span class="p">,</span><span class="w">
│ │ │ │ +               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-185">(</span><span class="p" data-group-id="1715123072-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="1715123072-186">]</span><span class="p" data-group-id="1715123072-185">)</span><span class="p">,</span><span class="w">
│ │ │ │ +               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-182">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">subst_file</span><span class="p" data-group-id="1715123072-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="1715123072-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="1715123072-189">(</span><span class="n">Src</span><span class="p" data-group-id="1715123072-189">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="1715123072-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="1715123072-190">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="1715123072-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="1715123072-191">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="1715123072-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7015677254-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7015677254-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="7015677254-194">(</span><span class="n">Src</span><span class="p" data-group-id="7015677254-194">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="7015677254-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7015677254-195">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1715123072-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="1715123072-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="1715123072-194">(</span><span class="n">Src</span><span class="p" data-group-id="1715123072-194">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="1715123072-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="1715123072-195">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%% subst(Str, Vars)</span><span class="w">
│ │ │ │  </span><span class="c1">%% Vars = [{Var, Val}]</span><span class="w">
│ │ │ │  </span><span class="c1">%% Var = Val = string()</span><span class="w">
│ │ │ │  </span><span class="c1">%% Substitute all occurrences of %Var% for Val in Str, using the list</span><span class="w">
│ │ │ │  </span><span class="c1">%% of variables in Vars.</span><span class="w">
│ │ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7015677254-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7015677254-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="7015677254-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-198">[</span><span class="p" data-group-id="7015677254-198">]</span><span class="p" data-group-id="7015677254-197">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="1715123072-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="1715123072-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="1715123072-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-198">[</span><span class="p" data-group-id="1715123072-198">]</span><span class="p" data-group-id="1715123072-197">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7015677254-199">(</span><span class="p" data-group-id="7015677254-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-201">(</span><span class="p" data-group-id="7015677254-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-203">[</span><span class="p" data-group-id="7015677254-203">]</span><span class="p" data-group-id="7015677254-201">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7015677254-204">(</span><span class="p" data-group-id="7015677254-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-206">(</span><span class="p" data-group-id="7015677254-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-208">[</span><span class="p" data-group-id="7015677254-208">]</span><span class="p" data-group-id="7015677254-206">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7015677254-209">(</span><span class="p" data-group-id="7015677254-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-211">(</span><span class="p" data-group-id="7015677254-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-213">[</span><span class="p" data-group-id="7015677254-213">]</span><span class="p" data-group-id="7015677254-211">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7015677254-214">(</span><span class="p" data-group-id="7015677254-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="7015677254-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-217">]</span><span class="p" data-group-id="7015677254-216">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="7015677254-218">(</span><span class="p" data-group-id="7015677254-219">[</span><span class="p" data-group-id="7015677254-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7015677254-220">(</span><span class="n">Result</span><span class="p" data-group-id="7015677254-220">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-221">(</span><span class="p" data-group-id="7015677254-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7015677254-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7015677254-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="7015677254-223">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7015677254-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7015677254-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="7015677254-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7015677254-226">}</span><span class="p" data-group-id="7015677254-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="7015677254-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7015677254-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-228">)</span><span class="p" data-group-id="7015677254-227">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="1715123072-199">(</span><span class="p" data-group-id="1715123072-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-201">(</span><span class="p" data-group-id="1715123072-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-203">[</span><span class="p" data-group-id="1715123072-203">]</span><span class="p" data-group-id="1715123072-201">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="1715123072-204">(</span><span class="p" data-group-id="1715123072-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-206">(</span><span class="p" data-group-id="1715123072-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-208">[</span><span class="p" data-group-id="1715123072-208">]</span><span class="p" data-group-id="1715123072-206">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="1715123072-209">(</span><span class="p" data-group-id="1715123072-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-211">(</span><span class="p" data-group-id="1715123072-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-213">[</span><span class="p" data-group-id="1715123072-213">]</span><span class="p" data-group-id="1715123072-211">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="1715123072-214">(</span><span class="p" data-group-id="1715123072-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="1715123072-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-217">]</span><span class="p" data-group-id="1715123072-216">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="1715123072-218">(</span><span class="p" data-group-id="1715123072-219">[</span><span class="p" data-group-id="1715123072-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="1715123072-220">(</span><span class="n">Result</span><span class="p" data-group-id="1715123072-220">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-221">(</span><span class="p" data-group-id="1715123072-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="1715123072-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="1715123072-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="1715123072-223">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="1715123072-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="1715123072-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1715123072-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1715123072-226">}</span><span class="p" data-group-id="1715123072-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="1715123072-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="1715123072-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-228">)</span><span class="p" data-group-id="1715123072-227">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="7015677254-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7015677254-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-231">]</span><span class="p" data-group-id="7015677254-230">]</span><span class="p" data-group-id="7015677254-229">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="1715123072-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1715123072-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-231">]</span><span class="p" data-group-id="1715123072-230">]</span><span class="p" data-group-id="1715123072-229">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-232">(</span><span class="p" data-group-id="7015677254-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7015677254-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7015677254-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7015677254-235">]</span><span class="p" data-group-id="7015677254-234">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="7015677254-236">(</span><span class="p" data-group-id="7015677254-237">[</span><span class="p" data-group-id="7015677254-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7015677254-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="7015677254-238">(</span><span class="p" data-group-id="7015677254-239">[</span><span class="p" data-group-id="7015677254-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7015677254-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7015677254-241">]</span><span class="p" data-group-id="7015677254-240">]</span><span class="p" data-group-id="7015677254-238">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="7015677254-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-244">[</span><span class="p" data-group-id="7015677254-244">]</span><span class="p" data-group-id="7015677254-243">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="7015677254-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7015677254-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="7015677254-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="7015677254-247">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="7015677254-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7015677254-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-232">(</span><span class="p" data-group-id="1715123072-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1715123072-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="1715123072-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="1715123072-235">]</span><span class="p" data-group-id="1715123072-234">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="1715123072-236">(</span><span class="p" data-group-id="1715123072-237">[</span><span class="p" data-group-id="1715123072-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="1715123072-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="1715123072-238">(</span><span class="p" data-group-id="1715123072-239">[</span><span class="p" data-group-id="1715123072-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1715123072-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1715123072-241">]</span><span class="p" data-group-id="1715123072-240">]</span><span class="p" data-group-id="1715123072-238">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="1715123072-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-244">[</span><span class="p" data-group-id="1715123072-244">]</span><span class="p" data-group-id="1715123072-243">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="1715123072-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1715123072-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="1715123072-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="1715123072-247">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="1715123072-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1715123072-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="7015677254-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7015677254-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="7015677254-250">(</span><span class="n">Src</span><span class="p" data-group-id="7015677254-250">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="7015677254-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7015677254-251">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="1715123072-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="1715123072-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="1715123072-250">(</span><span class="n">Src</span><span class="p" data-group-id="1715123072-250">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="1715123072-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="1715123072-251">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">write_file</span><span class="p" data-group-id="7015677254-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="7015677254-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="7015677254-253">(</span><span class="p" data-group-id="7015677254-253">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7015677254-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7015677254-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-256">[</span><span class="ss">write</span><span class="p" data-group-id="7015677254-256">]</span><span class="p" data-group-id="7015677254-255">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="7015677254-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="7015677254-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="7015677254-258">)</span><span class="p" data-group-id="7015677254-257">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7015677254-259">(</span><span class="n">Fd</span><span class="p" data-group-id="7015677254-259">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">read_txt_file</span><span class="p" data-group-id="7015677254-260">(</span><span class="n">File</span><span class="p" data-group-id="7015677254-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="7015677254-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="7015677254-262">(</span><span class="n">File</span><span class="p" data-group-id="7015677254-262">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7015677254-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="7015677254-264">(</span><span class="n">Bin</span><span class="p" data-group-id="7015677254-264">)</span><span class="p" data-group-id="7015677254-263">}</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="7015677254-265">(</span><span class="n">Dir</span><span class="p" data-group-id="7015677254-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="7015677254-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7015677254-267">[</span><span class="n">Dir</span><span class="p" data-group-id="7015677254-267">]</span><span class="p" data-group-id="7015677254-266">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">remove_all_files</span><span class="p" data-group-id="7015677254-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="7015677254-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7015677254-269">(</span><span class="nf">fun</span><span class="p" data-group-id="7015677254-270">(</span><span class="n">File</span><span class="p" data-group-id="7015677254-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7015677254-271">(</span><span class="p" data-group-id="7015677254-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="7015677254-272">]</span><span class="p" data-group-id="7015677254-271">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="7015677254-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="7015677254-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">write_file</span><span class="p" data-group-id="1715123072-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="1715123072-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="1715123072-253">(</span><span class="p" data-group-id="1715123072-253">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1715123072-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1715123072-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-256">[</span><span class="ss">write</span><span class="p" data-group-id="1715123072-256">]</span><span class="p" data-group-id="1715123072-255">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="1715123072-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="1715123072-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="1715123072-258">)</span><span class="p" data-group-id="1715123072-257">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1715123072-259">(</span><span class="n">Fd</span><span class="p" data-group-id="1715123072-259">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">read_txt_file</span><span class="p" data-group-id="1715123072-260">(</span><span class="n">File</span><span class="p" data-group-id="1715123072-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="1715123072-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="1715123072-262">(</span><span class="n">File</span><span class="p" data-group-id="1715123072-262">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1715123072-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1715123072-264">(</span><span class="n">Bin</span><span class="p" data-group-id="1715123072-264">)</span><span class="p" data-group-id="1715123072-263">}</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="1715123072-265">(</span><span class="n">Dir</span><span class="p" data-group-id="1715123072-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="1715123072-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1715123072-267">[</span><span class="n">Dir</span><span class="p" data-group-id="1715123072-267">]</span><span class="p" data-group-id="1715123072-266">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">remove_all_files</span><span class="p" data-group-id="1715123072-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="1715123072-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="1715123072-269">(</span><span class="nf">fun</span><span class="p" data-group-id="1715123072-270">(</span><span class="n">File</span><span class="p" data-group-id="1715123072-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="1715123072-271">(</span><span class="p" data-group-id="1715123072-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="1715123072-272">]</span><span class="p" data-group-id="1715123072-271">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="1715123072-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="1715123072-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │                                </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                                  </span><span class="p" data-group-id="7015677254-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="7015677254-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="7015677254-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="7015677254-275">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="7015677254-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="7015677254-276">)</span><span class="p">,</span><span class="w">
│ │ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="7015677254-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="7015677254-277">)</span><span class="p">;</span><span class="w">
│ │ │ │ +                                  </span><span class="p" data-group-id="1715123072-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="1715123072-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="1715123072-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="1715123072-275">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="1715123072-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="1715123072-276">)</span><span class="p">,</span><span class="w">
│ │ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="1715123072-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="1715123072-277">)</span><span class="p">;</span><span class="w">
│ │ │ │                                </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7015677254-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="7015677254-278">)</span><span class="w">
│ │ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="1715123072-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="1715123072-278">)</span><span class="w">
│ │ │ │                            </span><span class="k">end</span><span class="w">
│ │ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="7015677254-269">)</span><span class="p">.</span></code></pre>
│ │ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="1715123072-269">)</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/content.opf
│ │ │ │ ├── OEBPS/content.opf
│ │ │ │ │ @@ -1,14 +1,14 @@
│ │ │ │ │  <?xml version="1.0" encoding="utf-8"?>
│ │ │ │ │  <package xmlns="http://www.idpf.org/2007/opf" unique-identifier="project-Erlang System Documentation" version="3.0">
│ │ │ │ │    <metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
│ │ │ │ │      <dc:title>Erlang System Documentation - 27.3.4.3</dc:title>
│ │ │ │ │ -    <dc:identifier id="project-Erlang System Documentation">urn:uuid:1381d819-5afb-a28c-c4a6-46da8c7da982</dc:identifier>
│ │ │ │ │ +    <dc:identifier id="project-Erlang System Documentation">urn:uuid:23713987-4c55-c523-e654-c689aad3cc6b</dc:identifier>
│ │ │ │ │      <dc:language>en</dc:language>
│ │ │ │ │ -    <meta property="dcterms:modified">2025-09-15T16:39:48Z</meta>
│ │ │ │ │ +    <meta property="dcterms:modified">2025-10-04T11:40:33Z</meta>
│ │ │ │ │    </metadata>
│ │ │ │ │    <manifest>
│ │ │ │ │      <item id="nav" href="nav.xhtml" media-type="application/xhtml+xml" properties="nav scripted"/>
│ │ │ │ │      <item id="cover" href="title.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="readme" href="readme.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="installation_guide" href="installation_guide.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="install" href="install.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │ @@ -82,21 +82,21 @@
│ │ │ │ │      <item id="c_portdriver" href="c_portdriver.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="cnode" href="cnode.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="nif" href="nif.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="debugging" href="debugging.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="embedded" href="embedded.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
│ │ │ │ │      <item id="epub-lsjciytm-js" href="dist/epub-LSJCIYTM.js" media-type="text/javascript"/>
│ │ │ │ │      <item id="epub-erlang-espt6bqv-css" href="dist/epub-erlang-ESPT6BQV.css" media-type="text/css"/>
│ │ │ │ │ +    <item id="dist2-gif" href="assets/dist2.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="erlang-logo-png" href="assets/erlang-logo.png" media-type="image/png"/>
│ │ │ │ │      <item id="dist1-gif" href="assets/dist1.gif" media-type="image/gif"/>
│ │ │ │ │ -    <item id="dist2-gif" href="assets/dist2.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="dist3-gif" href="assets/dist3.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="dist4-gif" href="assets/dist4.gif" media-type="image/gif"/>
│ │ │ │ │ -    <item id="dist5-gif" href="assets/dist5.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="ballpoint-pen-svg" href="assets/ballpoint-pen.svg" media-type="image/svg+xml"/>
│ │ │ │ │ +    <item id="dist5-gif" href="assets/dist5.gif" media-type="image/gif"/>
│ │ │ │ │      <item id="logo" href="assets/logo.png" media-type="image/png"/>
│ │ │ │ │    </manifest>
│ │ │ │ │    <spine>
│ │ │ │ │      <itemref idref="cover"/>
│ │ │ │ │      <itemref idref="nav"/>
│ │ │ │ │      <itemref idref="readme"/>
│ │ │ │ │      <itemref idref="installation_guide"/>
│ │ │ ├── OEBPS/conc_prog.xhtml
│ │ │ │ @@ -37,107 +37,107 @@
│ │ │ │  threads of execution in an Erlang program and to allow these threads to
│ │ │ │  communicate with each other. In Erlang, each thread of execution is called a
│ │ │ │  <em>process</em>.</p><p>(Aside: the term &quot;process&quot; is usually used when the threads of execution share
│ │ │ │  no data with each other and the term &quot;thread&quot; when they share data in some way.
│ │ │ │  Threads of execution in Erlang share no data, that is why they are called
│ │ │ │  processes).</p><p>The Erlang BIF <code class="inline">spawn</code> is used to create a new process:
│ │ │ │  <code class="inline">spawn(Module, Exported_Function, List of Arguments)</code>. Consider the following
│ │ │ │ -module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4186583755-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="4186583755-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0235077261-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="0235077261-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4186583755-2">(</span><span class="p" data-group-id="4186583755-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4186583755-3">]</span><span class="p" data-group-id="4186583755-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0235077261-2">(</span><span class="p" data-group-id="0235077261-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0235077261-3">]</span><span class="p" data-group-id="0235077261-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="4186583755-4">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4186583755-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="0235077261-4">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0235077261-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">done</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="4186583755-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="4186583755-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4186583755-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4186583755-7">[</span><span class="n">What</span><span class="p" data-group-id="4186583755-7">]</span><span class="p" data-group-id="4186583755-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">say_something</span><span class="p" data-group-id="4186583755-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4186583755-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4186583755-9">(</span><span class="p" data-group-id="4186583755-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4186583755-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4186583755-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4186583755-11">]</span><span class="p" data-group-id="4186583755-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4186583755-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4186583755-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4186583755-13">]</span><span class="p" data-group-id="4186583755-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="6250705820-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="6250705820-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6250705820-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="6250705820-2">}</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="6250705820-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6250705820-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="0235077261-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="0235077261-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0235077261-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235077261-7">[</span><span class="n">What</span><span class="p" data-group-id="0235077261-7">]</span><span class="p" data-group-id="0235077261-6">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">say_something</span><span class="p" data-group-id="0235077261-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0235077261-8">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0235077261-9">(</span><span class="p" data-group-id="0235077261-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0235077261-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235077261-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0235077261-11">]</span><span class="p" data-group-id="0235077261-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0235077261-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235077261-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0235077261-13">]</span><span class="p" data-group-id="0235077261-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="6344282884-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="6344282884-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6344282884-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="6344282884-2">}</span><span class="gp unselectable">
│ │ │ │ +6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="6344282884-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6344282884-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">done</span></code></pre><p>As shown, the function <code class="inline">say_something</code> writes its first argument the number of
│ │ │ │  times specified by second argument. The function <code class="inline">start</code> starts two Erlang
│ │ │ │  processes, one that writes &quot;hello&quot; three times and one that writes &quot;goodbye&quot;
│ │ │ │  three times. Both processes use the function <code class="inline">say_something</code>. Notice that a
│ │ │ │  function used in this way by <code class="inline">spawn</code>, to start a process, must be exported from
│ │ │ │ -the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0245190360-1">(</span><span class="p" data-group-id="0245190360-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5882719813-1">(</span><span class="p" data-group-id="5882719813-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.63</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │ │  </span><span class="ss">goodbye</span></code></pre><p>Notice that it did not write &quot;hello&quot; three times and then &quot;goodbye&quot; three times.
│ │ │ │  Instead, the first process wrote a &quot;hello&quot;, the second a &quot;goodbye&quot;, the first
│ │ │ │  another &quot;hello&quot; and so forth. But where did the <code class="inline">&lt;0.63.0&gt;</code> come from? The return
│ │ │ │  value of a function is the return value of the last &quot;thing&quot; in the function. The
│ │ │ │ -last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="0720843006-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0720843006-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0720843006-2">]</span><span class="p" data-group-id="0720843006-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │ │ +last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="7925299316-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7925299316-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7925299316-2">]</span><span class="p" data-group-id="7925299316-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │ │  process. So <code class="inline">&lt;0.63.0&gt;</code> is the pid of the <code class="inline">spawn</code> function call above. The next
│ │ │ │  example shows how to use pids.</p><p>Notice also that ~p is used instead of ~w in <a href="../../../lib/stdlib/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a>. To quote <a href="../../../lib/stdlib/doc/html/io.html#tilde_p">the manual</a>:</p><blockquote><p>~p Writes the data with standard syntax in the same way as ~w, but breaks terms
│ │ │ │  whose printed representation is longer than one line into many lines and indents
│ │ │ │  each line sensibly. It also tries to detect flat lists of printable characters and
│ │ │ │  to output these as strings</p></blockquote><h2 id="message-passing" class="section-heading">
│ │ │ │    <a href="#message-passing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Message Passing</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the following example two processes are created and they send messages to
│ │ │ │ -each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4720354117-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="4720354117-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6688264329-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="6688264329-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4720354117-2">(</span><span class="p" data-group-id="4720354117-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4720354117-3">]</span><span class="p" data-group-id="4720354117-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6688264329-2">(</span><span class="p" data-group-id="6688264329-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6688264329-3">]</span><span class="p" data-group-id="6688264329-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="4720354117-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4720354117-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="6688264329-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="6688264329-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4720354117-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720354117-6">[</span><span class="p" data-group-id="4720354117-6">]</span><span class="p" data-group-id="4720354117-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6688264329-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6688264329-6">[</span><span class="p" data-group-id="6688264329-6">]</span><span class="p" data-group-id="6688264329-5">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="4720354117-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4720354117-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4720354117-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4720354117-9">(</span><span class="p" data-group-id="4720354117-9">)</span><span class="p" data-group-id="4720354117-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="6688264329-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="6688264329-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6688264329-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6688264329-9">(</span><span class="p" data-group-id="6688264329-9">)</span><span class="p" data-group-id="6688264329-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4720354117-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720354117-11">[</span><span class="p" data-group-id="4720354117-11">]</span><span class="p" data-group-id="4720354117-10">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6688264329-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6688264329-11">[</span><span class="p" data-group-id="6688264329-11">]</span><span class="p" data-group-id="6688264329-10">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="4720354117-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4720354117-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="6688264329-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="6688264329-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="4720354117-13">(</span><span class="p" data-group-id="4720354117-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="6688264329-13">(</span><span class="p" data-group-id="6688264329-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4720354117-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720354117-15">[</span><span class="p" data-group-id="4720354117-15">]</span><span class="p" data-group-id="4720354117-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4720354117-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4720354117-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4720354117-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720354117-18">[</span><span class="p" data-group-id="4720354117-18">]</span><span class="p" data-group-id="4720354117-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6688264329-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6688264329-15">[</span><span class="p" data-group-id="6688264329-15">]</span><span class="p" data-group-id="6688264329-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6688264329-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6688264329-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6688264329-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6688264329-18">[</span><span class="p" data-group-id="6688264329-18">]</span><span class="p" data-group-id="6688264329-17">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="4720354117-19">(</span><span class="p" data-group-id="4720354117-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="6688264329-19">(</span><span class="p" data-group-id="6688264329-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4720354117-20">(</span><span class="p" data-group-id="4720354117-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4720354117-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720354117-22">[</span><span class="p" data-group-id="4720354117-22">]</span><span class="p" data-group-id="4720354117-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4720354117-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4720354117-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4720354117-24">]</span><span class="p" data-group-id="4720354117-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="6415444605-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="6415444605-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6415444605-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="6415444605-2">}</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="w"> </span><span class="nf">start</span><span class="p" data-group-id="6415444605-3">(</span><span class="p" data-group-id="6415444605-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="6688264329-20">(</span><span class="p" data-group-id="6688264329-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6688264329-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6688264329-22">[</span><span class="p" data-group-id="6688264329-22">]</span><span class="p" data-group-id="6688264329-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="6688264329-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6688264329-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="6688264329-24">]</span><span class="p" data-group-id="6688264329-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="2227489656-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="2227489656-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2227489656-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="2227489656-2">}</span><span class="gp unselectable">
│ │ │ │ +2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="w"> </span><span class="nf">start</span><span class="p" data-group-id="2227489656-3">(</span><span class="p" data-group-id="2227489656-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.36</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8372719524-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8372719524-2">[</span><span class="p" data-group-id="8372719524-2">]</span><span class="p" data-group-id="8372719524-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ │ -&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="9939176736-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9939176736-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9939176736-2">]</span><span class="p" data-group-id="9939176736-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="8439505921-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="8439505921-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0195935816-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0195935816-2">[</span><span class="p" data-group-id="0195935816-2">]</span><span class="p" data-group-id="0195935816-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ │ +&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="9504733308-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9504733308-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9504733308-2">]</span><span class="p" data-group-id="9504733308-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="4255051254-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4255051254-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6140324080-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6140324080-2">[</span><span class="p" data-group-id="6140324080-2">]</span><span class="p" data-group-id="6140324080-1">)</span><span class="p">;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6140324080-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6140324080-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6140324080-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6140324080-5">[</span><span class="p" data-group-id="6140324080-5">]</span><span class="p" data-group-id="6140324080-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9811071712-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9811071712-2">[</span><span class="p" data-group-id="9811071712-2">]</span><span class="p" data-group-id="9811071712-1">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9811071712-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9811071712-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9811071712-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9811071712-5">[</span><span class="p" data-group-id="9811071712-5">]</span><span class="p" data-group-id="9811071712-4">)</span><span class="p">,</span><span class="w">
│ │ │ │          </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="nf">pong</span><span class="p" data-group-id="6140324080-6">(</span><span class="p" data-group-id="6140324080-6">)</span><span class="w">
│ │ │ │ +        </span><span class="nf">pong</span><span class="p" data-group-id="9811071712-6">(</span><span class="p" data-group-id="9811071712-6">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> construct is used to allow processes to wait for messages from
│ │ │ │  other processes. It has the following format:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │     </span><span class="ss">pattern1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │         </span><span class="ss">actions1</span><span class="p">;</span><span class="w">
│ │ │ │     </span><span class="ss">pattern2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │         </span><span class="ss">actions2</span><span class="p">;</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ @@ -158,84 +158,84 @@
│ │ │ │  queue (keeping the first message and any other messages in the queue). If the
│ │ │ │  second message does not match, the third message is tried, and so on, until the
│ │ │ │  end of the queue is reached. If the end of the queue is reached, the process
│ │ │ │  blocks (stops execution) and waits until a new message is received and this
│ │ │ │  procedure is repeated.</p><p>The Erlang implementation is &quot;clever&quot; and minimizes the number of times each
│ │ │ │  message is tested against the patterns in each <code class="inline">receive</code>.</p><p>Now back to the ping pong example.</p><p>&quot;Pong&quot; is waiting for messages. If the atom <code class="inline">finished</code> is received, &quot;pong&quot;
│ │ │ │  writes &quot;Pong finished&quot; to the output and, as it has nothing more to do,
│ │ │ │ -terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4020999112-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4020999112-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │ │ +terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8948250094-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8948250094-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │ │  process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span></code></pre><p>Notice how the operator &quot;!&quot; is used to send messages. The syntax of &quot;!&quot; is:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Message</span></code></pre><p>That is, <code class="inline">Message</code> (any Erlang term) is sent to the process with identity <code class="inline">Pid</code>.</p><p>After sending the message <code class="inline">pong</code> to the process &quot;ping&quot;, &quot;pong&quot; calls the <code class="inline">pong</code>
│ │ │ │  function again, which causes it to get back to the <code class="inline">receive</code> again and wait for
│ │ │ │ -another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="5434549511-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="5434549511-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │ │ +another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="3668139987-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3668139987-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │ │  since the value of the first argument is 3 (not 0) (first clause head is
│ │ │ │ -<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1770519859-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1770519859-2">(</span><span class="p" data-group-id="1770519859-2">)</span><span class="p" data-group-id="1770519859-1">}</span><span class="p">,</span></code></pre><p><a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │ │ +<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8950096814-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8950096814-2">(</span><span class="p" data-group-id="8950096814-2">)</span><span class="p" data-group-id="8950096814-1">}</span><span class="p">,</span></code></pre><p><a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../../lib/../erts/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │ │  pid of &quot;ping&quot;. (Recall the code for &quot;pong&quot;, this lands up in the variable
│ │ │ │  <code class="inline">Ping_PID</code> in the <code class="inline">receive</code> previously explained.)</p><p>&quot;Ping&quot; now waits for a reply from &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2954527731-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2954527731-2">[</span><span class="p" data-group-id="2954527731-2">]</span><span class="p" data-group-id="2954527731-1">)</span><span class="w">
│ │ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0940200060-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0940200060-2">[</span><span class="p" data-group-id="0940200060-2">]</span><span class="p" data-group-id="0940200060-1">)</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><p>It writes &quot;Ping received pong&quot; when this reply arrives, after which &quot;ping&quot; calls
│ │ │ │ -the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="9703196369-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9703196369-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ │ -occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="6845702465-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="6845702465-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="1052907426-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="1052907426-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ │ +occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="4819701360-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4819701360-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6845702465-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6845702465-3">[</span><span class="p" data-group-id="6845702465-3">]</span><span class="p" data-group-id="6845702465-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4819701360-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4819701360-3">[</span><span class="p" data-group-id="4819701360-3">]</span><span class="p" data-group-id="4819701360-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │ │  above) and &quot;ping finished&quot; is written to the output. &quot;Ping&quot; then terminates as
│ │ │ │  it has nothing left to do.</p><h2 id="registered-process-names" class="section-heading">
│ │ │ │    <a href="#registered-process-names" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Registered Process Names</span>
│ │ │ │  </h2>
│ │ │ │  <p>In the above example, &quot;pong&quot; was first created to be able to give the identity
│ │ │ │  of &quot;pong&quot; when &quot;ping&quot; was started. That is, in some way &quot;ping&quot; must be able to
│ │ │ │  know the identity of &quot;pong&quot; to be able to send a message to it. Sometimes
│ │ │ │  processes which need to know each other's identities are started independently
│ │ │ │  of each other. Erlang thus provides a mechanism for processes to be given names
│ │ │ │  so that these names can be used as identities instead of pids. This is done by
│ │ │ │ -using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="8761161820-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="8761161820-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ │ -the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4869959935-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="4869959935-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="2578985462-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2578985462-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ │ +the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5224969213-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="5224969213-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4869959935-2">(</span><span class="p" data-group-id="4869959935-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4869959935-3">]</span><span class="p" data-group-id="4869959935-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5224969213-2">(</span><span class="p" data-group-id="5224969213-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5224969213-3">]</span><span class="p" data-group-id="5224969213-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="4869959935-4">(</span><span class="mi">0</span><span class="p" data-group-id="4869959935-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="5224969213-4">(</span><span class="mi">0</span><span class="p" data-group-id="5224969213-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4869959935-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4869959935-6">[</span><span class="p" data-group-id="4869959935-6">]</span><span class="p" data-group-id="4869959935-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5224969213-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224969213-6">[</span><span class="p" data-group-id="5224969213-6">]</span><span class="p" data-group-id="5224969213-5">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="4869959935-7">(</span><span class="n">N</span><span class="p" data-group-id="4869959935-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4869959935-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4869959935-9">(</span><span class="p" data-group-id="4869959935-9">)</span><span class="p" data-group-id="4869959935-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="5224969213-7">(</span><span class="n">N</span><span class="p" data-group-id="5224969213-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5224969213-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5224969213-9">(</span><span class="p" data-group-id="5224969213-9">)</span><span class="p" data-group-id="5224969213-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4869959935-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4869959935-11">[</span><span class="p" data-group-id="4869959935-11">]</span><span class="p" data-group-id="4869959935-10">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5224969213-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224969213-11">[</span><span class="p" data-group-id="5224969213-11">]</span><span class="p" data-group-id="5224969213-10">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="4869959935-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4869959935-12">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="5224969213-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5224969213-12">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="4869959935-13">(</span><span class="p" data-group-id="4869959935-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="5224969213-13">(</span><span class="p" data-group-id="5224969213-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4869959935-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4869959935-15">[</span><span class="p" data-group-id="4869959935-15">]</span><span class="p" data-group-id="4869959935-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4869959935-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4869959935-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4869959935-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4869959935-18">[</span><span class="p" data-group-id="4869959935-18">]</span><span class="p" data-group-id="4869959935-17">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5224969213-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224969213-15">[</span><span class="p" data-group-id="5224969213-15">]</span><span class="p" data-group-id="5224969213-14">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5224969213-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5224969213-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5224969213-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224969213-18">[</span><span class="p" data-group-id="5224969213-18">]</span><span class="p" data-group-id="5224969213-17">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="4869959935-19">(</span><span class="p" data-group-id="4869959935-19">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="5224969213-19">(</span><span class="p" data-group-id="5224969213-19">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4869959935-20">(</span><span class="p" data-group-id="4869959935-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4869959935-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="4869959935-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4869959935-23">[</span><span class="p" data-group-id="4869959935-23">]</span><span class="p" data-group-id="4869959935-22">)</span><span class="p" data-group-id="4869959935-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4869959935-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4869959935-25">[</span><span class="mi">3</span><span class="p" data-group-id="4869959935-25">]</span><span class="p" data-group-id="4869959935-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="1470344598-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="1470344598-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1470344598-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="1470344598-2">}</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1470344598-3">(</span><span class="p" data-group-id="1470344598-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="5224969213-20">(</span><span class="p" data-group-id="5224969213-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="5224969213-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5224969213-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224969213-23">[</span><span class="p" data-group-id="5224969213-23">]</span><span class="p" data-group-id="5224969213-22">)</span><span class="p" data-group-id="5224969213-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5224969213-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5224969213-25">[</span><span class="mi">3</span><span class="p" data-group-id="5224969213-25">]</span><span class="p" data-group-id="5224969213-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="1842148286-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="1842148286-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1842148286-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="1842148286-2">}</span><span class="gp unselectable">
│ │ │ │ +3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1842148286-3">(</span><span class="p" data-group-id="1842148286-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.38</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="6857285396-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6857285396-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6857285396-3">[</span><span class="p" data-group-id="6857285396-3">]</span><span class="p" data-group-id="6857285396-2">)</span><span class="p" data-group-id="6857285396-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ │ -process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9153071884-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9153071884-2">(</span><span class="p" data-group-id="9153071884-2">)</span><span class="p" data-group-id="9153071884-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="5861791133-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5861791133-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5861791133-3">[</span><span class="p" data-group-id="5861791133-3">]</span><span class="p" data-group-id="5861791133-2">)</span><span class="p" data-group-id="5861791133-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ │ +process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5349998055-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5349998055-2">(</span><span class="p" data-group-id="5349998055-2">)</span><span class="p" data-group-id="5349998055-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │ │    <a href="#distributed-programming" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Distributed Programming</span>
│ │ │ │  </h2>
│ │ │ │  <p>Let us rewrite the ping pong program with &quot;ping&quot; and &quot;pong&quot; on different
│ │ │ │  computers. First a few things are needed to set up to get this to work. The
│ │ │ │ @@ -255,106 +255,106 @@
│ │ │ │  of the file. This is a requirement.</p><p>When you start an Erlang system that is going to talk to other Erlang systems,
│ │ │ │  you must give it a name, for example:</p><pre><code class="text">$ erl -sname my_name</code></pre><p>We will see more details of this later. If you want to experiment with
│ │ │ │  distributed Erlang, but you only have one computer to work on, you can start two
│ │ │ │  separate Erlang systems on the same computer but give them different names. Each
│ │ │ │  Erlang system running on a computer is called an <em>Erlang node</em>.</p><p>(Note: <code class="inline">erl -sname</code> assumes that all nodes are in the same IP domain and we can
│ │ │ │  use only the first component of the IP address, if we want to use nodes in
│ │ │ │  different domains we use <code class="inline">-name</code> instead, but then all IP address must be given
│ │ │ │ -in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2442643164-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="2442643164-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0150893161-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="0150893161-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2442643164-2">(</span><span class="p" data-group-id="2442643164-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2442643164-3">]</span><span class="p" data-group-id="2442643164-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0150893161-2">(</span><span class="p" data-group-id="0150893161-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0150893161-3">]</span><span class="p" data-group-id="0150893161-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2442643164-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2442643164-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2442643164-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2442643164-7">[</span><span class="p" data-group-id="2442643164-7">]</span><span class="p" data-group-id="2442643164-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="0150893161-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0150893161-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0150893161-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0150893161-7">[</span><span class="p" data-group-id="0150893161-7">]</span><span class="p" data-group-id="0150893161-6">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2442643164-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2442643164-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2442643164-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2442643164-11">(</span><span class="p" data-group-id="2442643164-11">)</span><span class="p" data-group-id="2442643164-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="0150893161-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0150893161-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0150893161-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0150893161-11">(</span><span class="p" data-group-id="0150893161-11">)</span><span class="p" data-group-id="0150893161-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2442643164-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2442643164-13">[</span><span class="p" data-group-id="2442643164-13">]</span><span class="p" data-group-id="2442643164-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0150893161-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0150893161-13">[</span><span class="p" data-group-id="0150893161-13">]</span><span class="p" data-group-id="0150893161-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="2442643164-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="0150893161-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="2442643164-15">(</span><span class="p" data-group-id="2442643164-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="0150893161-15">(</span><span class="p" data-group-id="0150893161-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2442643164-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2442643164-17">[</span><span class="p" data-group-id="2442643164-17">]</span><span class="p" data-group-id="2442643164-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2442643164-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2442643164-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2442643164-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2442643164-20">[</span><span class="p" data-group-id="2442643164-20">]</span><span class="p" data-group-id="2442643164-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0150893161-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0150893161-17">[</span><span class="p" data-group-id="0150893161-17">]</span><span class="p" data-group-id="0150893161-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0150893161-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="0150893161-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0150893161-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0150893161-20">[</span><span class="p" data-group-id="0150893161-20">]</span><span class="p" data-group-id="0150893161-19">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="2442643164-21">(</span><span class="p" data-group-id="2442643164-21">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="0150893161-21">(</span><span class="p" data-group-id="0150893161-21">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="2442643164-22">(</span><span class="p" data-group-id="2442643164-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2442643164-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2442643164-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2442643164-25">[</span><span class="p" data-group-id="2442643164-25">]</span><span class="p" data-group-id="2442643164-24">)</span><span class="p" data-group-id="2442643164-23">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="0150893161-22">(</span><span class="p" data-group-id="0150893161-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0150893161-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0150893161-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0150893161-25">[</span><span class="p" data-group-id="0150893161-25">]</span><span class="p" data-group-id="0150893161-24">)</span><span class="p" data-group-id="0150893161-23">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="2442643164-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2442643164-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2442643164-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2442643164-28">]</span><span class="p" data-group-id="2442643164-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="0150893161-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0150893161-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0150893161-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0150893161-28">]</span><span class="p" data-group-id="0150893161-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │ │  started on kosken, called ping, and then a node on gollum, called pong.</p><p>On kosken (on a Linux/UNIX system):</p><pre><code class="text">kosken&gt; erl -sname ping
│ │ │ │  Erlang (BEAM) emulator version 5.2.3.7 [hipe] [threads:0]
│ │ │ │  
│ │ │ │  Eshell V5.2.3.7  (abort with ^G)
│ │ │ │  (ping@kosken)1&gt;</code></pre><p>On gollum:</p><pre><code class="text">gollum&gt; erl -sname pong
│ │ │ │  Erlang (BEAM) emulator version 5.2.3.7 [hipe] [threads:0]
│ │ │ │  
│ │ │ │  Eshell V5.2.3.7  (abort with ^G)
│ │ │ │ -(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="1549117530-1">(</span><span class="p" data-group-id="1549117530-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="9280318575-1">(</span><span class="p" data-group-id="9280318575-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span></code></pre><p>And the &quot;ping&quot; process on kosken is started (from the code above you can see
│ │ │ │  that a parameter of the <code class="inline">start_ping</code> function is the node name of the Erlang
│ │ │ │ -system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="6521765592-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="6521765592-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="2051417735-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="2051417735-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.37</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>As shown, the ping pong program has run. On the &quot;pong&quot; side:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)2&gt; </span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="nf">finished</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8478581222-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="8478581222-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │ │ +</span><span class="p" data-group-id="0306468493-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="0306468493-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │ │  unchanged, the following lines work in the same way irrespective of on which
│ │ │ │ -node the &quot;ping&quot; process is executes:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4615795374-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4615795374-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4615795374-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4615795374-3">[</span><span class="p" data-group-id="4615795374-3">]</span><span class="p" data-group-id="4615795374-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +node the &quot;ping&quot; process is executes:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4556867820-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="4556867820-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4556867820-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4556867820-3">[</span><span class="p" data-group-id="4556867820-3">]</span><span class="p" data-group-id="4556867820-2">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span></code></pre><p>Thus, Erlang pids contain information about where the process executes. So if
│ │ │ │  you know the pid of a process, the <code class="inline">!</code> operator can be used to send it a
│ │ │ │ -message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2193763202-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2193763202-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2193763202-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2193763202-3">(</span><span class="p" data-group-id="2193763202-3">)</span><span class="p" data-group-id="2193763202-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │ │ +message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6491695970-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6491695970-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6491695970-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6491695970-3">(</span><span class="p" data-group-id="6491695970-3">)</span><span class="p" data-group-id="6491695970-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │ │  <code class="inline">registered_name</code>.</p><p>In the previous example, &quot;ping&quot; and &quot;pong&quot; were started from the shells of two
│ │ │ │  separate Erlang nodes. <code class="inline">spawn</code> can also be used to start processes in other
│ │ │ │  nodes.</p><p>The next example is the ping pong program, yet again, but this time &quot;ping&quot; is
│ │ │ │ -started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6868661484-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="6868661484-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8193880298-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="8193880298-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6868661484-2">(</span><span class="p" data-group-id="6868661484-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6868661484-3">]</span><span class="p" data-group-id="6868661484-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8193880298-2">(</span><span class="p" data-group-id="8193880298-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8193880298-3">]</span><span class="p" data-group-id="8193880298-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="6868661484-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6868661484-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6868661484-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6868661484-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6868661484-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6868661484-7">[</span><span class="p" data-group-id="6868661484-7">]</span><span class="p" data-group-id="6868661484-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="8193880298-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8193880298-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8193880298-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8193880298-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8193880298-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8193880298-7">[</span><span class="p" data-group-id="8193880298-7">]</span><span class="p" data-group-id="8193880298-6">)</span><span class="p">;</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="6868661484-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6868661484-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6868661484-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6868661484-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6868661484-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6868661484-11">(</span><span class="p" data-group-id="6868661484-11">)</span><span class="p" data-group-id="6868661484-10">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="8193880298-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8193880298-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8193880298-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8193880298-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8193880298-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8193880298-11">(</span><span class="p" data-group-id="8193880298-11">)</span><span class="p" data-group-id="8193880298-10">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6868661484-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6868661484-13">[</span><span class="p" data-group-id="6868661484-13">]</span><span class="p" data-group-id="6868661484-12">)</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8193880298-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8193880298-13">[</span><span class="p" data-group-id="8193880298-13">]</span><span class="p" data-group-id="8193880298-12">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="6868661484-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="6868661484-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="8193880298-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8193880298-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="6868661484-15">(</span><span class="p" data-group-id="6868661484-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="8193880298-15">(</span><span class="p" data-group-id="8193880298-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6868661484-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6868661484-17">[</span><span class="p" data-group-id="6868661484-17">]</span><span class="p" data-group-id="6868661484-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="6868661484-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6868661484-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6868661484-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6868661484-20">[</span><span class="p" data-group-id="6868661484-20">]</span><span class="p" data-group-id="6868661484-19">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8193880298-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8193880298-17">[</span><span class="p" data-group-id="8193880298-17">]</span><span class="p" data-group-id="8193880298-16">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="8193880298-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8193880298-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8193880298-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8193880298-20">[</span><span class="p" data-group-id="8193880298-20">]</span><span class="p" data-group-id="8193880298-19">)</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="6868661484-21">(</span><span class="p" data-group-id="6868661484-21">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="8193880298-21">(</span><span class="p" data-group-id="8193880298-21">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="6868661484-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="6868661484-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="6868661484-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6868661484-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6868661484-25">[</span><span class="p" data-group-id="6868661484-25">]</span><span class="p" data-group-id="6868661484-24">)</span><span class="p" data-group-id="6868661484-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6868661484-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6868661484-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="6868661484-28">(</span><span class="p" data-group-id="6868661484-28">)</span><span class="p" data-group-id="6868661484-27">]</span><span class="p" data-group-id="6868661484-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ │ -been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2455486865-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="2455486865-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="8193880298-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="8193880298-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="8193880298-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8193880298-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8193880298-25">[</span><span class="p" data-group-id="8193880298-25">]</span><span class="p" data-group-id="8193880298-24">)</span><span class="p" data-group-id="8193880298-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8193880298-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8193880298-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="8193880298-28">(</span><span class="p" data-group-id="8193880298-28">)</span><span class="p" data-group-id="8193880298-27">]</span><span class="p" data-group-id="8193880298-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ │ +been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0479060860-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="0479060860-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">3934.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ │ @@ -421,184 +421,184 @@
│ │ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1312290223-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="1312290223-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1312290223-2">(</span><span class="p" data-group-id="1312290223-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1312290223-3">]</span><span class="p" data-group-id="1312290223-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9582059462-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="9582059462-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9582059462-2">(</span><span class="p" data-group-id="9582059462-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9582059462-3">]</span><span class="p" data-group-id="9582059462-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="1312290223-4">(</span><span class="p" data-group-id="1312290223-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="9582059462-4">(</span><span class="p" data-group-id="9582059462-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]</span><span class="w">
│ │ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="1312290223-5">(</span><span class="n">User_List</span><span class="p" data-group-id="1312290223-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="9582059462-5">(</span><span class="n">User_List</span><span class="p" data-group-id="9582059462-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1312290223-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="1312290223-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1312290223-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="1312290223-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="1312290223-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="1312290223-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1312290223-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="1312290223-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="1312290223-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1312290223-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-15">[</span><span class="n">User_List</span><span class="p" data-group-id="1312290223-15">]</span><span class="p" data-group-id="1312290223-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="1312290223-16">(</span><span class="n">User_List</span><span class="p" data-group-id="1312290223-16">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9582059462-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="9582059462-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-7">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9582059462-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9582059462-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="9582059462-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="9582059462-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9582059462-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9582059462-11">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9582059462-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-13">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9582059462-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-15">[</span><span class="n">User_List</span><span class="p" data-group-id="9582059462-15">]</span><span class="p" data-group-id="9582059462-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9582059462-16">(</span><span class="n">User_List</span><span class="p" data-group-id="9582059462-16">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="1312290223-17">(</span><span class="p" data-group-id="1312290223-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1312290223-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1312290223-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-20">[</span><span class="p" data-group-id="1312290223-21">[</span><span class="p" data-group-id="1312290223-21">]</span><span class="p" data-group-id="1312290223-20">]</span><span class="p" data-group-id="1312290223-19">)</span><span class="p" data-group-id="1312290223-18">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="9582059462-17">(</span><span class="p" data-group-id="9582059462-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9582059462-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9582059462-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-20">[</span><span class="p" data-group-id="9582059462-21">[</span><span class="p" data-group-id="9582059462-21">]</span><span class="p" data-group-id="9582059462-20">]</span><span class="p" data-group-id="9582059462-19">)</span><span class="p" data-group-id="9582059462-18">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="1312290223-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="9582059462-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="1312290223-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="9582059462-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="1312290223-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="9582059462-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="1312290223-25">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1312290223-26">[</span><span class="p" data-group-id="1312290223-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1312290223-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="9582059462-25">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9582059462-26">[</span><span class="p" data-group-id="9582059462-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9582059462-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="1312290223-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="1312290223-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-29">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="9582059462-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="9582059462-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-29">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% Server transfers a message between user</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="1312290223-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="9582059462-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="1312290223-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9582059462-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="1312290223-32">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-33">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-34">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1312290223-34">}</span><span class="p" data-group-id="1312290223-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="1312290223-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-35">)</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9582059462-32">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-33">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-34">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9582059462-34">}</span><span class="p" data-group-id="9582059462-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9582059462-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-35">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="1312290223-36">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="9582059462-36">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="1312290223-37">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1312290223-37">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9582059462-37">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9582059462-37">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-38">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="1312290223-38">}</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-39">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-40">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1312290223-40">}</span><span class="p" data-group-id="1312290223-39">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-41">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-41">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="1312290223-42">}</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-38">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="9582059462-38">}</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-39">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-40">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9582059462-40">}</span><span class="p" data-group-id="9582059462-39">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-41">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-41">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9582059462-42">}</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="1312290223-43">(</span><span class="n">Name</span><span class="p" data-group-id="1312290223-43">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="1312290223-44">(</span><span class="ss">mess_client</span><span class="p" data-group-id="1312290223-44">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="9582059462-43">(</span><span class="n">Name</span><span class="p" data-group-id="9582059462-43">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9582059462-44">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9582059462-44">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="1312290223-45">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="1312290223-46">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-47">[</span><span class="nf">server_node</span><span class="p" data-group-id="1312290223-48">(</span><span class="p" data-group-id="1312290223-48">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1312290223-47">]</span><span class="p" data-group-id="1312290223-46">)</span><span class="p" data-group-id="1312290223-45">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="9582059462-45">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="9582059462-46">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-47">[</span><span class="nf">server_node</span><span class="p" data-group-id="9582059462-48">(</span><span class="p" data-group-id="9582059462-48">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9582059462-47">]</span><span class="p" data-group-id="9582059462-46">)</span><span class="p" data-group-id="9582059462-45">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="1312290223-49">(</span><span class="p" data-group-id="1312290223-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="9582059462-49">(</span><span class="p" data-group-id="9582059462-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="1312290223-50">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="1312290223-51">(</span><span class="ss">mess_client</span><span class="p" data-group-id="1312290223-51">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="9582059462-50">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9582059462-51">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9582059462-51">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-52">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-52">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-52">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-52">}</span><span class="p">,</span><span class="w">
│ │ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% The client process which runs on each server node</span><span class="w">
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="1312290223-53">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1312290223-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1312290223-54">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="1312290223-54">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-55">{</span><span class="nf">self</span><span class="p" data-group-id="1312290223-56">(</span><span class="p" data-group-id="1312290223-56">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="1312290223-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="1312290223-57">(</span><span class="p" data-group-id="1312290223-57">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="1312290223-58">(</span><span class="n">Server_Node</span><span class="p" data-group-id="1312290223-58">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9582059462-53">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9582059462-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9582059462-54">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9582059462-54">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-55">{</span><span class="nf">self</span><span class="p" data-group-id="9582059462-56">(</span><span class="p" data-group-id="9582059462-56">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9582059462-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="9582059462-57">(</span><span class="p" data-group-id="9582059462-57">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9582059462-58">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9582059462-58">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="1312290223-59">(</span><span class="n">Server_Node</span><span class="p" data-group-id="1312290223-59">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9582059462-59">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9582059462-59">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1312290223-60">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="1312290223-60">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-61">{</span><span class="nf">self</span><span class="p" data-group-id="1312290223-62">(</span><span class="p" data-group-id="1312290223-62">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="1312290223-61">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="1312290223-63">(</span><span class="ss">normal</span><span class="p" data-group-id="1312290223-63">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-64">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-64">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="p" data-group-id="1312290223-65">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="1312290223-65">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1312290223-66">{</span><span class="nf">self</span><span class="p" data-group-id="1312290223-67">(</span><span class="p" data-group-id="1312290223-67">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-66">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="1312290223-68">(</span><span class="p" data-group-id="1312290223-68">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-69">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-69">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1312290223-70">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-71">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1312290223-71">]</span><span class="p" data-group-id="1312290223-70">)</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9582059462-60">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9582059462-60">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-61">{</span><span class="nf">self</span><span class="p" data-group-id="9582059462-62">(</span><span class="p" data-group-id="9582059462-62">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="9582059462-61">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9582059462-63">(</span><span class="ss">normal</span><span class="p" data-group-id="9582059462-63">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-64">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-64">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="p" data-group-id="9582059462-65">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9582059462-65">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9582059462-66">{</span><span class="nf">self</span><span class="p" data-group-id="9582059462-67">(</span><span class="p" data-group-id="9582059462-67">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-66">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="9582059462-68">(</span><span class="p" data-group-id="9582059462-68">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-69">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-69">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9582059462-70">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-71">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9582059462-71">]</span><span class="p" data-group-id="9582059462-70">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="1312290223-72">(</span><span class="n">Server_Node</span><span class="p" data-group-id="1312290223-72">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9582059462-72">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9582059462-72">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="1312290223-73">(</span><span class="p" data-group-id="1312290223-73">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="9582059462-73">(</span><span class="p" data-group-id="9582059462-73">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-74">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="1312290223-74">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1312290223-75">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-76">[</span><span class="n">Why</span><span class="p" data-group-id="1312290223-76">]</span><span class="p" data-group-id="1312290223-75">)</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="1312290223-77">(</span><span class="ss">normal</span><span class="p" data-group-id="1312290223-77">)</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="1312290223-78">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="1312290223-78">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1312290223-79">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1312290223-80">[</span><span class="n">What</span><span class="p" data-group-id="1312290223-80">]</span><span class="p" data-group-id="1312290223-79">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-74">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="9582059462-74">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9582059462-75">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-76">[</span><span class="n">Why</span><span class="p" data-group-id="9582059462-76">]</span><span class="p" data-group-id="9582059462-75">)</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9582059462-77">(</span><span class="ss">normal</span><span class="p" data-group-id="9582059462-77">)</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="9582059462-78">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="9582059462-78">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9582059462-79">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9582059462-80">[</span><span class="n">What</span><span class="p" data-group-id="9582059462-80">]</span><span class="p" data-group-id="9582059462-79">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To use this program, you need to:</p><ul><li>Configure the <code class="inline">server_node()</code> function.</li><li>Copy the compiled code (<code class="inline">messenger.beam</code>) to the directory on each computer
│ │ │ │  where you start Erlang.</li></ul><p>In the following example using this program, nodes are started on four different
│ │ │ │  computers. If you do not have that many machines available on your network, you
│ │ │ │  can start several nodes on the same machine.</p><p>Four Erlang nodes are started up: messenger@super, c1@bilbo, c2@kosken,
│ │ │ │ -c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="0544813527-1">(</span><span class="p" data-group-id="0544813527-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="9895326867-1">(</span><span class="ss">peter</span><span class="p" data-group-id="9895326867-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="2173282539-1">(</span><span class="p" data-group-id="2173282539-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="0899711213-1">(</span><span class="ss">peter</span><span class="p" data-group-id="0899711213-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="9267339039-1">(</span><span class="ss">james</span><span class="p" data-group-id="9267339039-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="6643678477-1">(</span><span class="ss">james</span><span class="p" data-group-id="6643678477-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="0582037731-1">(</span><span class="ss">fred</span><span class="p" data-group-id="0582037731-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="1376800969-1">(</span><span class="ss">fred</span><span class="p" data-group-id="1376800969-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ │ -</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="5929961971-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5929961971-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="7307879791-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7307879791-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="ss">sent</span></code></pre><p>Fred receives the message and sends a message to Peter and logs off:</p><pre><code class="makeup erlang" translate="no"><span class="n">Message</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="nc">peter</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ │ -(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="2724479862-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="2724479862-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="1639860409-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="1639860409-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="nf">sent</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2724479862-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="2724479862-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="2724479862-3">(</span><span class="p" data-group-id="2724479862-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="3524020901-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="3524020901-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1639860409-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="1639860409-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="1639860409-3">(</span><span class="p" data-group-id="1639860409-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="8062722101-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="8062722101-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ │  </span><span class="ss">receiver_not_found</span></code></pre><p>But this fails as Fred has already logged off.</p><p>First let us look at some of the new concepts that have been introduced.</p><p>There are two versions of the <code class="inline">server_transfer</code> function: one with four
│ │ │ │  arguments (<code class="inline">server_transfer/4</code>) and one with five (<code class="inline">server_transfer/5</code>). These
│ │ │ │  are regarded by Erlang as two separate functions.</p><p>Notice how to write the <code class="inline">server</code> function so that it calls itself, through
│ │ │ │  <code class="inline">server(User_List)</code>, and thus creates a loop. The Erlang compiler is &quot;clever&quot;
│ │ │ │  and optimizes the code so that this really is a sort of loop and not a proper
│ │ │ │  function call. But this only works if there is no code after the call.
│ │ │ │  Otherwise, the compiler expects the call to return and make a proper function
│ │ │ │  call. This would result in the process getting bigger and bigger for every loop.</p><p>Functions in the <code class="inline">lists</code> module are used. This is a very useful module and a
│ │ │ │  study of the manual page is recommended (<code class="inline">erl -man lists</code>).
│ │ │ │  <code class="inline">lists:keymember(Key,Position,Lists)</code> looks through a list of tuples and looks
│ │ │ │  at <code class="inline">Position</code> in each tuple to see if it is the same as <code class="inline">Key</code>. The first element
│ │ │ │  is position 1. If it finds a tuple where the element at <code class="inline">Position</code> is the same
│ │ │ │ -as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="1839861895-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1839861895-2">[</span><span class="p" data-group-id="1839861895-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1839861895-3">}</span><span class="p">,</span><span class="p" data-group-id="1839861895-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1839861895-4">}</span><span class="p">,</span><span class="p" data-group-id="1839861895-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1839861895-5">}</span><span class="p">,</span><span class="p" data-group-id="1839861895-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="1839861895-6">}</span><span class="p" data-group-id="1839861895-2">]</span><span class="p" data-group-id="1839861895-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6426512243-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6426512243-2">[</span><span class="p" data-group-id="6426512243-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6426512243-3">}</span><span class="p">,</span><span class="p" data-group-id="6426512243-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6426512243-4">}</span><span class="p">,</span><span class="p" data-group-id="6426512243-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6426512243-5">}</span><span class="p">,</span><span class="p" data-group-id="6426512243-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6426512243-6">}</span><span class="p" data-group-id="6426512243-2">]</span><span class="p" data-group-id="6426512243-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="1839861895-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1839861895-8">[</span><span class="p" data-group-id="1839861895-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1839861895-9">}</span><span class="p">,</span><span class="p" data-group-id="1839861895-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1839861895-10">}</span><span class="p">,</span><span class="p" data-group-id="1839861895-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1839861895-11">}</span><span class="p">,</span><span class="p" data-group-id="1839861895-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="1839861895-12">}</span><span class="p" data-group-id="1839861895-8">]</span><span class="p" data-group-id="1839861895-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="6426512243-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6426512243-8">[</span><span class="p" data-group-id="6426512243-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6426512243-9">}</span><span class="p">,</span><span class="p" data-group-id="6426512243-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6426512243-10">}</span><span class="p">,</span><span class="p" data-group-id="6426512243-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6426512243-11">}</span><span class="p">,</span><span class="p" data-group-id="6426512243-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="6426512243-12">}</span><span class="p" data-group-id="6426512243-8">]</span><span class="p" data-group-id="6426512243-7">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">false</span></code></pre><p><code class="inline">lists:keydelete</code> works in the same way but deletes the first tuple found (if
│ │ │ │ -any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="7771273481-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7771273481-2">[</span><span class="p" data-group-id="7771273481-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="7771273481-3">}</span><span class="p">,</span><span class="p" data-group-id="7771273481-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7771273481-4">}</span><span class="p">,</span><span class="p" data-group-id="7771273481-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7771273481-5">}</span><span class="p">,</span><span class="p" data-group-id="7771273481-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="7771273481-6">}</span><span class="p" data-group-id="7771273481-2">]</span><span class="p" data-group-id="7771273481-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7771273481-7">[</span><span class="p" data-group-id="7771273481-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="7771273481-8">}</span><span class="p">,</span><span class="p" data-group-id="7771273481-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="7771273481-9">}</span><span class="p">,</span><span class="p" data-group-id="7771273481-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="7771273481-10">}</span><span class="p" data-group-id="7771273481-7">]</span></code></pre><p><code class="inline">lists:keysearch</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │ │ +any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="2579417037-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2579417037-2">[</span><span class="p" data-group-id="2579417037-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="2579417037-3">}</span><span class="p">,</span><span class="p" data-group-id="2579417037-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="2579417037-4">}</span><span class="p">,</span><span class="p" data-group-id="2579417037-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2579417037-5">}</span><span class="p">,</span><span class="p" data-group-id="2579417037-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="2579417037-6">}</span><span class="p" data-group-id="2579417037-2">]</span><span class="p" data-group-id="2579417037-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2579417037-7">[</span><span class="p" data-group-id="2579417037-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="2579417037-8">}</span><span class="p">,</span><span class="p" data-group-id="2579417037-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="2579417037-9">}</span><span class="p">,</span><span class="p" data-group-id="2579417037-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="2579417037-10">}</span><span class="p" data-group-id="2579417037-7">]</span></code></pre><p><code class="inline">lists:keysearch</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │ │  <code class="inline">{value,Tuple_Found}</code> or the atom <code class="inline">false</code>.</p><p>There are many very useful functions in the <code class="inline">lists</code> module.</p><p>An Erlang process (conceptually) runs until it does a <code class="inline">receive</code> and there is no
│ │ │ │  message which it wants to receive in the message queue. &quot;conceptually&quot; is used
│ │ │ │  here because the Erlang system shares the CPU time between the active processes
│ │ │ │  in the system.</p><p>A process terminates when there is nothing more for it to do, that is, the last
│ │ │ │  function it calls simply returns and does not call another function. Another way
│ │ │ │  for a process to terminate is for it to call <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a>. The argument
│ │ │ │  to <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a> has a special meaning, which is discussed later. In this
│ │ │ │  example, <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a> is done, which has the same effect as a
│ │ │ │  process running out of functions to call.</p><p>The BIF <a href="../../../lib/../erts/doc/html/erlang.html#whereis/1"><code class="inline">whereis(RegisteredName)</code></a> checks if a registered process
│ │ │ │  of name <code class="inline">RegisteredName</code> exists. If it exists, the pid of that process is
│ │ │ │  returned. If it does not exist, the atom <code class="inline">undefined</code> is returned.</p><p>You should by now be able to understand most of the code in the
│ │ │ │  messenger-module. Let us study one case in detail: a message is sent from one
│ │ │ │ -user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="6052566603-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6052566603-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="2529207163-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="2529207163-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1573286569-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1573286569-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6819887018-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="6819887018-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6819887018-2">{</span><span class="nf">self</span><span class="p" data-group-id="6819887018-3">(</span><span class="p" data-group-id="6819887018-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6819887018-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="7292075620-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7292075620-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9097394828-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9097394828-1">)</span></code></pre><p>If <code class="inline">keysearch</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ │ -sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2676952676-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="2676952676-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │ │ +user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="2632954433-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2632954433-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="2563509679-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="2563509679-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5984757696-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="5984757696-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6323379924-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="6323379924-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6323379924-2">{</span><span class="nf">self</span><span class="p" data-group-id="6323379924-3">(</span><span class="p" data-group-id="6323379924-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="6323379924-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="9061704337-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9061704337-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7503156365-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7503156365-1">)</span></code></pre><p>If <code class="inline">keysearch</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ │ +sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3752106943-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="3752106943-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../../lib/../erts/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │ │  and terminates. If <code class="inline">keysearch</code> returns <code class="inline">{value,{From,Name}}</code> it is certain that
│ │ │ │ -the user is logged on and that his name (peter) is in variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="6221942413-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="6221942413-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │ │ +the user is logged on and that his name (peter) is in variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="9669776091-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9669776091-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │ │  function <code class="inline">server_transfer/4</code>. Another <code class="inline">keysearch</code> is done on <code class="inline">User_List</code> to find
│ │ │ │ -the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9072861600-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9072861600-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │ │ +the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="1595511594-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1595511594-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │ │  returns the atom <code class="inline">false</code>, fred is not logged on and the following message is
│ │ │ │ -sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1771854065-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="1771854065-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keysearch</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4715114580-1">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4715114580-2">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="4715114580-2">}</span><span class="p" data-group-id="4715114580-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0637064616-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0637064616-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5702393167-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="5702393167-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3942808597-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3942808597-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3942808597-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3942808597-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3942808597-3">]</span><span class="p" data-group-id="3942808597-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │ │ +sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7873372870-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="7873372870-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keysearch</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7448258953-1">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7448258953-2">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="7448258953-2">}</span><span class="p" data-group-id="7448258953-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8589534854-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8589534854-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2904381683-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="2904381683-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8601173999-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8601173999-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8601173999-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8601173999-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8601173999-3">]</span><span class="p" data-group-id="8601173999-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/commoncaveats.xhtml
│ │ │ │ @@ -23,31 +23,31 @@
│ │ │ │  <p>This section lists a few constructs to watch out for.</p><h2 id="operator" class="section-heading">
│ │ │ │    <a href="#operator" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Operator <code class="inline">++</code></span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">++</code> operator copies its left-hand side operand. That is clearly
│ │ │ │ -seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="5571314636-1">(</span><span class="p" data-group-id="5571314636-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5571314636-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5571314636-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5571314636-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="5571314636-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5571314636-4">)</span><span class="p" data-group-id="5571314636-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="5571314636-5">(</span><span class="p" data-group-id="5571314636-6">[</span><span class="p" data-group-id="5571314636-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5571314636-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="5342346149-1">(</span><span class="p" data-group-id="5342346149-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5342346149-2">]</span><span class="p" data-group-id="5342346149-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="5342346149-3">(</span><span class="n">T</span><span class="p" data-group-id="5342346149-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5342346149-4">[</span><span class="n">H</span><span class="p" data-group-id="5342346149-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">naive_reverse</span><span class="p" data-group-id="5342346149-5">(</span><span class="p" data-group-id="5342346149-6">[</span><span class="p" data-group-id="5342346149-6">]</span><span class="p" data-group-id="5342346149-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5342346149-7">[</span><span class="p" data-group-id="5342346149-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ │ -result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="2428950322-1">(</span><span class="n">List</span><span class="p" data-group-id="2428950322-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="2428950322-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2428950322-3">[</span><span class="p" data-group-id="2428950322-3">]</span><span class="p" data-group-id="2428950322-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="6291850659-1">(</span><span class="p" data-group-id="6291850659-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6291850659-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="6291850659-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6291850659-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="6291850659-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="6291850659-4">)</span><span class="p" data-group-id="6291850659-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="6291850659-5">(</span><span class="p" data-group-id="6291850659-6">[</span><span class="p" data-group-id="6291850659-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="6291850659-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="3717639495-1">(</span><span class="p" data-group-id="3717639495-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3717639495-2">]</span><span class="p" data-group-id="3717639495-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="3717639495-3">(</span><span class="n">T</span><span class="p" data-group-id="3717639495-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3717639495-4">[</span><span class="n">H</span><span class="p" data-group-id="3717639495-4">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">naive_reverse</span><span class="p" data-group-id="3717639495-5">(</span><span class="p" data-group-id="3717639495-6">[</span><span class="p" data-group-id="3717639495-6">]</span><span class="p" data-group-id="3717639495-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3717639495-7">[</span><span class="p" data-group-id="3717639495-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ │ +result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="4016219639-1">(</span><span class="n">List</span><span class="p" data-group-id="4016219639-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="4016219639-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4016219639-3">[</span><span class="p" data-group-id="4016219639-3">]</span><span class="p" data-group-id="4016219639-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="2428950322-4">(</span><span class="p" data-group-id="2428950322-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2428950322-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2428950322-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="2428950322-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2428950322-7">[</span><span class="n">H</span><span class="p" data-group-id="2428950322-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2428950322-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="2428950322-8">(</span><span class="p" data-group-id="2428950322-9">[</span><span class="p" data-group-id="2428950322-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2428950322-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="4016219639-4">(</span><span class="p" data-group-id="4016219639-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4016219639-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4016219639-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="4016219639-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4016219639-7">[</span><span class="n">H</span><span class="p" data-group-id="4016219639-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4016219639-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="4016219639-8">(</span><span class="p" data-group-id="4016219639-9">[</span><span class="p" data-group-id="4016219639-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="4016219639-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Each list element is copied only once. The growing result <code class="inline">Acc</code> is the right-hand
│ │ │ │ -side operand, which it is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="8762047567-1">(</span><span class="p" data-group-id="8762047567-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8762047567-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8762047567-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="8762047567-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8762047567-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="8762047567-4">]</span><span class="p" data-group-id="8762047567-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="8762047567-5">(</span><span class="p" data-group-id="8762047567-6">[</span><span class="p" data-group-id="8762047567-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8762047567-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +side operand, which it is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="2939344969-1">(</span><span class="p" data-group-id="2939344969-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2939344969-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2939344969-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="2939344969-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2939344969-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2939344969-4">]</span><span class="p" data-group-id="2939344969-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="2939344969-5">(</span><span class="p" data-group-id="2939344969-6">[</span><span class="p" data-group-id="2939344969-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2939344969-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>In principle, this is slightly more efficient because the list element <code class="inline">[H]</code>
│ │ │ │  is not built before being copied and discarded. In practice, the compiler
│ │ │ │  rewrites <code class="inline">[H] ++ Acc</code> to <code class="inline">[H|Acc]</code>.</p><h2 id="timer-module" class="section-heading">
│ │ │ │    <a href="#timer-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Timer Module</span>
│ │ │ │ @@ -65,77 +65,77 @@
│ │ │ │  therefore harmless.</p><h2 id="accidental-copying-and-loss-of-sharing" class="section-heading">
│ │ │ │    <a href="#accidental-copying-and-loss-of-sharing" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Accidental Copying and Loss of Sharing</span>
│ │ │ │  </h2>
│ │ │ │  <p>When spawning a new process using a fun, one can accidentally copy more data to
│ │ │ │ -the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="6387348483-1">(</span><span class="n">State</span><span class="p" data-group-id="6387348483-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="6387348483-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6387348483-3">(</span><span class="p" data-group-id="6387348483-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6387348483-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6387348483-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="6387348483-5">]</span><span class="p" data-group-id="6387348483-4">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="6387348483-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │ │ +the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="2617462839-1">(</span><span class="n">State</span><span class="p" data-group-id="2617462839-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2617462839-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2617462839-3">(</span><span class="p" data-group-id="2617462839-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2617462839-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2617462839-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="2617462839-5">]</span><span class="p" data-group-id="2617462839-4">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="2617462839-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │ │  rest of the <code class="inline">state</code> record is not used. However, when the <a href="../../../lib/../erts/doc/html/erlang.html#spawn/1"><code class="inline">spawn/1</code></a>
│ │ │ │ -function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="4954301755-1">(</span><span class="n">State</span><span class="p" data-group-id="4954301755-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4954301755-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4954301755-3">(</span><span class="p" data-group-id="4954301755-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4954301755-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4954301755-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="4954301755-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4954301755-6">)</span><span class="p" data-group-id="4954301755-5">]</span><span class="p" data-group-id="4954301755-4">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="4954301755-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ │ -behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="0791892374-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0791892374-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0791892374-2">(</span><span class="p" data-group-id="0791892374-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0791892374-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0791892374-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ │ -map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="3423136201-1">(</span><span class="p" data-group-id="3423136201-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="3423136201-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="3423136201-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="3423136201-3">)</span><span class="p" data-group-id="3423136201-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │ │ +function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="7881856135-1">(</span><span class="n">State</span><span class="p" data-group-id="7881856135-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7881856135-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7881856135-3">(</span><span class="p" data-group-id="7881856135-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7881856135-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7881856135-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="7881856135-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7881856135-6">)</span><span class="p" data-group-id="7881856135-5">]</span><span class="p" data-group-id="7881856135-4">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="7881856135-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ │ +behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="3945086504-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3945086504-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3945086504-2">(</span><span class="p" data-group-id="3945086504-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3945086504-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3945086504-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ │ +map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="0994485594-1">(</span><span class="p" data-group-id="0994485594-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0994485594-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="0994485594-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="0994485594-3">)</span><span class="p" data-group-id="0994485594-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │ │  newly created process.</p><p>An unnecessary copy of 10000 element list can be bad enough, but it can get even
│ │ │ │  worse if the <code class="inline">state</code> record contains <em>shared subterms</em>. Here is a simple example
│ │ │ │ -of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7288138901-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="7288138901-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ │ -the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="2313436539-1">(</span><span class="p" data-group-id="2313436539-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="2313436539-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2313436539-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="2313436539-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2313436539-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="2313436539-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2313436539-5">[</span><span class="mi">0</span><span class="p" data-group-id="2313436539-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="2313436539-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="2313436539-6">)</span><span class="p" data-group-id="2313436539-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="2313436539-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">Shared</span><span class="p" data-group-id="2313436539-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │ │ +of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3773047552-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="3773047552-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ │ +the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="5946134017-1">(</span><span class="p" data-group-id="5946134017-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="5946134017-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5946134017-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5946134017-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5946134017-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="5946134017-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5946134017-5">[</span><span class="mi">0</span><span class="p" data-group-id="5946134017-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="5946134017-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="5946134017-6">)</span><span class="p" data-group-id="5946134017-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="5946134017-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">Shared</span><span class="p" data-group-id="5946134017-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │ │  record will be 32 heap words. When the record is copied to the newly created
│ │ │ │  process, sharing will be lost and the size of the copied <code class="inline">data</code> field will be
│ │ │ │  131070 heap words. More details about
│ │ │ │  <a href="eff_guide_processes.xhtml#loss-of-sharing">loss off sharing</a> are found in a later
│ │ │ │  section.</p><p>To avoid the problem, outside of the fun extract only the fields of the record
│ │ │ │ -that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="0445960371-1">(</span><span class="n">State</span><span class="p" data-group-id="0445960371-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="7080158610-1">(</span><span class="n">State</span><span class="p" data-group-id="7080158610-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="0445960371-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0445960371-3">(</span><span class="p" data-group-id="0445960371-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0445960371-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0445960371-5">[</span><span class="n">Info</span><span class="p" data-group-id="0445960371-5">]</span><span class="p" data-group-id="0445960371-4">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="0445960371-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ │ -used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="7142978751-1">(</span><span class="n">State</span><span class="p" data-group-id="7142978751-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="7142978751-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7142978751-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7142978751-3">(</span><span class="nf">fun</span><span class="p" data-group-id="7142978751-4">(</span><span class="p" data-group-id="7142978751-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7142978751-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7142978751-6">[</span><span class="n">Info</span><span class="p" data-group-id="7142978751-6">]</span><span class="p" data-group-id="7142978751-5">)</span><span class="w">
│ │ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="7142978751-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1" class="section-heading">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7080158610-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7080158610-3">(</span><span class="p" data-group-id="7080158610-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7080158610-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7080158610-5">[</span><span class="n">Info</span><span class="p" data-group-id="7080158610-5">]</span><span class="p" data-group-id="7080158610-4">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="7080158610-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ │ +used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="0731800580-1">(</span><span class="n">State</span><span class="p" data-group-id="0731800580-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="0731800580-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0731800580-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0731800580-3">(</span><span class="nf">fun</span><span class="p" data-group-id="0731800580-4">(</span><span class="p" data-group-id="0731800580-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0731800580-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0731800580-6">[</span><span class="n">Info</span><span class="p" data-group-id="0731800580-6">]</span><span class="p" data-group-id="0731800580-5">)</span><span class="w">
│ │ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="0731800580-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1" class="section-heading">
│ │ │ │    <a href="#list_to_atom-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">list_to_atom/1</span>
│ │ │ │  </h2>
│ │ │ │  <p>Atoms are not garbage-collected. Once an atom is created, it is never removed.
│ │ │ │  The emulator terminates if the limit for the number of atoms (1,048,576 by
│ │ │ │  default) is reached.</p><p>Therefore, converting arbitrary input strings to atoms can be dangerous in a
│ │ │ │  system that runs continuously. If only certain well-defined atoms are allowed as
│ │ │ │  input, <a href="../../../lib/../erts/doc/html/erlang.html#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a> or
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#binary_to_existing_atom/1"><code class="inline">binary_to_existing_atom/1</code></a> can be used
│ │ │ │  to guard against a denial-of-service attack. (All atoms that are allowed must
│ │ │ │  have been created earlier, for example, by using all of them in a module
│ │ │ │  and loading that module.)</p><p>Using <a href="../../../lib/../erts/doc/html/erlang.html#list_to_atom/1"><code class="inline">list_to_atom/1</code></a> to construct an atom that
│ │ │ │ -is passed to <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="4618396567-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="4618396567-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="4618396567-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4618396567-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │ │ +is passed to <a href="../../../lib/../erts/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="6733562666-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="6733562666-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="6733562666-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="6733562666-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │ │    <a href="#length-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">length/1</span>
│ │ │ │  </h2>
│ │ │ │  <p>The time for calculating the length of a list is proportional to the length of
│ │ │ │  the list, as opposed to <a href="../../../lib/../erts/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a>,
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#byte_size/1"><code class="inline">byte_size/1</code></a>, and <a href="../../../lib/../erts/doc/html/erlang.html#bit_size/1"><code class="inline">bit_size/1</code></a>, which all
│ │ │ │  execute in constant time.</p><p>Normally, there is no need to worry about the speed of <a href="../../../lib/../erts/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a>,
│ │ │ │  because it is efficiently implemented in C. In time-critical code, you might
│ │ │ │  want to avoid it if the input list could potentially be very long.</p><p>Some uses of <a href="../../../lib/../erts/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a> can be replaced by matching. For example,
│ │ │ │ -the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="8275836239-1">(</span><span class="n">L</span><span class="p" data-group-id="8275836239-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8275836239-2">(</span><span class="n">L</span><span class="p" data-group-id="8275836239-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2822040810-1">(</span><span class="p" data-group-id="2822040810-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="2822040810-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="2822040810-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4131077184-1">(</span><span class="n">L</span><span class="p" data-group-id="4131077184-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="4131077184-2">(</span><span class="n">L</span><span class="p" data-group-id="4131077184-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="9849030214-1">(</span><span class="p" data-group-id="9849030214-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="9849030214-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="9849030214-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>One slight difference is that <a href="../../../lib/../erts/doc/html/erlang.html#length/1"><code class="inline">length(L)</code></a> fails if <code class="inline">L</code> is an
│ │ │ │  improper list, while the pattern in the second code fragment accepts an improper
│ │ │ │  list.</p><h2 id="setelement-3" class="section-heading">
│ │ │ │    <a href="#setelement-3" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">setelement/3</span>
│ │ │ │ @@ -143,18 +143,18 @@
│ │ │ │  <p><a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> copies the tuple it modifies. Therefore,
│ │ │ │  updating a tuple in a loop using <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> creates a new
│ │ │ │  copy of the tuple every time.</p><p>There is one exception to the rule that the tuple is copied. If the compiler
│ │ │ │  clearly can see that destructively updating the tuple would give the same result
│ │ │ │  as if the tuple was copied, the call to <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> is
│ │ │ │  replaced with a special destructive <code class="inline">setelement</code> instruction. In the following
│ │ │ │  code sequence, the first <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call copies the tuple
│ │ │ │ -and modifies the ninth element:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="9568851072-1">(</span><span class="n">T0</span><span class="p" data-group-id="9568851072-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="9568851072-2">(</span><span class="n">T0</span><span class="p" data-group-id="9568851072-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="9568851072-3">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="9568851072-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="9568851072-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="9568851072-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">setelement</span><span class="p" data-group-id="9568851072-5">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="9568851072-5">)</span><span class="p">.</span></code></pre><p>The two following <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls modify the tuple in
│ │ │ │ +and modifies the ninth element:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="7652242050-1">(</span><span class="n">T0</span><span class="p" data-group-id="7652242050-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="7652242050-2">(</span><span class="n">T0</span><span class="p" data-group-id="7652242050-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="7652242050-3">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="7652242050-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="7652242050-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="7652242050-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">setelement</span><span class="p" data-group-id="7652242050-5">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="7652242050-5">)</span><span class="p">.</span></code></pre><p>The two following <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls modify the tuple in
│ │ │ │  place.</p><p>For the optimization to be applied, <em>all</em> the following conditions must be true:</p><ul><li>The tuple argument must be known to be a tuple of a known size.</li><li>The indices must be integer literals, not variables or expressions.</li><li>The indices must be given in descending order.</li><li>There must be no calls to another function in between the calls to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a>.</li><li>The tuple returned from one <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call must only be
│ │ │ │  used in the subsequent call to <a href="../../../lib/../erts/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a>.</li></ul><p>If the code cannot be structured as in the <code class="inline">multiple_setelement/1</code> example, the
│ │ │ │  best way to modify multiple elements in a large tuple is to convert the tuple to
│ │ │ │  a list, modify the list, and convert it back to a tuple.</p><h2 id="size-1" class="section-heading">
│ │ │ │    <a href="#size-1" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ ├── OEBPS/code_loading.xhtml
│ │ │ │ @@ -27,16 +27,16 @@
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Compilation</span>
│ │ │ │  </h2>
│ │ │ │  <p>Erlang programs must be <em>compiled</em> to object code. The compiler can generate a
│ │ │ │  new file that contains the object code. The current abstract machine, which runs
│ │ │ │  the object code, is called BEAM, therefore the object files get the suffix
│ │ │ │ -<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="1833069857-1">(</span><span class="n">Module</span><span class="p" data-group-id="1833069857-1">)</span><span class="w">
│ │ │ │ -</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="1833069857-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="1833069857-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │ │ +<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../../lib/compiler/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="9733583548-1">(</span><span class="n">Module</span><span class="p" data-group-id="9733583548-1">)</span><span class="w">
│ │ │ │ +</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="9733583548-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="9733583548-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │ │  loads <code class="inline">Module</code>.</p><p>There is also a module <code class="inline">make</code>, which provides a set of functions similar to the
│ │ │ │  UNIX type Make functions, see module <a href="../../../lib/tools/doc/html/make.html"><code class="inline">make</code></a> in Tools.</p><p>The compiler can also be accessed from the OS prompt using the
│ │ │ │  <a href="../../../lib/../erts/doc/html/erl_cmd.xhtml">erl</a> executable in ERTS.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -compile Module1...ModuleN</span><span class="w">
│ │ │ │  </span><span class="c1">% erl -make</span></code></pre><p>The <code class="inline">erlc</code> program provides way to compile modules from the OS
│ │ │ │  shell, see the <a href="../../../lib/../erts/doc/html/erlc_cmd.xhtml">erlc</a> executable in ERTS. It
│ │ │ │  understands a number of flags that can be used to define macros, add search
│ │ │ │  paths for include files, and more.</p><pre><code class="text">% erlc &lt;flags&gt; File1.erl...FileN.erl</code></pre><p><a href="" id="loading"></a></p><h2 id="code-loading" class="section-heading">
│ │ │ │ @@ -61,51 +61,51 @@
│ │ │ │  When a module is loaded into the system for the first time, the code becomes
│ │ │ │  'current'. If then a new instance of the module is loaded, the code of the
│ │ │ │  previous instance becomes 'old' and the new instance becomes 'current'.</p><p>Both old and current code is valid, and can be evaluated concurrently. Fully
│ │ │ │  qualified function calls always refer to current code. Old code can still be
│ │ │ │  evaluated because of processes lingering in the old code.</p><p>If a third instance of the module is loaded, the code server removes (purges)
│ │ │ │  the old code and any processes lingering in it is terminated. Then the third
│ │ │ │  instance becomes 'current' and the previously current code becomes 'old'.</p><p>To change from old code to current code, a process must make a fully qualified
│ │ │ │ -function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6023730262-1">(</span><span class="ss">m</span><span class="p" data-group-id="6023730262-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6023730262-2">(</span><span class="p" data-group-id="6023730262-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6023730262-3">]</span><span class="p" data-group-id="6023730262-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6921572349-1">(</span><span class="ss">m</span><span class="p" data-group-id="6921572349-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6921572349-2">(</span><span class="p" data-group-id="6921572349-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6921572349-3">]</span><span class="p" data-group-id="6921572349-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="6023730262-4">(</span><span class="p" data-group-id="6023730262-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="6921572349-4">(</span><span class="p" data-group-id="6921572349-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │          </span><span class="ss">code_switch</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="6023730262-5">(</span><span class="p" data-group-id="6023730262-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="6921572349-5">(</span><span class="p" data-group-id="6921572349-5">)</span><span class="p">;</span><span class="w">
│ │ │ │          </span><span class="n">Msg</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="6023730262-6">(</span><span class="p" data-group-id="6023730262-6">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6921572349-6">(</span><span class="p" data-group-id="6921572349-6">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To make the process change code, send the message <code class="inline">code_switch</code> to it. The
│ │ │ │  process then makes a fully qualified call to <code class="inline">m:loop()</code> and changes to current
│ │ │ │  code. Notice that <code class="inline">m:loop/0</code> must be exported.</p><p>For code replacement of funs to work, use the syntax
│ │ │ │  <code class="inline">fun Module:FunctionName/Arity</code>.</p><p><a href="" id="on_load"></a></p><h2 id="running-a-function-when-a-module-is-loaded" class="section-heading">
│ │ │ │    <a href="#running-a-function-when-a-module-is-loaded" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running a Function When a Module is Loaded</span>
│ │ │ │  </h2>
│ │ │ │  <p>The <code class="inline">-on_load()</code> directive names a function that is to be run automatically when
│ │ │ │ -a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="3541185386-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="3541185386-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │ │ +a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="5729083235-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="5729083235-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │ │  process (which terminates as soon as the function returns).</p><p>The function must return <code class="inline">ok</code> if the module is to become the new current code
│ │ │ │  for the module and become callable.</p><p>Returning any other value or generating an exception causes the new code to be
│ │ │ │  unloaded. If the return value is not an atom, a warning error report is sent to
│ │ │ │  the error logger.</p><p>If there already is current code for the module, that code will remain current
│ │ │ │  and can be called until the <code class="inline">on_load</code> function has returned. If the <code class="inline">on_load</code>
│ │ │ │  function fails, the current code (if any) will remain current. If there is no
│ │ │ │  current code for a module, any process that makes an external call to the module
│ │ │ │  before the <code class="inline">on_load</code> function has finished will be suspended until the <code class="inline">on_load</code>
│ │ │ │  function have finished.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, if the <code class="inline">on_load</code> function failed, any previously current
│ │ │ │  code would become old, essentially leaving the system without any working and
│ │ │ │  reachable instance of the module.</p></section><p>In embedded mode, first all modules are loaded. Then all <code class="inline">on_load</code> functions are
│ │ │ │  called. The system is terminated unless all of the <code class="inline">on_load</code> functions return
│ │ │ │ -<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3779245707-1">(</span><span class="ss">m</span><span class="p" data-group-id="3779245707-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="3779245707-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3779245707-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0389016382-1">(</span><span class="ss">m</span><span class="p" data-group-id="0389016382-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="0389016382-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0389016382-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="3779245707-3">(</span><span class="p" data-group-id="3779245707-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="0389016382-3">(</span><span class="p" data-group-id="0389016382-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">NifPath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">    </span><span class="c1">%Set up the path to the NIF library.</span><span class="w">
│ │ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">       </span><span class="c1">%Initialize the Info term</span><span class="w">
│ │ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="3779245707-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="3779245707-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../../lib/../erts/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="0389016382-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="0389016382-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../../lib/../erts/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │ │  report is sent to the error loader.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/c_portdriver.xhtml
│ │ │ │ @@ -56,112 +56,112 @@
│ │ │ │  <p>Like a port program, the port communicates with an Erlang process. All
│ │ │ │  communication goes through one Erlang process that is the <em>connected process</em> of
│ │ │ │  the port driver. Terminating this process closes the port driver.</p><p>Before the port is created, the driver must be loaded. This is done with the
│ │ │ │  function <a href="../../../lib/kernel/doc/html/erl_ddll.html#load_driver/2"><code class="inline">erl_ddll:load_driver/2</code></a>, with the name of the shared library as
│ │ │ │  argument.</p><p>The port is then created using the BIF <a href="../../../lib/../erts/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a>, with the
│ │ │ │  tuple <code class="inline">{spawn, DriverName}</code> as the first argument. The string <code class="inline">SharedLib</code> is the
│ │ │ │  name of the port driver. The second argument is a list of options, none in this
│ │ │ │ -case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8072758498-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="8072758498-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8072758498-2">(</span><span class="p" data-group-id="8072758498-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8072758498-3">]</span><span class="p" data-group-id="8072758498-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1697655952-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="1697655952-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1697655952-2">(</span><span class="p" data-group-id="1697655952-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1697655952-3">]</span><span class="p" data-group-id="1697655952-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8072758498-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="8072758498-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="8072758498-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="8072758498-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="1697655952-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="1697655952-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="1697655952-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="1697655952-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8072758498-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="8072758498-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="8072758498-7">(</span><span class="p" data-group-id="8072758498-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="8072758498-8">}</span><span class="p" data-group-id="8072758498-7">)</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="1697655952-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="1697655952-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="1697655952-7">(</span><span class="p" data-group-id="1697655952-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="1697655952-8">}</span><span class="p" data-group-id="1697655952-7">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8072758498-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8072758498-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="8072758498-10">]</span><span class="p" data-group-id="8072758498-9">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="1697655952-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1697655952-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="1697655952-10">]</span><span class="p" data-group-id="1697655952-9">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8072758498-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="8072758498-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="8072758498-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8072758498-13">(</span><span class="p" data-group-id="8072758498-13">)</span><span class="p" data-group-id="8072758498-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="8072758498-14">(</span><span class="p" data-group-id="8072758498-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="8072758498-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8072758498-16">[</span><span class="p" data-group-id="8072758498-16">]</span><span class="p" data-group-id="8072758498-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="8072758498-17">(</span><span class="n">Port</span><span class="p" data-group-id="8072758498-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ │ -message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4223362204-1">(</span><span class="n">X</span><span class="p" data-group-id="4223362204-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4223362204-2">(</span><span class="p" data-group-id="4223362204-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4223362204-3">}</span><span class="p" data-group-id="4223362204-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="4223362204-4">(</span><span class="n">Y</span><span class="p" data-group-id="4223362204-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4223362204-5">(</span><span class="p" data-group-id="4223362204-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4223362204-6">}</span><span class="p" data-group-id="4223362204-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1697655952-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="1697655952-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="1697655952-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1697655952-13">(</span><span class="p" data-group-id="1697655952-13">)</span><span class="p" data-group-id="1697655952-12">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="1697655952-14">(</span><span class="p" data-group-id="1697655952-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="1697655952-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1697655952-16">[</span><span class="p" data-group-id="1697655952-16">]</span><span class="p" data-group-id="1697655952-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="1697655952-17">(</span><span class="n">Port</span><span class="p" data-group-id="1697655952-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ │ +message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2512756177-1">(</span><span class="n">X</span><span class="p" data-group-id="2512756177-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="2512756177-2">(</span><span class="p" data-group-id="2512756177-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2512756177-3">}</span><span class="p" data-group-id="2512756177-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="2512756177-4">(</span><span class="n">Y</span><span class="p" data-group-id="2512756177-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="2512756177-5">(</span><span class="p" data-group-id="2512756177-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2512756177-6">}</span><span class="p" data-group-id="2512756177-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="4223362204-7">(</span><span class="n">Msg</span><span class="p" data-group-id="4223362204-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4223362204-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4223362204-9">(</span><span class="p" data-group-id="4223362204-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4223362204-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="2512756177-7">(</span><span class="n">Msg</span><span class="p" data-group-id="2512756177-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2512756177-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2512756177-9">(</span><span class="p" data-group-id="2512756177-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2512756177-8">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4223362204-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4223362204-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="2512756177-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2512756177-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="n">Result</span><span class="w">
│ │ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="8260818463-1">(</span><span class="n">Port</span><span class="p" data-group-id="8260818463-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="6379556717-1">(</span><span class="n">Port</span><span class="p" data-group-id="6379556717-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="8260818463-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8260818463-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8260818463-3">{</span><span class="nf">self</span><span class="p" data-group-id="8260818463-4">(</span><span class="p" data-group-id="8260818463-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260818463-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="8260818463-6">(</span><span class="n">Msg</span><span class="p" data-group-id="8260818463-6">)</span><span class="p" data-group-id="8260818463-5">}</span><span class="p" data-group-id="8260818463-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="6379556717-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="6379556717-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6379556717-3">{</span><span class="nf">self</span><span class="p" data-group-id="6379556717-4">(</span><span class="p" data-group-id="6379556717-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6379556717-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="6379556717-6">(</span><span class="n">Msg</span><span class="p" data-group-id="6379556717-6">)</span><span class="p" data-group-id="6379556717-5">}</span><span class="p" data-group-id="6379556717-3">}</span><span class="p">,</span><span class="w">
│ │ │ │              </span><span class="k">receive</span><span class="w">
│ │ │ │ -                </span><span class="p" data-group-id="8260818463-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260818463-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8260818463-8">}</span><span class="p" data-group-id="8260818463-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8260818463-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="8260818463-10">(</span><span class="n">Data</span><span class="p" data-group-id="8260818463-10">)</span><span class="p" data-group-id="8260818463-9">}</span><span class="w">
│ │ │ │ +                </span><span class="p" data-group-id="6379556717-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6379556717-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6379556717-8">}</span><span class="p" data-group-id="6379556717-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6379556717-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="6379556717-10">(</span><span class="n">Data</span><span class="p" data-group-id="6379556717-10">)</span><span class="p" data-group-id="6379556717-9">}</span><span class="w">
│ │ │ │              </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="8260818463-11">(</span><span class="n">Port</span><span class="p" data-group-id="8260818463-11">)</span><span class="w">
│ │ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6379556717-11">(</span><span class="n">Port</span><span class="p" data-group-id="6379556717-11">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="0823428659-1">(</span><span class="p" data-group-id="0823428659-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0823428659-2">}</span><span class="p" data-group-id="0823428659-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0823428659-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0823428659-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="0823428659-4">(</span><span class="p" data-group-id="0823428659-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0823428659-5">}</span><span class="p" data-group-id="0823428659-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0823428659-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0823428659-6">]</span><span class="p">.</span><span class="w">
│ │ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="7447861397-1">(</span><span class="p" data-group-id="7447861397-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7447861397-2">}</span><span class="p" data-group-id="7447861397-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7447861397-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7447861397-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="7447861397-4">(</span><span class="p" data-group-id="7447861397-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7447861397-5">}</span><span class="p" data-group-id="7447861397-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7447861397-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7447861397-6">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="0823428659-7">(</span><span class="p" data-group-id="0823428659-8">[</span><span class="n">Int</span><span class="p" data-group-id="0823428659-8">]</span><span class="p" data-group-id="0823428659-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="7447861397-7">(</span><span class="p" data-group-id="7447861397-8">[</span><span class="n">Int</span><span class="p" data-group-id="7447861397-8">]</span><span class="p" data-group-id="7447861397-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │ │  detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1834364036-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="1834364036-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1834364036-2">(</span><span class="p" data-group-id="1834364036-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1834364036-3">]</span><span class="p" data-group-id="1834364036-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1834364036-4">(</span><span class="p" data-group-id="1834364036-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1834364036-5">]</span><span class="p" data-group-id="1834364036-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4701500013-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="4701500013-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4701500013-2">(</span><span class="p" data-group-id="4701500013-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4701500013-3">]</span><span class="p" data-group-id="4701500013-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4701500013-4">(</span><span class="p" data-group-id="4701500013-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4701500013-5">]</span><span class="p" data-group-id="4701500013-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="1834364036-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="1834364036-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="1834364036-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="1834364036-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="4701500013-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="4701500013-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="4701500013-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="4701500013-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │  	</span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="1834364036-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="1834364036-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="1834364036-9">(</span><span class="p" data-group-id="1834364036-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="1834364036-10">}</span><span class="p" data-group-id="1834364036-9">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4701500013-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="4701500013-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ │ +	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="4701500013-9">(</span><span class="p" data-group-id="4701500013-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="4701500013-10">}</span><span class="p" data-group-id="4701500013-9">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1834364036-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1834364036-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="1834364036-12">]</span><span class="p" data-group-id="1834364036-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4701500013-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4701500013-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="4701500013-12">]</span><span class="p" data-group-id="4701500013-11">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1834364036-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="1834364036-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1834364036-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1834364036-15">(</span><span class="p" data-group-id="1834364036-15">)</span><span class="p" data-group-id="1834364036-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="1834364036-16">(</span><span class="p" data-group-id="1834364036-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="1834364036-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1834364036-18">[</span><span class="p" data-group-id="1834364036-18">]</span><span class="p" data-group-id="1834364036-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="1834364036-19">(</span><span class="n">Port</span><span class="p" data-group-id="1834364036-19">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4701500013-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="4701500013-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="4701500013-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4701500013-15">(</span><span class="p" data-group-id="4701500013-15">)</span><span class="p" data-group-id="4701500013-14">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4701500013-16">(</span><span class="p" data-group-id="4701500013-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="4701500013-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4701500013-18">[</span><span class="p" data-group-id="4701500013-18">]</span><span class="p" data-group-id="4701500013-16">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="4701500013-19">(</span><span class="n">Port</span><span class="p" data-group-id="4701500013-19">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="1834364036-20">(</span><span class="p" data-group-id="1834364036-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="4701500013-20">(</span><span class="p" data-group-id="4701500013-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="1834364036-21">(</span><span class="n">X</span><span class="p" data-group-id="1834364036-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="1834364036-22">(</span><span class="p" data-group-id="1834364036-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1834364036-23">}</span><span class="p" data-group-id="1834364036-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="1834364036-24">(</span><span class="n">Y</span><span class="p" data-group-id="1834364036-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="1834364036-25">(</span><span class="p" data-group-id="1834364036-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1834364036-26">}</span><span class="p" data-group-id="1834364036-25">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="4701500013-21">(</span><span class="n">X</span><span class="p" data-group-id="4701500013-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4701500013-22">(</span><span class="p" data-group-id="4701500013-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4701500013-23">}</span><span class="p" data-group-id="4701500013-22">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="4701500013-24">(</span><span class="n">Y</span><span class="p" data-group-id="4701500013-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4701500013-25">(</span><span class="p" data-group-id="4701500013-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4701500013-26">}</span><span class="p" data-group-id="4701500013-25">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="1834364036-27">(</span><span class="n">Msg</span><span class="p" data-group-id="1834364036-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1834364036-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1834364036-29">(</span><span class="p" data-group-id="1834364036-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1834364036-28">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="4701500013-27">(</span><span class="n">Msg</span><span class="p" data-group-id="4701500013-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4701500013-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4701500013-29">(</span><span class="p" data-group-id="4701500013-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4701500013-28">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="1834364036-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1834364036-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4701500013-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4701500013-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="1834364036-31">(</span><span class="n">Port</span><span class="p" data-group-id="1834364036-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="4701500013-31">(</span><span class="n">Port</span><span class="p" data-group-id="4701500013-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="1834364036-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1834364036-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1834364036-33">{</span><span class="nf">self</span><span class="p" data-group-id="1834364036-34">(</span><span class="p" data-group-id="1834364036-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1834364036-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="1834364036-36">(</span><span class="n">Msg</span><span class="p" data-group-id="1834364036-36">)</span><span class="p" data-group-id="1834364036-35">}</span><span class="p" data-group-id="1834364036-33">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4701500013-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4701500013-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4701500013-33">{</span><span class="nf">self</span><span class="p" data-group-id="4701500013-34">(</span><span class="p" data-group-id="4701500013-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4701500013-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4701500013-36">(</span><span class="n">Msg</span><span class="p" data-group-id="4701500013-36">)</span><span class="p" data-group-id="4701500013-35">}</span><span class="p" data-group-id="4701500013-33">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="1834364036-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1834364036-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1834364036-38">}</span><span class="p" data-group-id="1834364036-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1834364036-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="1834364036-40">(</span><span class="n">Data</span><span class="p" data-group-id="1834364036-40">)</span><span class="p" data-group-id="1834364036-39">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="4701500013-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4701500013-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4701500013-38">}</span><span class="p" data-group-id="4701500013-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4701500013-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4701500013-40">(</span><span class="n">Data</span><span class="p" data-group-id="4701500013-40">)</span><span class="p" data-group-id="4701500013-39">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="1834364036-41">(</span><span class="n">Port</span><span class="p" data-group-id="1834364036-41">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="4701500013-41">(</span><span class="n">Port</span><span class="p" data-group-id="4701500013-41">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1834364036-42">{</span><span class="nf">self</span><span class="p" data-group-id="1834364036-43">(</span><span class="p" data-group-id="1834364036-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="1834364036-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4701500013-42">{</span><span class="nf">self</span><span class="p" data-group-id="4701500013-43">(</span><span class="p" data-group-id="4701500013-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4701500013-42">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="1834364036-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="1834364036-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="1834364036-45">(</span><span class="ss">normal</span><span class="p" data-group-id="1834364036-45">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="4701500013-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4701500013-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="4701500013-45">(</span><span class="ss">normal</span><span class="p" data-group-id="4701500013-45">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="1834364036-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1834364036-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1834364036-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1834364036-48">[</span><span class="n">Reason</span><span class="p" data-group-id="1834364036-48">]</span><span class="p" data-group-id="1834364036-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="1834364036-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="1834364036-49">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="4701500013-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4701500013-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4701500013-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4701500013-48">[</span><span class="n">Reason</span><span class="p" data-group-id="4701500013-48">]</span><span class="p" data-group-id="4701500013-47">)</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="4701500013-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4701500013-49">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="1834364036-50">(</span><span class="p" data-group-id="1834364036-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1834364036-51">}</span><span class="p" data-group-id="1834364036-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1834364036-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1834364036-52">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="1834364036-53">(</span><span class="p" data-group-id="1834364036-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1834364036-54">}</span><span class="p" data-group-id="1834364036-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1834364036-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1834364036-55">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4701500013-50">(</span><span class="p" data-group-id="4701500013-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4701500013-51">}</span><span class="p" data-group-id="4701500013-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4701500013-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4701500013-52">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="4701500013-53">(</span><span class="p" data-group-id="4701500013-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4701500013-54">}</span><span class="p" data-group-id="4701500013-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4701500013-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4701500013-55">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="1834364036-56">(</span><span class="p" data-group-id="1834364036-57">[</span><span class="n">Int</span><span class="p" data-group-id="1834364036-57">]</span><span class="p" data-group-id="1834364036-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="4701500013-56">(</span><span class="p" data-group-id="4701500013-57">[</span><span class="n">Int</span><span class="p" data-group-id="4701500013-57">]</span><span class="p" data-group-id="4701500013-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │ │    <a href="#c-driver" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">C Driver</span>
│ │ │ │  </h2>
│ │ │ │  <p>The C driver is a module that is compiled and linked into a shared library. It
│ │ │ │  uses a driver structure and includes the header file <code class="inline">erl_driver.h</code>.</p><p>The driver structure is filled with the driver name and function pointers. It is
│ │ │ │ @@ -252,22 +252,22 @@
│ │ │ │    <a href="#running-the-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running the Example</span>
│ │ │ │  </h2>
│ │ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o example_drv.so -fpic -shared complex.c port_driver.c
│ │ │ │  windows&gt; cl -LD -MD -Fe example_drv.dll complex.c port_driver.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="8582370410-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="8582370410-1">]</span><span class="w"> </span><span class="p" data-group-id="8582370410-2">[</span><span class="ss">source</span><span class="p" data-group-id="8582370410-2">]</span><span class="w"> </span><span class="p" data-group-id="8582370410-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="8582370410-3">]</span><span class="w"> </span><span class="p" data-group-id="8582370410-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8582370410-4">]</span><span class="w"> </span><span class="p" data-group-id="8582370410-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="8582370410-5">]</span><span class="w"> </span><span class="p" data-group-id="8582370410-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8582370410-6">]</span><span class="w"> </span><span class="p" data-group-id="8582370410-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="8582370410-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="8263948495-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="8263948495-1">]</span><span class="w"> </span><span class="p" data-group-id="8263948495-2">[</span><span class="ss">source</span><span class="p" data-group-id="8263948495-2">]</span><span class="w"> </span><span class="p" data-group-id="8263948495-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="8263948495-3">]</span><span class="w"> </span><span class="p" data-group-id="8263948495-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8263948495-4">]</span><span class="w"> </span><span class="p" data-group-id="8263948495-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="8263948495-5">]</span><span class="w"> </span><span class="p" data-group-id="8263948495-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8263948495-6">]</span><span class="w"> </span><span class="p" data-group-id="8263948495-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="8263948495-7">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="8582370410-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="8582370410-9">(</span><span class="p" data-group-id="8582370410-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="8582370410-8">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="8582370410-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="8582370410-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8582370410-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="8582370410-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8846455818-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="8846455818-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="8263948495-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="8263948495-9">(</span><span class="p" data-group-id="8263948495-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="8263948495-8">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="8263948495-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="8263948495-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8263948495-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="8263948495-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4554347920-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="4554347920-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="8846455818-2">(</span><span class="mi">3</span><span class="p" data-group-id="8846455818-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="4554347920-2">(</span><span class="mi">3</span><span class="p" data-group-id="4554347920-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8846455818-3">(</span><span class="mi">5</span><span class="p" data-group-id="8846455818-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="4554347920-3">(</span><span class="mi">5</span><span class="p" data-group-id="4554347920-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="8846455818-4">(</span><span class="p" data-group-id="8846455818-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="4554347920-4">(</span><span class="p" data-group-id="4554347920-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/c_port.xhtml
│ │ │ │ @@ -53,101 +53,101 @@
│ │ │ │  external program, if it is written properly).</p><p>The port is created using the BIF <a href="../../../lib/../erts/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a> with
│ │ │ │  <code class="inline">{spawn,ExtPrg}</code> as the first argument. The string <code class="inline">ExtPrg</code> is the name of the
│ │ │ │  external program, including any command line arguments. The second argument is a
│ │ │ │  list of options, in this case only <code class="inline">{packet,2}</code>. This option says that a 2 byte
│ │ │ │  length indicator is to be used to simplify the communication between C and
│ │ │ │  Erlang. The Erlang port automatically adds the length indicator, but this must
│ │ │ │  be done explicitly in the external C program.</p><p>The process is also set to trap exits, which enables detection of failure of the
│ │ │ │ -external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0053960964-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="0053960964-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0053960964-2">(</span><span class="p" data-group-id="0053960964-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0053960964-3">]</span><span class="p" data-group-id="0053960964-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7804573680-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="7804573680-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7804573680-2">(</span><span class="p" data-group-id="7804573680-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7804573680-3">]</span><span class="p" data-group-id="7804573680-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0053960964-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0053960964-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">spawn</span><span class="p" data-group-id="0053960964-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0053960964-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="0053960964-6">]</span><span class="p" data-group-id="0053960964-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="7804573680-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="7804573680-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">spawn</span><span class="p" data-group-id="7804573680-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7804573680-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="7804573680-6">]</span><span class="p" data-group-id="7804573680-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0053960964-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0053960964-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="0053960964-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0053960964-9">(</span><span class="p" data-group-id="0053960964-9">)</span><span class="p" data-group-id="0053960964-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nf">process_flag</span><span class="p" data-group-id="0053960964-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0053960964-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0053960964-11">(</span><span class="p" data-group-id="0053960964-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0053960964-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0053960964-13">[</span><span class="p" data-group-id="0053960964-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0053960964-14">}</span><span class="p" data-group-id="0053960964-13">]</span><span class="p" data-group-id="0053960964-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="0053960964-15">(</span><span class="n">Port</span><span class="p" data-group-id="0053960964-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ │ -message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1858286371-1">(</span><span class="n">X</span><span class="p" data-group-id="1858286371-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="1858286371-2">(</span><span class="p" data-group-id="1858286371-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1858286371-3">}</span><span class="p" data-group-id="1858286371-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="1858286371-4">(</span><span class="n">Y</span><span class="p" data-group-id="1858286371-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="1858286371-5">(</span><span class="p" data-group-id="1858286371-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1858286371-6">}</span><span class="p" data-group-id="1858286371-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7804573680-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="7804573680-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="7804573680-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7804573680-9">(</span><span class="p" data-group-id="7804573680-9">)</span><span class="p" data-group-id="7804573680-8">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="nf">process_flag</span><span class="p" data-group-id="7804573680-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7804573680-10">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7804573680-11">(</span><span class="p" data-group-id="7804573680-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="7804573680-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7804573680-13">[</span><span class="p" data-group-id="7804573680-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7804573680-14">}</span><span class="p" data-group-id="7804573680-13">]</span><span class="p" data-group-id="7804573680-11">)</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="7804573680-15">(</span><span class="n">Port</span><span class="p" data-group-id="7804573680-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ │ +message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5241603129-1">(</span><span class="n">X</span><span class="p" data-group-id="5241603129-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="5241603129-2">(</span><span class="p" data-group-id="5241603129-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5241603129-3">}</span><span class="p" data-group-id="5241603129-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="5241603129-4">(</span><span class="n">Y</span><span class="p" data-group-id="5241603129-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="5241603129-5">(</span><span class="p" data-group-id="5241603129-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5241603129-6">}</span><span class="p" data-group-id="5241603129-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="1858286371-7">(</span><span class="n">Msg</span><span class="p" data-group-id="1858286371-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1858286371-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1858286371-9">(</span><span class="p" data-group-id="1858286371-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1858286371-8">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="5241603129-7">(</span><span class="n">Msg</span><span class="p" data-group-id="5241603129-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5241603129-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5241603129-9">(</span><span class="p" data-group-id="5241603129-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5241603129-8">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1858286371-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1858286371-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5241603129-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5241603129-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │        </span><span class="n">Result</span><span class="w">
│ │ │ │ -  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4266994597-1">(</span><span class="n">Port</span><span class="p" data-group-id="4266994597-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="5043939246-1">(</span><span class="n">Port</span><span class="p" data-group-id="5043939246-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4266994597-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4266994597-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4266994597-3">{</span><span class="nf">self</span><span class="p" data-group-id="4266994597-4">(</span><span class="p" data-group-id="4266994597-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4266994597-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4266994597-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4266994597-6">)</span><span class="p" data-group-id="4266994597-5">}</span><span class="p" data-group-id="4266994597-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5043939246-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5043939246-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5043939246-3">{</span><span class="nf">self</span><span class="p" data-group-id="5043939246-4">(</span><span class="p" data-group-id="5043939246-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5043939246-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="5043939246-6">(</span><span class="n">Msg</span><span class="p" data-group-id="5043939246-6">)</span><span class="p" data-group-id="5043939246-5">}</span><span class="p" data-group-id="5043939246-3">}</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="4266994597-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4266994597-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4266994597-8">}</span><span class="p" data-group-id="4266994597-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4266994597-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4266994597-10">(</span><span class="n">Data</span><span class="p" data-group-id="4266994597-10">)</span><span class="p" data-group-id="4266994597-9">}</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="5043939246-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5043939246-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5043939246-8">}</span><span class="p" data-group-id="5043939246-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5043939246-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="5043939246-10">(</span><span class="n">Data</span><span class="p" data-group-id="5043939246-10">)</span><span class="p" data-group-id="5043939246-9">}</span><span class="w">
│ │ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -      </span><span class="nf">loop</span><span class="p" data-group-id="4266994597-11">(</span><span class="n">Port</span><span class="p" data-group-id="4266994597-11">)</span><span class="w">
│ │ │ │ +      </span><span class="nf">loop</span><span class="p" data-group-id="5043939246-11">(</span><span class="n">Port</span><span class="p" data-group-id="5043939246-11">)</span><span class="w">
│ │ │ │    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="9352400272-1">(</span><span class="p" data-group-id="9352400272-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9352400272-2">}</span><span class="p" data-group-id="9352400272-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9352400272-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9352400272-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="9352400272-4">(</span><span class="p" data-group-id="9352400272-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9352400272-5">}</span><span class="p" data-group-id="9352400272-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9352400272-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9352400272-6">]</span><span class="p">.</span><span class="w">
│ │ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="6091147501-1">(</span><span class="p" data-group-id="6091147501-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6091147501-2">}</span><span class="p" data-group-id="6091147501-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6091147501-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6091147501-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="6091147501-4">(</span><span class="p" data-group-id="6091147501-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6091147501-5">}</span><span class="p" data-group-id="6091147501-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6091147501-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6091147501-6">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="9352400272-7">(</span><span class="p" data-group-id="9352400272-8">[</span><span class="n">Int</span><span class="p" data-group-id="9352400272-8">]</span><span class="p" data-group-id="9352400272-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ │ -detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0371512883-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="0371512883-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0371512883-2">(</span><span class="p" data-group-id="0371512883-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0371512883-3">]</span><span class="p" data-group-id="0371512883-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0371512883-4">(</span><span class="p" data-group-id="0371512883-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0371512883-5">]</span><span class="p" data-group-id="0371512883-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ -
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0371512883-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0371512883-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="0371512883-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0371512883-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="0371512883-8">]</span><span class="p" data-group-id="0371512883-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="0371512883-9">(</span><span class="p" data-group-id="0371512883-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="6091147501-7">(</span><span class="p" data-group-id="6091147501-8">[</span><span class="n">Int</span><span class="p" data-group-id="6091147501-8">]</span><span class="p" data-group-id="6091147501-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ │ +detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7063000851-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="7063000851-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7063000851-2">(</span><span class="p" data-group-id="7063000851-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7063000851-3">]</span><span class="p" data-group-id="7063000851-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7063000851-4">(</span><span class="p" data-group-id="7063000851-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7063000851-5">]</span><span class="p" data-group-id="7063000851-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="7063000851-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="7063000851-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7063000851-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7063000851-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="7063000851-8">]</span><span class="p" data-group-id="7063000851-7">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="7063000851-9">(</span><span class="p" data-group-id="7063000851-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="0371512883-10">(</span><span class="n">X</span><span class="p" data-group-id="0371512883-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0371512883-11">(</span><span class="p" data-group-id="0371512883-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0371512883-12">}</span><span class="p" data-group-id="0371512883-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="0371512883-13">(</span><span class="n">Y</span><span class="p" data-group-id="0371512883-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="0371512883-14">(</span><span class="p" data-group-id="0371512883-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0371512883-15">}</span><span class="p" data-group-id="0371512883-14">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="7063000851-10">(</span><span class="n">X</span><span class="p" data-group-id="7063000851-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="7063000851-11">(</span><span class="p" data-group-id="7063000851-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7063000851-12">}</span><span class="p" data-group-id="7063000851-11">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="7063000851-13">(</span><span class="n">Y</span><span class="p" data-group-id="7063000851-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="7063000851-14">(</span><span class="p" data-group-id="7063000851-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7063000851-15">}</span><span class="p" data-group-id="7063000851-14">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="0371512883-16">(</span><span class="n">Msg</span><span class="p" data-group-id="0371512883-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0371512883-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0371512883-18">(</span><span class="p" data-group-id="0371512883-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0371512883-17">}</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="7063000851-16">(</span><span class="n">Msg</span><span class="p" data-group-id="7063000851-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7063000851-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7063000851-18">(</span><span class="p" data-group-id="7063000851-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7063000851-17">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0371512883-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0371512883-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="7063000851-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7063000851-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0371512883-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="0371512883-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="0371512883-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0371512883-22">(</span><span class="p" data-group-id="0371512883-22">)</span><span class="p" data-group-id="0371512883-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="0371512883-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0371512883-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0371512883-24">(</span><span class="p" data-group-id="0371512883-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="0371512883-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0371512883-26">[</span><span class="p" data-group-id="0371512883-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0371512883-27">}</span><span class="p" data-group-id="0371512883-26">]</span><span class="p" data-group-id="0371512883-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="0371512883-28">(</span><span class="n">Port</span><span class="p" data-group-id="0371512883-28">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7063000851-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="7063000851-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7063000851-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7063000851-22">(</span><span class="p" data-group-id="7063000851-22">)</span><span class="p" data-group-id="7063000851-21">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="7063000851-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7063000851-23">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="7063000851-24">(</span><span class="p" data-group-id="7063000851-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="7063000851-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7063000851-26">[</span><span class="p" data-group-id="7063000851-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7063000851-27">}</span><span class="p" data-group-id="7063000851-26">]</span><span class="p" data-group-id="7063000851-24">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7063000851-28">(</span><span class="n">Port</span><span class="p" data-group-id="7063000851-28">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="0371512883-29">(</span><span class="n">Port</span><span class="p" data-group-id="0371512883-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="7063000851-29">(</span><span class="n">Port</span><span class="p" data-group-id="7063000851-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0371512883-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="0371512883-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0371512883-31">{</span><span class="nf">self</span><span class="p" data-group-id="0371512883-32">(</span><span class="p" data-group-id="0371512883-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0371512883-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="0371512883-34">(</span><span class="n">Msg</span><span class="p" data-group-id="0371512883-34">)</span><span class="p" data-group-id="0371512883-33">}</span><span class="p" data-group-id="0371512883-31">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="7063000851-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7063000851-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7063000851-31">{</span><span class="nf">self</span><span class="p" data-group-id="7063000851-32">(</span><span class="p" data-group-id="7063000851-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7063000851-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="7063000851-34">(</span><span class="n">Msg</span><span class="p" data-group-id="7063000851-34">)</span><span class="p" data-group-id="7063000851-33">}</span><span class="p" data-group-id="7063000851-31">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="0371512883-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0371512883-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0371512883-36">}</span><span class="p" data-group-id="0371512883-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0371512883-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="0371512883-38">(</span><span class="n">Data</span><span class="p" data-group-id="0371512883-38">)</span><span class="p" data-group-id="0371512883-37">}</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="7063000851-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7063000851-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7063000851-36">}</span><span class="p" data-group-id="7063000851-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7063000851-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="7063000851-38">(</span><span class="n">Data</span><span class="p" data-group-id="7063000851-38">)</span><span class="p" data-group-id="7063000851-37">}</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="0371512883-39">(</span><span class="n">Port</span><span class="p" data-group-id="0371512883-39">)</span><span class="p">;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="7063000851-39">(</span><span class="n">Port</span><span class="p" data-group-id="7063000851-39">)</span><span class="p">;</span><span class="w">
│ │ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0371512883-40">{</span><span class="nf">self</span><span class="p" data-group-id="0371512883-41">(</span><span class="p" data-group-id="0371512883-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="0371512883-40">}</span><span class="p">,</span><span class="w">
│ │ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7063000851-40">{</span><span class="nf">self</span><span class="p" data-group-id="7063000851-41">(</span><span class="p" data-group-id="7063000851-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="7063000851-40">}</span><span class="p">,</span><span class="w">
│ │ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ │ -		</span><span class="p" data-group-id="0371512883-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="0371512883-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="0371512883-43">(</span><span class="ss">normal</span><span class="p" data-group-id="0371512883-43">)</span><span class="w">
│ │ │ │ +		</span><span class="p" data-group-id="7063000851-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="7063000851-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="7063000851-43">(</span><span class="ss">normal</span><span class="p" data-group-id="7063000851-43">)</span><span class="w">
│ │ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ │ -	</span><span class="p" data-group-id="0371512883-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0371512883-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="0371512883-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="0371512883-45">)</span><span class="w">
│ │ │ │ +	</span><span class="p" data-group-id="7063000851-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7063000851-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="7063000851-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="7063000851-45">)</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="0371512883-46">(</span><span class="p" data-group-id="0371512883-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0371512883-47">}</span><span class="p" data-group-id="0371512883-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0371512883-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="0371512883-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="0371512883-49">(</span><span class="p" data-group-id="0371512883-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0371512883-50">}</span><span class="p" data-group-id="0371512883-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0371512883-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0371512883-51">]</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="7063000851-46">(</span><span class="p" data-group-id="7063000851-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7063000851-47">}</span><span class="p" data-group-id="7063000851-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7063000851-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7063000851-48">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="7063000851-49">(</span><span class="p" data-group-id="7063000851-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7063000851-50">}</span><span class="p" data-group-id="7063000851-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7063000851-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7063000851-51">]</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="0371512883-52">(</span><span class="p" data-group-id="0371512883-53">[</span><span class="n">Int</span><span class="p" data-group-id="0371512883-53">]</span><span class="p" data-group-id="0371512883-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="7063000851-52">(</span><span class="p" data-group-id="7063000851-53">[</span><span class="n">Int</span><span class="p" data-group-id="7063000851-53">]</span><span class="p" data-group-id="7063000851-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │ │    <a href="#c-program" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">C Program</span>
│ │ │ │  </h2>
│ │ │ │  <p>On the C side, it is necessary to write functions for receiving and sending data
│ │ │ │  with 2 byte length indicators from/to Erlang. By default, the C program is to
│ │ │ │ @@ -238,22 +238,22 @@
│ │ │ │  and terminates.</p><h2 id="running-the-example" class="section-heading">
│ │ │ │    <a href="#running-the-example" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Running the Example</span>
│ │ │ │  </h2>
│ │ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">$ gcc -o extprg complex.c erl_comm.c port.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="9830404950-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="9830404950-1">]</span><span class="w"> </span><span class="p" data-group-id="9830404950-2">[</span><span class="ss">source</span><span class="p" data-group-id="9830404950-2">]</span><span class="w"> </span><span class="p" data-group-id="9830404950-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="9830404950-3">]</span><span class="w"> </span><span class="p" data-group-id="9830404950-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9830404950-4">]</span><span class="w"> </span><span class="p" data-group-id="9830404950-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="9830404950-5">]</span><span class="w"> </span><span class="p" data-group-id="9830404950-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="9830404950-6">]</span><span class="w"> </span><span class="p" data-group-id="9830404950-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="9830404950-7">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="4143155976-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="4143155976-1">]</span><span class="w"> </span><span class="p" data-group-id="4143155976-2">[</span><span class="ss">source</span><span class="p" data-group-id="4143155976-2">]</span><span class="w"> </span><span class="p" data-group-id="4143155976-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4143155976-3">]</span><span class="w"> </span><span class="p" data-group-id="4143155976-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="4143155976-4">]</span><span class="w"> </span><span class="p" data-group-id="4143155976-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="4143155976-5">]</span><span class="w"> </span><span class="p" data-group-id="4143155976-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4143155976-6">]</span><span class="w"> </span><span class="p" data-group-id="4143155976-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="4143155976-7">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="9830404950-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="9830404950-9">(</span><span class="p" data-group-id="9830404950-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="9830404950-8">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="9830404950-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="9830404950-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9830404950-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="9830404950-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6071295582-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="6071295582-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="4143155976-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="4143155976-9">(</span><span class="p" data-group-id="4143155976-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="4143155976-8">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4143155976-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="4143155976-10">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4143155976-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="4143155976-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2835965575-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="2835965575-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ │ -3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="6071295582-2">(</span><span class="mi">3</span><span class="p" data-group-id="6071295582-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="2835965575-2">(</span><span class="mi">3</span><span class="p" data-group-id="2835965575-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="6071295582-3">(</span><span class="mi">5</span><span class="p" data-group-id="6071295582-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="2835965575-3">(</span><span class="mi">5</span><span class="p" data-group-id="2835965575-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ │ -5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6071295582-4">(</span><span class="p" data-group-id="6071295582-4">)</span><span class="p">.</span><span class="w">
│ │ │ │ +5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2835965575-4">(</span><span class="p" data-group-id="2835965575-4">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/bit_syntax.xhtml
│ │ │ │ @@ -24,48 +24,48 @@
│ │ │ │    <a href="#introduction" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Introduction</span>
│ │ │ │  </h2>
│ │ │ │  <p>The complete specification for the bit syntax appears in the
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml#bit-syntax-expressions">Reference Manual</a>.</p><p>In Erlang, a Bin is used for constructing binaries and matching binary patterns.
│ │ │ │ -A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4897366530-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="4897366530-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ │ -enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2788995306-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="2788995306-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6495888721-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="6495888721-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │ │ +A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7586348873-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="7586348873-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ │ +enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8138794292-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="8138794292-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7336815104-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="7336815104-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │ │  not need to be divisible by 8. If the number of bits is divisible by 8, the
│ │ │ │  bitstring is also a binary.</p><p>Each element specifies a certain <em>segment</em> of the bitstring. A segment is a set
│ │ │ │  of contiguous bits of the binary (not necessarily on a byte boundary). The first
│ │ │ │  element specifies the initial segment, the second element specifies the
│ │ │ │  following segment, and so on.</p><p>The following examples illustrate how binaries are constructed, or matched, and
│ │ │ │  how elements and tails are specified.</p><h3 id="examples" class="section-heading">
│ │ │ │    <a href="#examples" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Examples</span>
│ │ │ │  </h3>
│ │ │ │  <p><em>Example 1:</em> A binary can be constructed from a set of constants or a string
│ │ │ │ -literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6840559284-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="6840559284-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6840559284-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="6840559284-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em>Similarly, a binary can be constructed from a set of bound
│ │ │ │ +literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9917312841-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="9917312841-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9917312841-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="9917312841-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em>Similarly, a binary can be constructed from a set of bound
│ │ │ │  variables:</p><pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4890080043-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4890080043-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6065566479-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="6065566479-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │ │  variable <code class="inline">C</code> to specify a 16-bits segment of <code class="inline">Bin2</code>.</p><p><a href="../../../lib/../erts/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin2)</code></a> evaluates to <code class="inline">[1, 17, 00, 42]</code>.</p><p><em>Example 3:</em> A Bin can also be used for matching. <code class="inline">D</code>, <code class="inline">E</code>, and <code class="inline">F</code> are unbound
│ │ │ │ -variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3824856905-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3824856905-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │ │ +variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3983369516-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3983369516-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │ │  <code class="inline">binary_to_list(F) = [42]</code>.</p><p><em>Example 4:</em> The following is a more elaborate example of matching. Here,
│ │ │ │  <code class="inline">Dgram</code> is bound to the consecutive bytes of an IP datagram of IP protocol
│ │ │ │ -version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5608806740-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="5608806740-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5608806740-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="5608806740-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0923587946-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="0923587946-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0923587946-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="0923587946-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="5608806740-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="5608806740-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="0923587946-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="0923587946-3">)</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="k">case</span><span class="w"> </span><span class="n">Dgram</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="5608806740-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="0923587946-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="n">ID</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">Flgs</span><span class="p">:</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">FragOff</span><span class="p">:</span><span class="mi">13</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="n">TTL</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">HdrChkSum</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ │        </span><span class="n">SrcIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w">
│ │ │ │ -      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5608806740-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="5608806740-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="5608806740-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="5608806740-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5608806740-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │ │ +      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0923587946-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="0923587946-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="0923587946-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="0923587946-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0923587946-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Here, the segment corresponding to the <code class="inline">Opts</code> variable has a <em>type modifier</em>,
│ │ │ │  specifying that <code class="inline">Opts</code> is to bind to a binary. All other variables have the
│ │ │ │  default type equal to unsigned integer.</p><p>An IP datagram header is of variable length. This length is measured in the
│ │ │ │  number of 32-bit words and is given in the segment corresponding to <code class="inline">HLen</code>. The
│ │ │ │  minimum value of <code class="inline">HLen</code> is 5. It is the segment corresponding to <code class="inline">Opts</code> that is
│ │ │ │  variable, so if <code class="inline">HLen</code> is equal to 5, <code class="inline">Opts</code> becomes an empty binary.</p><p>The tail variables <code class="inline">RestDgram</code> and <code class="inline">Data</code> bind to binaries, as all tail
│ │ │ │ @@ -123,77 +123,77 @@
│ │ │ │  <p>This section describes the rules for constructing binaries using the bit syntax.
│ │ │ │  Unlike when constructing lists or tuples, the construction of a binary can fail
│ │ │ │  with a <code class="inline">badarg</code> exception.</p><p>There can be zero or more segments in a binary to be constructed. The expression
│ │ │ │  <code class="inline">&lt;&lt;&gt;&gt;</code> constructs a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. There are no
│ │ │ │  alignment rules for individual segments of type <code class="inline">integer</code> and <code class="inline">float</code>. For
│ │ │ │  binaries and bitstrings without size, the unit specifies the alignment. Since
│ │ │ │  the default alignment for the <code class="inline">binary</code> type is 8, the size of a binary segment
│ │ │ │ -must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8064123938-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="8064123938-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │ │ +must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9329734963-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="9329734963-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │ │  type defaults to <code class="inline">unit:8</code>. A <code class="inline">badarg</code> exception is generated if <code class="inline">Bin</code> consist
│ │ │ │  of, for example, 17 bits.</p><p>The <code class="inline">Bitstring</code> variable can consist of any number of bits, for example, 0, 1,
│ │ │ │  8, 11, 17, 42, and so on. This is because the default <code class="inline">unit</code> for bitstrings
│ │ │ │  is 1.</p><p>For clarity, it is recommended not to change the unit size for binaries.
│ │ │ │  Instead, use <code class="inline">binary</code> when you need byte alignment and <code class="inline">bitstring</code> when you need
│ │ │ │  bit alignment.</p><p>The following example successfully constructs a bitstring of 7 bits, provided
│ │ │ │ -that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0300895262-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="0300895262-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │ │ +that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3204251517-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="3204251517-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │ │  However, for syntactical reasons, both <code class="inline">Value</code> and <code class="inline">Size</code> must be enclosed in
│ │ │ │  parenthesis if the expression consists of anything more than a single literal or
│ │ │ │ -a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6306831367-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6306831367-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ │ -compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8541986993-1">&lt;&lt;</span><span class="p" data-group-id="8541986993-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8541986993-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8541986993-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │ │ +a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3667094425-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3667094425-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ │ +compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8153565557-1">&lt;&lt;</span><span class="p" data-group-id="8153565557-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8153565557-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="8153565557-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │ │    <a href="#including-literal-strings" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Including Literal Strings</span>
│ │ │ │  </h3>
│ │ │ │ -<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0304111394-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0304111394-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8759420331-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="8759420331-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │ │ +<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9607519449-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9607519449-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8960128197-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="8960128197-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Matching Binaries</span>
│ │ │ │  </h2>
│ │ │ │  <p>This section describes the rules for matching binaries, using the bit syntax.</p><p>There can be zero or more segments in a binary pattern. A binary pattern can
│ │ │ │  occur wherever patterns are allowed, including inside other patterns. Binary
│ │ │ │  patterns cannot be nested. The pattern <code class="inline">&lt;&lt;&gt;&gt;</code> matches a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. A segment of type
│ │ │ │  <code class="inline">binary</code> must have a size evenly divisible by 8 (or divisible by the unit size,
│ │ │ │  if the unit size has been changed). A segment of type <code class="inline">bitstring</code> has no
│ │ │ │  restrictions on the size. A segment of type <code class="inline">float</code> must have size 64 or 32.</p><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When matching <code class="inline">Value</code>, value must be either a variable or an integer, or a
│ │ │ │  floating point literal. Expressions are not allowed.</p><p><code class="inline">Size</code> must be a
│ │ │ │  <a href="../../../lib/../system/doc/html/expressions.xhtml#guard-expressions">guard expression</a>, which can use
│ │ │ │ -literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2576471754-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2576471754-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2576471754-2">&gt;&gt;</span><span class="p" data-group-id="2576471754-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="2576471754-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="2576471754-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ │ -<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1656797445-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="1656797445-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1656797445-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1656797445-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1656797445-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="1656797445-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │ │ +literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6860539067-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6860539067-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6860539067-2">&gt;&gt;</span><span class="p" data-group-id="6860539067-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="6860539067-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="6860539067-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ │ +<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5599840864-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="5599840864-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5599840864-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5599840864-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5599840864-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="5599840864-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │ │  an integer.</p></section><h3 id="binding-and-using-a-size-variable" class="section-heading">
│ │ │ │    <a href="#binding-and-using-a-size-variable" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Binding and Using a Size Variable</span>
│ │ │ │  </h3>
│ │ │ │  <p>There is one exception to the rule that a variable that is used as size must be
│ │ │ │  previously bound. It is possible to match and bind a variable, and use it as a
│ │ │ │ -size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="8210555723-1">(</span><span class="p" data-group-id="8210555723-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8210555723-2">&gt;&gt;</span><span class="p" data-group-id="8210555723-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="8210555723-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="8210555723-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ │ -used at the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="0810820842-1">(</span><span class="p" data-group-id="0810820842-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="0810820842-3">(</span><span class="p" data-group-id="0810820842-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="0810820842-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="0810820842-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0810820842-2">&gt;&gt;</span><span class="p" data-group-id="0810820842-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="0810820842-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="0810820842-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │ │ +size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="3841109478-1">(</span><span class="p" data-group-id="3841109478-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3841109478-2">&gt;&gt;</span><span class="p" data-group-id="3841109478-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3841109478-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="3841109478-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ │ +used at the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="8845012953-1">(</span><span class="p" data-group-id="8845012953-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="8845012953-3">(</span><span class="p" data-group-id="8845012953-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="8845012953-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="8845012953-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8845012953-2">&gt;&gt;</span><span class="p" data-group-id="8845012953-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8845012953-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="8845012953-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │ │  subtract one byte to get the size of the payload.</p><h3 id="getting-the-rest-of-the-binary-or-bitstring" class="section-heading">
│ │ │ │    <a href="#getting-the-rest-of-the-binary-or-bitstring" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Getting the Rest of the Binary or Bitstring</span>
│ │ │ │  </h3>
│ │ │ │ -<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="3371781291-1">(</span><span class="p" data-group-id="3371781291-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3371781291-2">&gt;&gt;</span><span class="p" data-group-id="3371781291-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5422389194-1">(</span><span class="p" data-group-id="5422389194-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="5422389194-2">&gt;&gt;</span><span class="p" data-group-id="5422389194-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │ │ +<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6518955096-1">(</span><span class="p" data-group-id="6518955096-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6518955096-2">&gt;&gt;</span><span class="p" data-group-id="6518955096-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="3843027117-1">(</span><span class="p" data-group-id="3843027117-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="3843027117-2">&gt;&gt;</span><span class="p" data-group-id="3843027117-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │ │    <a href="#appending-to-a-binary" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Appending to a Binary</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="9664785390-1">(</span><span class="n">T</span><span class="p" data-group-id="9664785390-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="9664785390-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664785390-3">&lt;&lt;</span><span class="p" data-group-id="9664785390-3">&gt;&gt;</span><span class="p" data-group-id="9664785390-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="6115691014-1">(</span><span class="n">T</span><span class="p" data-group-id="6115691014-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="6115691014-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6115691014-3">&lt;&lt;</span><span class="p" data-group-id="6115691014-3">&gt;&gt;</span><span class="p" data-group-id="6115691014-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="9664785390-4">(</span><span class="p" data-group-id="9664785390-5">[</span><span class="p" data-group-id="9664785390-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="9664785390-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9664785390-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9664785390-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="9664785390-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9664785390-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="9664785390-8">&gt;&gt;</span><span class="p" data-group-id="9664785390-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="9664785390-9">(</span><span class="p" data-group-id="9664785390-10">[</span><span class="p" data-group-id="9664785390-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9664785390-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="6115691014-4">(</span><span class="p" data-group-id="6115691014-5">[</span><span class="p" data-group-id="6115691014-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="6115691014-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6115691014-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6115691014-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="6115691014-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6115691014-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="6115691014-8">&gt;&gt;</span><span class="p" data-group-id="6115691014-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="6115691014-9">(</span><span class="p" data-group-id="6115691014-10">[</span><span class="p" data-group-id="6115691014-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6115691014-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/binaryhandling.xhtml
│ │ │ │ @@ -19,43 +19,43 @@
│ │ │ │  
│ │ │ │      <h1 id="content">
│ │ │ │  Constructing and Matching Binaries
│ │ │ │      </h1>
│ │ │ │  <p>This section gives a few examples on how to handle binaries in an efficient way.
│ │ │ │  The sections that follow take an in-depth look at how binaries are implemented
│ │ │ │  and how to best take advantages of the optimizations done by the compiler and
│ │ │ │ -runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="0654083734-1">(</span><span class="n">List</span><span class="p" data-group-id="0654083734-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="0654083734-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0654083734-3">&lt;&lt;</span><span class="p" data-group-id="0654083734-3">&gt;&gt;</span><span class="p" data-group-id="0654083734-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6206534902-1">(</span><span class="n">List</span><span class="p" data-group-id="6206534902-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6206534902-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6206534902-3">&lt;&lt;</span><span class="p" data-group-id="6206534902-3">&gt;&gt;</span><span class="p" data-group-id="6206534902-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="0654083734-4">(</span><span class="p" data-group-id="0654083734-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0654083734-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0654083734-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="0654083734-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0654083734-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="0654083734-7">&gt;&gt;</span><span class="p" data-group-id="0654083734-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="0654083734-8">(</span><span class="p" data-group-id="0654083734-9">[</span><span class="p" data-group-id="0654083734-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0654083734-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6206534902-4">(</span><span class="p" data-group-id="6206534902-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6206534902-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6206534902-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6206534902-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6206534902-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="6206534902-7">&gt;&gt;</span><span class="p" data-group-id="6206534902-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6206534902-8">(</span><span class="p" data-group-id="6206534902-9">[</span><span class="p" data-group-id="6206534902-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6206534902-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Appending data to a binary as in the example is efficient because it is
│ │ │ │  specially optimized by the runtime system to avoid copying the <code class="inline">Acc</code> binary
│ │ │ │ -every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9372131387-1">(</span><span class="n">List</span><span class="p" data-group-id="9372131387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9372131387-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9372131387-3">&lt;&lt;</span><span class="p" data-group-id="9372131387-3">&gt;&gt;</span><span class="p" data-group-id="9372131387-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1373938160-1">(</span><span class="n">List</span><span class="p" data-group-id="1373938160-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1373938160-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1373938160-3">&lt;&lt;</span><span class="p" data-group-id="1373938160-3">&gt;&gt;</span><span class="p" data-group-id="1373938160-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9372131387-4">(</span><span class="p" data-group-id="9372131387-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9372131387-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9372131387-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9372131387-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9372131387-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9372131387-7">&gt;&gt;</span><span class="p" data-group-id="9372131387-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9372131387-8">(</span><span class="p" data-group-id="9372131387-9">[</span><span class="p" data-group-id="9372131387-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9372131387-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1373938160-4">(</span><span class="p" data-group-id="1373938160-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1373938160-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1373938160-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1373938160-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1373938160-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1373938160-7">&gt;&gt;</span><span class="p" data-group-id="1373938160-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1373938160-8">(</span><span class="p" data-group-id="1373938160-9">[</span><span class="p" data-group-id="1373938160-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1373938160-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>This is not efficient for long lists because the <code class="inline">Acc</code> binary is copied every
│ │ │ │ -time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9274220585-1">(</span><span class="n">List</span><span class="p" data-group-id="9274220585-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9274220585-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9274220585-3">(</span><span class="n">List</span><span class="p" data-group-id="9274220585-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9274220585-4">&lt;&lt;</span><span class="p" data-group-id="9274220585-4">&gt;&gt;</span><span class="p" data-group-id="9274220585-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8139553318-1">(</span><span class="n">List</span><span class="p" data-group-id="8139553318-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8139553318-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="8139553318-3">(</span><span class="n">List</span><span class="p" data-group-id="8139553318-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8139553318-4">&lt;&lt;</span><span class="p" data-group-id="8139553318-4">&gt;&gt;</span><span class="p" data-group-id="8139553318-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9274220585-5">(</span><span class="p" data-group-id="9274220585-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9274220585-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9274220585-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9274220585-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9274220585-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="9274220585-8">&gt;&gt;</span><span class="p" data-group-id="9274220585-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9274220585-9">(</span><span class="p" data-group-id="9274220585-10">[</span><span class="p" data-group-id="9274220585-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9274220585-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1273873797-1">(</span><span class="p" data-group-id="1273873797-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1273873797-2">]</span><span class="p" data-group-id="1273873797-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1273873797-3">(</span><span class="n">T</span><span class="p" data-group-id="1273873797-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1273873797-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="1273873797-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1273873797-5">(</span><span class="p" data-group-id="1273873797-6">[</span><span class="p" data-group-id="1273873797-6">]</span><span class="p" data-group-id="1273873797-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1273873797-7">&lt;&lt;</span><span class="p" data-group-id="1273873797-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ │ -given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="4656253705-1">(</span><span class="p" data-group-id="4656253705-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4656253705-2">&gt;&gt;</span><span class="p" data-group-id="4656253705-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="4656253705-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="4656253705-4">(</span><span class="n">T</span><span class="p" data-group-id="4656253705-4">)</span><span class="p" data-group-id="4656253705-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="4656253705-5">(</span><span class="p" data-group-id="4656253705-6">&lt;&lt;</span><span class="p" data-group-id="4656253705-6">&gt;&gt;</span><span class="p" data-group-id="4656253705-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4656253705-7">[</span><span class="p" data-group-id="4656253705-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8139553318-5">(</span><span class="p" data-group-id="8139553318-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8139553318-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8139553318-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8139553318-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8139553318-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8139553318-8">&gt;&gt;</span><span class="p" data-group-id="8139553318-7">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8139553318-9">(</span><span class="p" data-group-id="8139553318-10">[</span><span class="p" data-group-id="8139553318-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8139553318-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4505575862-1">(</span><span class="p" data-group-id="4505575862-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4505575862-2">]</span><span class="p" data-group-id="4505575862-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4505575862-3">(</span><span class="n">T</span><span class="p" data-group-id="4505575862-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4505575862-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="4505575862-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="4505575862-5">(</span><span class="p" data-group-id="4505575862-6">[</span><span class="p" data-group-id="4505575862-6">]</span><span class="p" data-group-id="4505575862-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4505575862-7">&lt;&lt;</span><span class="p" data-group-id="4505575862-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ │ +given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9525661207-1">(</span><span class="p" data-group-id="9525661207-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9525661207-2">&gt;&gt;</span><span class="p" data-group-id="9525661207-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9525661207-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9525661207-4">(</span><span class="n">T</span><span class="p" data-group-id="9525661207-4">)</span><span class="p" data-group-id="9525661207-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9525661207-5">(</span><span class="p" data-group-id="9525661207-6">&lt;&lt;</span><span class="p" data-group-id="9525661207-6">&gt;&gt;</span><span class="p" data-group-id="9525661207-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9525661207-7">[</span><span class="p" data-group-id="9525661207-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │ │    <a href="#how-binaries-are-implemented" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">How Binaries are Implemented</span>
│ │ │ │  </h2>
│ │ │ │  <p>Internally, binaries and bitstrings are implemented in the same way. In this
│ │ │ │  section, they are called <em>binaries</em> because that is what they are called in the
│ │ │ │ @@ -110,29 +110,29 @@
│ │ │ │  called referential transparency) of Erlang would break.</p><h2 id="constructing-binaries" class="section-heading">
│ │ │ │    <a href="#constructing-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Constructing Binaries</span>
│ │ │ │  </h2>
│ │ │ │  <p>Appending to a binary or bitstring in the following way is specially optimized
│ │ │ │ -to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8389941532-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8389941532-1">&gt;&gt;</span><span class="w">
│ │ │ │ +to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7466110049-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7466110049-1">&gt;&gt;</span><span class="w">
│ │ │ │  </span><span class="c1">%% - OR -</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8389941532-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8389941532-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │ │ +</span><span class="p" data-group-id="7466110049-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7466110049-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │ │  effective in most circumstances (for exceptions, see
│ │ │ │  <a href="binaryhandling.xhtml#forced_copying">Circumstances That Force Copying</a>). The
│ │ │ │  optimization in its basic form does not need any help from the compiler.
│ │ │ │  However, the compiler add hints to the runtime system when it is safe to apply
│ │ │ │  the optimization in a more efficient way.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The compiler support for making the optimization more efficient was added in
│ │ │ │  Erlang/OTP 26.</p></section><p>To explain how the basic optimization works, let us examine the following code
│ │ │ │ -line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1736752615-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="1736752615-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ │ -</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1736752615-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1736752615-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1736752615-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1736752615-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ │ -</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1736752615-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="1736752615-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ │ -</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1736752615-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="1736752615-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1736752615-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="1736752615-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │ │ +line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7739153731-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="7739153731-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ │ +</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7739153731-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7739153731-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7739153731-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7739153731-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ │ +</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7739153731-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="7739153731-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ │ +</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7739153731-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="7739153731-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7739153731-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="7739153731-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │ │  <a href="binaryhandling.xhtml#heap_binary">heap binary</a> to the <code class="inline">Bin0</code> variable.</p></li><li><p>Line 2 is an append operation. As <code class="inline">Bin0</code> has not been involved in an append
│ │ │ │  operation, a new <a href="binaryhandling.xhtml#refc_binary">refc binary</a> is created and
│ │ │ │  the contents of <code class="inline">Bin0</code> is copied into it. The <em>ProcBin</em> part of the refc
│ │ │ │  binary has its size set to the size of the data stored in the binary, while
│ │ │ │  the binary object has extra space allocated. The size of the binary object is
│ │ │ │  either twice the size of <code class="inline">Bin1</code> or 256, whichever is larger. In this case it
│ │ │ │  is 256.</p></li><li><p>Line 3 is more interesting. <code class="inline">Bin1</code> <em>has</em> been used in an append operation, and
│ │ │ │ @@ -158,23 +158,23 @@
│ │ │ │  handle an append operation to a heap binary by copying it to a refc binary (line
│ │ │ │  2), and also handle an append operation to a previous version of the binary by
│ │ │ │  copying it (line 5). The support for doing that does not come for free. For
│ │ │ │  example, to make it possible to know when it is necessary to copy the binary,
│ │ │ │  for every append operation, the runtime system must create a sub binary.</p><p>When the compiler can determine that none of those situations need to be handled
│ │ │ │  and that the append operation cannot possibly fail, the compiler generates code
│ │ │ │  that causes the runtime system to apply a more efficient variant of the
│ │ │ │ -optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3234305747-1">(</span><span class="ss">repack</span><span class="p" data-group-id="3234305747-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3234305747-2">(</span><span class="p" data-group-id="3234305747-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3234305747-3">]</span><span class="p" data-group-id="3234305747-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1008272976-1">(</span><span class="ss">repack</span><span class="p" data-group-id="1008272976-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1008272976-2">(</span><span class="p" data-group-id="1008272976-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1008272976-3">]</span><span class="p" data-group-id="1008272976-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="3234305747-4">(</span><span class="n">Bin</span><span class="p" data-group-id="3234305747-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="3234305747-5">(</span><span class="n">Bin</span><span class="p" data-group-id="3234305747-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="3234305747-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3234305747-7">&lt;&lt;</span><span class="p" data-group-id="3234305747-7">&gt;&gt;</span><span class="p" data-group-id="3234305747-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="1008272976-4">(</span><span class="n">Bin</span><span class="p" data-group-id="1008272976-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="1008272976-5">(</span><span class="n">Bin</span><span class="p" data-group-id="1008272976-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="1008272976-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1008272976-7">&lt;&lt;</span><span class="p" data-group-id="1008272976-7">&gt;&gt;</span><span class="p" data-group-id="1008272976-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="3234305747-8">(</span><span class="p" data-group-id="3234305747-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3234305747-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3234305747-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="3234305747-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3234305747-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3234305747-11">&gt;&gt;</span><span class="p" data-group-id="3234305747-10">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="3234305747-12">(</span><span class="p" data-group-id="3234305747-13">&lt;&lt;</span><span class="p" data-group-id="3234305747-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3234305747-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="1008272976-8">(</span><span class="p" data-group-id="1008272976-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1008272976-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1008272976-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="1008272976-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1008272976-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1008272976-11">&gt;&gt;</span><span class="p" data-group-id="1008272976-10">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="1008272976-12">(</span><span class="p" data-group-id="1008272976-13">&lt;&lt;</span><span class="p" data-group-id="1008272976-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1008272976-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">Result</span><span class="p">.</span></code></pre><p>The <code class="inline">repack/2</code> function only keeps a single version of the binary, so there is
│ │ │ │  never any need to copy the binary. The compiler rewrites the creation of the
│ │ │ │  empty binary in <code class="inline">repack/1</code> to instead create a refc binary with 256 bytes
│ │ │ │  already reserved; thus, the append operation in <code class="inline">repack/2</code> never needs to handle
│ │ │ │  a binary not prepared for appending.</p><p><a href="" id="forced_copying"></a></p><h3 id="circumstances-that-force-copying" class="section-heading">
│ │ │ │    <a href="#circumstances-that-force-copying" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -186,72 +186,72 @@
│ │ │ │  reason is that the binary object can be moved (reallocated) during an append
│ │ │ │  operation, and when that happens, the pointer in the ProcBin must be updated. If
│ │ │ │  there would be more than one ProcBin pointing to the binary object, it would not
│ │ │ │  be possible to find and update all of them.</p><p>Therefore, certain operations on a binary mark it so that any future append
│ │ │ │  operation will be forced to copy the binary. In most cases, the binary object
│ │ │ │  will be shrunk at the same time to reclaim the extra space allocated for
│ │ │ │  growing.</p><p>When appending to a binary as follows, only the binary returned from the latest
│ │ │ │ -append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8443869137-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8443869137-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │ │ +append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8671756075-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8671756075-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │ │  be cheap, while appending to <code class="inline">Bin0</code> will force the creation of a new binary and
│ │ │ │  copying of the contents of <code class="inline">Bin0</code>.</p><p>If a binary is sent as a message to a process or port, the binary will be shrunk
│ │ │ │  and any further append operation will copy the binary data into a new binary.
│ │ │ │  For example, in the following code fragment <code class="inline">Bin1</code> will be copied in the third
│ │ │ │ -line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8649900807-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8649900807-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2295281795-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2295281795-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │  </span><span class="n">PortOrPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8649900807-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8649900807-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2295281795-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2295281795-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │ │  using <a href="../../../lib/../erts/doc/html/erlang.html#port_command/2"><code class="inline">erlang:port_command/2</code></a>, or pass it to
│ │ │ │  <a href="../../../lib/../erts/doc/html/erl_nif.xhtml#enif_inspect_binary">enif_inspect_binary</a> in a NIF.</p><p>Matching a binary will also cause it to shrink and the next append operation
│ │ │ │ -will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1008404660-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1008404660-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1008404660-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1008404660-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1008404660-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1008404660-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.xhtml#match_context">match context</a> contains a
│ │ │ │ +will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4153749749-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4153749749-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4153749749-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4153749749-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4153749749-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4153749749-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.xhtml#match_context">match context</a> contains a
│ │ │ │  direct pointer to the binary data.</p><p>If a process simply keeps binaries (either in &quot;loop data&quot; or in the process
│ │ │ │  dictionary), the garbage collector can eventually shrink the binaries. If only
│ │ │ │  one such binary is kept, it will not be shrunk. If the process later appends to
│ │ │ │  a binary that has been shrunk, the binary object will be reallocated to make
│ │ │ │  place for the data to be appended.</p><h2 id="matching-binaries" class="section-heading">
│ │ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Matching Binaries</span>
│ │ │ │  </h2>
│ │ │ │ -<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8397295811-1">(</span><span class="p" data-group-id="8397295811-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8397295811-2">&gt;&gt;</span><span class="p" data-group-id="8397295811-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8397295811-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8397295811-4">(</span><span class="n">T</span><span class="p" data-group-id="8397295811-4">)</span><span class="p" data-group-id="8397295811-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="8397295811-5">(</span><span class="p" data-group-id="8397295811-6">&lt;&lt;</span><span class="p" data-group-id="8397295811-6">&gt;&gt;</span><span class="p" data-group-id="8397295811-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8397295811-7">[</span><span class="p" data-group-id="8397295811-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │ │ +<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1997730687-1">(</span><span class="p" data-group-id="1997730687-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1997730687-2">&gt;&gt;</span><span class="p" data-group-id="1997730687-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="1997730687-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1997730687-4">(</span><span class="n">T</span><span class="p" data-group-id="1997730687-4">)</span><span class="p" data-group-id="1997730687-3">]</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="1997730687-5">(</span><span class="p" data-group-id="1997730687-6">&lt;&lt;</span><span class="p" data-group-id="1997730687-6">&gt;&gt;</span><span class="p" data-group-id="1997730687-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1997730687-7">[</span><span class="p" data-group-id="1997730687-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │ │  <a href="binaryhandling.xhtml#match_context">match context</a> is created. The match context
│ │ │ │  points to the first byte of the binary. 1 byte is matched out and the match
│ │ │ │  context is updated to point to the second byte in the binary.</p><p>At this point it would make sense to create a
│ │ │ │  <a href="binaryhandling.xhtml#sub_binary">sub binary</a>, but in this particular example the
│ │ │ │  compiler sees that there will soon be a call to a function (in this case, to
│ │ │ │  <code class="inline">my_binary_to_list/1</code> itself) that immediately will create a new match context
│ │ │ │  and discard the sub binary.</p><p>Therefore <code class="inline">my_binary_to_list/1</code> calls itself with the match context instead of
│ │ │ │  with a sub binary. The instruction that initializes the matching operation
│ │ │ │  basically does nothing when it sees that it was passed a match context instead
│ │ │ │  of a binary.</p><p>When the end of the binary is reached and the second clause matches, the match
│ │ │ │  context will simply be discarded (removed in the next garbage collection, as
│ │ │ │  there is no longer any reference to it).</p><p>To summarize, <code class="inline">my_binary_to_list/1</code> only needs to create <em>one</em> match context and
│ │ │ │  no sub binaries.</p><p>Notice that the match context in <code class="inline">my_binary_to_list/1</code> was discarded when the
│ │ │ │  entire binary had been traversed. What happens if the iteration stops before it
│ │ │ │ -has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="0524670999-1">(</span><span class="p" data-group-id="0524670999-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0524670999-2">&gt;&gt;</span><span class="p" data-group-id="0524670999-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="3193247078-1">(</span><span class="p" data-group-id="3193247078-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3193247078-2">&gt;&gt;</span><span class="p" data-group-id="3193247078-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0524670999-3">(</span><span class="p" data-group-id="0524670999-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0524670999-4">&gt;&gt;</span><span class="p" data-group-id="0524670999-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="0524670999-5">(</span><span class="n">T</span><span class="p" data-group-id="0524670999-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0524670999-6">(</span><span class="p" data-group-id="0524670999-7">&lt;&lt;</span><span class="p" data-group-id="0524670999-7">&gt;&gt;</span><span class="p" data-group-id="0524670999-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0524670999-8">&lt;&lt;</span><span class="p" data-group-id="0524670999-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="3193247078-3">(</span><span class="p" data-group-id="3193247078-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3193247078-4">&gt;&gt;</span><span class="p" data-group-id="3193247078-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="3193247078-5">(</span><span class="n">T</span><span class="p" data-group-id="3193247078-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="3193247078-6">(</span><span class="p" data-group-id="3193247078-7">&lt;&lt;</span><span class="p" data-group-id="3193247078-7">&gt;&gt;</span><span class="p" data-group-id="3193247078-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3193247078-8">&lt;&lt;</span><span class="p" data-group-id="3193247078-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │ │  second clause:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0932968360-1">(</span><span class="p" data-group-id="0932968360-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0932968360-2">&gt;&gt;</span><span class="p" data-group-id="0932968360-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="0932968360-3">(</span><span class="n">T</span><span class="p" data-group-id="0932968360-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="1778787643-1">(</span><span class="p" data-group-id="1778787643-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1778787643-2">&gt;&gt;</span><span class="p" data-group-id="1778787643-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="2566808550-1">(</span><span class="p" data-group-id="2566808550-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2566808550-2">&gt;&gt;</span><span class="p" data-group-id="2566808550-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="2566808550-3">(</span><span class="n">T</span><span class="p" data-group-id="2566808550-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="3277507352-1">(</span><span class="p" data-group-id="3277507352-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3277507352-2">&gt;&gt;</span><span class="p" data-group-id="3277507352-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Therefore, <code class="inline">after_zero/1</code> builds one match context and one sub binary (assuming
│ │ │ │ -it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2586350389-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2586350389-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2586350389-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2586350389-3">(</span><span class="n">Acc</span><span class="p" data-group-id="2586350389-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="2586350389-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2586350389-4">(</span><span class="p" data-group-id="2586350389-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2586350389-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="2586350389-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2586350389-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2586350389-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2586350389-7">(</span><span class="p" data-group-id="2586350389-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2586350389-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="2586350389-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2586350389-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2586350389-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2586350389-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2586350389-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │ │ +it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="7003071829-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7003071829-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="7003071829-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7003071829-3">(</span><span class="n">Acc</span><span class="p" data-group-id="7003071829-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="7003071829-2">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="7003071829-4">(</span><span class="p" data-group-id="7003071829-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7003071829-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="7003071829-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="7003071829-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="7003071829-6">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="7003071829-7">(</span><span class="p" data-group-id="7003071829-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7003071829-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="7003071829-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="7003071829-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7003071829-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="7003071829-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="7003071829-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │ │  and it adds an instruction to the first clause that converts <code class="inline">Buffer</code> from a
│ │ │ │  match context to a sub binary (or do nothing if <code class="inline">Buffer</code> is a binary already).</p><p>But in more complicated code, how can one know whether the optimization is
│ │ │ │  applied or not?</p><p><a href="" id="bin_opt_info"></a></p><h3 id="option-bin_opt_info" class="section-heading">
│ │ │ │    <a href="#option-bin_opt_info" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Option bin_opt_info</span>
│ │ │ │ @@ -259,35 +259,35 @@
│ │ │ │  <p>Use the <code class="inline">bin_opt_info</code> option to have the compiler print a lot of information
│ │ │ │  about binary optimizations. It can be given either to the compiler or <code class="inline">erlc</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">erlc</span><span class="w"> </span><span class="o">+</span><span class="ss">bin_opt_info</span><span class="w"> </span><span class="n">Mod</span><span class="p">.</span><span class="ss">erl</span></code></pre><p>or passed through an environment variable:</p><pre><code class="makeup erlang" translate="no"><span class="ss">export</span><span class="w"> </span><span class="n">ERL_COMPILER_OPTIONS</span><span class="o">=</span><span class="ss">bin_opt_info</span></code></pre><p>Notice that the <code class="inline">bin_opt_info</code> is not meant to be a permanent option added to
│ │ │ │  your <code class="inline">Makefile</code>s, because all messages that it generates cannot be eliminated.
│ │ │ │  Therefore, passing the option through the environment is in most cases the most
│ │ │ │  practical approach.</p><p>The warnings look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">60</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">binary</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">returned</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">function</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">62</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">context</span><span class="w"> </span><span class="ss">reused</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="8095249444-1">(</span><span class="p" data-group-id="8095249444-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8095249444-2">&gt;&gt;</span><span class="p" data-group-id="8095249444-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="5922910182-1">(</span><span class="p" data-group-id="5922910182-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5922910182-2">&gt;&gt;</span><span class="p" data-group-id="5922910182-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │           </span><span class="c1">%% BINARY CREATED: binary is returned from the function</span><span class="w">
│ │ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="8095249444-3">(</span><span class="p" data-group-id="8095249444-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8095249444-4">&gt;&gt;</span><span class="p" data-group-id="8095249444-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="5922910182-3">(</span><span class="p" data-group-id="5922910182-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5922910182-4">&gt;&gt;</span><span class="p" data-group-id="5922910182-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │           </span><span class="c1">%% OPTIMIZED: match context reused</span><span class="w">
│ │ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="8095249444-5">(</span><span class="n">T</span><span class="p" data-group-id="8095249444-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="8095249444-6">(</span><span class="p" data-group-id="8095249444-7">&lt;&lt;</span><span class="p" data-group-id="8095249444-7">&gt;&gt;</span><span class="p" data-group-id="8095249444-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="8095249444-8">&lt;&lt;</span><span class="p" data-group-id="8095249444-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="5922910182-5">(</span><span class="n">T</span><span class="p" data-group-id="5922910182-5">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="5922910182-6">(</span><span class="p" data-group-id="5922910182-7">&lt;&lt;</span><span class="p" data-group-id="5922910182-7">&gt;&gt;</span><span class="p" data-group-id="5922910182-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5922910182-8">&lt;&lt;</span><span class="p" data-group-id="5922910182-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │ │  be delayed, because it will be returned. The warning for the second clause says
│ │ │ │  that a sub binary will not be created (yet).</p><h3 id="unused-variables" class="section-heading">
│ │ │ │    <a href="#unused-variables" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Unused Variables</span>
│ │ │ │  </h3>
│ │ │ │  <p>The compiler figures out if a variable is unused. The same code is generated for
│ │ │ │ -each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="3479659559-1">(</span><span class="p" data-group-id="3479659559-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3479659559-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3479659559-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="3479659559-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3479659559-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">count1</span><span class="p" data-group-id="3479659559-4">(</span><span class="p" data-group-id="3479659559-5">&lt;&lt;</span><span class="p" data-group-id="3479659559-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3479659559-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │ +each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="5691631567-1">(</span><span class="p" data-group-id="5691631567-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5691631567-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="5691631567-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="5691631567-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5691631567-3">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">count1</span><span class="p" data-group-id="5691631567-4">(</span><span class="p" data-group-id="5691631567-5">&lt;&lt;</span><span class="p" data-group-id="5691631567-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="5691631567-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="3479659559-6">(</span><span class="p" data-group-id="3479659559-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3479659559-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3479659559-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="3479659559-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3479659559-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="3479659559-9">(</span><span class="p" data-group-id="3479659559-10">&lt;&lt;</span><span class="p" data-group-id="3479659559-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3479659559-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="5691631567-6">(</span><span class="p" data-group-id="5691631567-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5691631567-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="5691631567-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="5691631567-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5691631567-8">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="5691631567-9">(</span><span class="p" data-group-id="5691631567-10">&lt;&lt;</span><span class="p" data-group-id="5691631567-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="5691631567-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="3479659559-11">(</span><span class="p" data-group-id="3479659559-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3479659559-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3479659559-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="3479659559-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3479659559-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="3479659559-14">(</span><span class="p" data-group-id="3479659559-15">&lt;&lt;</span><span class="p" data-group-id="3479659559-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3479659559-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="5691631567-11">(</span><span class="p" data-group-id="5691631567-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5691631567-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="5691631567-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="5691631567-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5691631567-13">)</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="5691631567-14">(</span><span class="p" data-group-id="5691631567-15">&lt;&lt;</span><span class="p" data-group-id="5691631567-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="5691631567-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │ │  out.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/benchmarking.xhtml
│ │ │ │ @@ -49,16 +49,16 @@
│ │ │ │  fast as possible, what can we do? One way could be to generate more
│ │ │ │  than two bytes at the time.</p><pre><code class="text">% erlperf 'rand:bytes(100).' 'crypto:strong_rand_bytes(100).'
│ │ │ │  Code                                   ||        QPS       Time   Rel
│ │ │ │  rand:bytes(100).                        1    2124 Ki     470 ns  100%
│ │ │ │  crypto:strong_rand_bytes(100).          1    1915 Ki     522 ns   90%</code></pre><p><a href="../../../lib/stdlib/doc/html/rand.html#bytes/1"><code class="inline">rand:bytes/1</code></a> is still faster when we generate 100 bytes at the time,
│ │ │ │  but the relative difference is smaller.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlperf &#39;rand:bytes(1000).&#39; &#39;crypto:strong_rand_bytes(1000).&#39;</span><span class="w">
│ │ │ │  </span><span class="n">Code</span><span class="w">                                    </span><span class="p">||</span><span class="w">        </span><span class="n">QPS</span><span class="w">       </span><span class="n">Time</span><span class="w">   </span><span class="n">Rel</span><span class="w">
│ │ │ │ -</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="6755713749-1">(</span><span class="mi">1000</span><span class="p" data-group-id="6755713749-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ │ -</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="6755713749-2">(</span><span class="mi">1000</span><span class="p" data-group-id="6755713749-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at the time, <a href="../../../lib/crypto/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │ │ +</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="2606989258-1">(</span><span class="mi">1000</span><span class="p" data-group-id="2606989258-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ │ +</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="2606989258-2">(</span><span class="mi">1000</span><span class="p" data-group-id="2606989258-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at the time, <a href="../../../lib/crypto/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │ │  now the fastest.</p><h2 id="benchmarking-using-erlang-otp-functionality" class="section-heading">
│ │ │ │    <a href="#benchmarking-using-erlang-otp-functionality" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Benchmarking using Erlang/OTP functionality</span>
│ │ │ │  </h2>
│ │ │ │  <p>Benchmarks can measure wall-clock time or CPU time.</p><ul><li><p><a href="../../../lib/stdlib/doc/html/timer.html#tc/3"><code class="inline">timer:tc/3</code></a> measures wall-clock time. The advantage with wall-clock time is
│ │ │ ├── OEBPS/appup_cookbook.xhtml
│ │ │ │ @@ -25,18 +25,18 @@
│ │ │ │    <a href="#changing-a-functional-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing a Functional Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>When a functional module has been changed, for example, if a new function has
│ │ │ │  been added or a bug has been corrected, simple code replacement is sufficient,
│ │ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8942922912-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8942922912-2">[</span><span class="p" data-group-id="8942922912-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8942922912-4">[</span><span class="p" data-group-id="8942922912-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="8942922912-5">}</span><span class="p" data-group-id="8942922912-4">]</span><span class="p" data-group-id="8942922912-3">}</span><span class="p" data-group-id="8942922912-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8942922912-6">[</span><span class="p" data-group-id="8942922912-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8942922912-8">[</span><span class="p" data-group-id="8942922912-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="8942922912-9">}</span><span class="p" data-group-id="8942922912-8">]</span><span class="p" data-group-id="8942922912-7">}</span><span class="p" data-group-id="8942922912-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8942922912-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6553088658-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6553088658-2">[</span><span class="p" data-group-id="6553088658-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6553088658-4">[</span><span class="p" data-group-id="6553088658-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="6553088658-5">}</span><span class="p" data-group-id="6553088658-4">]</span><span class="p" data-group-id="6553088658-3">}</span><span class="p" data-group-id="6553088658-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6553088658-6">[</span><span class="p" data-group-id="6553088658-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6553088658-8">[</span><span class="p" data-group-id="6553088658-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="6553088658-9">}</span><span class="p" data-group-id="6553088658-8">]</span><span class="p" data-group-id="6553088658-7">}</span><span class="p" data-group-id="6553088658-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6553088658-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │ │    <a href="#changing-a-residence-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing a Residence Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>In a system implemented according to the OTP design principles, all processes,
│ │ │ │  except system processes and special processes, reside in one of the behaviours
│ │ │ │ @@ -47,46 +47,46 @@
│ │ │ │    <a href="#changing-a-callback-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing a Callback Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>A callback module is a functional module, and for code extensions simple code
│ │ │ │  replacement is sufficient.</p><p><em>Example</em></p><p>When adding a function to <code class="inline">ch3</code>, as described in the example in
│ │ │ │ -<a href="release_handling.xhtml#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8300389881-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8300389881-2">[</span><span class="p" data-group-id="8300389881-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8300389881-4">[</span><span class="p" data-group-id="8300389881-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8300389881-5">}</span><span class="p" data-group-id="8300389881-4">]</span><span class="p" data-group-id="8300389881-3">}</span><span class="p" data-group-id="8300389881-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8300389881-6">[</span><span class="p" data-group-id="8300389881-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8300389881-8">[</span><span class="p" data-group-id="8300389881-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="8300389881-9">}</span><span class="p" data-group-id="8300389881-8">]</span><span class="p" data-group-id="8300389881-7">}</span><span class="p" data-group-id="8300389881-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8300389881-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │ │ +<a href="release_handling.xhtml#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0795207470-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0795207470-2">[</span><span class="p" data-group-id="0795207470-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0795207470-4">[</span><span class="p" data-group-id="0795207470-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0795207470-5">}</span><span class="p" data-group-id="0795207470-4">]</span><span class="p" data-group-id="0795207470-3">}</span><span class="p" data-group-id="0795207470-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0795207470-6">[</span><span class="p" data-group-id="0795207470-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0795207470-8">[</span><span class="p" data-group-id="0795207470-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0795207470-9">}</span><span class="p" data-group-id="0795207470-8">]</span><span class="p" data-group-id="0795207470-7">}</span><span class="p" data-group-id="0795207470-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0795207470-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │ │  <a href="appup_cookbook.xhtml#int_state">Changing Internal State</a>.</p><p><a href="" id="int_state"></a></p><h2 id="changing-internal-state" class="section-heading">
│ │ │ │    <a href="#changing-internal-state" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Internal State</span>
│ │ │ │  </h2>
│ │ │ │  <p>In this case, simple code replacement is not sufficient. The process must
│ │ │ │  explicitly transform its state using the callback function <code class="inline">code_change/3</code> before
│ │ │ │  switching to the new version of the callback module. Thus, synchronized code
│ │ │ │  replacement is used.</p><p><em>Example</em></p><p>Consider the <code class="inline">ch3</code> module from
│ │ │ │  <a href="gen_server_concepts.xhtml#ex">gen_server Behaviour</a>. The internal state is a term
│ │ │ │  <code class="inline">Chs</code> representing the available channels. Assume you want to add a counter <code class="inline">N</code>,
│ │ │ │  which keeps track of the number of <code class="inline">alloc</code> requests so far. This means that the
│ │ │ │ -format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2029077496-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2029077496-2">[</span><span class="p" data-group-id="2029077496-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029077496-4">[</span><span class="p" data-group-id="2029077496-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029077496-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029077496-7">[</span><span class="p" data-group-id="2029077496-7">]</span><span class="p" data-group-id="2029077496-6">}</span><span class="p" data-group-id="2029077496-5">}</span><span class="p" data-group-id="2029077496-4">]</span><span class="p" data-group-id="2029077496-3">}</span><span class="p" data-group-id="2029077496-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2029077496-8">[</span><span class="p" data-group-id="2029077496-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029077496-10">[</span><span class="p" data-group-id="2029077496-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029077496-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2029077496-13">[</span><span class="p" data-group-id="2029077496-13">]</span><span class="p" data-group-id="2029077496-12">}</span><span class="p" data-group-id="2029077496-11">}</span><span class="p" data-group-id="2029077496-10">]</span><span class="p" data-group-id="2029077496-9">}</span><span class="p" data-group-id="2029077496-8">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2029077496-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │ │ +format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8260667695-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8260667695-2">[</span><span class="p" data-group-id="8260667695-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260667695-4">[</span><span class="p" data-group-id="8260667695-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260667695-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260667695-7">[</span><span class="p" data-group-id="8260667695-7">]</span><span class="p" data-group-id="8260667695-6">}</span><span class="p" data-group-id="8260667695-5">}</span><span class="p" data-group-id="8260667695-4">]</span><span class="p" data-group-id="8260667695-3">}</span><span class="p" data-group-id="8260667695-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8260667695-8">[</span><span class="p" data-group-id="8260667695-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260667695-10">[</span><span class="p" data-group-id="8260667695-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260667695-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8260667695-13">[</span><span class="p" data-group-id="8260667695-13">]</span><span class="p" data-group-id="8260667695-12">}</span><span class="p" data-group-id="8260667695-11">}</span><span class="p" data-group-id="8260667695-10">]</span><span class="p" data-group-id="8260667695-9">}</span><span class="p" data-group-id="8260667695-8">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8260667695-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │ │  which says that the affected processes are to do a state transformation before
│ │ │ │  loading the new version of the module. This is done by the processes calling the
│ │ │ │  callback function <code class="inline">code_change/3</code> (see <a href="../../../lib/stdlib/doc/html/gen_server.html"><code class="inline">gen_server</code></a> in STDLIB).
│ │ │ │ -The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9670244551-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="9670244551-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2630970424-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="2630970424-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9670244551-2">(</span><span class="p" data-group-id="9670244551-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="9670244551-3">]</span><span class="p" data-group-id="9670244551-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2630970424-2">(</span><span class="p" data-group-id="2630970424-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="2630970424-3">]</span><span class="p" data-group-id="2630970424-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="9670244551-4">(</span><span class="p" data-group-id="9670244551-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="9670244551-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9670244551-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="9670244551-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="9670244551-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9670244551-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9670244551-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="9670244551-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="9670244551-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9670244551-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9670244551-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9670244551-10">}</span><span class="p" data-group-id="9670244551-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="2630970424-4">(</span><span class="p" data-group-id="2630970424-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="2630970424-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2630970424-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="2630970424-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="2630970424-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2630970424-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2630970424-7">}</span><span class="p">;</span><span class="w">
│ │ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="2630970424-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="2630970424-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="2630970424-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2630970424-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2630970424-10">}</span><span class="p" data-group-id="2630970424-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │ │  a upgrade. The term <code class="inline">Vsn</code> is fetched from the 'original' version of the module,
│ │ │ │  that is, the version you are upgrading from, or downgrading to.</p><p>The version is defined by the module attribute <code class="inline">vsn</code>, if any. There is no such
│ │ │ │  attribute in <code class="inline">ch3</code>, so in this case the version is the checksum (a huge integer)
│ │ │ │  of the beam file, an uninteresting value, which is ignored.</p><p>The other callback functions of <code class="inline">ch3</code> must also be modified and perhaps a new
│ │ │ │  interface function must be added, but this is not shown here.</p><h2 id="module-dependencies" class="section-heading">
│ │ │ │    <a href="#module-dependencies" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -95,67 +95,67 @@
│ │ │ │  </h2>
│ │ │ │  <p>Assume that a module is extended by adding an interface function, as in the
│ │ │ │  example in <a href="release_handling.xhtml#appup">Release Handling</a>, where a function
│ │ │ │  <code class="inline">available/0</code> is added to <code class="inline">ch3</code>.</p><p>If a call is added to this function, say in module <code class="inline">m1</code>, a runtime error could
│ │ │ │  can occur during release upgrade if the new version of <code class="inline">m1</code> is loaded first and
│ │ │ │  calls <code class="inline">ch3:available/0</code> before the new version of <code class="inline">ch3</code> is loaded.</p><p>Thus, <code class="inline">ch3</code> must be loaded before <code class="inline">m1</code>, in the upgrade case, and conversely in
│ │ │ │  the downgrade case. <code class="inline">m1</code> is said to be <em>dependent on</em> <code class="inline">ch3</code>. In a release
│ │ │ │ -handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1952987410-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="1952987410-1">}</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1952987410-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1952987410-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="1952987410-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="1952987410-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │ │ +handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0200763980-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="0200763980-1">}</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0200763980-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0200763980-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="0200763980-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="0200763980-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │ │  upgrading from &quot;1&quot; to &quot;2&quot;, or downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="ss">myapp</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="6575643051-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6575643051-2">[</span><span class="p" data-group-id="6575643051-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6575643051-4">[</span><span class="p" data-group-id="6575643051-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6575643051-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="6575643051-6">]</span><span class="p" data-group-id="6575643051-5">}</span><span class="p" data-group-id="6575643051-4">]</span><span class="p" data-group-id="6575643051-3">}</span><span class="p" data-group-id="6575643051-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6575643051-7">[</span><span class="p" data-group-id="6575643051-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6575643051-9">[</span><span class="p" data-group-id="6575643051-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6575643051-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="6575643051-11">]</span><span class="p" data-group-id="6575643051-10">}</span><span class="p" data-group-id="6575643051-9">]</span><span class="p" data-group-id="6575643051-8">}</span><span class="p" data-group-id="6575643051-7">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6575643051-1">}</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6201515760-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6201515760-2">[</span><span class="p" data-group-id="6201515760-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6201515760-4">[</span><span class="p" data-group-id="6201515760-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6201515760-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="6201515760-6">]</span><span class="p" data-group-id="6201515760-5">}</span><span class="p" data-group-id="6201515760-4">]</span><span class="p" data-group-id="6201515760-3">}</span><span class="p" data-group-id="6201515760-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6201515760-7">[</span><span class="p" data-group-id="6201515760-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6201515760-9">[</span><span class="p" data-group-id="6201515760-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6201515760-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="6201515760-11">]</span><span class="p" data-group-id="6201515760-10">}</span><span class="p" data-group-id="6201515760-9">]</span><span class="p" data-group-id="6201515760-8">}</span><span class="p" data-group-id="6201515760-7">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6201515760-1">}</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │  </span><span class="ss">ch_app</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="p" data-group-id="6575643051-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6575643051-13">[</span><span class="p" data-group-id="6575643051-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6575643051-15">[</span><span class="p" data-group-id="6575643051-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6575643051-16">}</span><span class="p" data-group-id="6575643051-15">]</span><span class="p" data-group-id="6575643051-14">}</span><span class="p" data-group-id="6575643051-13">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6575643051-17">[</span><span class="p" data-group-id="6575643051-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6575643051-19">[</span><span class="p" data-group-id="6575643051-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6575643051-20">}</span><span class="p" data-group-id="6575643051-19">]</span><span class="p" data-group-id="6575643051-18">}</span><span class="p" data-group-id="6575643051-17">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6575643051-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6682374253-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6682374253-2">[</span><span class="p" data-group-id="6682374253-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="6682374253-4">[</span><span class="p" data-group-id="6682374253-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6682374253-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6682374253-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6682374253-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="6682374253-7">]</span><span class="p" data-group-id="6682374253-6">}</span><span class="p" data-group-id="6682374253-4">]</span><span class="p" data-group-id="6682374253-3">}</span><span class="p" data-group-id="6682374253-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="6682374253-8">[</span><span class="p" data-group-id="6682374253-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="6682374253-10">[</span><span class="p" data-group-id="6682374253-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6682374253-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6682374253-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6682374253-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="6682374253-13">]</span><span class="p" data-group-id="6682374253-12">}</span><span class="p" data-group-id="6682374253-10">]</span><span class="p" data-group-id="6682374253-9">}</span><span class="p" data-group-id="6682374253-8">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="6682374253-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │ │ +</span><span class="p" data-group-id="6201515760-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6201515760-13">[</span><span class="p" data-group-id="6201515760-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6201515760-15">[</span><span class="p" data-group-id="6201515760-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6201515760-16">}</span><span class="p" data-group-id="6201515760-15">]</span><span class="p" data-group-id="6201515760-14">}</span><span class="p" data-group-id="6201515760-13">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6201515760-17">[</span><span class="p" data-group-id="6201515760-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6201515760-19">[</span><span class="p" data-group-id="6201515760-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6201515760-20">}</span><span class="p" data-group-id="6201515760-19">]</span><span class="p" data-group-id="6201515760-18">}</span><span class="p" data-group-id="6201515760-17">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6201515760-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3297360105-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3297360105-2">[</span><span class="p" data-group-id="3297360105-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3297360105-4">[</span><span class="p" data-group-id="3297360105-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3297360105-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3297360105-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3297360105-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="3297360105-7">]</span><span class="p" data-group-id="3297360105-6">}</span><span class="p" data-group-id="3297360105-4">]</span><span class="p" data-group-id="3297360105-3">}</span><span class="p" data-group-id="3297360105-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3297360105-8">[</span><span class="p" data-group-id="3297360105-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3297360105-10">[</span><span class="p" data-group-id="3297360105-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3297360105-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3297360105-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3297360105-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="3297360105-13">]</span><span class="p" data-group-id="3297360105-12">}</span><span class="p" data-group-id="3297360105-10">]</span><span class="p" data-group-id="3297360105-9">}</span><span class="p" data-group-id="3297360105-8">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3297360105-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │ │  difference between up- and downgrading and generates a correct <code class="inline">relup</code>, where
│ │ │ │  <code class="inline">ch3</code> is loaded before <code class="inline">m1</code> when upgrading, but <code class="inline">m1</code> is loaded before <code class="inline">ch3</code> when
│ │ │ │  downgrading.</p><p><a href="" id="spec"></a></p><h2 id="changing-code-for-a-special-process" class="section-heading">
│ │ │ │    <a href="#changing-code-for-a-special-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Code for a Special Process</span>
│ │ │ │  </h2>
│ │ │ │  <p>In this case, simple code replacement is not sufficient. When a new version of a
│ │ │ │  residence module for a special process is loaded, the process must make a fully
│ │ │ │  qualified call to its loop function to switch to the new code. Thus,
│ │ │ │  synchronized code replacement must be used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The name(s) of the user-defined residence module(s) must be listed in the
│ │ │ │  <code class="inline">Modules</code> part of the child specification for the special process. Otherwise
│ │ │ │  the release handler cannot find the process.</p></section><p><em>Example</em></p><p>Consider the example <code class="inline">ch4</code> in <a href="spec_proc.xhtml#ex">sys and proc_lib</a>.
│ │ │ │ -When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6755735528-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6755735528-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6755735528-3">[</span><span class="p" data-group-id="6755735528-3">]</span><span class="p" data-group-id="6755735528-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6755735528-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="6755735528-4">]</span><span class="p" data-group-id="6755735528-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │ │ +When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3065213453-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3065213453-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3065213453-3">[</span><span class="p" data-group-id="3065213453-3">]</span><span class="p" data-group-id="3065213453-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3065213453-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="3065213453-4">]</span><span class="p" data-group-id="3065213453-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │ │  to be loaded when upgrading from version &quot;1&quot; to &quot;2&quot; of this application,
│ │ │ │ -<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0813413936-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0813413936-2">[</span><span class="p" data-group-id="0813413936-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0813413936-4">[</span><span class="p" data-group-id="0813413936-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0813413936-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0813413936-7">[</span><span class="p" data-group-id="0813413936-7">]</span><span class="p" data-group-id="0813413936-6">}</span><span class="p" data-group-id="0813413936-5">}</span><span class="p" data-group-id="0813413936-4">]</span><span class="p" data-group-id="0813413936-3">}</span><span class="p" data-group-id="0813413936-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="0813413936-8">[</span><span class="p" data-group-id="0813413936-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0813413936-10">[</span><span class="p" data-group-id="0813413936-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0813413936-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0813413936-13">[</span><span class="p" data-group-id="0813413936-13">]</span><span class="p" data-group-id="0813413936-12">}</span><span class="p" data-group-id="0813413936-11">}</span><span class="p" data-group-id="0813413936-10">]</span><span class="p" data-group-id="0813413936-9">}</span><span class="p" data-group-id="0813413936-8">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="0813413936-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │ │ +<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0805775858-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0805775858-2">[</span><span class="p" data-group-id="0805775858-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0805775858-4">[</span><span class="p" data-group-id="0805775858-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0805775858-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0805775858-7">[</span><span class="p" data-group-id="0805775858-7">]</span><span class="p" data-group-id="0805775858-6">}</span><span class="p" data-group-id="0805775858-5">}</span><span class="p" data-group-id="0805775858-4">]</span><span class="p" data-group-id="0805775858-3">}</span><span class="p" data-group-id="0805775858-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="0805775858-8">[</span><span class="p" data-group-id="0805775858-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0805775858-10">[</span><span class="p" data-group-id="0805775858-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0805775858-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0805775858-13">[</span><span class="p" data-group-id="0805775858-13">]</span><span class="p" data-group-id="0805775858-12">}</span><span class="p" data-group-id="0805775858-11">}</span><span class="p" data-group-id="0805775858-10">]</span><span class="p" data-group-id="0805775858-9">}</span><span class="p" data-group-id="0805775858-8">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="0805775858-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │ │  instruction makes the special process call the callback function
│ │ │ │  <code class="inline">system_code_change/4</code>, a function the user must implement. The term <code class="inline">Extra</code>, in
│ │ │ │ -this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1632784232-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="1632784232-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9674067750-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="9674067750-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1632784232-2">(</span><span class="p" data-group-id="1632784232-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="1632784232-3">]</span><span class="p" data-group-id="1632784232-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9674067750-2">(</span><span class="p" data-group-id="9674067750-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="9674067750-3">]</span><span class="p" data-group-id="9674067750-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">system_code_change</span><span class="p" data-group-id="1632784232-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="1632784232-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="1632784232-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="1632784232-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │ │ +</span><span class="nf">system_code_change</span><span class="p" data-group-id="9674067750-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="9674067750-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9674067750-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9674067750-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │ │  function <a href="../../../lib/stdlib/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg(Request, From, Parent, Module, Deb, State)</code></a>, and called by the special
│ │ │ │  process when a system message is received. In <code class="inline">ch4</code>, the internal
│ │ │ │  state is the set of available channels <code class="inline">Chs</code>.</li><li>The second argument is the name of the module (<code class="inline">ch4</code>).</li><li>The third argument is <code class="inline">Vsn</code> or <code class="inline">{down,Vsn}</code>, as described for
│ │ │ │  <a href="../../../lib/stdlib/doc/html/gen_server.html#c:code_change/3"><code class="inline">gen_server:code_change/3</code></a> in
│ │ │ │  <a href="appup_cookbook.xhtml#code_change">Changing Internal State</a>.</li></ul><p>In this case, all arguments but the first are ignored and the function simply
│ │ │ │  returns the internal state again. This is enough if the code only has been
│ │ │ │  extended. If instead the internal state is changed (similar to the example in
│ │ │ │ @@ -176,85 +176,85 @@
│ │ │ │    <span class="text">Changing Properties</span>
│ │ │ │  </h3>
│ │ │ │  <p>Since the supervisor is to change its internal state, synchronized code
│ │ │ │  replacement is required. However, a special <code class="inline">update</code> instruction must be used.</p><p>First, the new version of the callback module must be loaded, both in the case
│ │ │ │  of upgrade and downgrade. Then the new return value of <code class="inline">init/1</code> can be checked
│ │ │ │  and the internal state be changed accordingly.</p><p>The following <code class="inline">upgrade</code> instruction is used for supervisors:</p><pre><code class="text">{update, Module, supervisor}</code></pre><p><em>Example</em></p><p>To change the restart strategy of <code class="inline">ch_sup</code> (from
│ │ │ │  <a href="sup_princ.xhtml#ex">Supervisor Behaviour</a>) from <code class="inline">one_for_one</code> to <code class="inline">one_for_all</code>,
│ │ │ │ -change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6011576415-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="6011576415-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6143110949-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="6143110949-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6011576415-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6011576415-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="6011576415-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6011576415-4">{</span><span class="p" data-group-id="6011576415-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6011576415-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6011576415-4">}</span><span class="p" data-group-id="6011576415-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9647584217-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9647584217-2">[</span><span class="p" data-group-id="9647584217-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647584217-4">[</span><span class="p" data-group-id="9647584217-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9647584217-5">}</span><span class="p" data-group-id="9647584217-4">]</span><span class="p" data-group-id="9647584217-3">}</span><span class="p" data-group-id="9647584217-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9647584217-6">[</span><span class="p" data-group-id="9647584217-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647584217-8">[</span><span class="p" data-group-id="9647584217-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9647584217-9">}</span><span class="p" data-group-id="9647584217-8">]</span><span class="p" data-group-id="9647584217-7">}</span><span class="p" data-group-id="9647584217-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9647584217-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="6143110949-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="6143110949-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="6143110949-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143110949-4">{</span><span class="p" data-group-id="6143110949-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6143110949-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6143110949-4">}</span><span class="p" data-group-id="6143110949-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4347534631-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4347534631-2">[</span><span class="p" data-group-id="4347534631-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4347534631-4">[</span><span class="p" data-group-id="4347534631-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4347534631-5">}</span><span class="p" data-group-id="4347534631-4">]</span><span class="p" data-group-id="4347534631-3">}</span><span class="p" data-group-id="4347534631-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4347534631-6">[</span><span class="p" data-group-id="4347534631-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4347534631-8">[</span><span class="p" data-group-id="4347534631-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4347534631-9">}</span><span class="p" data-group-id="4347534631-8">]</span><span class="p" data-group-id="4347534631-7">}</span><span class="p" data-group-id="4347534631-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="4347534631-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │ │    <a href="#changing-child-specifications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Child Specifications</span>
│ │ │ │  </h3>
│ │ │ │  <p>The instruction, and thus the <code class="inline">.appup</code> file, when changing an existing child
│ │ │ │ -specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3791191707-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3791191707-2">[</span><span class="p" data-group-id="3791191707-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3791191707-4">[</span><span class="p" data-group-id="3791191707-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3791191707-5">}</span><span class="p" data-group-id="3791191707-4">]</span><span class="p" data-group-id="3791191707-3">}</span><span class="p" data-group-id="3791191707-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="3791191707-6">[</span><span class="p" data-group-id="3791191707-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3791191707-8">[</span><span class="p" data-group-id="3791191707-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3791191707-9">}</span><span class="p" data-group-id="3791191707-8">]</span><span class="p" data-group-id="3791191707-7">}</span><span class="p" data-group-id="3791191707-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="3791191707-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │ │ +specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1798248034-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1798248034-2">[</span><span class="p" data-group-id="1798248034-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1798248034-4">[</span><span class="p" data-group-id="1798248034-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="1798248034-5">}</span><span class="p" data-group-id="1798248034-4">]</span><span class="p" data-group-id="1798248034-3">}</span><span class="p" data-group-id="1798248034-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1798248034-6">[</span><span class="p" data-group-id="1798248034-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1798248034-8">[</span><span class="p" data-group-id="1798248034-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="1798248034-9">}</span><span class="p" data-group-id="1798248034-8">]</span><span class="p" data-group-id="1798248034-7">}</span><span class="p" data-group-id="1798248034-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1798248034-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │ │  start function only specifies how the child process is to be restarted, if
│ │ │ │  needed later on.</p><p>The id of the child specification cannot be changed.</p><p>Changing the <code class="inline">Modules</code> field of the child specification can affect the release
│ │ │ │  handling process itself, as this field is used to identify which processes are
│ │ │ │  affected when doing a synchronized code replacement.</p><p><a href="" id="sup_add"></a></p><h3 id="adding-and-deleting-child-processes" class="section-heading">
│ │ │ │    <a href="#adding-and-deleting-child-processes" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding and Deleting Child Processes</span>
│ │ │ │  </h3>
│ │ │ │  <p>As stated earlier, changing child specifications does not affect existing child
│ │ │ │  processes. New child specifications are automatically added, but not deleted.
│ │ │ │  Child processes are not automatically started or terminated, this must be done
│ │ │ │  using <code class="inline">apply</code> instructions.</p><p><em>Example</em></p><p>Assume a new child process <code class="inline">m1</code> is to be added to <code class="inline">ch_sup</code> when
│ │ │ │  upgrading <code class="inline">ch_app</code> from &quot;1&quot; to &quot;2&quot;. This means <code class="inline">m1</code> is to be deleted when
│ │ │ │ -downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2669478574-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2669478574-2">[</span><span class="p" data-group-id="2669478574-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="2669478574-4">[</span><span class="p" data-group-id="2669478574-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2669478574-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2669478574-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2669478574-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2669478574-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2669478574-8">]</span><span class="p" data-group-id="2669478574-7">}</span><span class="p" data-group-id="2669478574-6">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="2669478574-4">]</span><span class="p" data-group-id="2669478574-3">}</span><span class="p" data-group-id="2669478574-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2669478574-9">[</span><span class="p" data-group-id="2669478574-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="2669478574-11">[</span><span class="p" data-group-id="2669478574-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2669478574-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2669478574-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2669478574-14">]</span><span class="p" data-group-id="2669478574-13">}</span><span class="p" data-group-id="2669478574-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2669478574-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2669478574-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2669478574-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="2669478574-17">]</span><span class="p" data-group-id="2669478574-16">}</span><span class="p" data-group-id="2669478574-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2669478574-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2669478574-18">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="2669478574-11">]</span><span class="p" data-group-id="2669478574-10">}</span><span class="p" data-group-id="2669478574-9">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2669478574-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │ │ +downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8905334529-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8905334529-2">[</span><span class="p" data-group-id="8905334529-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8905334529-4">[</span><span class="p" data-group-id="8905334529-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="8905334529-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8905334529-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8905334529-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8905334529-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8905334529-8">]</span><span class="p" data-group-id="8905334529-7">}</span><span class="p" data-group-id="8905334529-6">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8905334529-4">]</span><span class="p" data-group-id="8905334529-3">}</span><span class="p" data-group-id="8905334529-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8905334529-9">[</span><span class="p" data-group-id="8905334529-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8905334529-11">[</span><span class="p" data-group-id="8905334529-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8905334529-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8905334529-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8905334529-14">]</span><span class="p" data-group-id="8905334529-13">}</span><span class="p" data-group-id="8905334529-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8905334529-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8905334529-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8905334529-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="8905334529-17">]</span><span class="p" data-group-id="8905334529-16">}</span><span class="p" data-group-id="8905334529-15">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="8905334529-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="8905334529-18">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="8905334529-11">]</span><span class="p" data-group-id="8905334529-10">}</span><span class="p" data-group-id="8905334529-9">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8905334529-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │ │  supervisor is not registered, it cannot be accessed directly from the script.
│ │ │ │  Instead a help function that finds the pid of the supervisor and calls
│ │ │ │  <code class="inline">supervisor:restart_child</code>, and so on, must be written. This function is then to
│ │ │ │  be called from the script using the <code class="inline">apply</code> instruction.</p><p>If the module <code class="inline">m1</code> is introduced in version &quot;2&quot; of <code class="inline">ch_app</code>, it must also be
│ │ │ │ -loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9474023381-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9474023381-2">[</span><span class="p" data-group-id="9474023381-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9474023381-4">[</span><span class="p" data-group-id="9474023381-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9474023381-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9474023381-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9474023381-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9474023381-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474023381-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474023381-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9474023381-9">]</span><span class="p" data-group-id="9474023381-8">}</span><span class="p" data-group-id="9474023381-7">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9474023381-4">]</span><span class="p" data-group-id="9474023381-3">}</span><span class="p" data-group-id="9474023381-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9474023381-10">[</span><span class="p" data-group-id="9474023381-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9474023381-12">[</span><span class="p" data-group-id="9474023381-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474023381-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474023381-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9474023381-15">]</span><span class="p" data-group-id="9474023381-14">}</span><span class="p" data-group-id="9474023381-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9474023381-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474023381-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474023381-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9474023381-18">]</span><span class="p" data-group-id="9474023381-17">}</span><span class="p" data-group-id="9474023381-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9474023381-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9474023381-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="9474023381-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9474023381-20">}</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="9474023381-12">]</span><span class="p" data-group-id="9474023381-11">}</span><span class="p" data-group-id="9474023381-10">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9474023381-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │ │ +loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5348140992-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5348140992-2">[</span><span class="p" data-group-id="5348140992-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5348140992-4">[</span><span class="p" data-group-id="5348140992-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5348140992-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5348140992-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5348140992-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5348140992-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5348140992-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5348140992-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5348140992-9">]</span><span class="p" data-group-id="5348140992-8">}</span><span class="p" data-group-id="5348140992-7">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5348140992-4">]</span><span class="p" data-group-id="5348140992-3">}</span><span class="p" data-group-id="5348140992-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5348140992-10">[</span><span class="p" data-group-id="5348140992-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5348140992-12">[</span><span class="p" data-group-id="5348140992-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5348140992-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5348140992-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5348140992-15">]</span><span class="p" data-group-id="5348140992-14">}</span><span class="p" data-group-id="5348140992-13">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5348140992-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5348140992-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5348140992-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5348140992-18">]</span><span class="p" data-group-id="5348140992-17">}</span><span class="p" data-group-id="5348140992-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5348140992-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="5348140992-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="5348140992-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="5348140992-20">}</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="5348140992-12">]</span><span class="p" data-group-id="5348140992-11">}</span><span class="p" data-group-id="5348140992-10">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5348140992-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │ │  <code class="inline">m1</code> must be loaded, and the supervisor child specification changed, before the
│ │ │ │  new child process can be started. When downgrading, the child process must be
│ │ │ │  terminated before the child specification is changed and the module is deleted.</p><h2 id="adding-or-deleting-a-module" class="section-heading">
│ │ │ │    <a href="#adding-or-deleting-a-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Adding or Deleting a Module</span>
│ │ │ │  </h2>
│ │ │ │ -<p>_Example</p><p>_ A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5083170454-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5083170454-2">[</span><span class="p" data-group-id="5083170454-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5083170454-4">[</span><span class="p" data-group-id="5083170454-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="5083170454-5">}</span><span class="p" data-group-id="5083170454-4">]</span><span class="p" data-group-id="5083170454-3">}</span><span class="p" data-group-id="5083170454-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5083170454-6">[</span><span class="p" data-group-id="5083170454-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5083170454-8">[</span><span class="p" data-group-id="5083170454-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="5083170454-9">}</span><span class="p" data-group-id="5083170454-8">]</span><span class="p" data-group-id="5083170454-7">}</span><span class="p" data-group-id="5083170454-6">]</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │ │ +<p>_Example</p><p>_ A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6363785337-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6363785337-2">[</span><span class="p" data-group-id="6363785337-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6363785337-4">[</span><span class="p" data-group-id="6363785337-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="6363785337-5">}</span><span class="p" data-group-id="6363785337-4">]</span><span class="p" data-group-id="6363785337-3">}</span><span class="p" data-group-id="6363785337-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="6363785337-6">[</span><span class="p" data-group-id="6363785337-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6363785337-8">[</span><span class="p" data-group-id="6363785337-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="6363785337-9">}</span><span class="p" data-group-id="6363785337-8">]</span><span class="p" data-group-id="6363785337-7">}</span><span class="p" data-group-id="6363785337-6">]</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │ │    <a href="#starting-or-terminating-a-process" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting or Terminating a Process</span>
│ │ │ │  </h2>
│ │ │ │  <p>In a system structured according to the OTP design principles, any process would
│ │ │ │  be a child process belonging to a supervisor, see
│ │ │ │ @@ -274,29 +274,29 @@
│ │ │ │    <span class="text">Restarting an Application</span>
│ │ │ │  </h2>
│ │ │ │  <p>Restarting an application is useful when a change is too complicated to be made
│ │ │ │  without restarting the processes, for example, if the supervisor hierarchy has
│ │ │ │  been restructured.</p><p><em>Example</em></p><p>When adding a child <code class="inline">m1</code> to <code class="inline">ch_sup</code>, as in
│ │ │ │  <a href="appup_cookbook.xhtml#sup_add">Adding and Deleting Child Processes</a> in Changing a
│ │ │ │  Supervisor, an alternative to updating the supervisor is to restart the entire
│ │ │ │ -application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4554425600-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4554425600-2">[</span><span class="p" data-group-id="4554425600-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4554425600-4">[</span><span class="p" data-group-id="4554425600-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4554425600-5">}</span><span class="p" data-group-id="4554425600-4">]</span><span class="p" data-group-id="4554425600-3">}</span><span class="p" data-group-id="4554425600-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4554425600-6">[</span><span class="p" data-group-id="4554425600-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4554425600-8">[</span><span class="p" data-group-id="4554425600-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="4554425600-9">}</span><span class="p" data-group-id="4554425600-8">]</span><span class="p" data-group-id="4554425600-7">}</span><span class="p" data-group-id="4554425600-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4554425600-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │ │ +application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7248134320-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7248134320-2">[</span><span class="p" data-group-id="7248134320-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7248134320-4">[</span><span class="p" data-group-id="7248134320-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="7248134320-5">}</span><span class="p" data-group-id="7248134320-4">]</span><span class="p" data-group-id="7248134320-3">}</span><span class="p" data-group-id="7248134320-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7248134320-6">[</span><span class="p" data-group-id="7248134320-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7248134320-8">[</span><span class="p" data-group-id="7248134320-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="7248134320-9">}</span><span class="p" data-group-id="7248134320-8">]</span><span class="p" data-group-id="7248134320-7">}</span><span class="p" data-group-id="7248134320-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7248134320-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │ │    <a href="#changing-an-application-specification" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing an Application Specification</span>
│ │ │ │  </h2>
│ │ │ │  <p>When installing a release, the application specifications are automatically
│ │ │ │  updated before evaluating the <code class="inline">relup</code> script. Thus, no instructions are needed
│ │ │ │ -in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4921607707-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4921607707-2">[</span><span class="p" data-group-id="4921607707-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4921607707-4">[</span><span class="p" data-group-id="4921607707-4">]</span><span class="p" data-group-id="4921607707-3">}</span><span class="p" data-group-id="4921607707-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4921607707-5">[</span><span class="p" data-group-id="4921607707-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4921607707-7">[</span><span class="p" data-group-id="4921607707-7">]</span><span class="p" data-group-id="4921607707-6">}</span><span class="p" data-group-id="4921607707-5">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="4921607707-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │ │ +in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7544197159-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7544197159-2">[</span><span class="p" data-group-id="7544197159-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7544197159-4">[</span><span class="p" data-group-id="7544197159-4">]</span><span class="p" data-group-id="7544197159-3">}</span><span class="p" data-group-id="7544197159-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="7544197159-5">[</span><span class="p" data-group-id="7544197159-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7544197159-7">[</span><span class="p" data-group-id="7544197159-7">]</span><span class="p" data-group-id="7544197159-6">}</span><span class="p" data-group-id="7544197159-5">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="7544197159-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │ │    <a href="#changing-application-configuration" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Application Configuration</span>
│ │ │ │  </h2>
│ │ │ │  <p>Changing an application configuration by updating the <code class="inline">env</code> key in the <code class="inline">.app</code>
│ │ │ │  file is an instance of changing an application specification, see the previous
│ │ │ │ @@ -311,26 +311,26 @@
│ │ │ │  applications apply to primary applications only. There are no corresponding
│ │ │ │  instructions for included applications. However, since an included application
│ │ │ │  is really a supervision tree with a topmost supervisor, started as a child
│ │ │ │  process to a supervisor in the including application, a <code class="inline">.relup</code> file can be
│ │ │ │  manually created.</p><p><em>Example</em></p><p>Assume there is a release containing an application <code class="inline">prim_app</code>, which
│ │ │ │  have a supervisor <code class="inline">prim_sup</code> in its supervision tree.</p><p>In a new version of the release, the application <code class="inline">ch_app</code> is to be included in
│ │ │ │  <code class="inline">prim_app</code>. That is, its topmost supervisor <code class="inline">ch_sup</code> is to be started as a child
│ │ │ │ -process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0328773397-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0328773397-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0328773397-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0328773397-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -          </span><span class="p" data-group-id="0328773397-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="p" data-group-id="0328773397-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0328773397-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="0328773397-7">[</span><span class="p" data-group-id="0328773397-7">]</span><span class="p" data-group-id="0328773397-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="0328773397-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="0328773397-8">]</span><span class="p" data-group-id="0328773397-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0328773397-4">]</span><span class="p" data-group-id="0328773397-3">}</span><span class="p" data-group-id="0328773397-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4375693522-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4375693522-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4375693522-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="4375693522-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9061218692-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9061218692-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="9061218692-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9061218692-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ +          </span><span class="p" data-group-id="9061218692-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="p" data-group-id="9061218692-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9061218692-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="9061218692-7">[</span><span class="p" data-group-id="9061218692-7">]</span><span class="p" data-group-id="9061218692-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="9061218692-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="9061218692-8">]</span><span class="p" data-group-id="9061218692-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9061218692-4">]</span><span class="p" data-group-id="9061218692-3">}</span><span class="p" data-group-id="9061218692-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4758462566-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="4758462566-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4758462566-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="4758462566-3">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="4375693522-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4375693522-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4375693522-5">]</span><span class="p" data-group-id="4375693522-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="4758462566-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4758462566-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4758462566-5">]</span><span class="p" data-group-id="4758462566-4">}</span><span class="p">,</span><span class="w">
│ │ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="4375693522-2">]</span><span class="p" data-group-id="4375693522-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │ │ + </span><span class="p" data-group-id="4758462566-2">]</span><span class="p" data-group-id="4758462566-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │ │   ...,
│ │ │ │   [...,
│ │ │ │    {prim_app, &quot;2&quot;},
│ │ │ │    {ch_app, &quot;1&quot;}]}.</code></pre><p>The included application can be started in two ways. This is described in the
│ │ │ │  next two sections.</p><h3 id="application-restart" class="section-heading">
│ │ │ │    <a href="#application-restart" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │ @@ -385,74 +385,74 @@
│ │ │ │  <p><em>Step 4b)</em> Another way to start the included application (or stop it in the case
│ │ │ │  of downgrade) is by combining instructions for adding and removing child
│ │ │ │  processes to/from <code class="inline">prim_sup</code> with instructions for loading/unloading all
│ │ │ │  <code class="inline">ch_app</code> code and its application specification.</p><p>Again, the <code class="inline">.relup</code> file is created manually, either from scratch or by editing a
│ │ │ │  generated version. Load all code for <code class="inline">ch_app</code> first, and also load the
│ │ │ │  application specification, before <code class="inline">prim_sup</code> is updated. When downgrading,
│ │ │ │  <code class="inline">prim_sup</code> is to updated first, before the code for <code class="inline">ch_app</code> and its application
│ │ │ │ -specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7824121901-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7824121901-2">[</span><span class="p" data-group-id="7824121901-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="7824121901-4">[</span><span class="p" data-group-id="7824121901-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="7824121901-5">[</span><span class="p" data-group-id="7824121901-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="7824121901-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="7824121901-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="7824121901-8">]</span><span class="p" data-group-id="7824121901-7">}</span><span class="p" data-group-id="7824121901-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="7824121901-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="7824121901-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7824121901-11">]</span><span class="p" data-group-id="7824121901-10">}</span><span class="p" data-group-id="7824121901-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3739477110-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3739477110-2">[</span><span class="p" data-group-id="3739477110-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3739477110-4">[</span><span class="p" data-group-id="3739477110-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3739477110-5">[</span><span class="p" data-group-id="3739477110-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="3739477110-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="3739477110-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="3739477110-8">]</span><span class="p" data-group-id="3739477110-7">}</span><span class="p" data-group-id="3739477110-6">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="3739477110-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="3739477110-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3739477110-11">]</span><span class="p" data-group-id="3739477110-10">}</span><span class="p" data-group-id="3739477110-9">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7824121901-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7824121901-13">}</span><span class="p" data-group-id="7824121901-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7824121901-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7824121901-15">}</span><span class="p" data-group-id="7824121901-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7824121901-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7824121901-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="7824121901-18">]</span><span class="p" data-group-id="7824121901-17">}</span><span class="p" data-group-id="7824121901-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="7824121901-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7824121901-20">]</span><span class="p" data-group-id="7824121901-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7824121901-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7824121901-22">}</span><span class="p" data-group-id="7824121901-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="7824121901-24">[</span><span class="p" data-group-id="7824121901-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="7824121901-26">[</span><span class="p" data-group-id="7824121901-26">]</span><span class="p" data-group-id="7824121901-25">}</span><span class="p" data-group-id="7824121901-24">]</span><span class="p" data-group-id="7824121901-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="7824121901-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7824121901-28">]</span><span class="p" data-group-id="7824121901-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7824121901-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="7824121901-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="7824121901-31">]</span><span class="p" data-group-id="7824121901-30">}</span><span class="p" data-group-id="7824121901-29">}</span><span class="p" data-group-id="7824121901-5">]</span><span class="p" data-group-id="7824121901-3">}</span><span class="p" data-group-id="7824121901-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="7824121901-32">[</span><span class="p" data-group-id="7824121901-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="7824121901-34">[</span><span class="p" data-group-id="7824121901-34">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="7824121901-35">[</span><span class="p" data-group-id="7824121901-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="7824121901-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="7824121901-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7824121901-38">]</span><span class="p" data-group-id="7824121901-37">}</span><span class="p" data-group-id="7824121901-36">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3739477110-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3739477110-13">}</span><span class="p" data-group-id="3739477110-12">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3739477110-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3739477110-15">}</span><span class="p" data-group-id="3739477110-14">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3739477110-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3739477110-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="3739477110-18">]</span><span class="p" data-group-id="3739477110-17">}</span><span class="p" data-group-id="3739477110-16">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="3739477110-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3739477110-20">]</span><span class="p" data-group-id="3739477110-19">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3739477110-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3739477110-22">}</span><span class="p" data-group-id="3739477110-21">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="3739477110-24">[</span><span class="p" data-group-id="3739477110-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="3739477110-26">[</span><span class="p" data-group-id="3739477110-26">]</span><span class="p" data-group-id="3739477110-25">}</span><span class="p" data-group-id="3739477110-24">]</span><span class="p" data-group-id="3739477110-23">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="3739477110-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3739477110-28">]</span><span class="p" data-group-id="3739477110-27">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3739477110-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="3739477110-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="3739477110-31">]</span><span class="p" data-group-id="3739477110-30">}</span><span class="p" data-group-id="3739477110-29">}</span><span class="p" data-group-id="3739477110-5">]</span><span class="p" data-group-id="3739477110-3">}</span><span class="p" data-group-id="3739477110-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="3739477110-32">[</span><span class="p" data-group-id="3739477110-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3739477110-34">[</span><span class="p" data-group-id="3739477110-34">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="3739477110-35">[</span><span class="p" data-group-id="3739477110-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="3739477110-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="3739477110-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3739477110-38">]</span><span class="p" data-group-id="3739477110-37">}</span><span class="p" data-group-id="3739477110-36">}</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7824121901-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="7824121901-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="7824121901-41">]</span><span class="p" data-group-id="7824121901-40">}</span><span class="p" data-group-id="7824121901-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7824121901-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="7824121901-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="7824121901-44">]</span><span class="p" data-group-id="7824121901-43">}</span><span class="p" data-group-id="7824121901-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="7824121901-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7824121901-46">]</span><span class="p" data-group-id="7824121901-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7824121901-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7824121901-48">}</span><span class="p" data-group-id="7824121901-47">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="7824121901-50">[</span><span class="p" data-group-id="7824121901-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="7824121901-52">[</span><span class="p" data-group-id="7824121901-52">]</span><span class="p" data-group-id="7824121901-51">}</span><span class="p" data-group-id="7824121901-50">]</span><span class="p" data-group-id="7824121901-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="7824121901-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7824121901-54">]</span><span class="p" data-group-id="7824121901-53">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="7824121901-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7824121901-56">}</span><span class="p" data-group-id="7824121901-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="7824121901-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7824121901-58">}</span><span class="p" data-group-id="7824121901-57">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="7824121901-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="7824121901-60">]</span><span class="p" data-group-id="7824121901-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="7824121901-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7824121901-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="7824121901-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="7824121901-63">]</span><span class="p" data-group-id="7824121901-62">}</span><span class="p" data-group-id="7824121901-61">}</span><span class="p" data-group-id="7824121901-35">]</span><span class="p" data-group-id="7824121901-33">}</span><span class="p" data-group-id="7824121901-32">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="7824121901-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3739477110-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="3739477110-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="3739477110-41">]</span><span class="p" data-group-id="3739477110-40">}</span><span class="p" data-group-id="3739477110-39">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3739477110-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="3739477110-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="3739477110-44">]</span><span class="p" data-group-id="3739477110-43">}</span><span class="p" data-group-id="3739477110-42">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="3739477110-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3739477110-46">]</span><span class="p" data-group-id="3739477110-45">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="3739477110-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3739477110-48">}</span><span class="p" data-group-id="3739477110-47">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="3739477110-50">[</span><span class="p" data-group-id="3739477110-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="3739477110-52">[</span><span class="p" data-group-id="3739477110-52">]</span><span class="p" data-group-id="3739477110-51">}</span><span class="p" data-group-id="3739477110-50">]</span><span class="p" data-group-id="3739477110-49">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="3739477110-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="3739477110-54">]</span><span class="p" data-group-id="3739477110-53">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="3739477110-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3739477110-56">}</span><span class="p" data-group-id="3739477110-55">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="3739477110-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="3739477110-58">}</span><span class="p" data-group-id="3739477110-57">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="3739477110-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="3739477110-60">]</span><span class="p" data-group-id="3739477110-59">}</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="3739477110-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="3739477110-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="3739477110-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="3739477110-63">]</span><span class="p" data-group-id="3739477110-62">}</span><span class="p" data-group-id="3739477110-61">}</span><span class="p" data-group-id="3739477110-35">]</span><span class="p" data-group-id="3739477110-33">}</span><span class="p" data-group-id="3739477110-32">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="3739477110-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │ │    <a href="#changing-non-erlang-code" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Changing Non-Erlang Code</span>
│ │ │ │  </h2>
│ │ │ │  <p>Changing code for a program written in another programming language than Erlang,
│ │ │ │  for example, a port program, is application-dependent and OTP provides no
│ │ │ │  special support.</p><p><em>Example</em></p><p>When changing code for a port program, assume that the Erlang process
│ │ │ │  controlling the port is a <code class="inline">gen_server</code> <code class="inline">portc</code> and that the port is opened in
│ │ │ │ -the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0928248726-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0928248726-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6175318985-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6175318985-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="0928248726-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="0928248726-3">(</span><span class="n">App</span><span class="p" data-group-id="0928248726-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="0928248726-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0928248726-4">(</span><span class="p" data-group-id="0928248726-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="0928248726-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0928248726-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0928248726-6">]</span><span class="p" data-group-id="0928248726-4">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="6175318985-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="6175318985-3">(</span><span class="n">App</span><span class="p" data-group-id="6175318985-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="6175318985-2">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="6175318985-4">(</span><span class="p" data-group-id="6175318985-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="6175318985-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175318985-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6175318985-6">]</span><span class="p" data-group-id="6175318985-4">)</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="0928248726-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0928248726-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0928248726-8">}</span><span class="p" data-group-id="0928248726-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │ │ +    </span><span class="p" data-group-id="6175318985-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="6175318985-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6175318985-8">}</span><span class="p" data-group-id="6175318985-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │ │  extended with a <code class="inline">code_change/3</code> function, which closes the old port and opens a
│ │ │ │  new port. (If necessary, the <code class="inline">gen_server</code> can first request data that must be
│ │ │ │ -saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="2283206797-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="2283206797-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="4157236283-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="4157236283-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">close</span><span class="p">,</span><span class="w">
│ │ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ │ -        </span><span class="p" data-group-id="2283206797-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="2283206797-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +        </span><span class="p" data-group-id="4157236283-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="4157236283-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │              </span><span class="ss">true</span><span class="w">
│ │ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="2283206797-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="2283206797-4">(</span><span class="n">App</span><span class="p" data-group-id="2283206797-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="2283206797-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2283206797-5">(</span><span class="p" data-group-id="2283206797-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="2283206797-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283206797-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2283206797-7">]</span><span class="p" data-group-id="2283206797-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ -    </span><span class="p" data-group-id="2283206797-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="2283206797-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2283206797-9">}</span><span class="p" data-group-id="2283206797-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ │ -file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2635707351-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2635707351-2">[</span><span class="p" data-group-id="2635707351-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2635707351-4">[</span><span class="p" data-group-id="2635707351-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2635707351-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="2635707351-6">}</span><span class="p" data-group-id="2635707351-5">}</span><span class="p" data-group-id="2635707351-4">]</span><span class="p" data-group-id="2635707351-3">}</span><span class="p" data-group-id="2635707351-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="2635707351-7">[</span><span class="p" data-group-id="2635707351-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2635707351-9">[</span><span class="p" data-group-id="2635707351-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2635707351-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="2635707351-11">}</span><span class="p" data-group-id="2635707351-10">}</span><span class="p" data-group-id="2635707351-9">]</span><span class="p" data-group-id="2635707351-8">}</span><span class="p" data-group-id="2635707351-7">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="2635707351-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ │ -the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="0755184898-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0755184898-2">[</span><span class="p" data-group-id="0755184898-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="0755184898-4">[</span><span class="ss">priv</span><span class="p" data-group-id="0755184898-4">]</span><span class="p" data-group-id="0755184898-3">}</span><span class="p" data-group-id="0755184898-2">]</span><span class="p" data-group-id="0755184898-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4157236283-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="4157236283-4">(</span><span class="n">App</span><span class="p" data-group-id="4157236283-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="4157236283-3">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4157236283-5">(</span><span class="p" data-group-id="4157236283-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="4157236283-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4157236283-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4157236283-7">]</span><span class="p" data-group-id="4157236283-5">)</span><span class="p">,</span><span class="w">
│ │ │ │ +    </span><span class="p" data-group-id="4157236283-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="4157236283-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4157236283-9">}</span><span class="p" data-group-id="4157236283-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ │ +file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8311525539-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8311525539-2">[</span><span class="p" data-group-id="8311525539-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8311525539-4">[</span><span class="p" data-group-id="8311525539-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8311525539-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="8311525539-6">}</span><span class="p" data-group-id="8311525539-5">}</span><span class="p" data-group-id="8311525539-4">]</span><span class="p" data-group-id="8311525539-3">}</span><span class="p" data-group-id="8311525539-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="8311525539-7">[</span><span class="p" data-group-id="8311525539-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8311525539-9">[</span><span class="p" data-group-id="8311525539-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8311525539-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="8311525539-11">}</span><span class="p" data-group-id="8311525539-10">}</span><span class="p" data-group-id="8311525539-9">]</span><span class="p" data-group-id="8311525539-8">}</span><span class="p" data-group-id="8311525539-7">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="8311525539-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ │ +the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7278628143-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7278628143-2">[</span><span class="p" data-group-id="7278628143-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="7278628143-4">[</span><span class="ss">priv</span><span class="p" data-group-id="7278628143-4">]</span><span class="p" data-group-id="7278628143-3">}</span><span class="p" data-group-id="7278628143-2">]</span><span class="p" data-group-id="7278628143-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="runtime-system-restart-and-upgrade" class="section-heading">
│ │ │ │    <a href="#runtime-system-restart-and-upgrade" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Runtime System Restart and Upgrade</span>
│ │ │ │  </h2>
│ │ │ │  <p>Two upgrade instructions restart the runtime system:</p><ul><li><p><code class="inline">restart_new_emulator</code></p><p>Intended when ERTS, Kernel, STDLIB, or SASL is upgraded. It is automatically
│ │ │ │ @@ -460,20 +460,20 @@
│ │ │ │  executed before all other upgrade instructions. For more information about
│ │ │ │  this instruction, see restart_new_emulator (Low-Level) in
│ │ │ │  <a href="release_handling.xhtml#restart_new_emulator_instr">Release Handling Instructions</a>.</p></li><li><p><code class="inline">restart_emulator</code></p><p>Used when a restart of the runtime system is required after all other upgrade
│ │ │ │  instructions are executed. For more information about this instruction, see
│ │ │ │  restart_emulator (Low-Level) in
│ │ │ │  <a href="release_handling.xhtml#restart_emulator_instr">Release Handling Instructions</a>.</p></li></ul><p>If a runtime system restart is necessary and no upgrade instructions are needed,
│ │ │ │  that is, if the restart itself is enough for the upgraded applications to start
│ │ │ │ -running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1517949098-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1517949098-2">[</span><span class="p" data-group-id="1517949098-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1517949098-4">[</span><span class="p" data-group-id="1517949098-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1517949098-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="1517949098-5">]</span><span class="p" data-group-id="1517949098-3">}</span><span class="p" data-group-id="1517949098-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1517949098-6">[</span><span class="p" data-group-id="1517949098-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1517949098-8">[</span><span class="p" data-group-id="1517949098-8">]</span><span class="p">,</span><span class="w">
│ │ │ │ -   </span><span class="p" data-group-id="1517949098-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="1517949098-9">]</span><span class="p" data-group-id="1517949098-7">}</span><span class="p" data-group-id="1517949098-6">]</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1517949098-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │ │ +running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9518367727-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9518367727-2">[</span><span class="p" data-group-id="9518367727-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="9518367727-4">[</span><span class="p" data-group-id="9518367727-4">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="9518367727-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="9518367727-5">]</span><span class="p" data-group-id="9518367727-3">}</span><span class="p" data-group-id="9518367727-2">]</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9518367727-6">[</span><span class="p" data-group-id="9518367727-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="9518367727-8">[</span><span class="p" data-group-id="9518367727-8">]</span><span class="p">,</span><span class="w">
│ │ │ │ +   </span><span class="p" data-group-id="9518367727-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="9518367727-9">]</span><span class="p" data-group-id="9518367727-7">}</span><span class="p" data-group-id="9518367727-6">]</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9518367727-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │ │  of release packages, automatic path updates, and so on, can be used without
│ │ │ │  having to specify <code class="inline">.appup</code> files.</p>
│ │ │ │  
│ │ │ │    </body>
│ │ │ │  </html>
│ │ │ ├── OEBPS/applications.xhtml
│ │ │ │ @@ -40,34 +40,34 @@
│ │ │ │  <a href="applications.xhtml#app_dir">directory structure</a>.</p><p><a href="" id="callback_module"></a></p><h2 id="application-callback-module" class="section-heading">
│ │ │ │    <a href="#application-callback-module" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Callback Module</span>
│ │ │ │  </h2>
│ │ │ │  <p>How to start and stop the code for the application, including its supervision
│ │ │ │ -tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="5077082301-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="5077082301-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5077082301-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="5077082301-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5077082301-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5077082301-3">}</span><span class="w">
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="5077082301-4">(</span><span class="n">State</span><span class="p" data-group-id="5077082301-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │ │ +tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="1022468120-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="1022468120-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1022468120-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="1022468120-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="1022468120-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1022468120-3">}</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="1022468120-4">(</span><span class="n">State</span><span class="p" data-group-id="1022468120-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │ │  supervision tree by starting the top supervisor. It is expected to return the
│ │ │ │  pid of the top supervisor and an optional term, <code class="inline">State</code>, which defaults to
│ │ │ │  <code class="inline">[]</code>. This term is passed as is to <code class="inline">stop/1</code>.</li><li><code class="inline">StartType</code> is usually the atom <code class="inline">normal</code>. It has other values only in the case
│ │ │ │  of a takeover or failover; see
│ │ │ │  <a href="distributed_applications.xhtml">Distributed Applications</a>.</li><li><code class="inline">StartArgs</code> is defined by the key <code class="inline">mod</code> in the
│ │ │ │  <a href="applications.xhtml#appl_res_file">application resource file</a>.</li><li><code class="inline">stop/1</code> is called <em>after</em> the application has been stopped and is to do any
│ │ │ │  necessary cleaning up. The actual stopping of the application, that is,
│ │ │ │  shutting down the supervision tree, is handled automatically as described in
│ │ │ │  <a href="applications.xhtml#stopping">Starting and Stopping Applications</a>.</li></ul><p><a href="" id="ch_app"></a></p><p>Example of an application callback module for packaging the supervision tree
│ │ │ │ -from <a href="sup_princ.xhtml#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8529259926-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8529259926-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8529259926-2">(</span><span class="ss">application</span><span class="p" data-group-id="8529259926-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +from <a href="sup_princ.xhtml#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3534778894-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="3534778894-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3534778894-2">(</span><span class="ss">application</span><span class="p" data-group-id="3534778894-2">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="w">
│ │ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8529259926-3">(</span><span class="p" data-group-id="8529259926-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8529259926-4">]</span><span class="p" data-group-id="8529259926-3">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3534778894-3">(</span><span class="p" data-group-id="3534778894-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3534778894-4">]</span><span class="p" data-group-id="3534778894-3">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8529259926-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8529259926-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ -    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8529259926-6">(</span><span class="p" data-group-id="8529259926-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="3534778894-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="3534778894-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3534778894-6">(</span><span class="p" data-group-id="3534778894-6">)</span><span class="p">.</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="8529259926-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="8529259926-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="3534778894-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="3534778894-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>A library application that cannot be started or stopped does not need any
│ │ │ │  application callback module.</p><p><a href="" id="appl_res_file"></a></p><h2 id="application-resource-file" class="section-heading">
│ │ │ │    <a href="#application-resource-file" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Resource File</span>
│ │ │ │  </h2>
│ │ │ │ @@ -78,22 +78,22 @@
│ │ │ │  keys.</li></ul><p>The contents of a minimal <code class="inline">.app</code> file for a library application <code class="inline">libapp</code> looks
│ │ │ │  as follows:</p><pre><code class="text">{application, libapp, []}.</code></pre><p>The contents of a minimal <code class="inline">.app</code> file <code class="inline">ch_app.app</code> for a supervision tree
│ │ │ │  application like <code class="inline">ch_app</code> looks as follows:</p><pre><code class="text">{application, ch_app,
│ │ │ │   [{mod, {ch_app,[]}}]}.</code></pre><p>The key <code class="inline">mod</code> defines the callback module and start argument of the application,
│ │ │ │  in this case <code class="inline">ch_app</code> and <code class="inline">[]</code>, respectively. This means that the following is
│ │ │ │  called when the application is to be started:</p><pre><code class="text">ch_app:start(normal, [])</code></pre><p>The following is called when the application is stopped:</p><pre><code class="text">ch_app:stop([])</code></pre><p>When using <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a>, the Erlang/OTP tools for packaging code (see Section
│ │ │ │  <a href="release_structure.xhtml">Releases</a>), the keys <code class="inline">description</code>, <code class="inline">vsn</code>, <code class="inline">modules</code>,
│ │ │ │ -<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1064084442-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1064084442-2">[</span><span class="p" data-group-id="1064084442-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="1064084442-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1064084442-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1064084442-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1064084442-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1064084442-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1064084442-6">]</span><span class="p" data-group-id="1064084442-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1064084442-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1064084442-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="1064084442-8">]</span><span class="p" data-group-id="1064084442-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1064084442-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1064084442-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1064084442-10">]</span><span class="p" data-group-id="1064084442-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="1064084442-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1064084442-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="1064084442-13">[</span><span class="p" data-group-id="1064084442-13">]</span><span class="p" data-group-id="1064084442-12">}</span><span class="p" data-group-id="1064084442-11">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1064084442-2">]</span><span class="p" data-group-id="1064084442-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │ │ +<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2848385886-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2848385886-2">[</span><span class="p" data-group-id="2848385886-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="2848385886-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2848385886-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2848385886-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2848385886-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2848385886-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2848385886-6">]</span><span class="p" data-group-id="2848385886-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2848385886-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2848385886-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="2848385886-8">]</span><span class="p" data-group-id="2848385886-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2848385886-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2848385886-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="2848385886-10">]</span><span class="p" data-group-id="2848385886-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="2848385886-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2848385886-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="2848385886-13">[</span><span class="p" data-group-id="2848385886-13">]</span><span class="p" data-group-id="2848385886-12">}</span><span class="p" data-group-id="2848385886-11">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2848385886-2">]</span><span class="p" data-group-id="2848385886-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │ │  this list when generating boot scripts and tar files. A module must only
│ │ │ │  be included in one application. Defaults to <code class="inline">[]</code>.</li><li><code class="inline">registered</code> - All names of registered processes in the application.
│ │ │ │  <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to detect name clashes between applications.
│ │ │ │  Defaults to <code class="inline">[]</code>.</li><li><code class="inline">applications</code> - All applications that must be started before this
│ │ │ │  application is started. <a href="../../../lib/sasl/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to generate correct boot
│ │ │ │  scripts. Defaults to <code class="inline">[]</code>. Notice that all applications have dependencies to
│ │ │ │  at least Kernel and STDLIB.</li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>For details about the syntax and contents of the application resource file,
│ │ │ │ @@ -205,38 +205,38 @@
│ │ │ │  stop applications.</p><h2 id="loading-and-unloading-applications" class="section-heading">
│ │ │ │    <a href="#loading-and-unloading-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Loading and Unloading Applications</span>
│ │ │ │  </h2>
│ │ │ │  <p>Before an application can be started, it must be <em>loaded</em>. The application
│ │ │ │ -controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="9890242246-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9890242246-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="9738433137-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9738433137-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="9890242246-2">(</span><span class="p" data-group-id="9890242246-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="9890242246-3">[</span><span class="p" data-group-id="9890242246-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="9890242246-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9890242246-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="9890242246-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="9890242246-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9890242246-6">}</span><span class="p" data-group-id="9890242246-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="9738433137-2">(</span><span class="p" data-group-id="9738433137-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="9738433137-3">[</span><span class="p" data-group-id="9738433137-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="9738433137-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9738433137-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="9738433137-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="9738433137-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9738433137-6">}</span><span class="p" data-group-id="9738433137-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │ │  unloaded. The information about the application is erased from the internal
│ │ │ │ -database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="8673818029-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8673818029-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="5416796914-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="5416796914-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="8673818029-2">(</span><span class="p" data-group-id="8673818029-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8673818029-3">[</span><span class="p" data-group-id="8673818029-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="8673818029-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8673818029-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="8673818029-5">}</span><span class="p" data-group-id="8673818029-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │ │ +4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="5416796914-2">(</span><span class="p" data-group-id="5416796914-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5416796914-3">[</span><span class="p" data-group-id="5416796914-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="5416796914-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="5416796914-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="5416796914-5">}</span><span class="p" data-group-id="5416796914-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │ │  application. Code loading is handled in the usual way by the code server.</p></section><p><a href="" id="stopping"></a></p><h2 id="starting-and-stopping-applications" class="section-heading">
│ │ │ │    <a href="#starting-and-stopping-applications" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Starting and Stopping Applications</span>
│ │ │ │  </h2>
│ │ │ │ -<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1513882036-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="1513882036-1">)</span><span class="p">.</span><span class="w">
│ │ │ │ +<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2027645305-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2027645305-1">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="1513882036-2">(</span><span class="p" data-group-id="1513882036-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="1513882036-3">[</span><span class="p" data-group-id="1513882036-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="1513882036-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1513882036-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="1513882036-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="1513882036-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1513882036-6">}</span><span class="p" data-group-id="1513882036-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │ │ +6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="2027645305-2">(</span><span class="p" data-group-id="2027645305-2">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="2027645305-3">[</span><span class="p" data-group-id="2027645305-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="2027645305-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2027645305-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="2027645305-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="2027645305-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="2027645305-6">}</span><span class="p" data-group-id="2027645305-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │ │  it using <a href="../../../lib/kernel/doc/html/application.html#load/1"><code class="inline">application:load/1</code></a>. It checks the value of the <code class="inline">applications</code> key to
│ │ │ │  ensure that all applications that are to be started before this application are
│ │ │ │  running.</p><p><a href="" id="application_master"></a></p><p>Following that, the application controller creates an <em>application master</em> for
│ │ │ │  the application.</p><p>The application master establishes itself as the <a href="../../../lib/../erts/doc/html/erlang.html#group_leader/0">group
│ │ │ │  leader</a> of all processes in the application
│ │ │ │  and will forward I/O to the previous group leader.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The purpose of the application master being the group leader is to easily
│ │ │ │  keep track of which processes that belong to the application. That is needed
│ │ │ │ @@ -252,55 +252,55 @@
│ │ │ │  defined by the <code class="inline">mod</code> key.</p><h2 id="configuring-an-application" class="section-heading">
│ │ │ │    <a href="#configuring-an-application" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Configuring an Application</span>
│ │ │ │  </h2>
│ │ │ │  <p>An application can be configured using <em>configuration parameters</em>. These are a
│ │ │ │ -list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5387632886-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5387632886-2">[</span><span class="p" data-group-id="5387632886-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="5387632886-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5387632886-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="5387632886-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5387632886-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5387632886-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="5387632886-6">]</span><span class="p" data-group-id="5387632886-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5387632886-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5387632886-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="5387632886-8">]</span><span class="p" data-group-id="5387632886-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5387632886-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5387632886-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="5387632886-10">]</span><span class="p" data-group-id="5387632886-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5387632886-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5387632886-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="5387632886-13">[</span><span class="p" data-group-id="5387632886-13">]</span><span class="p" data-group-id="5387632886-12">}</span><span class="p" data-group-id="5387632886-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ -  </span><span class="p" data-group-id="5387632886-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5387632886-15">[</span><span class="p" data-group-id="5387632886-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="5387632886-16">}</span><span class="p" data-group-id="5387632886-15">]</span><span class="p" data-group-id="5387632886-14">}</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="5387632886-2">]</span><span class="p" data-group-id="5387632886-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │ │ +list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1303571073-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1303571073-2">[</span><span class="p" data-group-id="1303571073-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="1303571073-3">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1303571073-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1303571073-4">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1303571073-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1303571073-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1303571073-6">]</span><span class="p" data-group-id="1303571073-5">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1303571073-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1303571073-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="1303571073-8">]</span><span class="p" data-group-id="1303571073-7">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1303571073-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1303571073-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1303571073-10">]</span><span class="p" data-group-id="1303571073-9">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1303571073-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1303571073-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="1303571073-13">[</span><span class="p" data-group-id="1303571073-13">]</span><span class="p" data-group-id="1303571073-12">}</span><span class="p" data-group-id="1303571073-11">}</span><span class="p">,</span><span class="w">
│ │ │ │ +  </span><span class="p" data-group-id="1303571073-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1303571073-15">[</span><span class="p" data-group-id="1303571073-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="1303571073-16">}</span><span class="p" data-group-id="1303571073-15">]</span><span class="p" data-group-id="1303571073-14">}</span><span class="w">
│ │ │ │ + </span><span class="p" data-group-id="1303571073-2">]</span><span class="p" data-group-id="1303571073-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │ │  value of a configuration parameter by calling <code class="inline">application:get_env(App, Par)</code> or
│ │ │ │  a number of similar functions. For more information, see module <a href="../../../lib/kernel/doc/html/application.html"><code class="inline">application</code></a>
│ │ │ │  in Kernel.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="8277570859-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="8277570859-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="8277570859-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="8277570859-2">]</span><span class="w"> </span><span class="p" data-group-id="8277570859-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="8277570859-3">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="5891615697-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="5891615697-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="5891615697-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="5891615697-2">]</span><span class="w"> </span><span class="p" data-group-id="5891615697-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="5891615697-3">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="8277570859-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="8277570859-4">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8277570859-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8277570859-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="5891615697-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="5891615697-4">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5891615697-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="5891615697-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="8277570859-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="8277570859-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8277570859-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="8277570859-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="5891615697-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="5891615697-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="5891615697-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="5891615697-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │ │  configuration file</em>. This is a file that contains configuration parameters for
│ │ │ │ -relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8858962983-1">[</span><span class="p" data-group-id="8858962983-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8858962983-3">[</span><span class="p" data-group-id="8858962983-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="8858962983-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8858962983-3">]</span><span class="p" data-group-id="8858962983-2">}</span><span class="p">,</span><span class="w">
│ │ │ │ +relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1964884069-1">[</span><span class="p" data-group-id="1964884069-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1964884069-3">[</span><span class="p" data-group-id="1964884069-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="1964884069-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1964884069-3">]</span><span class="p" data-group-id="1964884069-2">}</span><span class="p">,</span><span class="w">
│ │ │ │   </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ │ - </span><span class="p" data-group-id="8858962983-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8858962983-6">[</span><span class="p" data-group-id="8858962983-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="8858962983-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8858962983-6">]</span><span class="p" data-group-id="8858962983-5">}</span><span class="p" data-group-id="8858962983-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │ │ + </span><span class="p" data-group-id="1964884069-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1964884069-6">[</span><span class="p" data-group-id="1964884069-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="1964884069-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1964884069-6">]</span><span class="p" data-group-id="1964884069-5">}</span><span class="p" data-group-id="1964884069-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │ │  started with the command-line argument <code class="inline">-config Name</code>. For details, see
│ │ │ │  <a href="../../../lib/kernel/doc/html/config.xhtml"><code class="inline">config</code></a> in Kernel.</p><p><em>Example:</em></p><p>A file <code class="inline">test.config</code> is created with the following contents:</p><pre><code class="text">[{ch_app, [{file, &quot;testlog&quot;}]}].</code></pre><p>The value of <code class="inline">file</code> overrides the value of <code class="inline">file</code> as defined in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -config test</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="8028902872-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="8028902872-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="8028902872-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="8028902872-2">]</span><span class="w"> </span><span class="p" data-group-id="8028902872-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="8028902872-3">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="6474903887-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="6474903887-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="6474903887-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="6474903887-2">]</span><span class="w"> </span><span class="p" data-group-id="6474903887-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="6474903887-3">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="8028902872-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="8028902872-4">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8028902872-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8028902872-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="6474903887-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="6474903887-4">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6474903887-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6474903887-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="8028902872-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="8028902872-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8028902872-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="8028902872-7">}</span></code></pre><p>If <a href="release_handling.xhtml#sys">release handling</a> is used, exactly one system
│ │ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="6474903887-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="6474903887-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="6474903887-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="6474903887-7">}</span></code></pre><p>If <a href="release_handling.xhtml#sys">release handling</a> is used, exactly one system
│ │ │ │  configuration file is to be used and that file is to be called <code class="inline">sys.config</code>.</p><p>The values in the <code class="inline">.app</code> file and the values in a system configuration file can
│ │ │ │  be overridden directly from the command line:</p><pre><code class="text">% erl -ApplName Par1 Val1 ... ParN ValN</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -ch_app file &#39;&quot;testlog&quot;&#39;</span><span class="w">
│ │ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="8613312374-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="8613312374-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="8613312374-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="8613312374-2">]</span><span class="w"> </span><span class="p" data-group-id="8613312374-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="8613312374-3">]</span><span class="w">
│ │ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="1705286621-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="1705286621-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="1705286621-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="1705286621-2">]</span><span class="w"> </span><span class="p" data-group-id="1705286621-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="1705286621-3">]</span><span class="w">
│ │ │ │  
│ │ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="8613312374-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="8613312374-4">)</span><span class="gp unselectable">
│ │ │ │ -1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8613312374-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8613312374-5">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="1705286621-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="1705286621-4">)</span><span class="gp unselectable">
│ │ │ │ +1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1705286621-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="1705286621-5">)</span><span class="p">.</span><span class="w">
│ │ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="8613312374-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="8613312374-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ -</span><span class="p" data-group-id="8613312374-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="8613312374-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="1705286621-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="1705286621-6">)</span><span class="p">.</span><span class="w">
│ │ │ │ +</span><span class="p" data-group-id="1705286621-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="1705286621-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │ │    <a href="#application-start-types" class="hover-link">
│ │ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ │    </a>
│ │ │ │    <span class="text">Application Start Types</span>
│ │ │ │  </h2>
│ │ │ │  <p>A <em>start type</em> is defined when starting the application:</p><pre><code class="text">application:start(Application, Type)</code></pre><p><code class="inline">application:start(Application)</code> is the same as calling
│ │ │ │  <code class="inline">application:start(Application, temporary)</code>. The type can also be <code class="inline">permanent</code> or
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/applications.html
│ │ │ @@ -135,34 +135,34 @@
│ │ │  <a href="applications.html#app_dir">directory structure</a>.</p><p><a href="" id="callback_module"></a></p><h2 id="application-callback-module" class="section-heading">
│ │ │    <a href="#application-callback-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Callback Module</span>
│ │ │  </h2>
│ │ │  <p>How to start and stop the code for the application, including its supervision
│ │ │ -tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="9870310905-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="9870310905-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9870310905-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="9870310905-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9870310905-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9870310905-3">}</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="9870310905-4">(</span><span class="n">State</span><span class="p" data-group-id="9870310905-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │ +tree, is described by two callback functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start</span><span class="p" data-group-id="2932243508-1">(</span><span class="n">StartType</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="2932243508-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2932243508-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2932243508-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="2932243508-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2932243508-3">}</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="2932243508-4">(</span><span class="n">State</span><span class="p" data-group-id="2932243508-4">)</span></code></pre><ul><li><code class="inline">start/2</code> is called when starting the application and is to create the
│ │ │  supervision tree by starting the top supervisor. It is expected to return the
│ │ │  pid of the top supervisor and an optional term, <code class="inline">State</code>, which defaults to
│ │ │  <code class="inline">[]</code>. This term is passed as is to <code class="inline">stop/1</code>.</li><li><code class="inline">StartType</code> is usually the atom <code class="inline">normal</code>. It has other values only in the case
│ │ │  of a takeover or failover; see
│ │ │  <a href="distributed_applications.html">Distributed Applications</a>.</li><li><code class="inline">StartArgs</code> is defined by the key <code class="inline">mod</code> in the
│ │ │  <a href="applications.html#appl_res_file">application resource file</a>.</li><li><code class="inline">stop/1</code> is called <em>after</em> the application has been stopped and is to do any
│ │ │  necessary cleaning up. The actual stopping of the application, that is,
│ │ │  shutting down the supervision tree, is handled automatically as described in
│ │ │  <a href="applications.html#stopping">Starting and Stopping Applications</a>.</li></ul><p><a href="" id="ch_app"></a></p><p>Example of an application callback module for packaging the supervision tree
│ │ │ -from <a href="sup_princ.html#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4715398818-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="4715398818-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4715398818-2">(</span><span class="ss">application</span><span class="p" data-group-id="4715398818-2">)</span><span class="p">.</span><span class="w">
│ │ │ +from <a href="sup_princ.html#ex">Supervisor Behaviour</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8875514598-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="8875514598-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8875514598-2">(</span><span class="ss">application</span><span class="p" data-group-id="8875514598-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4715398818-3">(</span><span class="p" data-group-id="4715398818-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4715398818-4">]</span><span class="p" data-group-id="4715398818-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8875514598-3">(</span><span class="p" data-group-id="8875514598-4">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8875514598-4">]</span><span class="p" data-group-id="8875514598-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4715398818-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4715398818-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4715398818-6">(</span><span class="p" data-group-id="4715398818-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="8875514598-5">(</span><span class="p">_</span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8875514598-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ch_sup</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8875514598-6">(</span><span class="p" data-group-id="8875514598-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4715398818-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="4715398818-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="8875514598-7">(</span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="8875514598-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>A library application that cannot be started or stopped does not need any
│ │ │  application callback module.</p><p><a href="" id="appl_res_file"></a></p><h2 id="application-resource-file" class="section-heading">
│ │ │    <a href="#application-resource-file" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Resource File</span>
│ │ │  </h2>
│ │ │ @@ -173,22 +173,22 @@
│ │ │  keys.</li></ul><p>The contents of a minimal <code class="inline">.app</code> file for a library application <code class="inline">libapp</code> looks
│ │ │  as follows:</p><pre><code class="text">{application, libapp, []}.</code></pre><p>The contents of a minimal <code class="inline">.app</code> file <code class="inline">ch_app.app</code> for a supervision tree
│ │ │  application like <code class="inline">ch_app</code> looks as follows:</p><pre><code class="text">{application, ch_app,
│ │ │   [{mod, {ch_app,[]}}]}.</code></pre><p>The key <code class="inline">mod</code> defines the callback module and start argument of the application,
│ │ │  in this case <code class="inline">ch_app</code> and <code class="inline">[]</code>, respectively. This means that the following is
│ │ │  called when the application is to be started:</p><pre><code class="text">ch_app:start(normal, [])</code></pre><p>The following is called when the application is stopped:</p><pre><code class="text">ch_app:stop([])</code></pre><p>When using <a href="../../lib/sasl-4.2.2/doc/html/systools.html"><code class="inline">systools</code></a>, the Erlang/OTP tools for packaging code (see Section
│ │ │  <a href="release_structure.html">Releases</a>), the keys <code class="inline">description</code>, <code class="inline">vsn</code>, <code class="inline">modules</code>,
│ │ │ -<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9042014952-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9042014952-2">[</span><span class="p" data-group-id="9042014952-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="9042014952-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9042014952-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9042014952-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9042014952-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9042014952-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9042014952-6">]</span><span class="p" data-group-id="9042014952-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9042014952-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9042014952-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="9042014952-8">]</span><span class="p" data-group-id="9042014952-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9042014952-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9042014952-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="9042014952-10">]</span><span class="p" data-group-id="9042014952-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9042014952-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9042014952-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="9042014952-13">[</span><span class="p" data-group-id="9042014952-13">]</span><span class="p" data-group-id="9042014952-12">}</span><span class="p" data-group-id="9042014952-11">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9042014952-2">]</span><span class="p" data-group-id="9042014952-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../lib/sasl-4.2.2/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │ +<code class="inline">registered</code>, and <code class="inline">applications</code> are also to be specified:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4393952147-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4393952147-2">[</span><span class="p" data-group-id="4393952147-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4393952147-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4393952147-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4393952147-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4393952147-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4393952147-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4393952147-6">]</span><span class="p" data-group-id="4393952147-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4393952147-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4393952147-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4393952147-8">]</span><span class="p" data-group-id="4393952147-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4393952147-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4393952147-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4393952147-10">]</span><span class="p" data-group-id="4393952147-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4393952147-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4393952147-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4393952147-13">[</span><span class="p" data-group-id="4393952147-13">]</span><span class="p" data-group-id="4393952147-12">}</span><span class="p" data-group-id="4393952147-11">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4393952147-2">]</span><span class="p" data-group-id="4393952147-1">}</span><span class="p">.</span></code></pre><ul><li><code class="inline">description</code> - A short description, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">vsn</code> - Version number, a string. Defaults to <code class="inline">&quot;&quot;</code>.</li><li><code class="inline">modules</code> - All modules <em>introduced</em> by this application. <a href="../../lib/sasl-4.2.2/doc/html/systools.html"><code class="inline">systools</code></a> uses
│ │ │  this list when generating boot scripts and tar files. A module must only
│ │ │  be included in one application. Defaults to <code class="inline">[]</code>.</li><li><code class="inline">registered</code> - All names of registered processes in the application.
│ │ │  <a href="../../lib/sasl-4.2.2/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to detect name clashes between applications.
│ │ │  Defaults to <code class="inline">[]</code>.</li><li><code class="inline">applications</code> - All applications that must be started before this
│ │ │  application is started. <a href="../../lib/sasl-4.2.2/doc/html/systools.html"><code class="inline">systools</code></a> uses this list to generate correct boot
│ │ │  scripts. Defaults to <code class="inline">[]</code>. Notice that all applications have dependencies to
│ │ │  at least Kernel and STDLIB.</li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>For details about the syntax and contents of the application resource file,
│ │ │ @@ -300,38 +300,38 @@
│ │ │  stop applications.</p><h2 id="loading-and-unloading-applications" class="section-heading">
│ │ │    <a href="#loading-and-unloading-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Loading and Unloading Applications</span>
│ │ │  </h2>
│ │ │  <p>Before an application can be started, it must be <em>loaded</em>. The application
│ │ │ -controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="0978184080-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0978184080-1">)</span><span class="p">.</span><span class="w">
│ │ │ +controller reads and stores the information from the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="0596524117-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0596524117-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="0978184080-2">(</span><span class="p" data-group-id="0978184080-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0978184080-3">[</span><span class="p" data-group-id="0978184080-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="0978184080-4">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0978184080-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="0978184080-5">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0978184080-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0978184080-6">}</span><span class="p" data-group-id="0978184080-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="0596524117-2">(</span><span class="p" data-group-id="0596524117-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0596524117-3">[</span><span class="p" data-group-id="0596524117-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="0596524117-4">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0596524117-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="0596524117-5">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0596524117-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="0596524117-6">}</span><span class="p" data-group-id="0596524117-3">]</span></code></pre><p>An application that has been stopped, or has never been started, can be
│ │ │  unloaded. The information about the application is erased from the internal
│ │ │ -database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="0180512499-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="0180512499-1">)</span><span class="p">.</span><span class="w">
│ │ │ +database of the application controller.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">unload</span><span class="p" data-group-id="9443238244-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9443238244-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="0180512499-2">(</span><span class="p" data-group-id="0180512499-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0180512499-3">[</span><span class="p" data-group-id="0180512499-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="0180512499-4">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0180512499-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="0180512499-5">}</span><span class="p" data-group-id="0180512499-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │ +4&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">loaded_applications</span><span class="p" data-group-id="9443238244-2">(</span><span class="p" data-group-id="9443238244-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9443238244-3">[</span><span class="p" data-group-id="9443238244-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="9443238244-4">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9443238244-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="9443238244-5">}</span><span class="p" data-group-id="9443238244-3">]</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Loading/unloading an application does not load/unload the code used by the
│ │ │  application. Code loading is handled in the usual way by the code server.</p></section><p><a href="" id="stopping"></a></p><h2 id="starting-and-stopping-applications" class="section-heading">
│ │ │    <a href="#starting-and-stopping-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting and Stopping Applications</span>
│ │ │  </h2>
│ │ │ -<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9737242248-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9737242248-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>An application is started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5157520511-1">(</span><span class="ss">ch_app</span><span class="p" data-group-id="5157520511-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="9737242248-2">(</span><span class="p" data-group-id="9737242248-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9737242248-3">[</span><span class="p" data-group-id="9737242248-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="9737242248-4">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9737242248-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="9737242248-5">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9737242248-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9737242248-6">}</span><span class="p" data-group-id="9737242248-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │ +6&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">which_applications</span><span class="p" data-group-id="5157520511-2">(</span><span class="p" data-group-id="5157520511-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5157520511-3">[</span><span class="p" data-group-id="5157520511-4">{</span><span class="ss">kernel</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;2.8.1.3&quot;</span><span class="p" data-group-id="5157520511-4">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5157520511-5">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="s">&quot;ERTS  CXC 138 10&quot;</span><span class="p">,</span><span class="s">&quot;1.11.4.3&quot;</span><span class="p" data-group-id="5157520511-5">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5157520511-6">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;Channel allocator&quot;</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="5157520511-6">}</span><span class="p" data-group-id="5157520511-3">]</span></code></pre><p>If the application is not already loaded, the application controller first loads
│ │ │  it using <a href="../../lib/kernel-10.2.7.2/doc/html/application.html#load/1"><code class="inline">application:load/1</code></a>. It checks the value of the <code class="inline">applications</code> key to
│ │ │  ensure that all applications that are to be started before this application are
│ │ │  running.</p><p><a href="" id="application_master"></a></p><p>Following that, the application controller creates an <em>application master</em> for
│ │ │  the application.</p><p>The application master establishes itself as the <a href="../../erts-15.2.7.2/doc/html/erlang.html#group_leader/0">group
│ │ │  leader</a> of all processes in the application
│ │ │  and will forward I/O to the previous group leader.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The purpose of the application master being the group leader is to easily
│ │ │  keep track of which processes that belong to the application. That is needed
│ │ │ @@ -347,55 +347,55 @@
│ │ │  defined by the <code class="inline">mod</code> key.</p><h2 id="configuring-an-application" class="section-heading">
│ │ │    <a href="#configuring-an-application" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Configuring an Application</span>
│ │ │  </h2>
│ │ │  <p>An application can be configured using <em>configuration parameters</em>. These are a
│ │ │ -list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9832430067-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9832430067-2">[</span><span class="p" data-group-id="9832430067-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="9832430067-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9832430067-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9832430067-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9832430067-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9832430067-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9832430067-6">]</span><span class="p" data-group-id="9832430067-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9832430067-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9832430067-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="9832430067-8">]</span><span class="p" data-group-id="9832430067-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9832430067-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9832430067-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="9832430067-10">]</span><span class="p" data-group-id="9832430067-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9832430067-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9832430067-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="9832430067-13">[</span><span class="p" data-group-id="9832430067-13">]</span><span class="p" data-group-id="9832430067-12">}</span><span class="p" data-group-id="9832430067-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9832430067-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9832430067-15">[</span><span class="p" data-group-id="9832430067-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="9832430067-16">}</span><span class="p" data-group-id="9832430067-15">]</span><span class="p" data-group-id="9832430067-14">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9832430067-2">]</span><span class="p" data-group-id="9832430067-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │ +list of <code class="inline">{Par,Val}</code> tuples specified by a key <code class="inline">env</code> in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4177736983-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4177736983-2">[</span><span class="p" data-group-id="4177736983-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="4177736983-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4177736983-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="4177736983-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4177736983-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4177736983-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4177736983-6">]</span><span class="p" data-group-id="4177736983-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4177736983-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4177736983-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="4177736983-8">]</span><span class="p" data-group-id="4177736983-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4177736983-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4177736983-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="4177736983-10">]</span><span class="p" data-group-id="4177736983-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4177736983-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4177736983-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="4177736983-13">[</span><span class="p" data-group-id="4177736983-13">]</span><span class="p" data-group-id="4177736983-12">}</span><span class="p" data-group-id="4177736983-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4177736983-14">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4177736983-15">[</span><span class="p" data-group-id="4177736983-16">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="4177736983-16">}</span><span class="p" data-group-id="4177736983-15">]</span><span class="p" data-group-id="4177736983-14">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4177736983-2">]</span><span class="p" data-group-id="4177736983-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Par</code> is to be an atom. <code class="inline">Val</code> is any term. The application can retrieve the
│ │ │  value of a configuration parameter by calling <code class="inline">application:get_env(App, Par)</code> or
│ │ │  a number of similar functions. For more information, see module <a href="../../lib/kernel-10.2.7.2/doc/html/application.html"><code class="inline">application</code></a>
│ │ │  in Kernel.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="2857154287-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="2857154287-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="2857154287-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="2857154287-2">]</span><span class="w"> </span><span class="p" data-group-id="2857154287-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="2857154287-3">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="6109804736-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="6109804736-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="6109804736-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="6109804736-2">]</span><span class="w"> </span><span class="p" data-group-id="6109804736-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="6109804736-3">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="2857154287-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="2857154287-4">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2857154287-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="2857154287-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="6109804736-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="6109804736-4">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6109804736-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6109804736-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="2857154287-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="2857154287-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2857154287-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="2857154287-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="6109804736-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="6109804736-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6109804736-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6109804736-7">}</span></code></pre><p>The values in the <code class="inline">.app</code> file can be overridden by values in a <em>system
│ │ │  configuration file</em>. This is a file that contains configuration parameters for
│ │ │ -relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0095351366-1">[</span><span class="p" data-group-id="0095351366-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0095351366-3">[</span><span class="p" data-group-id="0095351366-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="0095351366-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0095351366-3">]</span><span class="p" data-group-id="0095351366-2">}</span><span class="p">,</span><span class="w">
│ │ │ +relevant applications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1522136436-1">[</span><span class="p" data-group-id="1522136436-2">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522136436-3">[</span><span class="p" data-group-id="1522136436-4">{</span><span class="n">Par11</span><span class="p">,</span><span class="n">Val11</span><span class="p" data-group-id="1522136436-4">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1522136436-3">]</span><span class="p" data-group-id="1522136436-2">}</span><span class="p">,</span><span class="w">
│ │ │   </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0095351366-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0095351366-6">[</span><span class="p" data-group-id="0095351366-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="0095351366-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0095351366-6">]</span><span class="p" data-group-id="0095351366-5">}</span><span class="p" data-group-id="0095351366-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │ + </span><span class="p" data-group-id="1522136436-5">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1522136436-6">[</span><span class="p" data-group-id="1522136436-7">{</span><span class="n">ParN1</span><span class="p">,</span><span class="n">ValN1</span><span class="p" data-group-id="1522136436-7">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1522136436-6">]</span><span class="p" data-group-id="1522136436-5">}</span><span class="p" data-group-id="1522136436-1">]</span><span class="p">.</span></code></pre><p>The system configuration is to be called <code class="inline">Name.config</code> and Erlang is to be
│ │ │  started with the command-line argument <code class="inline">-config Name</code>. For details, see
│ │ │  <a href="../../lib/kernel-10.2.7.2/doc/html/config.html"><code class="inline">config</code></a> in Kernel.</p><p><em>Example:</em></p><p>A file <code class="inline">test.config</code> is created with the following contents:</p><pre><code class="text">[{ch_app, [{file, &quot;testlog&quot;}]}].</code></pre><p>The value of <code class="inline">file</code> overrides the value of <code class="inline">file</code> as defined in the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -config test</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="9103366951-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="9103366951-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="9103366951-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="9103366951-2">]</span><span class="w"> </span><span class="p" data-group-id="9103366951-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="9103366951-3">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="9682594079-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="9682594079-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="9682594079-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="9682594079-2">]</span><span class="w"> </span><span class="p" data-group-id="9682594079-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="9682594079-3">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="9103366951-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="9103366951-4">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9103366951-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9103366951-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="9682594079-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="9682594079-4">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9682594079-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9682594079-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="9103366951-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="9103366951-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9103366951-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="9103366951-7">}</span></code></pre><p>If <a href="release_handling.html#sys">release handling</a> is used, exactly one system
│ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="9682594079-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="9682594079-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9682594079-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="9682594079-7">}</span></code></pre><p>If <a href="release_handling.html#sys">release handling</a> is used, exactly one system
│ │ │  configuration file is to be used and that file is to be called <code class="inline">sys.config</code>.</p><p>The values in the <code class="inline">.app</code> file and the values in a system configuration file can
│ │ │  be overridden directly from the command line:</p><pre><code class="text">% erl -ApplName Par1 Val1 ... ParN ValN</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -ch_app file &#39;&quot;testlog&quot;&#39;</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="6071197796-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="6071197796-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="6071197796-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="6071197796-2">]</span><span class="w"> </span><span class="p" data-group-id="6071197796-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="6071197796-3">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="p" data-group-id="9509771807-1">(</span><span class="n">BEAM</span><span class="p" data-group-id="9509771807-1">)</span><span class="w"> </span><span class="ss">emulator</span><span class="w"> </span><span class="ss">version</span><span class="w"> </span><span class="mf">5.2</span><span class="p">.</span><span class="mf">3.6</span><span class="w"> </span><span class="p" data-group-id="9509771807-2">[</span><span class="ss">hipe</span><span class="p" data-group-id="9509771807-2">]</span><span class="w"> </span><span class="p" data-group-id="9509771807-3">[</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="9509771807-3">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="6071197796-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="6071197796-4">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6071197796-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="6071197796-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">2.3</span><span class="p">.</span><span class="mi">6</span><span class="w">  </span><span class="p" data-group-id="9509771807-4">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="9509771807-4">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9509771807-5">(</span><span class="ss">ch_app</span><span class="p" data-group-id="9509771807-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="6071197796-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="6071197796-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6071197796-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="6071197796-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │ +2&gt; </span><span class="nc">application</span><span class="p">:</span><span class="nf">get_env</span><span class="p" data-group-id="9509771807-6">(</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">file</span><span class="p" data-group-id="9509771807-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9509771807-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;testlog&quot;</span><span class="p" data-group-id="9509771807-7">}</span></code></pre><h2 id="application-start-types" class="section-heading">
│ │ │    <a href="#application-start-types" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Start Types</span>
│ │ │  </h2>
│ │ │  <p>A <em>start type</em> is defined when starting the application:</p><pre><code class="text">application:start(Application, Type)</code></pre><p><code class="inline">application:start(Application)</code> is the same as calling
│ │ │  <code class="inline">application:start(Application, temporary)</code>. The type can also be <code class="inline">permanent</code> or
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/appup_cookbook.html
│ │ │ @@ -120,18 +120,18 @@
│ │ │    <a href="#changing-a-functional-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing a Functional Module</span>
│ │ │  </h2>
│ │ │  <p>When a functional module has been changed, for example, if a new function has
│ │ │  been added or a bug has been corrected, simple code replacement is sufficient,
│ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6825216224-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6825216224-2">[</span><span class="p" data-group-id="6825216224-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6825216224-4">[</span><span class="p" data-group-id="6825216224-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="6825216224-5">}</span><span class="p" data-group-id="6825216224-4">]</span><span class="p" data-group-id="6825216224-3">}</span><span class="p" data-group-id="6825216224-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6825216224-6">[</span><span class="p" data-group-id="6825216224-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6825216224-8">[</span><span class="p" data-group-id="6825216224-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="6825216224-9">}</span><span class="p" data-group-id="6825216224-8">]</span><span class="p" data-group-id="6825216224-7">}</span><span class="p" data-group-id="6825216224-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6825216224-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2142995600-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2142995600-2">[</span><span class="p" data-group-id="2142995600-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2142995600-4">[</span><span class="p" data-group-id="2142995600-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="2142995600-5">}</span><span class="p" data-group-id="2142995600-4">]</span><span class="p" data-group-id="2142995600-3">}</span><span class="p" data-group-id="2142995600-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2142995600-6">[</span><span class="p" data-group-id="2142995600-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2142995600-8">[</span><span class="p" data-group-id="2142995600-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="2142995600-9">}</span><span class="p" data-group-id="2142995600-8">]</span><span class="p" data-group-id="2142995600-7">}</span><span class="p" data-group-id="2142995600-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2142995600-1">}</span><span class="p">.</span></code></pre><h2 id="changing-a-residence-module" class="section-heading">
│ │ │    <a href="#changing-a-residence-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing a Residence Module</span>
│ │ │  </h2>
│ │ │  <p>In a system implemented according to the OTP design principles, all processes,
│ │ │  except system processes and special processes, reside in one of the behaviours
│ │ │ @@ -142,46 +142,46 @@
│ │ │    <a href="#changing-a-callback-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing a Callback Module</span>
│ │ │  </h2>
│ │ │  <p>A callback module is a functional module, and for code extensions simple code
│ │ │  replacement is sufficient.</p><p><em>Example</em></p><p>When adding a function to <code class="inline">ch3</code>, as described in the example in
│ │ │ -<a href="release_handling.html#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0936666099-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0936666099-2">[</span><span class="p" data-group-id="0936666099-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0936666099-4">[</span><span class="p" data-group-id="0936666099-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0936666099-5">}</span><span class="p" data-group-id="0936666099-4">]</span><span class="p" data-group-id="0936666099-3">}</span><span class="p" data-group-id="0936666099-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0936666099-6">[</span><span class="p" data-group-id="0936666099-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0936666099-8">[</span><span class="p" data-group-id="0936666099-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0936666099-9">}</span><span class="p" data-group-id="0936666099-8">]</span><span class="p" data-group-id="0936666099-7">}</span><span class="p" data-group-id="0936666099-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0936666099-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │ +<a href="release_handling.html#appup">Release Handling</a>, <code class="inline">ch_app.appup</code> looks as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0589064664-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0589064664-2">[</span><span class="p" data-group-id="0589064664-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0589064664-4">[</span><span class="p" data-group-id="0589064664-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0589064664-5">}</span><span class="p" data-group-id="0589064664-4">]</span><span class="p" data-group-id="0589064664-3">}</span><span class="p" data-group-id="0589064664-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0589064664-6">[</span><span class="p" data-group-id="0589064664-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0589064664-8">[</span><span class="p" data-group-id="0589064664-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0589064664-9">}</span><span class="p" data-group-id="0589064664-8">]</span><span class="p" data-group-id="0589064664-7">}</span><span class="p" data-group-id="0589064664-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0589064664-1">}</span><span class="p">.</span></code></pre><p>OTP also supports changing the internal state of behaviour processes; see
│ │ │  <a href="appup_cookbook.html#int_state">Changing Internal State</a>.</p><p><a href="" id="int_state"></a></p><h2 id="changing-internal-state" class="section-heading">
│ │ │    <a href="#changing-internal-state" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Internal State</span>
│ │ │  </h2>
│ │ │  <p>In this case, simple code replacement is not sufficient. The process must
│ │ │  explicitly transform its state using the callback function <code class="inline">code_change/3</code> before
│ │ │  switching to the new version of the callback module. Thus, synchronized code
│ │ │  replacement is used.</p><p><em>Example</em></p><p>Consider the <code class="inline">ch3</code> module from
│ │ │  <a href="gen_server_concepts.html#ex">gen_server Behaviour</a>. The internal state is a term
│ │ │  <code class="inline">Chs</code> representing the available channels. Assume you want to add a counter <code class="inline">N</code>,
│ │ │  which keeps track of the number of <code class="inline">alloc</code> requests so far. This means that the
│ │ │ -format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3541580656-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3541580656-2">[</span><span class="p" data-group-id="3541580656-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3541580656-4">[</span><span class="p" data-group-id="3541580656-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3541580656-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3541580656-7">[</span><span class="p" data-group-id="3541580656-7">]</span><span class="p" data-group-id="3541580656-6">}</span><span class="p" data-group-id="3541580656-5">}</span><span class="p" data-group-id="3541580656-4">]</span><span class="p" data-group-id="3541580656-3">}</span><span class="p" data-group-id="3541580656-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3541580656-8">[</span><span class="p" data-group-id="3541580656-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3541580656-10">[</span><span class="p" data-group-id="3541580656-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3541580656-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3541580656-13">[</span><span class="p" data-group-id="3541580656-13">]</span><span class="p" data-group-id="3541580656-12">}</span><span class="p" data-group-id="3541580656-11">}</span><span class="p" data-group-id="3541580656-10">]</span><span class="p" data-group-id="3541580656-9">}</span><span class="p" data-group-id="3541580656-8">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3541580656-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │ +format must be changed to <code class="inline">{Chs,N}</code>.</p><p>The <code class="inline">.appup</code> file can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1918226208-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1918226208-2">[</span><span class="p" data-group-id="1918226208-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918226208-4">[</span><span class="p" data-group-id="1918226208-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918226208-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918226208-7">[</span><span class="p" data-group-id="1918226208-7">]</span><span class="p" data-group-id="1918226208-6">}</span><span class="p" data-group-id="1918226208-5">}</span><span class="p" data-group-id="1918226208-4">]</span><span class="p" data-group-id="1918226208-3">}</span><span class="p" data-group-id="1918226208-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1918226208-8">[</span><span class="p" data-group-id="1918226208-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918226208-10">[</span><span class="p" data-group-id="1918226208-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918226208-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918226208-13">[</span><span class="p" data-group-id="1918226208-13">]</span><span class="p" data-group-id="1918226208-12">}</span><span class="p" data-group-id="1918226208-11">}</span><span class="p" data-group-id="1918226208-10">]</span><span class="p" data-group-id="1918226208-9">}</span><span class="p" data-group-id="1918226208-8">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1918226208-1">}</span><span class="p">.</span></code></pre><p>The third element of the <code class="inline">update</code> instruction is a tuple <code class="inline">{advanced,Extra}</code>,
│ │ │  which says that the affected processes are to do a state transformation before
│ │ │  loading the new version of the module. This is done by the processes calling the
│ │ │  callback function <code class="inline">code_change/3</code> (see <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html"><code class="inline">gen_server</code></a> in STDLIB).
│ │ │ -The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5537817365-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="5537817365-1">)</span><span class="p">.</span><span class="w">
│ │ │ +The term <code class="inline">Extra</code>, in this case <code class="inline">[]</code>, is passed as is to the function:</p><p><a href="" id="code_change"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8471152678-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="8471152678-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5537817365-2">(</span><span class="p" data-group-id="5537817365-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="5537817365-3">]</span><span class="p" data-group-id="5537817365-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8471152678-2">(</span><span class="p" data-group-id="8471152678-3">[</span><span class="ss">code_change</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="8471152678-3">]</span><span class="p" data-group-id="8471152678-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="5537817365-4">(</span><span class="p" data-group-id="5537817365-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="5537817365-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5537817365-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="5537817365-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="5537817365-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5537817365-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5537817365-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">code_change</span><span class="p" data-group-id="5537817365-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="5537817365-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5537817365-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5537817365-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5537817365-10">}</span><span class="p" data-group-id="5537817365-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="8471152678-4">(</span><span class="p" data-group-id="8471152678-5">{</span><span class="ss">down</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vsn</span><span class="p" data-group-id="8471152678-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8471152678-6">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="8471152678-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="8471152678-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8471152678-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8471152678-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">code_change</span><span class="p" data-group-id="8471152678-8">(</span><span class="p">_</span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="8471152678-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8471152678-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8471152678-10">{</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8471152678-10">}</span><span class="p" data-group-id="8471152678-9">}</span><span class="p">.</span></code></pre><p>The first argument is <code class="inline">{down,Vsn}</code> if there is a downgrade, or <code class="inline">Vsn</code> if there is
│ │ │  a upgrade. The term <code class="inline">Vsn</code> is fetched from the 'original' version of the module,
│ │ │  that is, the version you are upgrading from, or downgrading to.</p><p>The version is defined by the module attribute <code class="inline">vsn</code>, if any. There is no such
│ │ │  attribute in <code class="inline">ch3</code>, so in this case the version is the checksum (a huge integer)
│ │ │  of the beam file, an uninteresting value, which is ignored.</p><p>The other callback functions of <code class="inline">ch3</code> must also be modified and perhaps a new
│ │ │  interface function must be added, but this is not shown here.</p><h2 id="module-dependencies" class="section-heading">
│ │ │    <a href="#module-dependencies" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -190,67 +190,67 @@
│ │ │  </h2>
│ │ │  <p>Assume that a module is extended by adding an interface function, as in the
│ │ │  example in <a href="release_handling.html#appup">Release Handling</a>, where a function
│ │ │  <code class="inline">available/0</code> is added to <code class="inline">ch3</code>.</p><p>If a call is added to this function, say in module <code class="inline">m1</code>, a runtime error could
│ │ │  can occur during release upgrade if the new version of <code class="inline">m1</code> is loaded first and
│ │ │  calls <code class="inline">ch3:available/0</code> before the new version of <code class="inline">ch3</code> is loaded.</p><p>Thus, <code class="inline">ch3</code> must be loaded before <code class="inline">m1</code>, in the upgrade case, and conversely in
│ │ │  the downgrade case. <code class="inline">m1</code> is said to be <em>dependent on</em> <code class="inline">ch3</code>. In a release
│ │ │ -handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7595187368-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="7595187368-1">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7595187368-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7595187368-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="7595187368-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="7595187368-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │ +handling instruction, this is expressed by the <code class="inline">DepMods</code> element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7428816772-1">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="7428816772-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7428816772-2">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7428816772-3">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="7428816772-3">}</span><span class="p">,</span><span class="w"> </span><span class="n">DepMods</span><span class="p" data-group-id="7428816772-2">}</span></code></pre><p><code class="inline">DepMods</code> is a list of modules, on which <code class="inline">Module</code> is dependent.</p><p><em>Example</em></p><p>The module <code class="inline">m1</code> in application <code class="inline">myapp</code> is dependent on <code class="inline">ch3</code> when
│ │ │  upgrading from &quot;1&quot; to &quot;2&quot;, or downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="ss">myapp</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="2935665377-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2935665377-2">[</span><span class="p" data-group-id="2935665377-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2935665377-4">[</span><span class="p" data-group-id="2935665377-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2935665377-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="2935665377-6">]</span><span class="p" data-group-id="2935665377-5">}</span><span class="p" data-group-id="2935665377-4">]</span><span class="p" data-group-id="2935665377-3">}</span><span class="p" data-group-id="2935665377-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2935665377-7">[</span><span class="p" data-group-id="2935665377-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2935665377-9">[</span><span class="p" data-group-id="2935665377-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2935665377-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="2935665377-11">]</span><span class="p" data-group-id="2935665377-10">}</span><span class="p" data-group-id="2935665377-9">]</span><span class="p" data-group-id="2935665377-8">}</span><span class="p" data-group-id="2935665377-7">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2935665377-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9293862951-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9293862951-2">[</span><span class="p" data-group-id="9293862951-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9293862951-4">[</span><span class="p" data-group-id="9293862951-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9293862951-6">[</span><span class="ss">ch3</span><span class="p" data-group-id="9293862951-6">]</span><span class="p" data-group-id="9293862951-5">}</span><span class="p" data-group-id="9293862951-4">]</span><span class="p" data-group-id="9293862951-3">}</span><span class="p" data-group-id="9293862951-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9293862951-7">[</span><span class="p" data-group-id="9293862951-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9293862951-9">[</span><span class="p" data-group-id="9293862951-10">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9293862951-11">[</span><span class="ss">ch3</span><span class="p" data-group-id="9293862951-11">]</span><span class="p" data-group-id="9293862951-10">}</span><span class="p" data-group-id="9293862951-9">]</span><span class="p" data-group-id="9293862951-8">}</span><span class="p" data-group-id="9293862951-7">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9293862951-1">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="ss">ch_app</span><span class="p">.</span><span class="nc">appup</span><span class="p">:</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="2935665377-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2935665377-13">[</span><span class="p" data-group-id="2935665377-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2935665377-15">[</span><span class="p" data-group-id="2935665377-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2935665377-16">}</span><span class="p" data-group-id="2935665377-15">]</span><span class="p" data-group-id="2935665377-14">}</span><span class="p" data-group-id="2935665377-13">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2935665377-17">[</span><span class="p" data-group-id="2935665377-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2935665377-19">[</span><span class="p" data-group-id="2935665377-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2935665377-20">}</span><span class="p" data-group-id="2935665377-19">]</span><span class="p" data-group-id="2935665377-18">}</span><span class="p" data-group-id="2935665377-17">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2935665377-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0141324348-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0141324348-2">[</span><span class="p" data-group-id="0141324348-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="0141324348-4">[</span><span class="p" data-group-id="0141324348-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0141324348-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0141324348-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0141324348-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="0141324348-7">]</span><span class="p" data-group-id="0141324348-6">}</span><span class="p" data-group-id="0141324348-4">]</span><span class="p" data-group-id="0141324348-3">}</span><span class="p" data-group-id="0141324348-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0141324348-8">[</span><span class="p" data-group-id="0141324348-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="0141324348-10">[</span><span class="p" data-group-id="0141324348-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="0141324348-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0141324348-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0141324348-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="0141324348-13">]</span><span class="p" data-group-id="0141324348-12">}</span><span class="p" data-group-id="0141324348-10">]</span><span class="p" data-group-id="0141324348-9">}</span><span class="p" data-group-id="0141324348-8">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0141324348-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │ +</span><span class="p" data-group-id="9293862951-12">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9293862951-13">[</span><span class="p" data-group-id="9293862951-14">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9293862951-15">[</span><span class="p" data-group-id="9293862951-16">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9293862951-16">}</span><span class="p" data-group-id="9293862951-15">]</span><span class="p" data-group-id="9293862951-14">}</span><span class="p" data-group-id="9293862951-13">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9293862951-17">[</span><span class="p" data-group-id="9293862951-18">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9293862951-19">[</span><span class="p" data-group-id="9293862951-20">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9293862951-20">}</span><span class="p" data-group-id="9293862951-19">]</span><span class="p" data-group-id="9293862951-18">}</span><span class="p" data-group-id="9293862951-17">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9293862951-12">}</span><span class="p">.</span></code></pre><p>If instead <code class="inline">m1</code> and <code class="inline">ch3</code> belong to the same application, the <code class="inline">.appup</code> file can
│ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2654696368-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2654696368-2">[</span><span class="p" data-group-id="2654696368-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2654696368-4">[</span><span class="p" data-group-id="2654696368-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2654696368-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2654696368-6">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2654696368-7">[</span><span class="ss">ch3</span><span class="p" data-group-id="2654696368-7">]</span><span class="p" data-group-id="2654696368-6">}</span><span class="p" data-group-id="2654696368-4">]</span><span class="p" data-group-id="2654696368-3">}</span><span class="p" data-group-id="2654696368-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2654696368-8">[</span><span class="p" data-group-id="2654696368-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2654696368-10">[</span><span class="p" data-group-id="2654696368-11">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2654696368-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2654696368-12">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2654696368-13">[</span><span class="ss">ch3</span><span class="p" data-group-id="2654696368-13">]</span><span class="p" data-group-id="2654696368-12">}</span><span class="p" data-group-id="2654696368-10">]</span><span class="p" data-group-id="2654696368-9">}</span><span class="p" data-group-id="2654696368-8">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2654696368-1">}</span><span class="p">.</span></code></pre><p><code class="inline">m1</code> is dependent on <code class="inline">ch3</code> also when downgrading. <code class="inline">systools</code> knows the
│ │ │  difference between up- and downgrading and generates a correct <code class="inline">relup</code>, where
│ │ │  <code class="inline">ch3</code> is loaded before <code class="inline">m1</code> when upgrading, but <code class="inline">m1</code> is loaded before <code class="inline">ch3</code> when
│ │ │  downgrading.</p><p><a href="" id="spec"></a></p><h2 id="changing-code-for-a-special-process" class="section-heading">
│ │ │    <a href="#changing-code-for-a-special-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Code for a Special Process</span>
│ │ │  </h2>
│ │ │  <p>In this case, simple code replacement is not sufficient. When a new version of a
│ │ │  residence module for a special process is loaded, the process must make a fully
│ │ │  qualified call to its loop function to switch to the new code. Thus,
│ │ │  synchronized code replacement must be used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The name(s) of the user-defined residence module(s) must be listed in the
│ │ │  <code class="inline">Modules</code> part of the child specification for the special process. Otherwise
│ │ │  the release handler cannot find the process.</p></section><p><em>Example</em></p><p>Consider the example <code class="inline">ch4</code> in <a href="spec_proc.html#ex">sys and proc_lib</a>.
│ │ │ -When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2223914728-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2223914728-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2223914728-3">[</span><span class="p" data-group-id="2223914728-3">]</span><span class="p" data-group-id="2223914728-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2223914728-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="2223914728-4">]</span><span class="p" data-group-id="2223914728-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │ +When started by a supervisor, the child specification can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9959031922-1">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9959031922-2">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9959031922-3">[</span><span class="p" data-group-id="9959031922-3">]</span><span class="p" data-group-id="9959031922-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="ss">permanent</span><span class="p">,</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9959031922-4">[</span><span class="ss">ch4</span><span class="p" data-group-id="9959031922-4">]</span><span class="p" data-group-id="9959031922-1">}</span></code></pre><p>If <code class="inline">ch4</code> is part of the application <code class="inline">sp_app</code> and a new version of the module is
│ │ │  to be loaded when upgrading from version &quot;1&quot; to &quot;2&quot; of this application,
│ │ │ -<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1948879364-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1948879364-2">[</span><span class="p" data-group-id="1948879364-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1948879364-4">[</span><span class="p" data-group-id="1948879364-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1948879364-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1948879364-7">[</span><span class="p" data-group-id="1948879364-7">]</span><span class="p" data-group-id="1948879364-6">}</span><span class="p" data-group-id="1948879364-5">}</span><span class="p" data-group-id="1948879364-4">]</span><span class="p" data-group-id="1948879364-3">}</span><span class="p" data-group-id="1948879364-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1948879364-8">[</span><span class="p" data-group-id="1948879364-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1948879364-10">[</span><span class="p" data-group-id="1948879364-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1948879364-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1948879364-13">[</span><span class="p" data-group-id="1948879364-13">]</span><span class="p" data-group-id="1948879364-12">}</span><span class="p" data-group-id="1948879364-11">}</span><span class="p" data-group-id="1948879364-10">]</span><span class="p" data-group-id="1948879364-9">}</span><span class="p" data-group-id="1948879364-8">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1948879364-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │ +<code class="inline">sp_app.appup</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0584769303-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0584769303-2">[</span><span class="p" data-group-id="0584769303-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0584769303-4">[</span><span class="p" data-group-id="0584769303-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0584769303-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0584769303-7">[</span><span class="p" data-group-id="0584769303-7">]</span><span class="p" data-group-id="0584769303-6">}</span><span class="p" data-group-id="0584769303-5">}</span><span class="p" data-group-id="0584769303-4">]</span><span class="p" data-group-id="0584769303-3">}</span><span class="p" data-group-id="0584769303-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0584769303-8">[</span><span class="p" data-group-id="0584769303-9">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0584769303-10">[</span><span class="p" data-group-id="0584769303-11">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0584769303-12">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0584769303-13">[</span><span class="p" data-group-id="0584769303-13">]</span><span class="p" data-group-id="0584769303-12">}</span><span class="p" data-group-id="0584769303-11">}</span><span class="p" data-group-id="0584769303-10">]</span><span class="p" data-group-id="0584769303-9">}</span><span class="p" data-group-id="0584769303-8">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0584769303-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">update</code> instruction must contain the tuple <code class="inline">{advanced,Extra}</code>. The
│ │ │  instruction makes the special process call the callback function
│ │ │  <code class="inline">system_code_change/4</code>, a function the user must implement. The term <code class="inline">Extra</code>, in
│ │ │ -this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4837431736-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="4837431736-1">)</span><span class="p">.</span><span class="w">
│ │ │ +this case <code class="inline">[]</code>, is passed as is to <code class="inline">system_code_change/4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3196372997-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="3196372997-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4837431736-2">(</span><span class="p" data-group-id="4837431736-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="4837431736-3">]</span><span class="p" data-group-id="4837431736-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3196372997-2">(</span><span class="p" data-group-id="3196372997-3">[</span><span class="ss">system_code_change</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="3196372997-3">]</span><span class="p" data-group-id="3196372997-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_code_change</span><span class="p" data-group-id="4837431736-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="4837431736-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4837431736-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4837431736-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │ +</span><span class="nf">system_code_change</span><span class="p" data-group-id="3196372997-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Extra</span><span class="p" data-group-id="3196372997-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3196372997-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3196372997-5">}</span><span class="p">.</span></code></pre><ul><li>The first argument is the internal state <code class="inline">State</code>, passed from
│ │ │  function <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg(Request, From, Parent, Module, Deb, State)</code></a>, and called by the special
│ │ │  process when a system message is received. In <code class="inline">ch4</code>, the internal
│ │ │  state is the set of available channels <code class="inline">Chs</code>.</li><li>The second argument is the name of the module (<code class="inline">ch4</code>).</li><li>The third argument is <code class="inline">Vsn</code> or <code class="inline">{down,Vsn}</code>, as described for
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#c:code_change/3"><code class="inline">gen_server:code_change/3</code></a> in
│ │ │  <a href="appup_cookbook.html#code_change">Changing Internal State</a>.</li></ul><p>In this case, all arguments but the first are ignored and the function simply
│ │ │  returns the internal state again. This is enough if the code only has been
│ │ │  extended. If instead the internal state is changed (similar to the example in
│ │ │ @@ -271,85 +271,85 @@
│ │ │    <span class="text">Changing Properties</span>
│ │ │  </h3>
│ │ │  <p>Since the supervisor is to change its internal state, synchronized code
│ │ │  replacement is required. However, a special <code class="inline">update</code> instruction must be used.</p><p>First, the new version of the callback module must be loaded, both in the case
│ │ │  of upgrade and downgrade. Then the new return value of <code class="inline">init/1</code> can be checked
│ │ │  and the internal state be changed accordingly.</p><p>The following <code class="inline">upgrade</code> instruction is used for supervisors:</p><pre><code class="text">{update, Module, supervisor}</code></pre><p><em>Example</em></p><p>To change the restart strategy of <code class="inline">ch_sup</code> (from
│ │ │  <a href="sup_princ.html#ex">Supervisor Behaviour</a>) from <code class="inline">one_for_one</code> to <code class="inline">one_for_all</code>,
│ │ │ -change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8865734426-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="8865734426-1">)</span><span class="p">.</span><span class="w">
│ │ │ +change the callback function <code class="inline">init/1</code> in <code class="inline">ch_sup.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7767149314-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="7767149314-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8865734426-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8865734426-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8865734426-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8865734426-4">{</span><span class="p" data-group-id="8865734426-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8865734426-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8865734426-4">}</span><span class="p" data-group-id="8865734426-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3590866495-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3590866495-2">[</span><span class="p" data-group-id="3590866495-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3590866495-4">[</span><span class="p" data-group-id="3590866495-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3590866495-5">}</span><span class="p" data-group-id="3590866495-4">]</span><span class="p" data-group-id="3590866495-3">}</span><span class="p" data-group-id="3590866495-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3590866495-6">[</span><span class="p" data-group-id="3590866495-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3590866495-8">[</span><span class="p" data-group-id="3590866495-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3590866495-9">}</span><span class="p" data-group-id="3590866495-8">]</span><span class="p" data-group-id="3590866495-7">}</span><span class="p" data-group-id="3590866495-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3590866495-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7767149314-2">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7767149314-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7767149314-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7767149314-4">{</span><span class="p" data-group-id="7767149314-5">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_all</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7767149314-5">}</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7767149314-4">}</span><span class="p" data-group-id="7767149314-3">}</span><span class="p">.</span></code></pre><p>The file <code class="inline">ch_app.appup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0880068893-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0880068893-2">[</span><span class="p" data-group-id="0880068893-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0880068893-4">[</span><span class="p" data-group-id="0880068893-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="0880068893-5">}</span><span class="p" data-group-id="0880068893-4">]</span><span class="p" data-group-id="0880068893-3">}</span><span class="p" data-group-id="0880068893-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0880068893-6">[</span><span class="p" data-group-id="0880068893-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0880068893-8">[</span><span class="p" data-group-id="0880068893-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="0880068893-9">}</span><span class="p" data-group-id="0880068893-8">]</span><span class="p" data-group-id="0880068893-7">}</span><span class="p" data-group-id="0880068893-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0880068893-1">}</span><span class="p">.</span></code></pre><h3 id="changing-child-specifications" class="section-heading">
│ │ │    <a href="#changing-child-specifications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Child Specifications</span>
│ │ │  </h3>
│ │ │  <p>The instruction, and thus the <code class="inline">.appup</code> file, when changing an existing child
│ │ │ -specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3035461627-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3035461627-2">[</span><span class="p" data-group-id="3035461627-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3035461627-4">[</span><span class="p" data-group-id="3035461627-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3035461627-5">}</span><span class="p" data-group-id="3035461627-4">]</span><span class="p" data-group-id="3035461627-3">}</span><span class="p" data-group-id="3035461627-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3035461627-6">[</span><span class="p" data-group-id="3035461627-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3035461627-8">[</span><span class="p" data-group-id="3035461627-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3035461627-9">}</span><span class="p" data-group-id="3035461627-8">]</span><span class="p" data-group-id="3035461627-7">}</span><span class="p" data-group-id="3035461627-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3035461627-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │ +specification, is the same as when changing properties as described earlier:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9611683812-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9611683812-2">[</span><span class="p" data-group-id="9611683812-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9611683812-4">[</span><span class="p" data-group-id="9611683812-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9611683812-5">}</span><span class="p" data-group-id="9611683812-4">]</span><span class="p" data-group-id="9611683812-3">}</span><span class="p" data-group-id="9611683812-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9611683812-6">[</span><span class="p" data-group-id="9611683812-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9611683812-8">[</span><span class="p" data-group-id="9611683812-9">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9611683812-9">}</span><span class="p" data-group-id="9611683812-8">]</span><span class="p" data-group-id="9611683812-7">}</span><span class="p" data-group-id="9611683812-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9611683812-1">}</span><span class="p">.</span></code></pre><p>The changes do not affect existing child processes. For example, changing the
│ │ │  start function only specifies how the child process is to be restarted, if
│ │ │  needed later on.</p><p>The id of the child specification cannot be changed.</p><p>Changing the <code class="inline">Modules</code> field of the child specification can affect the release
│ │ │  handling process itself, as this field is used to identify which processes are
│ │ │  affected when doing a synchronized code replacement.</p><p><a href="" id="sup_add"></a></p><h3 id="adding-and-deleting-child-processes" class="section-heading">
│ │ │    <a href="#adding-and-deleting-child-processes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding and Deleting Child Processes</span>
│ │ │  </h3>
│ │ │  <p>As stated earlier, changing child specifications does not affect existing child
│ │ │  processes. New child specifications are automatically added, but not deleted.
│ │ │  Child processes are not automatically started or terminated, this must be done
│ │ │  using <code class="inline">apply</code> instructions.</p><p><em>Example</em></p><p>Assume a new child process <code class="inline">m1</code> is to be added to <code class="inline">ch_sup</code> when
│ │ │  upgrading <code class="inline">ch_app</code> from &quot;1&quot; to &quot;2&quot;. This means <code class="inline">m1</code> is to be deleted when
│ │ │ -downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9376988157-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9376988157-2">[</span><span class="p" data-group-id="9376988157-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="9376988157-4">[</span><span class="p" data-group-id="9376988157-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9376988157-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9376988157-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376988157-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376988157-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9376988157-8">]</span><span class="p" data-group-id="9376988157-7">}</span><span class="p" data-group-id="9376988157-6">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="9376988157-4">]</span><span class="p" data-group-id="9376988157-3">}</span><span class="p" data-group-id="9376988157-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9376988157-9">[</span><span class="p" data-group-id="9376988157-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="9376988157-11">[</span><span class="p" data-group-id="9376988157-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376988157-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376988157-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9376988157-14">]</span><span class="p" data-group-id="9376988157-13">}</span><span class="p" data-group-id="9376988157-12">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9376988157-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376988157-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9376988157-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="9376988157-17">]</span><span class="p" data-group-id="9376988157-16">}</span><span class="p" data-group-id="9376988157-15">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9376988157-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="9376988157-18">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="9376988157-11">]</span><span class="p" data-group-id="9376988157-10">}</span><span class="p" data-group-id="9376988157-9">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9376988157-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │ +downgrading from &quot;2&quot; to &quot;1&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7831549122-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7831549122-2">[</span><span class="p" data-group-id="7831549122-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7831549122-4">[</span><span class="p" data-group-id="7831549122-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="7831549122-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7831549122-6">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831549122-7">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831549122-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="7831549122-8">]</span><span class="p" data-group-id="7831549122-7">}</span><span class="p" data-group-id="7831549122-6">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7831549122-4">]</span><span class="p" data-group-id="7831549122-3">}</span><span class="p" data-group-id="7831549122-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7831549122-9">[</span><span class="p" data-group-id="7831549122-10">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7831549122-11">[</span><span class="p" data-group-id="7831549122-12">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831549122-13">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831549122-14">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="7831549122-14">]</span><span class="p" data-group-id="7831549122-13">}</span><span class="p" data-group-id="7831549122-12">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7831549122-15">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831549122-16">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831549122-17">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="7831549122-17">]</span><span class="p" data-group-id="7831549122-16">}</span><span class="p" data-group-id="7831549122-15">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7831549122-18">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="7831549122-18">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7831549122-11">]</span><span class="p" data-group-id="7831549122-10">}</span><span class="p" data-group-id="7831549122-9">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7831549122-1">}</span><span class="p">.</span></code></pre><p>The order of the instructions is important.</p><p>The supervisor must be registered as <code class="inline">ch_sup</code> for the script to work. If the
│ │ │  supervisor is not registered, it cannot be accessed directly from the script.
│ │ │  Instead a help function that finds the pid of the supervisor and calls
│ │ │  <code class="inline">supervisor:restart_child</code>, and so on, must be written. This function is then to
│ │ │  be called from the script using the <code class="inline">apply</code> instruction.</p><p>If the module <code class="inline">m1</code> is introduced in version &quot;2&quot; of <code class="inline">ch_app</code>, it must also be
│ │ │ -loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4270786633-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4270786633-2">[</span><span class="p" data-group-id="4270786633-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4270786633-4">[</span><span class="p" data-group-id="4270786633-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4270786633-5">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4270786633-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4270786633-6">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4270786633-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4270786633-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4270786633-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4270786633-9">]</span><span class="p" data-group-id="4270786633-8">}</span><span class="p" data-group-id="4270786633-7">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4270786633-4">]</span><span class="p" data-group-id="4270786633-3">}</span><span class="p" data-group-id="4270786633-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="4270786633-10">[</span><span class="p" data-group-id="4270786633-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4270786633-12">[</span><span class="p" data-group-id="4270786633-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4270786633-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4270786633-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4270786633-15">]</span><span class="p" data-group-id="4270786633-14">}</span><span class="p" data-group-id="4270786633-13">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4270786633-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4270786633-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4270786633-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4270786633-18">]</span><span class="p" data-group-id="4270786633-17">}</span><span class="p" data-group-id="4270786633-16">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4270786633-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4270786633-19">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4270786633-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4270786633-20">}</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4270786633-12">]</span><span class="p" data-group-id="4270786633-11">}</span><span class="p" data-group-id="4270786633-10">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4270786633-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │ +loaded when upgrading and deleted when downgrading:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4676028368-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4676028368-2">[</span><span class="p" data-group-id="4676028368-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="4676028368-4">[</span><span class="p" data-group-id="4676028368-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4676028368-5">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4676028368-6">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4676028368-6">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4676028368-7">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4676028368-8">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">restart_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4676028368-9">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4676028368-9">]</span><span class="p" data-group-id="4676028368-8">}</span><span class="p" data-group-id="4676028368-7">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="4676028368-4">]</span><span class="p" data-group-id="4676028368-3">}</span><span class="p" data-group-id="4676028368-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4676028368-10">[</span><span class="p" data-group-id="4676028368-11">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="4676028368-12">[</span><span class="p" data-group-id="4676028368-13">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4676028368-14">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4676028368-15">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4676028368-15">]</span><span class="p" data-group-id="4676028368-14">}</span><span class="p" data-group-id="4676028368-13">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4676028368-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4676028368-17">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="w"> </span><span class="ss">delete_child</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4676028368-18">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4676028368-18">]</span><span class="p" data-group-id="4676028368-17">}</span><span class="p" data-group-id="4676028368-16">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4676028368-19">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4676028368-19">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4676028368-20">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m1</span><span class="p" data-group-id="4676028368-20">}</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="4676028368-12">]</span><span class="p" data-group-id="4676028368-11">}</span><span class="p" data-group-id="4676028368-10">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4676028368-1">}</span><span class="p">.</span></code></pre><p>As stated earlier, the order of the instructions is important. When upgrading,
│ │ │  <code class="inline">m1</code> must be loaded, and the supervisor child specification changed, before the
│ │ │  new child process can be started. When downgrading, the child process must be
│ │ │  terminated before the child specification is changed and the module is deleted.</p><h2 id="adding-or-deleting-a-module" class="section-heading">
│ │ │    <a href="#adding-or-deleting-a-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding or Deleting a Module</span>
│ │ │  </h2>
│ │ │ -<p>_Example</p><p>_ A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7750238821-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7750238821-2">[</span><span class="p" data-group-id="7750238821-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7750238821-4">[</span><span class="p" data-group-id="7750238821-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="7750238821-5">}</span><span class="p" data-group-id="7750238821-4">]</span><span class="p" data-group-id="7750238821-3">}</span><span class="p" data-group-id="7750238821-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7750238821-6">[</span><span class="p" data-group-id="7750238821-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7750238821-8">[</span><span class="p" data-group-id="7750238821-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="7750238821-9">}</span><span class="p" data-group-id="7750238821-8">]</span><span class="p" data-group-id="7750238821-7">}</span><span class="p" data-group-id="7750238821-6">]</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │ +<p>_Example</p><p>_ A new functional module <code class="inline">m</code> is added to <code class="inline">ch_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3957358168-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3957358168-2">[</span><span class="p" data-group-id="3957358168-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3957358168-4">[</span><span class="p" data-group-id="3957358168-5">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="3957358168-5">}</span><span class="p" data-group-id="3957358168-4">]</span><span class="p" data-group-id="3957358168-3">}</span><span class="p" data-group-id="3957358168-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3957358168-6">[</span><span class="p" data-group-id="3957358168-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3957358168-8">[</span><span class="p" data-group-id="3957358168-9">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="ss">m</span><span class="p" data-group-id="3957358168-9">}</span><span class="p" data-group-id="3957358168-8">]</span><span class="p" data-group-id="3957358168-7">}</span><span class="p" data-group-id="3957358168-6">]</span></code></pre><h2 id="starting-or-terminating-a-process" class="section-heading">
│ │ │    <a href="#starting-or-terminating-a-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting or Terminating a Process</span>
│ │ │  </h2>
│ │ │  <p>In a system structured according to the OTP design principles, any process would
│ │ │  be a child process belonging to a supervisor, see
│ │ │ @@ -369,29 +369,29 @@
│ │ │    <span class="text">Restarting an Application</span>
│ │ │  </h2>
│ │ │  <p>Restarting an application is useful when a change is too complicated to be made
│ │ │  without restarting the processes, for example, if the supervisor hierarchy has
│ │ │  been restructured.</p><p><em>Example</em></p><p>When adding a child <code class="inline">m1</code> to <code class="inline">ch_sup</code>, as in
│ │ │  <a href="appup_cookbook.html#sup_add">Adding and Deleting Child Processes</a> in Changing a
│ │ │  Supervisor, an alternative to updating the supervisor is to restart the entire
│ │ │ -application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3936655245-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3936655245-2">[</span><span class="p" data-group-id="3936655245-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3936655245-4">[</span><span class="p" data-group-id="3936655245-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="3936655245-5">}</span><span class="p" data-group-id="3936655245-4">]</span><span class="p" data-group-id="3936655245-3">}</span><span class="p" data-group-id="3936655245-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3936655245-6">[</span><span class="p" data-group-id="3936655245-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3936655245-8">[</span><span class="p" data-group-id="3936655245-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="3936655245-9">}</span><span class="p" data-group-id="3936655245-8">]</span><span class="p" data-group-id="3936655245-7">}</span><span class="p" data-group-id="3936655245-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3936655245-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │ +application:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5589903386-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5589903386-2">[</span><span class="p" data-group-id="5589903386-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5589903386-4">[</span><span class="p" data-group-id="5589903386-5">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="5589903386-5">}</span><span class="p" data-group-id="5589903386-4">]</span><span class="p" data-group-id="5589903386-3">}</span><span class="p" data-group-id="5589903386-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5589903386-6">[</span><span class="p" data-group-id="5589903386-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5589903386-8">[</span><span class="p" data-group-id="5589903386-9">{</span><span class="ss">restart_application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p" data-group-id="5589903386-9">}</span><span class="p" data-group-id="5589903386-8">]</span><span class="p" data-group-id="5589903386-7">}</span><span class="p" data-group-id="5589903386-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5589903386-1">}</span><span class="p">.</span></code></pre><p><a href="" id="app_spec"></a></p><h2 id="changing-an-application-specification" class="section-heading">
│ │ │    <a href="#changing-an-application-specification" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing an Application Specification</span>
│ │ │  </h2>
│ │ │  <p>When installing a release, the application specifications are automatically
│ │ │  updated before evaluating the <code class="inline">relup</code> script. Thus, no instructions are needed
│ │ │ -in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7400531122-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7400531122-2">[</span><span class="p" data-group-id="7400531122-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7400531122-4">[</span><span class="p" data-group-id="7400531122-4">]</span><span class="p" data-group-id="7400531122-3">}</span><span class="p" data-group-id="7400531122-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7400531122-5">[</span><span class="p" data-group-id="7400531122-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7400531122-7">[</span><span class="p" data-group-id="7400531122-7">]</span><span class="p" data-group-id="7400531122-6">}</span><span class="p" data-group-id="7400531122-5">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7400531122-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │ +in the <code class="inline">.appup</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9087253476-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9087253476-2">[</span><span class="p" data-group-id="9087253476-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9087253476-4">[</span><span class="p" data-group-id="9087253476-4">]</span><span class="p" data-group-id="9087253476-3">}</span><span class="p" data-group-id="9087253476-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9087253476-5">[</span><span class="p" data-group-id="9087253476-6">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9087253476-7">[</span><span class="p" data-group-id="9087253476-7">]</span><span class="p" data-group-id="9087253476-6">}</span><span class="p" data-group-id="9087253476-5">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9087253476-1">}</span><span class="p">.</span></code></pre><h2 id="changing-application-configuration" class="section-heading">
│ │ │    <a href="#changing-application-configuration" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Application Configuration</span>
│ │ │  </h2>
│ │ │  <p>Changing an application configuration by updating the <code class="inline">env</code> key in the <code class="inline">.app</code>
│ │ │  file is an instance of changing an application specification, see the previous
│ │ │ @@ -406,26 +406,26 @@
│ │ │  applications apply to primary applications only. There are no corresponding
│ │ │  instructions for included applications. However, since an included application
│ │ │  is really a supervision tree with a topmost supervisor, started as a child
│ │ │  process to a supervisor in the including application, a <code class="inline">.relup</code> file can be
│ │ │  manually created.</p><p><em>Example</em></p><p>Assume there is a release containing an application <code class="inline">prim_app</code>, which
│ │ │  have a supervisor <code class="inline">prim_sup</code> in its supervision tree.</p><p>In a new version of the release, the application <code class="inline">ch_app</code> is to be included in
│ │ │  <code class="inline">prim_app</code>. That is, its topmost supervisor <code class="inline">ch_sup</code> is to be started as a child
│ │ │ -process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8345096366-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8345096366-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8345096366-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8345096366-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="8345096366-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="8345096366-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8345096366-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="8345096366-7">[</span><span class="p" data-group-id="8345096366-7">]</span><span class="p" data-group-id="8345096366-6">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="8345096366-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="8345096366-8">]</span><span class="p" data-group-id="8345096366-5">}</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8345096366-4">]</span><span class="p" data-group-id="8345096366-3">}</span><span class="p" data-group-id="8345096366-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0116755819-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0116755819-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0116755819-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="0116755819-3">}</span><span class="p">,</span><span class="w">
│ │ │ +process to <code class="inline">prim_sup</code>.</p><p>The workflow is as follows:</p><p><em>Step 1)</em> Edit the code for <code class="inline">prim_sup</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4620788092-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4620788092-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4620788092-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4620788092-3">{</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="ss">supervisor</span><span class="w"> </span><span class="ss">flags</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="4620788092-4">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="4620788092-5">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4620788092-6">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="4620788092-7">[</span><span class="p" data-group-id="4620788092-7">]</span><span class="p" data-group-id="4620788092-6">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="ss">permanent</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="ss">supervisor</span><span class="p">,</span><span class="p" data-group-id="4620788092-8">[</span><span class="ss">ch_sup</span><span class="p" data-group-id="4620788092-8">]</span><span class="p" data-group-id="4620788092-5">}</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4620788092-4">]</span><span class="p" data-group-id="4620788092-3">}</span><span class="p" data-group-id="4620788092-2">}</span><span class="p">.</span></code></pre><p><em>Step 2)</em> Edit the <code class="inline">.app</code> file for <code class="inline">prim_app</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4239355437-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4239355437-2">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4239355437-3">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="4239355437-3">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0116755819-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0116755819-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="0116755819-5">]</span><span class="p" data-group-id="0116755819-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4239355437-4">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4239355437-5">[</span><span class="ss">ch_app</span><span class="p" data-group-id="4239355437-5">]</span><span class="p" data-group-id="4239355437-4">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0116755819-2">]</span><span class="p" data-group-id="0116755819-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │ + </span><span class="p" data-group-id="4239355437-2">]</span><span class="p" data-group-id="4239355437-1">}</span><span class="p">.</span></code></pre><p><em>Step 3)</em> Create a new <code class="inline">.rel</code> file, including <code class="inline">ch_app</code>:</p><pre><code class="text">{release,
│ │ │   ...,
│ │ │   [...,
│ │ │    {prim_app, &quot;2&quot;},
│ │ │    {ch_app, &quot;1&quot;}]}.</code></pre><p>The included application can be started in two ways. This is described in the
│ │ │  next two sections.</p><h3 id="application-restart" class="section-heading">
│ │ │    <a href="#application-restart" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -480,74 +480,74 @@
│ │ │  <p><em>Step 4b)</em> Another way to start the included application (or stop it in the case
│ │ │  of downgrade) is by combining instructions for adding and removing child
│ │ │  processes to/from <code class="inline">prim_sup</code> with instructions for loading/unloading all
│ │ │  <code class="inline">ch_app</code> code and its application specification.</p><p>Again, the <code class="inline">.relup</code> file is created manually, either from scratch or by editing a
│ │ │  generated version. Load all code for <code class="inline">ch_app</code> first, and also load the
│ │ │  application specification, before <code class="inline">prim_sup</code> is updated. When downgrading,
│ │ │  <code class="inline">prim_sup</code> is to updated first, before the code for <code class="inline">ch_app</code> and its application
│ │ │ -specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1489324361-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1489324361-2">[</span><span class="p" data-group-id="1489324361-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1489324361-4">[</span><span class="p" data-group-id="1489324361-4">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1489324361-5">[</span><span class="p" data-group-id="1489324361-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="1489324361-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="1489324361-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="1489324361-8">]</span><span class="p" data-group-id="1489324361-7">}</span><span class="p" data-group-id="1489324361-6">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="1489324361-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="1489324361-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="1489324361-11">]</span><span class="p" data-group-id="1489324361-10">}</span><span class="p" data-group-id="1489324361-9">}</span><span class="p">,</span><span class="w">
│ │ │ +specification are unloaded.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7636378676-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7636378676-2">[</span><span class="p" data-group-id="7636378676-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7636378676-4">[</span><span class="p" data-group-id="7636378676-4">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7636378676-5">[</span><span class="p" data-group-id="7636378676-6">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="7636378676-7">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="7636378676-8">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="7636378676-8">]</span><span class="p" data-group-id="7636378676-7">}</span><span class="p" data-group-id="7636378676-6">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-9">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="7636378676-10">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="p" data-group-id="7636378676-11">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7636378676-11">]</span><span class="p" data-group-id="7636378676-10">}</span><span class="p" data-group-id="7636378676-9">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="1489324361-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="1489324361-13">}</span><span class="p" data-group-id="1489324361-12">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="1489324361-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="1489324361-15">}</span><span class="p" data-group-id="1489324361-14">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="1489324361-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="1489324361-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="1489324361-18">]</span><span class="p" data-group-id="1489324361-17">}</span><span class="p" data-group-id="1489324361-16">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="1489324361-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="1489324361-20">]</span><span class="p" data-group-id="1489324361-19">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="1489324361-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="1489324361-22">}</span><span class="p" data-group-id="1489324361-21">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="1489324361-24">[</span><span class="p" data-group-id="1489324361-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="1489324361-26">[</span><span class="p" data-group-id="1489324361-26">]</span><span class="p" data-group-id="1489324361-25">}</span><span class="p" data-group-id="1489324361-24">]</span><span class="p" data-group-id="1489324361-23">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="1489324361-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="1489324361-28">]</span><span class="p" data-group-id="1489324361-27">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="1489324361-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="1489324361-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="1489324361-31">]</span><span class="p" data-group-id="1489324361-30">}</span><span class="p" data-group-id="1489324361-29">}</span><span class="p" data-group-id="1489324361-5">]</span><span class="p" data-group-id="1489324361-3">}</span><span class="p" data-group-id="1489324361-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1489324361-32">[</span><span class="p" data-group-id="1489324361-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1489324361-34">[</span><span class="p" data-group-id="1489324361-34">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1489324361-35">[</span><span class="p" data-group-id="1489324361-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="1489324361-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="1489324361-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="1489324361-38">]</span><span class="p" data-group-id="1489324361-37">}</span><span class="p" data-group-id="1489324361-36">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-12">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7636378676-13">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7636378676-13">}</span><span class="p" data-group-id="7636378676-12">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-14">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7636378676-15">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7636378676-15">}</span><span class="p" data-group-id="7636378676-14">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-16">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7636378676-17">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7636378676-18">[</span><span class="ss">ch_app</span><span class="p" data-group-id="7636378676-18">]</span><span class="p" data-group-id="7636378676-17">}</span><span class="p" data-group-id="7636378676-16">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-19">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="7636378676-20">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7636378676-20">]</span><span class="p" data-group-id="7636378676-19">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-21">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7636378676-22">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7636378676-22">}</span><span class="p" data-group-id="7636378676-21">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-23">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">up</span><span class="p">,</span><span class="p" data-group-id="7636378676-24">[</span><span class="p" data-group-id="7636378676-25">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="7636378676-26">[</span><span class="p" data-group-id="7636378676-26">]</span><span class="p" data-group-id="7636378676-25">}</span><span class="p" data-group-id="7636378676-24">]</span><span class="p" data-group-id="7636378676-23">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-27">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="7636378676-28">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7636378676-28">]</span><span class="p" data-group-id="7636378676-27">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-29">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7636378676-30">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">restart_child</span><span class="p">,</span><span class="p" data-group-id="7636378676-31">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="7636378676-31">]</span><span class="p" data-group-id="7636378676-30">}</span><span class="p" data-group-id="7636378676-29">}</span><span class="p" data-group-id="7636378676-5">]</span><span class="p" data-group-id="7636378676-3">}</span><span class="p" data-group-id="7636378676-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7636378676-32">[</span><span class="p" data-group-id="7636378676-33">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7636378676-34">[</span><span class="p" data-group-id="7636378676-34">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="7636378676-35">[</span><span class="p" data-group-id="7636378676-36">{</span><span class="ss">load_object_code</span><span class="p">,</span><span class="p" data-group-id="7636378676-37">{</span><span class="ss">prim_app</span><span class="p">,</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="p" data-group-id="7636378676-38">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7636378676-38">]</span><span class="p" data-group-id="7636378676-37">}</span><span class="p" data-group-id="7636378676-36">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">point_of_no_return</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="1489324361-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="1489324361-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="1489324361-41">]</span><span class="p" data-group-id="1489324361-40">}</span><span class="p" data-group-id="1489324361-39">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="1489324361-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="1489324361-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="1489324361-44">]</span><span class="p" data-group-id="1489324361-43">}</span><span class="p" data-group-id="1489324361-42">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="1489324361-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="1489324361-46">]</span><span class="p" data-group-id="1489324361-45">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="1489324361-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="1489324361-48">}</span><span class="p" data-group-id="1489324361-47">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="1489324361-50">[</span><span class="p" data-group-id="1489324361-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="1489324361-52">[</span><span class="p" data-group-id="1489324361-52">]</span><span class="p" data-group-id="1489324361-51">}</span><span class="p" data-group-id="1489324361-50">]</span><span class="p" data-group-id="1489324361-49">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="1489324361-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="1489324361-54">]</span><span class="p" data-group-id="1489324361-53">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="1489324361-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="1489324361-56">}</span><span class="p" data-group-id="1489324361-55">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="1489324361-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="1489324361-58">}</span><span class="p" data-group-id="1489324361-57">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="1489324361-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="1489324361-60">]</span><span class="p" data-group-id="1489324361-59">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1489324361-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="1489324361-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="1489324361-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="1489324361-63">]</span><span class="p" data-group-id="1489324361-62">}</span><span class="p" data-group-id="1489324361-61">}</span><span class="p" data-group-id="1489324361-35">]</span><span class="p" data-group-id="1489324361-33">}</span><span class="p" data-group-id="1489324361-32">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1489324361-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │ +    </span><span class="p" data-group-id="7636378676-39">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7636378676-40">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">terminate_child</span><span class="p">,</span><span class="p" data-group-id="7636378676-41">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="7636378676-41">]</span><span class="p" data-group-id="7636378676-40">}</span><span class="p" data-group-id="7636378676-39">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-42">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7636378676-43">{</span><span class="ss">supervisor</span><span class="p">,</span><span class="ss">delete_child</span><span class="p">,</span><span class="p" data-group-id="7636378676-44">[</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">ch_sup</span><span class="p" data-group-id="7636378676-44">]</span><span class="p" data-group-id="7636378676-43">}</span><span class="p" data-group-id="7636378676-42">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-45">{</span><span class="ss">suspend</span><span class="p">,</span><span class="p" data-group-id="7636378676-46">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7636378676-46">]</span><span class="p" data-group-id="7636378676-45">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-47">{</span><span class="ss">load</span><span class="p">,</span><span class="p" data-group-id="7636378676-48">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7636378676-48">}</span><span class="p" data-group-id="7636378676-47">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-49">{</span><span class="ss">code_change</span><span class="p">,</span><span class="ss">down</span><span class="p">,</span><span class="p" data-group-id="7636378676-50">[</span><span class="p" data-group-id="7636378676-51">{</span><span class="ss">prim_sup</span><span class="p">,</span><span class="p" data-group-id="7636378676-52">[</span><span class="p" data-group-id="7636378676-52">]</span><span class="p" data-group-id="7636378676-51">}</span><span class="p" data-group-id="7636378676-50">]</span><span class="p" data-group-id="7636378676-49">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-53">{</span><span class="ss">resume</span><span class="p">,</span><span class="p" data-group-id="7636378676-54">[</span><span class="ss">prim_sup</span><span class="p" data-group-id="7636378676-54">]</span><span class="p" data-group-id="7636378676-53">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-55">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="7636378676-56">{</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7636378676-56">}</span><span class="p" data-group-id="7636378676-55">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-57">{</span><span class="ss">remove</span><span class="p">,</span><span class="p" data-group-id="7636378676-58">{</span><span class="ss">ch3</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p">,</span><span class="ss">brutal_purge</span><span class="p" data-group-id="7636378676-58">}</span><span class="p" data-group-id="7636378676-57">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-59">{</span><span class="ss">purge</span><span class="p">,</span><span class="p" data-group-id="7636378676-60">[</span><span class="ss">ch_sup</span><span class="p">,</span><span class="ss">ch3</span><span class="p" data-group-id="7636378676-60">]</span><span class="p" data-group-id="7636378676-59">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7636378676-61">{</span><span class="nb">apply</span><span class="p">,</span><span class="p" data-group-id="7636378676-62">{</span><span class="ss">application</span><span class="p">,</span><span class="ss">unload</span><span class="p">,</span><span class="p" data-group-id="7636378676-63">[</span><span class="ss">ch_app</span><span class="p" data-group-id="7636378676-63">]</span><span class="p" data-group-id="7636378676-62">}</span><span class="p" data-group-id="7636378676-61">}</span><span class="p" data-group-id="7636378676-35">]</span><span class="p" data-group-id="7636378676-33">}</span><span class="p" data-group-id="7636378676-32">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7636378676-1">}</span><span class="p">.</span></code></pre><h2 id="changing-non-erlang-code" class="section-heading">
│ │ │    <a href="#changing-non-erlang-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Changing Non-Erlang Code</span>
│ │ │  </h2>
│ │ │  <p>Changing code for a program written in another programming language than Erlang,
│ │ │  for example, a port program, is application-dependent and OTP provides no
│ │ │  special support.</p><p><em>Example</em></p><p>When changing code for a port program, assume that the Erlang process
│ │ │  controlling the port is a <code class="inline">gen_server</code> <code class="inline">portc</code> and that the port is opened in
│ │ │ -the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2107742848-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2107742848-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the callback function <code class="inline">init/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0462891411-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0462891411-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="2107742848-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="2107742848-3">(</span><span class="n">App</span><span class="p" data-group-id="2107742848-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="2107742848-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2107742848-4">(</span><span class="p" data-group-id="2107742848-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="2107742848-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2107742848-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2107742848-6">]</span><span class="p" data-group-id="2107742848-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="0462891411-2">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="0462891411-3">(</span><span class="n">App</span><span class="p" data-group-id="0462891411-3">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="0462891411-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0462891411-4">(</span><span class="p" data-group-id="0462891411-5">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="0462891411-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0462891411-6">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0462891411-6">]</span><span class="p" data-group-id="0462891411-4">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2107742848-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="2107742848-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2107742848-8">}</span><span class="p" data-group-id="2107742848-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │ +    </span><span class="p" data-group-id="0462891411-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0462891411-8">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0462891411-8">}</span><span class="p" data-group-id="0462891411-7">}</span><span class="p">.</span></code></pre><p>If the port program is to be updated, the code for the <code class="inline">gen_server</code> can be
│ │ │  extended with a <code class="inline">code_change/3</code> function, which closes the old port and opens a
│ │ │  new port. (If necessary, the <code class="inline">gen_server</code> can first request data that must be
│ │ │ -saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="9425830311-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="9425830311-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +saved from the port program and pass this data to the new port):</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="0779982320-1">(</span><span class="p">_</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="ss">port</span><span class="p" data-group-id="0779982320-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">close</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9425830311-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="9425830311-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0779982320-2">{</span><span class="n">Port</span><span class="p">,</span><span class="ss">close</span><span class="p" data-group-id="0779982320-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="9425830311-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="9425830311-4">(</span><span class="n">App</span><span class="p" data-group-id="9425830311-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="9425830311-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9425830311-5">(</span><span class="p" data-group-id="9425830311-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="9425830311-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9425830311-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9425830311-7">]</span><span class="p" data-group-id="9425830311-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9425830311-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="9425830311-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9425830311-9">}</span><span class="p" data-group-id="9425830311-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ -file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7194823190-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7194823190-2">[</span><span class="p" data-group-id="7194823190-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7194823190-4">[</span><span class="p" data-group-id="7194823190-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7194823190-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="7194823190-6">}</span><span class="p" data-group-id="7194823190-5">}</span><span class="p" data-group-id="7194823190-4">]</span><span class="p" data-group-id="7194823190-3">}</span><span class="p" data-group-id="7194823190-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7194823190-7">[</span><span class="p" data-group-id="7194823190-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7194823190-9">[</span><span class="p" data-group-id="7194823190-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7194823190-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="7194823190-11">}</span><span class="p" data-group-id="7194823190-10">}</span><span class="p" data-group-id="7194823190-9">]</span><span class="p" data-group-id="7194823190-8">}</span><span class="p" data-group-id="7194823190-7">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7194823190-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ -the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="1568716624-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1568716624-2">[</span><span class="p" data-group-id="1568716624-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="1568716624-4">[</span><span class="ss">priv</span><span class="p" data-group-id="1568716624-4">]</span><span class="p" data-group-id="1568716624-3">}</span><span class="p" data-group-id="1568716624-2">]</span><span class="p" data-group-id="1568716624-1">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="n">PortPrg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="0779982320-3">(</span><span class="nc">code</span><span class="p">:</span><span class="nf">priv_dir</span><span class="p" data-group-id="0779982320-4">(</span><span class="n">App</span><span class="p" data-group-id="0779982320-4">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;portc&quot;</span><span class="p" data-group-id="0779982320-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0779982320-5">(</span><span class="p" data-group-id="0779982320-6">{</span><span class="nb">spawn</span><span class="p">,</span><span class="n">PortPrg</span><span class="p" data-group-id="0779982320-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0779982320-7">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0779982320-7">]</span><span class="p" data-group-id="0779982320-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0779982320-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0779982320-9">{</span><span class="ss">port</span><span class="o">=</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0779982320-9">}</span><span class="p" data-group-id="0779982320-8">}</span><span class="p">.</span></code></pre><p>Update the application version number in the <code class="inline">.app</code> file and write an <code class="inline">.appup</code>
│ │ │ +file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9235663343-1">[</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9235663343-2">[</span><span class="p" data-group-id="9235663343-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9235663343-4">[</span><span class="p" data-group-id="9235663343-5">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9235663343-6">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="9235663343-6">}</span><span class="p" data-group-id="9235663343-5">}</span><span class="p" data-group-id="9235663343-4">]</span><span class="p" data-group-id="9235663343-3">}</span><span class="p" data-group-id="9235663343-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="9235663343-7">[</span><span class="p" data-group-id="9235663343-8">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9235663343-9">[</span><span class="p" data-group-id="9235663343-10">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="ss">portc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9235663343-11">{</span><span class="ss">advanced</span><span class="p">,</span><span class="ss">port</span><span class="p" data-group-id="9235663343-11">}</span><span class="p" data-group-id="9235663343-10">}</span><span class="p" data-group-id="9235663343-9">]</span><span class="p" data-group-id="9235663343-8">}</span><span class="p" data-group-id="9235663343-7">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9235663343-1">]</span><span class="p">.</span></code></pre><p>Ensure that the <code class="inline">priv</code> directory, where the C program is located, is included in
│ │ │ +the new release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="6794623338-1">(</span><span class="s">&quot;my_release&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6794623338-2">[</span><span class="p" data-group-id="6794623338-3">{</span><span class="ss">dirs</span><span class="p">,</span><span class="p" data-group-id="6794623338-4">[</span><span class="ss">priv</span><span class="p" data-group-id="6794623338-4">]</span><span class="p" data-group-id="6794623338-3">}</span><span class="p" data-group-id="6794623338-2">]</span><span class="p" data-group-id="6794623338-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="runtime-system-restart-and-upgrade" class="section-heading">
│ │ │    <a href="#runtime-system-restart-and-upgrade" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Runtime System Restart and Upgrade</span>
│ │ │  </h2>
│ │ │  <p>Two upgrade instructions restart the runtime system:</p><ul><li><p><code class="inline">restart_new_emulator</code></p><p>Intended when ERTS, Kernel, STDLIB, or SASL is upgraded. It is automatically
│ │ │ @@ -555,22 +555,22 @@
│ │ │  executed before all other upgrade instructions. For more information about
│ │ │  this instruction, see restart_new_emulator (Low-Level) in
│ │ │  <a href="release_handling.html#restart_new_emulator_instr">Release Handling Instructions</a>.</p></li><li><p><code class="inline">restart_emulator</code></p><p>Used when a restart of the runtime system is required after all other upgrade
│ │ │  instructions are executed. For more information about this instruction, see
│ │ │  restart_emulator (Low-Level) in
│ │ │  <a href="release_handling.html#restart_emulator_instr">Release Handling Instructions</a>.</p></li></ul><p>If a runtime system restart is necessary and no upgrade instructions are needed,
│ │ │  that is, if the restart itself is enough for the upgraded applications to start
│ │ │ -running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8550965162-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8550965162-2">[</span><span class="p" data-group-id="8550965162-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8550965162-4">[</span><span class="p" data-group-id="8550965162-4">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8550965162-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="8550965162-5">]</span><span class="p" data-group-id="8550965162-3">}</span><span class="p" data-group-id="8550965162-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8550965162-6">[</span><span class="p" data-group-id="8550965162-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8550965162-8">[</span><span class="p" data-group-id="8550965162-8">]</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="8550965162-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="8550965162-9">]</span><span class="p" data-group-id="8550965162-7">}</span><span class="p" data-group-id="8550965162-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8550965162-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │ +running the new versions, a simple <code class="inline">.relup</code> file can be created manually:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3936055344-1">{</span><span class="s">&quot;B&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3936055344-2">[</span><span class="p" data-group-id="3936055344-3">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3936055344-4">[</span><span class="p" data-group-id="3936055344-4">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3936055344-5">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="3936055344-5">]</span><span class="p" data-group-id="3936055344-3">}</span><span class="p" data-group-id="3936055344-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="3936055344-6">[</span><span class="p" data-group-id="3936055344-7">{</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3936055344-8">[</span><span class="p" data-group-id="3936055344-8">]</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3936055344-9">[</span><span class="ss">restart_emulator</span><span class="p" data-group-id="3936055344-9">]</span><span class="p" data-group-id="3936055344-7">}</span><span class="p" data-group-id="3936055344-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3936055344-1">}</span><span class="p">.</span></code></pre><p>In this case, the release handler framework with automatic packing and unpacking
│ │ │  of release packages, automatic path updates, and so on, can be used without
│ │ │  having to specify <code class="inline">.appup</code> files.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/benchmarking.html
│ │ │ @@ -144,16 +144,16 @@
│ │ │  fast as possible, what can we do? One way could be to generate more
│ │ │  than two bytes at the time.</p><pre><code class="text">% erlperf 'rand:bytes(100).' 'crypto:strong_rand_bytes(100).'
│ │ │  Code                                   ||        QPS       Time   Rel
│ │ │  rand:bytes(100).                        1    2124 Ki     470 ns  100%
│ │ │  crypto:strong_rand_bytes(100).          1    1915 Ki     522 ns   90%</code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/rand.html#bytes/1"><code class="inline">rand:bytes/1</code></a> is still faster when we generate 100 bytes at the time,
│ │ │  but the relative difference is smaller.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlperf &#39;rand:bytes(1000).&#39; &#39;crypto:strong_rand_bytes(1000).&#39;</span><span class="w">
│ │ │  </span><span class="n">Code</span><span class="w">                                    </span><span class="p">||</span><span class="w">        </span><span class="n">QPS</span><span class="w">       </span><span class="n">Time</span><span class="w">   </span><span class="n">Rel</span><span class="w">
│ │ │ -</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="9551067700-1">(</span><span class="mi">1000</span><span class="p" data-group-id="9551067700-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ -</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="9551067700-2">(</span><span class="mi">1000</span><span class="p" data-group-id="9551067700-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at the time, <a href="../../lib/crypto-5.5.3/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │ +</span><span class="nc">crypto</span><span class="p">:</span><span class="nf">strong_rand_bytes</span><span class="p" data-group-id="0935028650-1">(</span><span class="mi">1000</span><span class="p" data-group-id="0935028650-1">)</span><span class="p">.</span><span class="w">          </span><span class="mi">1</span><span class="w">    </span><span class="mi">1518</span><span class="w"> </span><span class="n">Ki</span><span class="w">     </span><span class="mi">658</span><span class="w"> </span><span class="ss">ns</span><span class="w">  </span><span class="mi">100</span><span class="c1">%</span><span class="w">
│ │ │ +</span><span class="nc">rand</span><span class="p">:</span><span class="nf">bytes</span><span class="p" data-group-id="0935028650-2">(</span><span class="mi">1000</span><span class="p" data-group-id="0935028650-2">)</span><span class="p">.</span><span class="w">                        </span><span class="mi">1</span><span class="w">     </span><span class="mi">284</span><span class="w"> </span><span class="n">Ki</span><span class="w">    </span><span class="mi">3521</span><span class="w"> </span><span class="ss">ns</span><span class="w">   </span><span class="mi">19</span><span class="c1">%</span></code></pre><p>When we generate 1000 bytes at the time, <a href="../../lib/crypto-5.5.3/doc/html/crypto.html#strong_rand_bytes/1"><code class="inline">crypto:strong_rand_bytes/1</code></a> is
│ │ │  now the fastest.</p><h2 id="benchmarking-using-erlang-otp-functionality" class="section-heading">
│ │ │    <a href="#benchmarking-using-erlang-otp-functionality" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Benchmarking using Erlang/OTP functionality</span>
│ │ │  </h2>
│ │ │  <p>Benchmarks can measure wall-clock time or CPU time.</p><ul><li><p><a href="../../lib/stdlib-6.2.2.2/doc/html/timer.html#tc/3"><code class="inline">timer:tc/3</code></a> measures wall-clock time. The advantage with wall-clock time is
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/binaryhandling.html
│ │ │ @@ -114,43 +114,43 @@
│ │ │  
│ │ │      <span>Constructing and Matching Binaries</span>
│ │ │    </h1>
│ │ │  
│ │ │  <p>This section gives a few examples on how to handle binaries in an efficient way.
│ │ │  The sections that follow take an in-depth look at how binaries are implemented
│ │ │  and how to best take advantages of the optimizations done by the compiler and
│ │ │ -runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6014685532-1">(</span><span class="n">List</span><span class="p" data-group-id="6014685532-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6014685532-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6014685532-3">&lt;&lt;</span><span class="p" data-group-id="6014685532-3">&gt;&gt;</span><span class="p" data-group-id="6014685532-2">)</span><span class="p">.</span><span class="w">
│ │ │ +runtime system.</p><p>Binaries can be efficiently <em>built</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_list_to_binary</span><span class="p" data-group-id="7910428541-1">(</span><span class="n">List</span><span class="p" data-group-id="7910428541-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="7910428541-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7910428541-3">&lt;&lt;</span><span class="p" data-group-id="7910428541-3">&gt;&gt;</span><span class="p" data-group-id="7910428541-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6014685532-4">(</span><span class="p" data-group-id="6014685532-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6014685532-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6014685532-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6014685532-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6014685532-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="6014685532-7">&gt;&gt;</span><span class="p" data-group-id="6014685532-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="6014685532-8">(</span><span class="p" data-group-id="6014685532-9">[</span><span class="p" data-group-id="6014685532-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6014685532-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="7910428541-4">(</span><span class="p" data-group-id="7910428541-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7910428541-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7910428541-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="7910428541-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7910428541-7">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="7910428541-7">&gt;&gt;</span><span class="p" data-group-id="7910428541-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_list_to_binary</span><span class="p" data-group-id="7910428541-8">(</span><span class="p" data-group-id="7910428541-9">[</span><span class="p" data-group-id="7910428541-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7910428541-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Appending data to a binary as in the example is efficient because it is
│ │ │  specially optimized by the runtime system to avoid copying the <code class="inline">Acc</code> binary
│ │ │ -every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5325895619-1">(</span><span class="n">List</span><span class="p" data-group-id="5325895619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5325895619-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5325895619-3">&lt;&lt;</span><span class="p" data-group-id="5325895619-3">&gt;&gt;</span><span class="p" data-group-id="5325895619-2">)</span><span class="p">.</span><span class="w">
│ │ │ +every time.</p><p>Prepending data to a binary in a loop is not efficient:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3975213897-1">(</span><span class="n">List</span><span class="p" data-group-id="3975213897-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3975213897-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3975213897-3">&lt;&lt;</span><span class="p" data-group-id="3975213897-3">&gt;&gt;</span><span class="p" data-group-id="3975213897-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5325895619-4">(</span><span class="p" data-group-id="5325895619-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5325895619-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5325895619-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5325895619-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5325895619-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5325895619-7">&gt;&gt;</span><span class="p" data-group-id="5325895619-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="5325895619-8">(</span><span class="p" data-group-id="5325895619-9">[</span><span class="p" data-group-id="5325895619-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5325895619-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3975213897-4">(</span><span class="p" data-group-id="3975213897-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3975213897-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3975213897-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3975213897-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3975213897-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3975213897-7">&gt;&gt;</span><span class="p" data-group-id="3975213897-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="3975213897-8">(</span><span class="p" data-group-id="3975213897-9">[</span><span class="p" data-group-id="3975213897-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3975213897-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>This is not efficient for long lists because the <code class="inline">Acc</code> binary is copied every
│ │ │ -time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9238339549-1">(</span><span class="n">List</span><span class="p" data-group-id="9238339549-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9238339549-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9238339549-3">(</span><span class="n">List</span><span class="p" data-group-id="9238339549-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9238339549-4">&lt;&lt;</span><span class="p" data-group-id="9238339549-4">&gt;&gt;</span><span class="p" data-group-id="9238339549-2">)</span><span class="p">.</span><span class="w">
│ │ │ +time. One way to make the function more efficient is like this:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8919303204-1">(</span><span class="n">List</span><span class="p" data-group-id="8919303204-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8919303204-2">(</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="8919303204-3">(</span><span class="n">List</span><span class="p" data-group-id="8919303204-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8919303204-4">&lt;&lt;</span><span class="p" data-group-id="8919303204-4">&gt;&gt;</span><span class="p" data-group-id="8919303204-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9238339549-5">(</span><span class="p" data-group-id="9238339549-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9238339549-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9238339549-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9238339549-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9238339549-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="9238339549-8">&gt;&gt;</span><span class="p" data-group-id="9238339549-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="9238339549-9">(</span><span class="p" data-group-id="9238339549-10">[</span><span class="p" data-group-id="9238339549-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9238339549-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8910003759-1">(</span><span class="p" data-group-id="8910003759-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8910003759-2">]</span><span class="p" data-group-id="8910003759-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8910003759-3">(</span><span class="n">T</span><span class="p" data-group-id="8910003759-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8910003759-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8910003759-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8910003759-5">(</span><span class="p" data-group-id="8910003759-6">[</span><span class="p" data-group-id="8910003759-6">]</span><span class="p" data-group-id="8910003759-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8910003759-7">&lt;&lt;</span><span class="p" data-group-id="8910003759-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ -given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="2463078892-1">(</span><span class="p" data-group-id="2463078892-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2463078892-2">&gt;&gt;</span><span class="p" data-group-id="2463078892-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2463078892-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="2463078892-4">(</span><span class="n">T</span><span class="p" data-group-id="2463078892-4">)</span><span class="p" data-group-id="2463078892-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="2463078892-5">(</span><span class="p" data-group-id="2463078892-6">&lt;&lt;</span><span class="p" data-group-id="2463078892-6">&gt;&gt;</span><span class="p" data-group-id="2463078892-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2463078892-7">[</span><span class="p" data-group-id="2463078892-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8919303204-5">(</span><span class="p" data-group-id="8919303204-6">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8919303204-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8919303204-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8919303204-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8919303204-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="8919303204-8">&gt;&gt;</span><span class="p" data-group-id="8919303204-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="8919303204-9">(</span><span class="p" data-group-id="8919303204-10">[</span><span class="p" data-group-id="8919303204-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="8919303204-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Another way to avoid copying the binary each time is like this:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1702617806-1">(</span><span class="p" data-group-id="1702617806-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1702617806-2">]</span><span class="p" data-group-id="1702617806-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">RevTail</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1702617806-3">(</span><span class="n">T</span><span class="p" data-group-id="1702617806-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1702617806-4">&lt;&lt;</span><span class="n">RevTail</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">H</span><span class="p" data-group-id="1702617806-4">&gt;&gt;</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">rev_list_to_binary</span><span class="p" data-group-id="1702617806-5">(</span><span class="p" data-group-id="1702617806-6">[</span><span class="p" data-group-id="1702617806-6">]</span><span class="p" data-group-id="1702617806-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1702617806-7">&lt;&lt;</span><span class="p" data-group-id="1702617806-7">&gt;&gt;</span><span class="p">.</span></code></pre><p>Note that in each of the <strong>DO</strong> examples, the binary to be appended to is always
│ │ │ +given as the first segment.</p><p>Binaries can be efficiently <em>matched</em> in the following way:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="6925258452-1">(</span><span class="p" data-group-id="6925258452-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6925258452-2">&gt;&gt;</span><span class="p" data-group-id="6925258452-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6925258452-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="6925258452-4">(</span><span class="n">T</span><span class="p" data-group-id="6925258452-4">)</span><span class="p" data-group-id="6925258452-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="6925258452-5">(</span><span class="p" data-group-id="6925258452-6">&lt;&lt;</span><span class="p" data-group-id="6925258452-6">&gt;&gt;</span><span class="p" data-group-id="6925258452-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6925258452-7">[</span><span class="p" data-group-id="6925258452-7">]</span><span class="p">.</span></code></pre><h2 id="how-binaries-are-implemented" class="section-heading">
│ │ │    <a href="#how-binaries-are-implemented" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">How Binaries are Implemented</span>
│ │ │  </h2>
│ │ │  <p>Internally, binaries and bitstrings are implemented in the same way. In this
│ │ │  section, they are called <em>binaries</em> because that is what they are called in the
│ │ │ @@ -205,29 +205,29 @@
│ │ │  called referential transparency) of Erlang would break.</p><h2 id="constructing-binaries" class="section-heading">
│ │ │    <a href="#constructing-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Constructing Binaries</span>
│ │ │  </h2>
│ │ │  <p>Appending to a binary or bitstring in the following way is specially optimized
│ │ │ -to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2991167102-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2991167102-1">&gt;&gt;</span><span class="w">
│ │ │ +to avoid copying the binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1830546203-1">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1830546203-1">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% - OR -</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2991167102-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2991167102-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │ +</span><span class="p" data-group-id="1830546203-2">&lt;&lt;</span><span class="n">Binary</span><span class="o">/</span><span class="ss">bitstring</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1830546203-2">&gt;&gt;</span></code></pre><p>This optimization is applied by the runtime system in a way that makes it
│ │ │  effective in most circumstances (for exceptions, see
│ │ │  <a href="binaryhandling.html#forced_copying">Circumstances That Force Copying</a>). The
│ │ │  optimization in its basic form does not need any help from the compiler.
│ │ │  However, the compiler add hints to the runtime system when it is safe to apply
│ │ │  the optimization in a more efficient way.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The compiler support for making the optimization more efficient was added in
│ │ │  Erlang/OTP 26.</p></section><p>To explain how the basic optimization works, let us examine the following code
│ │ │ -line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4148232402-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="4148232402-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ -</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4148232402-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4148232402-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4148232402-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4148232402-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ -</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4148232402-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="4148232402-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ -</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4148232402-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="4148232402-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4148232402-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="4148232402-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │ +line by line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4570095562-1">&lt;&lt;</span><span class="mi">0</span><span class="p" data-group-id="4570095562-1">&gt;&gt;</span><span class="p">,</span><span class="w">                    </span><span class="c1">%% 1</span><span class="w">
│ │ │ +</span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4570095562-2">&lt;&lt;</span><span class="n">Bin0</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4570095562-2">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 2</span><span class="w">
│ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4570095562-3">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4570095562-3">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 3</span><span class="w">
│ │ │ +</span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4570095562-4">&lt;&lt;</span><span class="n">Bin2</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="4570095562-4">&gt;&gt;</span><span class="p">,</span><span class="w">    </span><span class="c1">%% 4</span><span class="w">
│ │ │ +</span><span class="n">Bin4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4570095562-5">&lt;&lt;</span><span class="n">Bin1</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="4570095562-5">&gt;&gt;</span><span class="p">,</span><span class="w">       </span><span class="c1">%% 5 !!!</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4570095562-6">{</span><span class="n">Bin4</span><span class="p">,</span><span class="n">Bin3</span><span class="p" data-group-id="4570095562-6">}</span><span class="w">                      </span><span class="c1">%% 6</span></code></pre><ul><li><p>Line 1 (marked with the <code class="inline">%% 1</code> comment), assigns a
│ │ │  <a href="binaryhandling.html#heap_binary">heap binary</a> to the <code class="inline">Bin0</code> variable.</p></li><li><p>Line 2 is an append operation. As <code class="inline">Bin0</code> has not been involved in an append
│ │ │  operation, a new <a href="binaryhandling.html#refc_binary">refc binary</a> is created and
│ │ │  the contents of <code class="inline">Bin0</code> is copied into it. The <em>ProcBin</em> part of the refc
│ │ │  binary has its size set to the size of the data stored in the binary, while
│ │ │  the binary object has extra space allocated. The size of the binary object is
│ │ │  either twice the size of <code class="inline">Bin1</code> or 256, whichever is larger. In this case it
│ │ │  is 256.</p></li><li><p>Line 3 is more interesting. <code class="inline">Bin1</code> <em>has</em> been used in an append operation, and
│ │ │ @@ -253,23 +253,23 @@
│ │ │  handle an append operation to a heap binary by copying it to a refc binary (line
│ │ │  2), and also handle an append operation to a previous version of the binary by
│ │ │  copying it (line 5). The support for doing that does not come for free. For
│ │ │  example, to make it possible to know when it is necessary to copy the binary,
│ │ │  for every append operation, the runtime system must create a sub binary.</p><p>When the compiler can determine that none of those situations need to be handled
│ │ │  and that the append operation cannot possibly fail, the compiler generates code
│ │ │  that causes the runtime system to apply a more efficient variant of the
│ │ │ -optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1295322251-1">(</span><span class="ss">repack</span><span class="p" data-group-id="1295322251-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1295322251-2">(</span><span class="p" data-group-id="1295322251-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1295322251-3">]</span><span class="p" data-group-id="1295322251-2">)</span><span class="p">.</span><span class="w">
│ │ │ +optimization.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2861749723-1">(</span><span class="ss">repack</span><span class="p" data-group-id="2861749723-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2861749723-2">(</span><span class="p" data-group-id="2861749723-3">[</span><span class="ss">repack</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2861749723-3">]</span><span class="p" data-group-id="2861749723-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="1295322251-4">(</span><span class="n">Bin</span><span class="p" data-group-id="1295322251-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="1295322251-5">(</span><span class="n">Bin</span><span class="p" data-group-id="1295322251-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="1295322251-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1295322251-7">&lt;&lt;</span><span class="p" data-group-id="1295322251-7">&gt;&gt;</span><span class="p" data-group-id="1295322251-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="2861749723-4">(</span><span class="n">Bin</span><span class="p" data-group-id="2861749723-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_binary</span><span class="p" data-group-id="2861749723-5">(</span><span class="n">Bin</span><span class="p" data-group-id="2861749723-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="2861749723-6">(</span><span class="n">Bin</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2861749723-7">&lt;&lt;</span><span class="p" data-group-id="2861749723-7">&gt;&gt;</span><span class="p" data-group-id="2861749723-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="1295322251-8">(</span><span class="p" data-group-id="1295322251-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1295322251-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1295322251-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">repack</span><span class="p" data-group-id="1295322251-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1295322251-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1295322251-11">&gt;&gt;</span><span class="p" data-group-id="1295322251-10">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">repack</span><span class="p" data-group-id="1295322251-12">(</span><span class="p" data-group-id="1295322251-13">&lt;&lt;</span><span class="p" data-group-id="1295322251-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1295322251-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="2861749723-8">(</span><span class="p" data-group-id="2861749723-9">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2861749723-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2861749723-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">repack</span><span class="p" data-group-id="2861749723-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2861749723-11">&lt;&lt;</span><span class="n">Result</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="2861749723-11">&gt;&gt;</span><span class="p" data-group-id="2861749723-10">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">repack</span><span class="p" data-group-id="2861749723-12">(</span><span class="p" data-group-id="2861749723-13">&lt;&lt;</span><span class="p" data-group-id="2861749723-13">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2861749723-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Result</span><span class="p">.</span></code></pre><p>The <code class="inline">repack/2</code> function only keeps a single version of the binary, so there is
│ │ │  never any need to copy the binary. The compiler rewrites the creation of the
│ │ │  empty binary in <code class="inline">repack/1</code> to instead create a refc binary with 256 bytes
│ │ │  already reserved; thus, the append operation in <code class="inline">repack/2</code> never needs to handle
│ │ │  a binary not prepared for appending.</p><p><a href="" id="forced_copying"></a></p><h3 id="circumstances-that-force-copying" class="section-heading">
│ │ │    <a href="#circumstances-that-force-copying" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -281,72 +281,72 @@
│ │ │  reason is that the binary object can be moved (reallocated) during an append
│ │ │  operation, and when that happens, the pointer in the ProcBin must be updated. If
│ │ │  there would be more than one ProcBin pointing to the binary object, it would not
│ │ │  be possible to find and update all of them.</p><p>Therefore, certain operations on a binary mark it so that any future append
│ │ │  operation will be forced to copy the binary. In most cases, the binary object
│ │ │  will be shrunk at the same time to reclaim the extra space allocated for
│ │ │  growing.</p><p>When appending to a binary as follows, only the binary returned from the latest
│ │ │ -append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1958452393-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1958452393-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │ +append operation will support further cheap append operations:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8274363931-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8274363931-1">&gt;&gt;</span></code></pre><p>In the code fragment in the beginning of this section, appending to <code class="inline">Bin</code> will
│ │ │  be cheap, while appending to <code class="inline">Bin0</code> will force the creation of a new binary and
│ │ │  copying of the contents of <code class="inline">Bin0</code>.</p><p>If a binary is sent as a message to a process or port, the binary will be shrunk
│ │ │  and any further append operation will copy the binary data into a new binary.
│ │ │  For example, in the following code fragment <code class="inline">Bin1</code> will be copied in the third
│ │ │ -line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2248271407-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2248271407-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ +line:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3261277071-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3261277071-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">PortOrPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2248271407-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="2248271407-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3261277071-2">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3261277071-2">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The same happens if you insert a binary into an Ets table, send it to a port
│ │ │  using <a href="../../erts-15.2.7.2/doc/html/erlang.html#port_command/2"><code class="inline">erlang:port_command/2</code></a>, or pass it to
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erl_nif.html#enif_inspect_binary">enif_inspect_binary</a> in a NIF.</p><p>Matching a binary will also cause it to shrink and the next append operation
│ │ │ -will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0027577314-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0027577314-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0027577314-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0027577314-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0027577314-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0027577314-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.html#match_context">match context</a> contains a
│ │ │ +will copy the binary data:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8152225946-1">&lt;&lt;</span><span class="n">Bin0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8152225946-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8152225946-2">&lt;&lt;</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8152225946-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin1</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8152225946-3">&lt;&lt;</span><span class="n">Bin1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8152225946-3">&gt;&gt;</span><span class="w">  </span><span class="c1">%% Bin1 will be COPIED</span></code></pre><p>The reason is that a <a href="binaryhandling.html#match_context">match context</a> contains a
│ │ │  direct pointer to the binary data.</p><p>If a process simply keeps binaries (either in &quot;loop data&quot; or in the process
│ │ │  dictionary), the garbage collector can eventually shrink the binaries. If only
│ │ │  one such binary is kept, it will not be shrunk. If the process later appends to
│ │ │  a binary that has been shrunk, the binary object will be reallocated to make
│ │ │  place for the data to be appended.</p><h2 id="matching-binaries" class="section-heading">
│ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Matching Binaries</span>
│ │ │  </h2>
│ │ │ -<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9492966414-1">(</span><span class="p" data-group-id="9492966414-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9492966414-2">&gt;&gt;</span><span class="p" data-group-id="9492966414-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9492966414-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9492966414-4">(</span><span class="n">T</span><span class="p" data-group-id="9492966414-4">)</span><span class="p" data-group-id="9492966414-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="9492966414-5">(</span><span class="p" data-group-id="9492966414-6">&lt;&lt;</span><span class="p" data-group-id="9492966414-6">&gt;&gt;</span><span class="p" data-group-id="9492966414-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9492966414-7">[</span><span class="p" data-group-id="9492966414-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │ +<p>Let us revisit the example in the beginning of the previous section:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">my_binary_to_list</span><span class="p" data-group-id="6894405618-1">(</span><span class="p" data-group-id="6894405618-2">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6894405618-2">&gt;&gt;</span><span class="p" data-group-id="6894405618-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6894405618-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="6894405618-4">(</span><span class="n">T</span><span class="p" data-group-id="6894405618-4">)</span><span class="p" data-group-id="6894405618-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_binary_to_list</span><span class="p" data-group-id="6894405618-5">(</span><span class="p" data-group-id="6894405618-6">&lt;&lt;</span><span class="p" data-group-id="6894405618-6">&gt;&gt;</span><span class="p" data-group-id="6894405618-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6894405618-7">[</span><span class="p" data-group-id="6894405618-7">]</span><span class="p">.</span></code></pre><p>The first time <code class="inline">my_binary_to_list/1</code> is called, a
│ │ │  <a href="binaryhandling.html#match_context">match context</a> is created. The match context
│ │ │  points to the first byte of the binary. 1 byte is matched out and the match
│ │ │  context is updated to point to the second byte in the binary.</p><p>At this point it would make sense to create a
│ │ │  <a href="binaryhandling.html#sub_binary">sub binary</a>, but in this particular example the
│ │ │  compiler sees that there will soon be a call to a function (in this case, to
│ │ │  <code class="inline">my_binary_to_list/1</code> itself) that immediately will create a new match context
│ │ │  and discard the sub binary.</p><p>Therefore <code class="inline">my_binary_to_list/1</code> calls itself with the match context instead of
│ │ │  with a sub binary. The instruction that initializes the matching operation
│ │ │  basically does nothing when it sees that it was passed a match context instead
│ │ │  of a binary.</p><p>When the end of the binary is reached and the second clause matches, the match
│ │ │  context will simply be discarded (removed in the next garbage collection, as
│ │ │  there is no longer any reference to it).</p><p>To summarize, <code class="inline">my_binary_to_list/1</code> only needs to create <em>one</em> match context and
│ │ │  no sub binaries.</p><p>Notice that the match context in <code class="inline">my_binary_to_list/1</code> was discarded when the
│ │ │  entire binary had been traversed. What happens if the iteration stops before it
│ │ │ -has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="0132519850-1">(</span><span class="p" data-group-id="0132519850-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0132519850-2">&gt;&gt;</span><span class="p" data-group-id="0132519850-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +has reached the end of the binary? Will the optimization still work?</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="5823661771-1">(</span><span class="p" data-group-id="5823661771-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5823661771-2">&gt;&gt;</span><span class="p" data-group-id="5823661771-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0132519850-3">(</span><span class="p" data-group-id="0132519850-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="0132519850-4">&gt;&gt;</span><span class="p" data-group-id="0132519850-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="0132519850-5">(</span><span class="n">T</span><span class="p" data-group-id="0132519850-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="0132519850-6">(</span><span class="p" data-group-id="0132519850-7">&lt;&lt;</span><span class="p" data-group-id="0132519850-7">&gt;&gt;</span><span class="p" data-group-id="0132519850-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0132519850-8">&lt;&lt;</span><span class="p" data-group-id="0132519850-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="5823661771-3">(</span><span class="p" data-group-id="5823661771-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5823661771-4">&gt;&gt;</span><span class="p" data-group-id="5823661771-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="5823661771-5">(</span><span class="n">T</span><span class="p" data-group-id="5823661771-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="5823661771-6">(</span><span class="p" data-group-id="5823661771-7">&lt;&lt;</span><span class="p" data-group-id="5823661771-7">&gt;&gt;</span><span class="p" data-group-id="5823661771-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5823661771-8">&lt;&lt;</span><span class="p" data-group-id="5823661771-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>Yes, it will. The compiler will remove the building of the sub binary in the
│ │ │  second clause:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="2845433892-1">(</span><span class="p" data-group-id="2845433892-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2845433892-2">&gt;&gt;</span><span class="p" data-group-id="2845433892-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="2845433892-3">(</span><span class="n">T</span><span class="p" data-group-id="2845433892-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="9432958040-1">(</span><span class="p" data-group-id="9432958040-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9432958040-2">&gt;&gt;</span><span class="p" data-group-id="9432958040-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="9397507694-1">(</span><span class="p" data-group-id="9397507694-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9397507694-2">&gt;&gt;</span><span class="p" data-group-id="9397507694-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="9397507694-3">(</span><span class="n">T</span><span class="p" data-group-id="9397507694-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>But it will generate code that builds a sub binary in the first clause:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="7950907542-1">(</span><span class="p" data-group-id="7950907542-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7950907542-2">&gt;&gt;</span><span class="p" data-group-id="7950907542-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Therefore, <code class="inline">after_zero/1</code> builds one match context and one sub binary (assuming
│ │ │ -it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6959241188-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6959241188-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6959241188-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="6959241188-3">(</span><span class="n">Acc</span><span class="p" data-group-id="6959241188-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="6959241188-2">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6959241188-4">(</span><span class="p" data-group-id="6959241188-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6959241188-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="6959241188-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6959241188-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6959241188-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6959241188-7">(</span><span class="p" data-group-id="6959241188-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6959241188-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="6959241188-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="6959241188-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6959241188-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="6959241188-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6959241188-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │ +it is passed a binary that contains a zero byte).</p><p>Code like the following will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2180289406-1">(</span><span class="n">Buffer</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2180289406-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2180289406-2">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2180289406-3">(</span><span class="n">Acc</span><span class="p" data-group-id="2180289406-3">)</span><span class="p">,</span><span class="n">Buffer</span><span class="p" data-group-id="2180289406-2">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2180289406-4">(</span><span class="p" data-group-id="2180289406-5">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2180289406-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="2180289406-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2180289406-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2180289406-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2180289406-7">(</span><span class="p" data-group-id="2180289406-8">&lt;&lt;</span><span class="n">Byte</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2180289406-8">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="p" data-group-id="2180289406-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">all_but_zeroes_to_list</span><span class="p" data-group-id="2180289406-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2180289406-10">[</span><span class="n">Byte</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2180289406-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Remaining</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="2180289406-9">)</span><span class="p">.</span></code></pre><p>The compiler removes building of sub binaries in the second and third clauses,
│ │ │  and it adds an instruction to the first clause that converts <code class="inline">Buffer</code> from a
│ │ │  match context to a sub binary (or do nothing if <code class="inline">Buffer</code> is a binary already).</p><p>But in more complicated code, how can one know whether the optimization is
│ │ │  applied or not?</p><p><a href="" id="bin_opt_info"></a></p><h3 id="option-bin_opt_info" class="section-heading">
│ │ │    <a href="#option-bin_opt_info" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Option bin_opt_info</span>
│ │ │ @@ -354,38 +354,38 @@
│ │ │  <p>Use the <code class="inline">bin_opt_info</code> option to have the compiler print a lot of information
│ │ │  about binary optimizations. It can be given either to the compiler or <code class="inline">erlc</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">erlc</span><span class="w"> </span><span class="o">+</span><span class="ss">bin_opt_info</span><span class="w"> </span><span class="n">Mod</span><span class="p">.</span><span class="ss">erl</span></code></pre><p>or passed through an environment variable:</p><pre><code class="makeup erlang" translate="no"><span class="ss">export</span><span class="w"> </span><span class="n">ERL_COMPILER_OPTIONS</span><span class="o">=</span><span class="ss">bin_opt_info</span></code></pre><p>Notice that the <code class="inline">bin_opt_info</code> is not meant to be a permanent option added to
│ │ │  your <code class="inline">Makefile</code>s, because all messages that it generates cannot be eliminated.
│ │ │  Therefore, passing the option through the environment is in most cases the most
│ │ │  practical approach.</p><p>The warnings look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">60</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">binary</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">returned</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">function</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">62</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">context</span><span class="w"> </span><span class="ss">reused</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="1336732496-1">(</span><span class="p" data-group-id="1336732496-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1336732496-2">&gt;&gt;</span><span class="p" data-group-id="1336732496-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">after_zero</span><span class="p" data-group-id="2345566163-1">(</span><span class="p" data-group-id="2345566163-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2345566163-2">&gt;&gt;</span><span class="p" data-group-id="2345566163-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │           </span><span class="c1">%% BINARY CREATED: binary is returned from the function</span><span class="w">
│ │ │      </span><span class="n">T</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="1336732496-3">(</span><span class="p" data-group-id="1336732496-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1336732496-4">&gt;&gt;</span><span class="p" data-group-id="1336732496-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="2345566163-3">(</span><span class="p" data-group-id="2345566163-4">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2345566163-4">&gt;&gt;</span><span class="p" data-group-id="2345566163-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │           </span><span class="c1">%% OPTIMIZED: match context reused</span><span class="w">
│ │ │ -    </span><span class="nf">after_zero</span><span class="p" data-group-id="1336732496-5">(</span><span class="n">T</span><span class="p" data-group-id="1336732496-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">after_zero</span><span class="p" data-group-id="1336732496-6">(</span><span class="p" data-group-id="1336732496-7">&lt;&lt;</span><span class="p" data-group-id="1336732496-7">&gt;&gt;</span><span class="p" data-group-id="1336732496-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1336732496-8">&lt;&lt;</span><span class="p" data-group-id="1336732496-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │ +    </span><span class="nf">after_zero</span><span class="p" data-group-id="2345566163-5">(</span><span class="n">T</span><span class="p" data-group-id="2345566163-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">after_zero</span><span class="p" data-group-id="2345566163-6">(</span><span class="p" data-group-id="2345566163-7">&lt;&lt;</span><span class="p" data-group-id="2345566163-7">&gt;&gt;</span><span class="p" data-group-id="2345566163-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2345566163-8">&lt;&lt;</span><span class="p" data-group-id="2345566163-8">&gt;&gt;</span><span class="p">.</span></code></pre><p>The warning for the first clause says that the creation of a sub binary cannot
│ │ │  be delayed, because it will be returned. The warning for the second clause says
│ │ │  that a sub binary will not be created (yet).</p><h3 id="unused-variables" class="section-heading">
│ │ │    <a href="#unused-variables" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Unused Variables</span>
│ │ │  </h3>
│ │ │  <p>The compiler figures out if a variable is unused. The same code is generated for
│ │ │ -each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="3935769102-1">(</span><span class="p" data-group-id="3935769102-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3935769102-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3935769102-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="3935769102-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3935769102-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">count1</span><span class="p" data-group-id="3935769102-4">(</span><span class="p" data-group-id="3935769102-5">&lt;&lt;</span><span class="p" data-group-id="3935769102-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3935769102-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ +each of the following functions:</p><pre><code class="makeup erlang" translate="no"><span class="nf">count1</span><span class="p" data-group-id="7254585224-1">(</span><span class="p" data-group-id="7254585224-2">&lt;&lt;</span><span class="p">_</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7254585224-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="7254585224-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count1</span><span class="p" data-group-id="7254585224-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="7254585224-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">count1</span><span class="p" data-group-id="7254585224-4">(</span><span class="p" data-group-id="7254585224-5">&lt;&lt;</span><span class="p" data-group-id="7254585224-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="7254585224-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="3935769102-6">(</span><span class="p" data-group-id="3935769102-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3935769102-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3935769102-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="3935769102-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3935769102-8">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">count2</span><span class="p" data-group-id="3935769102-9">(</span><span class="p" data-group-id="3935769102-10">&lt;&lt;</span><span class="p" data-group-id="3935769102-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3935769102-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="7254585224-6">(</span><span class="p" data-group-id="7254585224-7">&lt;&lt;</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7254585224-7">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="7254585224-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count2</span><span class="p" data-group-id="7254585224-8">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="7254585224-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">count2</span><span class="p" data-group-id="7254585224-9">(</span><span class="p" data-group-id="7254585224-10">&lt;&lt;</span><span class="p" data-group-id="7254585224-10">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="7254585224-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="3935769102-11">(</span><span class="p" data-group-id="3935769102-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3935769102-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3935769102-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="3935769102-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="3935769102-13">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">count3</span><span class="p" data-group-id="3935769102-14">(</span><span class="p" data-group-id="3935769102-15">&lt;&lt;</span><span class="p" data-group-id="3935769102-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="3935769102-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="7254585224-11">(</span><span class="p" data-group-id="7254585224-12">&lt;&lt;</span><span class="p">_</span><span class="n">H</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7254585224-12">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="7254585224-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">count3</span><span class="p" data-group-id="7254585224-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="7254585224-13">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">count3</span><span class="p" data-group-id="7254585224-14">(</span><span class="p" data-group-id="7254585224-15">&lt;&lt;</span><span class="p" data-group-id="7254585224-15">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="n">Count</span><span class="p" data-group-id="7254585224-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Count</span><span class="p">.</span></code></pre><p>In each iteration, the first 8 bits in the binary will be skipped, not matched
│ │ │  out.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="commoncaveats.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/bit_syntax.html
│ │ │ @@ -119,48 +119,48 @@
│ │ │    <a href="#introduction" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Introduction</span>
│ │ │  </h2>
│ │ │  <p>The complete specification for the bit syntax appears in the
│ │ │  <a href="../../doc/system/expressions.html#bit-syntax-expressions">Reference Manual</a>.</p><p>In Erlang, a Bin is used for constructing binaries and matching binary patterns.
│ │ │ -A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6928824266-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="6928824266-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ -enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4206225163-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="4206225163-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3424762164-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="3424762164-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │ +A Bin is written with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9707141287-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="9707141287-1">&gt;&gt;</span></code></pre><p>A Bin is a low-level sequence of bits or bytes. The purpose of a Bin is to
│ │ │ +enable construction of binaries:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8141465938-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="8141465938-1">&gt;&gt;</span></code></pre><p>All elements must be bound. Or match a binary:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5391958583-1">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">En</span><span class="p" data-group-id="5391958583-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span></code></pre><p>Here, <code class="inline">Bin</code> is bound and the elements are bound or unbound, as in any match.</p><p>A Bin does not need to consist of a whole number of bytes.</p><p>A <em>bitstring</em> is a sequence of zero or more bits, where the number of bits does
│ │ │  not need to be divisible by 8. If the number of bits is divisible by 8, the
│ │ │  bitstring is also a binary.</p><p>Each element specifies a certain <em>segment</em> of the bitstring. A segment is a set
│ │ │  of contiguous bits of the binary (not necessarily on a byte boundary). The first
│ │ │  element specifies the initial segment, the second element specifies the
│ │ │  following segment, and so on.</p><p>The following examples illustrate how binaries are constructed, or matched, and
│ │ │  how elements and tails are specified.</p><h3 id="examples" class="section-heading">
│ │ │    <a href="#examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Examples</span>
│ │ │  </h3>
│ │ │  <p><em>Example 1:</em> A binary can be constructed from a set of constants or a string
│ │ │ -literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5874783373-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="5874783373-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5874783373-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5874783373-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em>Similarly, a binary can be constructed from a set of bound
│ │ │ +literal:</p><pre><code class="makeup erlang" translate="no"><span class="n">Bin11</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1805228299-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="1805228299-1">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Bin12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1805228299-2">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1805228299-2">&gt;&gt;</span></code></pre><p>This gives two binaries of size 3, with the following evaluations:</p><ul><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin11)</code></a> evaluates to <code class="inline">[1, 17, 42]</code>.</li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin12)</code></a> evaluates to <code class="inline">[97, 98, 99]</code>.</li></ul><p><em>Example 2:</em>Similarly, a binary can be constructed from a set of bound
│ │ │  variables:</p><pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">17</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4669413303-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4669413303-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │ +</span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1886582185-1">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1886582185-1">&gt;&gt;</span></code></pre><p>This gives a binary of size 4. Here, a <em>size expression</em> is used for the
│ │ │  variable <code class="inline">C</code> to specify a 16-bits segment of <code class="inline">Bin2</code>.</p><p><a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_list/1"><code class="inline">binary_to_list(Bin2)</code></a> evaluates to <code class="inline">[1, 17, 00, 42]</code>.</p><p><em>Example 3:</em> A Bin can also be used for matching. <code class="inline">D</code>, <code class="inline">E</code>, and <code class="inline">F</code> are unbound
│ │ │ -variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4701590854-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4701590854-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │ +variables, and <code class="inline">Bin2</code> is bound, as in Example 2:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8170612253-1">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8170612253-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin2</span></code></pre><p>This gives <code class="inline">D = 273</code>, <code class="inline">E = 00</code>, and F binds to a binary of size 1:
│ │ │  <code class="inline">binary_to_list(F) = [42]</code>.</p><p><em>Example 4:</em> The following is a more elaborate example of matching. Here,
│ │ │  <code class="inline">Dgram</code> is bound to the consecutive bytes of an IP datagram of IP protocol
│ │ │ -version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9722746696-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="9722746696-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9722746696-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="9722746696-2">)</span><span class="p">.</span><span class="w">
│ │ │ +version 4. The ambition is to extract the header and the data of the datagram:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3657257812-1">(</span><span class="n">IP_VERSION</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3657257812-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3657257812-2">(</span><span class="n">IP_MIN_HDR_LEN</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="3657257812-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="9722746696-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="9722746696-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">DgramSize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="3657257812-3">(</span><span class="n">Dgram</span><span class="p" data-group-id="3657257812-3">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">case</span><span class="w"> </span><span class="n">Dgram</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9722746696-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3657257812-4">&lt;&lt;</span><span class="o">?</span><span class="n">IP_VERSION</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">HLen</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">SrvcType</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">TotLen</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="n">ID</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">Flgs</span><span class="p">:</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">FragOff</span><span class="p">:</span><span class="mi">13</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="n">TTL</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="n">HdrChkSum</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="n">SrcIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w">
│ │ │ -      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9722746696-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="9722746696-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="9722746696-5">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9722746696-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9722746696-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │ +      </span><span class="n">DestIP</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="n">RestDgram</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3657257812-4">&gt;&gt;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">HLen</span><span class="o">&gt;=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="n">HLen</span><span class="o">=&lt;</span><span class="n">DgramSize</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="n">OptsLen</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="o">*</span><span class="p" data-group-id="3657257812-5">(</span><span class="n">HLen</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">?</span><span class="n">IP_MIN_HDR_LEN</span><span class="p" data-group-id="3657257812-5">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3657257812-6">&lt;&lt;</span><span class="n">Opts</span><span class="p">:</span><span class="n">OptsLen</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Data</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3657257812-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RestDgram</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Here, the segment corresponding to the <code class="inline">Opts</code> variable has a <em>type modifier</em>,
│ │ │  specifying that <code class="inline">Opts</code> is to bind to a binary. All other variables have the
│ │ │  default type equal to unsigned integer.</p><p>An IP datagram header is of variable length. This length is measured in the
│ │ │  number of 32-bit words and is given in the segment corresponding to <code class="inline">HLen</code>. The
│ │ │  minimum value of <code class="inline">HLen</code> is 5. It is the segment corresponding to <code class="inline">Opts</code> that is
│ │ │  variable, so if <code class="inline">HLen</code> is equal to 5, <code class="inline">Opts</code> becomes an empty binary.</p><p>The tail variables <code class="inline">RestDgram</code> and <code class="inline">Data</code> bind to binaries, as all tail
│ │ │ @@ -218,80 +218,80 @@
│ │ │  <p>This section describes the rules for constructing binaries using the bit syntax.
│ │ │  Unlike when constructing lists or tuples, the construction of a binary can fail
│ │ │  with a <code class="inline">badarg</code> exception.</p><p>There can be zero or more segments in a binary to be constructed. The expression
│ │ │  <code class="inline">&lt;&lt;&gt;&gt;</code> constructs a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. There are no
│ │ │  alignment rules for individual segments of type <code class="inline">integer</code> and <code class="inline">float</code>. For
│ │ │  binaries and bitstrings without size, the unit specifies the alignment. Since
│ │ │  the default alignment for the <code class="inline">binary</code> type is 8, the size of a binary segment
│ │ │ -must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0300528613-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="0300528613-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │ +must be a multiple of 8 bits, that is, only whole bytes.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6293784595-1">&lt;&lt;</span><span class="n">Bin</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Bitstring</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="6293784595-1">&gt;&gt;</span></code></pre><p>The variable <code class="inline">Bin</code> must contain a whole number of bytes, because the <code class="inline">binary</code>
│ │ │  type defaults to <code class="inline">unit:8</code>. A <code class="inline">badarg</code> exception is generated if <code class="inline">Bin</code> consist
│ │ │  of, for example, 17 bits.</p><p>The <code class="inline">Bitstring</code> variable can consist of any number of bits, for example, 0, 1,
│ │ │  8, 11, 17, 42, and so on. This is because the default <code class="inline">unit</code> for bitstrings
│ │ │  is 1.</p><p>For clarity, it is recommended not to change the unit size for binaries.
│ │ │  Instead, use <code class="inline">binary</code> when you need byte alignment and <code class="inline">bitstring</code> when you need
│ │ │  bit alignment.</p><p>The following example successfully constructs a bitstring of 7 bits, provided
│ │ │ -that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7871334702-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="7871334702-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │ +that all of X and Y are integers:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0486275988-1">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">6</span><span class="p" data-group-id="0486275988-1">&gt;&gt;</span></code></pre><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When constructing binaries, <code class="inline">Value</code> and <code class="inline">Size</code> can be any Erlang expression.
│ │ │  However, for syntactical reasons, both <code class="inline">Value</code> and <code class="inline">Size</code> must be enclosed in
│ │ │  parenthesis if the expression consists of anything more than a single literal or
│ │ │ -a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5828121169-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="5828121169-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ -compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2583740090-1">&lt;&lt;</span><span class="p" data-group-id="2583740090-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2583740090-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2583740090-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │ +a variable. The following gives a compiler syntax error:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6410826021-1">&lt;&lt;</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="6410826021-1">&gt;&gt;</span></code></pre><p>This expression must be rewritten into the following, to be accepted by the
│ │ │ +compiler:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0381521626-1">&lt;&lt;</span><span class="p" data-group-id="0381521626-2">(</span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0381521626-2">)</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0381521626-1">&gt;&gt;</span></code></pre><h3 id="including-literal-strings" class="section-heading">
│ │ │    <a href="#including-literal-strings" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Including Literal Strings</span>
│ │ │  </h3>
│ │ │ -<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9267733082-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9267733082-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7127059302-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="7127059302-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │ +<p>A literal string can be written instead of an element:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7543522295-1">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7543522295-1">&gt;&gt;</span></code></pre><p>This is syntactic sugar for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1555777867-1">&lt;&lt;</span><span class="sc">$h</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$l</span><span class="p">,</span><span class="sc">$o</span><span class="p" data-group-id="1555777867-1">&gt;&gt;</span></code></pre><h2 id="matching-binaries" class="section-heading">
│ │ │    <a href="#matching-binaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Matching Binaries</span>
│ │ │  </h2>
│ │ │  <p>This section describes the rules for matching binaries, using the bit syntax.</p><p>There can be zero or more segments in a binary pattern. A binary pattern can
│ │ │  occur wherever patterns are allowed, including inside other patterns. Binary
│ │ │  patterns cannot be nested. The pattern <code class="inline">&lt;&lt;&gt;&gt;</code> matches a zero length binary.</p><p>Each segment in a binary can consist of zero or more bits. A segment of type
│ │ │  <code class="inline">binary</code> must have a size evenly divisible by 8 (or divisible by the unit size,
│ │ │  if the unit size has been changed). A segment of type <code class="inline">bitstring</code> has no
│ │ │  restrictions on the size. A segment of type <code class="inline">float</code> must have size 64 or 32.</p><p>As mentioned earlier, segments have the following general syntax:</p><p><code class="inline">Value:Size/TypeSpecifierList</code></p><p>When matching <code class="inline">Value</code>, value must be either a variable or an integer, or a
│ │ │  floating point literal. Expressions are not allowed.</p><p><code class="inline">Size</code> must be a
│ │ │  <a href="../../doc/system/expressions.html#guard-expressions">guard expression</a>, which can use
│ │ │ -literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6789973209-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6789973209-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6789973209-2">&gt;&gt;</span><span class="p" data-group-id="6789973209-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="6789973209-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="6789973209-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ -<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4428480013-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="4428480013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4428480013-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4428480013-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4428480013-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="4428480013-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │ +literals and previously bound variables. The following is not allowed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2399626900-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2399626900-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2399626900-2">&gt;&gt;</span><span class="p" data-group-id="2399626900-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="2399626900-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="2399626900-3">}</span><span class="p">.</span></code></pre><p>The two occurrences of <code class="inline">N</code> are not related. The compiler will complain that the
│ │ │ +<code class="inline">N</code> in the size field is unbound.</p><p>The correct way to write this example is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="3713703189-1">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="3713703189-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3713703189-2">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">N</span><span class="p">,</span><span class="n">T</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3713703189-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Bin</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="3713703189-3">{</span><span class="n">X</span><span class="p">,</span><span class="n">T</span><span class="p" data-group-id="3713703189-3">}</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Before OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable bound to
│ │ │  an integer.</p></section><h3 id="binding-and-using-a-size-variable" class="section-heading">
│ │ │    <a href="#binding-and-using-a-size-variable" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Binding and Using a Size Variable</span>
│ │ │  </h3>
│ │ │  <p>There is one exception to the rule that a variable that is used as size must be
│ │ │  previously bound. It is possible to match and bind a variable, and use it as a
│ │ │ -size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="7304035309-1">(</span><span class="p" data-group-id="7304035309-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7304035309-2">&gt;&gt;</span><span class="p" data-group-id="7304035309-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="7304035309-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="7304035309-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ -used at the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="4394539199-1">(</span><span class="p" data-group-id="4394539199-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="4394539199-3">(</span><span class="p" data-group-id="4394539199-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4394539199-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="4394539199-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4394539199-2">&gt;&gt;</span><span class="p" data-group-id="4394539199-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="4394539199-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="4394539199-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │ +size within the same binary pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="4785558805-1">(</span><span class="p" data-group-id="4785558805-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="n">Sz</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4785558805-2">&gt;&gt;</span><span class="p" data-group-id="4785558805-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="4785558805-3">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="4785558805-3">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is bound to the value in the first byte of the binary. <code class="inline">Sz</code> is then
│ │ │ +used at the number of bytes to match out as a binary.</p><p>Starting in OTP 23, the size can be a guard expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="6743433604-1">(</span><span class="p" data-group-id="6743433604-2">&lt;&lt;</span><span class="n">Sz</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Payload</span><span class="p">:</span><span class="p" data-group-id="6743433604-3">(</span><span class="p" data-group-id="6743433604-4">(</span><span class="n">Sz</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="6743433604-4">)</span><span class="o">*</span><span class="mi">8</span><span class="p" data-group-id="6743433604-3">)</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6743433604-2">&gt;&gt;</span><span class="p" data-group-id="6743433604-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="6743433604-5">{</span><span class="n">Payload</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="6743433604-5">}</span><span class="p">.</span></code></pre><p>Here <code class="inline">Sz</code> is the combined size of the header and the payload, so we will need to
│ │ │  subtract one byte to get the size of the payload.</p><h3 id="getting-the-rest-of-the-binary-or-bitstring" class="section-heading">
│ │ │    <a href="#getting-the-rest-of-the-binary-or-bitstring" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Getting the Rest of the Binary or Bitstring</span>
│ │ │  </h3>
│ │ │ -<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6316068722-1">(</span><span class="p" data-group-id="6316068722-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6316068722-2">&gt;&gt;</span><span class="p" data-group-id="6316068722-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2866736292-1">(</span><span class="p" data-group-id="2866736292-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="2866736292-2">&gt;&gt;</span><span class="p" data-group-id="2866736292-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │ +<p>To match out the rest of a binary, specify a binary field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="6007546398-1">(</span><span class="p" data-group-id="6007546398-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="6007546398-2">&gt;&gt;</span><span class="p" data-group-id="6007546398-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>The size of the tail must be evenly divisible by 8.</p><p>To match out the rest of a bitstring, specify a field without size:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5827384847-1">(</span><span class="p" data-group-id="5827384847-2">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">Rest</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="5827384847-2">&gt;&gt;</span><span class="p" data-group-id="5827384847-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>There are no restrictions on the number of bits in the tail.</p><h2 id="appending-to-a-binary" class="section-heading">
│ │ │    <a href="#appending-to-a-binary" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Appending to a Binary</span>
│ │ │  </h2>
│ │ │ -<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="0310083628-1">(</span><span class="n">T</span><span class="p" data-group-id="0310083628-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0310083628-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0310083628-3">&lt;&lt;</span><span class="p" data-group-id="0310083628-3">&gt;&gt;</span><span class="p" data-group-id="0310083628-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Appending to a binary in an efficient way can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">triples_to_bin</span><span class="p" data-group-id="7030362556-1">(</span><span class="n">T</span><span class="p" data-group-id="7030362556-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="7030362556-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7030362556-3">&lt;&lt;</span><span class="p" data-group-id="7030362556-3">&gt;&gt;</span><span class="p" data-group-id="7030362556-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0310083628-4">(</span><span class="p" data-group-id="0310083628-5">[</span><span class="p" data-group-id="0310083628-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="0310083628-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0310083628-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0310083628-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0310083628-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0310083628-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="0310083628-8">&gt;&gt;</span><span class="p" data-group-id="0310083628-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="0310083628-9">(</span><span class="p" data-group-id="0310083628-10">[</span><span class="p" data-group-id="0310083628-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0310083628-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="7030362556-4">(</span><span class="p" data-group-id="7030362556-5">[</span><span class="p" data-group-id="7030362556-6">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="n">Z</span><span class="p" data-group-id="7030362556-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7030362556-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7030362556-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">triples_to_bin</span><span class="p" data-group-id="7030362556-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7030362556-8">&lt;&lt;</span><span class="n">Acc</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="n">X</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Y</span><span class="p">:</span><span class="mi">32</span><span class="p">,</span><span class="n">Z</span><span class="p">:</span><span class="mi">32</span><span class="p" data-group-id="7030362556-8">&gt;&gt;</span><span class="p" data-group-id="7030362556-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">triples_to_bin</span><span class="p" data-group-id="7030362556-9">(</span><span class="p" data-group-id="7030362556-10">[</span><span class="p" data-group-id="7030362556-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="7030362556-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="list_comprehensions.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/c_port.html
│ │ │ @@ -148,101 +148,101 @@
│ │ │  external program, if it is written properly).</p><p>The port is created using the BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a> with
│ │ │  <code class="inline">{spawn,ExtPrg}</code> as the first argument. The string <code class="inline">ExtPrg</code> is the name of the
│ │ │  external program, including any command line arguments. The second argument is a
│ │ │  list of options, in this case only <code class="inline">{packet,2}</code>. This option says that a 2 byte
│ │ │  length indicator is to be used to simplify the communication between C and
│ │ │  Erlang. The Erlang port automatically adds the length indicator, but this must
│ │ │  be done explicitly in the external C program.</p><p>The process is also set to trap exits, which enables detection of failure of the
│ │ │ -external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9966021286-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="9966021286-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9966021286-2">(</span><span class="p" data-group-id="9966021286-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9966021286-3">]</span><span class="p" data-group-id="9966021286-2">)</span><span class="p">.</span><span class="w">
│ │ │ +external program:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2585469026-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="2585469026-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2585469026-2">(</span><span class="p" data-group-id="2585469026-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2585469026-3">]</span><span class="p" data-group-id="2585469026-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="9966021286-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9966021286-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">spawn</span><span class="p" data-group-id="9966021286-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9966021286-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="9966021286-6">]</span><span class="p" data-group-id="9966021286-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2585469026-4">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2585469026-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">spawn</span><span class="p" data-group-id="2585469026-5">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2585469026-6">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="2585469026-6">]</span><span class="p" data-group-id="2585469026-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9966021286-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9966021286-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="9966021286-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9966021286-9">(</span><span class="p" data-group-id="9966021286-9">)</span><span class="p" data-group-id="9966021286-8">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">process_flag</span><span class="p" data-group-id="9966021286-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9966021286-10">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9966021286-11">(</span><span class="p" data-group-id="9966021286-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="9966021286-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9966021286-13">[</span><span class="p" data-group-id="9966021286-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9966021286-14">}</span><span class="p" data-group-id="9966021286-13">]</span><span class="p" data-group-id="9966021286-11">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="9966021286-15">(</span><span class="n">Port</span><span class="p" data-group-id="9966021286-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ -message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="8553289783-1">(</span><span class="n">X</span><span class="p" data-group-id="8553289783-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="8553289783-2">(</span><span class="p" data-group-id="8553289783-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8553289783-3">}</span><span class="p" data-group-id="8553289783-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="8553289783-4">(</span><span class="n">Y</span><span class="p" data-group-id="8553289783-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">call_port</span><span class="p" data-group-id="8553289783-5">(</span><span class="p" data-group-id="8553289783-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8553289783-6">}</span><span class="p" data-group-id="8553289783-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2585469026-7">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="2585469026-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="2585469026-8">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2585469026-9">(</span><span class="p" data-group-id="2585469026-9">)</span><span class="p" data-group-id="2585469026-8">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">process_flag</span><span class="p" data-group-id="2585469026-10">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2585469026-10">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2585469026-11">(</span><span class="p" data-group-id="2585469026-12">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="2585469026-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2585469026-13">[</span><span class="p" data-group-id="2585469026-14">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2585469026-14">}</span><span class="p" data-group-id="2585469026-13">]</span><span class="p" data-group-id="2585469026-11">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="2585469026-15">(</span><span class="n">Port</span><span class="p" data-group-id="2585469026-15">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex1:foo/1</code> and <code class="inline">complex1:bar/1</code> can be implemented. Both send a
│ │ │ +message to the <code class="inline">complex</code> process and receive the following replies:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2769917862-1">(</span><span class="n">X</span><span class="p" data-group-id="2769917862-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="2769917862-2">(</span><span class="p" data-group-id="2769917862-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2769917862-3">}</span><span class="p" data-group-id="2769917862-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="2769917862-4">(</span><span class="n">Y</span><span class="p" data-group-id="2769917862-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">call_port</span><span class="p" data-group-id="2769917862-5">(</span><span class="p" data-group-id="2769917862-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2769917862-6">}</span><span class="p" data-group-id="2769917862-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="8553289783-7">(</span><span class="n">Msg</span><span class="p" data-group-id="8553289783-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8553289783-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8553289783-9">(</span><span class="p" data-group-id="8553289783-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8553289783-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="2769917862-7">(</span><span class="n">Msg</span><span class="p" data-group-id="2769917862-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2769917862-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2769917862-9">(</span><span class="p" data-group-id="2769917862-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2769917862-8">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8553289783-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="8553289783-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2769917862-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2769917862-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │        </span><span class="n">Result</span><span class="w">
│ │ │ -  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="7545318075-1">(</span><span class="n">Port</span><span class="p" data-group-id="7545318075-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process does the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="6483777160-1">(</span><span class="n">Port</span><span class="p" data-group-id="6483777160-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7545318075-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="7545318075-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7545318075-3">{</span><span class="nf">self</span><span class="p" data-group-id="7545318075-4">(</span><span class="p" data-group-id="7545318075-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7545318075-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="7545318075-6">(</span><span class="n">Msg</span><span class="p" data-group-id="7545318075-6">)</span><span class="p" data-group-id="7545318075-5">}</span><span class="p" data-group-id="7545318075-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6483777160-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="6483777160-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +      </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6483777160-3">{</span><span class="nf">self</span><span class="p" data-group-id="6483777160-4">(</span><span class="p" data-group-id="6483777160-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6483777160-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="6483777160-6">(</span><span class="n">Msg</span><span class="p" data-group-id="6483777160-6">)</span><span class="p" data-group-id="6483777160-5">}</span><span class="p" data-group-id="6483777160-3">}</span><span class="p">,</span><span class="w">
│ │ │        </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7545318075-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7545318075-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7545318075-8">}</span><span class="p" data-group-id="7545318075-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7545318075-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="7545318075-10">(</span><span class="n">Data</span><span class="p" data-group-id="7545318075-10">)</span><span class="p" data-group-id="7545318075-9">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6483777160-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6483777160-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6483777160-8">}</span><span class="p" data-group-id="6483777160-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +          </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6483777160-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="6483777160-10">(</span><span class="n">Data</span><span class="p" data-group-id="6483777160-10">)</span><span class="p" data-group-id="6483777160-9">}</span><span class="w">
│ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -      </span><span class="nf">loop</span><span class="p" data-group-id="7545318075-11">(</span><span class="n">Port</span><span class="p" data-group-id="7545318075-11">)</span><span class="w">
│ │ │ +      </span><span class="nf">loop</span><span class="p" data-group-id="6483777160-11">(</span><span class="n">Port</span><span class="p" data-group-id="6483777160-11">)</span><span class="w">
│ │ │    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="9306702092-1">(</span><span class="p" data-group-id="9306702092-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9306702092-2">}</span><span class="p" data-group-id="9306702092-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9306702092-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9306702092-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="9306702092-4">(</span><span class="p" data-group-id="9306702092-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9306702092-5">}</span><span class="p" data-group-id="9306702092-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9306702092-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9306702092-6">]</span><span class="p">.</span><span class="w">
│ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="5686361724-1">(</span><span class="p" data-group-id="5686361724-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5686361724-2">}</span><span class="p" data-group-id="5686361724-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5686361724-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5686361724-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="5686361724-4">(</span><span class="p" data-group-id="5686361724-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5686361724-5">}</span><span class="p" data-group-id="5686361724-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5686361724-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5686361724-6">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="9306702092-7">(</span><span class="p" data-group-id="9306702092-8">[</span><span class="n">Int</span><span class="p" data-group-id="9306702092-8">]</span><span class="p" data-group-id="9306702092-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ -detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4495971456-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="4495971456-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4495971456-2">(</span><span class="p" data-group-id="4495971456-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4495971456-3">]</span><span class="p" data-group-id="4495971456-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4495971456-4">(</span><span class="p" data-group-id="4495971456-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4495971456-5">]</span><span class="p" data-group-id="4495971456-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4495971456-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4495971456-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4495971456-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4495971456-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="4495971456-8">]</span><span class="p" data-group-id="4495971456-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4495971456-9">(</span><span class="p" data-group-id="4495971456-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="5686361724-7">(</span><span class="p" data-group-id="5686361724-8">[</span><span class="n">Int</span><span class="p" data-group-id="5686361724-8">]</span><span class="p" data-group-id="5686361724-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functionality for stopping the port and
│ │ │ +detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9425870728-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="9425870728-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9425870728-2">(</span><span class="p" data-group-id="9425870728-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9425870728-3">]</span><span class="p" data-group-id="9425870728-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9425870728-4">(</span><span class="p" data-group-id="9425870728-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9425870728-5">]</span><span class="p" data-group-id="9425870728-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9425870728-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9425870728-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9425870728-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9425870728-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="9425870728-8">]</span><span class="p" data-group-id="9425870728-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="9425870728-9">(</span><span class="p" data-group-id="9425870728-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="4495971456-10">(</span><span class="n">X</span><span class="p" data-group-id="4495971456-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4495971456-11">(</span><span class="p" data-group-id="4495971456-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4495971456-12">}</span><span class="p" data-group-id="4495971456-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="4495971456-13">(</span><span class="n">Y</span><span class="p" data-group-id="4495971456-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4495971456-14">(</span><span class="p" data-group-id="4495971456-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4495971456-15">}</span><span class="p" data-group-id="4495971456-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="9425870728-10">(</span><span class="n">X</span><span class="p" data-group-id="9425870728-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="9425870728-11">(</span><span class="p" data-group-id="9425870728-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9425870728-12">}</span><span class="p" data-group-id="9425870728-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="9425870728-13">(</span><span class="n">Y</span><span class="p" data-group-id="9425870728-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="9425870728-14">(</span><span class="p" data-group-id="9425870728-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9425870728-15">}</span><span class="p" data-group-id="9425870728-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="4495971456-16">(</span><span class="n">Msg</span><span class="p" data-group-id="4495971456-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4495971456-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4495971456-18">(</span><span class="p" data-group-id="4495971456-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4495971456-17">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="9425870728-16">(</span><span class="n">Msg</span><span class="p" data-group-id="9425870728-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9425870728-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9425870728-18">(</span><span class="p" data-group-id="9425870728-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9425870728-17">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="4495971456-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4495971456-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9425870728-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9425870728-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4495971456-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4495971456-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4495971456-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4495971456-22">(</span><span class="p" data-group-id="4495971456-22">)</span><span class="p" data-group-id="4495971456-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="4495971456-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4495971456-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4495971456-24">(</span><span class="p" data-group-id="4495971456-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4495971456-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4495971456-26">[</span><span class="p" data-group-id="4495971456-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4495971456-27">}</span><span class="p" data-group-id="4495971456-26">]</span><span class="p" data-group-id="4495971456-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4495971456-28">(</span><span class="n">Port</span><span class="p" data-group-id="4495971456-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9425870728-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9425870728-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9425870728-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9425870728-22">(</span><span class="p" data-group-id="9425870728-22">)</span><span class="p" data-group-id="9425870728-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="9425870728-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9425870728-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9425870728-24">(</span><span class="p" data-group-id="9425870728-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="9425870728-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9425870728-26">[</span><span class="p" data-group-id="9425870728-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9425870728-27">}</span><span class="p" data-group-id="9425870728-26">]</span><span class="p" data-group-id="9425870728-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="9425870728-28">(</span><span class="n">Port</span><span class="p" data-group-id="9425870728-28">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4495971456-29">(</span><span class="n">Port</span><span class="p" data-group-id="4495971456-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="9425870728-29">(</span><span class="n">Port</span><span class="p" data-group-id="9425870728-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="4495971456-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4495971456-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4495971456-31">{</span><span class="nf">self</span><span class="p" data-group-id="4495971456-32">(</span><span class="p" data-group-id="4495971456-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4495971456-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4495971456-34">(</span><span class="n">Msg</span><span class="p" data-group-id="4495971456-34">)</span><span class="p" data-group-id="4495971456-33">}</span><span class="p" data-group-id="4495971456-31">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9425870728-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9425870728-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9425870728-31">{</span><span class="nf">self</span><span class="p" data-group-id="9425870728-32">(</span><span class="p" data-group-id="9425870728-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9425870728-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="9425870728-34">(</span><span class="n">Msg</span><span class="p" data-group-id="9425870728-34">)</span><span class="p" data-group-id="9425870728-33">}</span><span class="p" data-group-id="9425870728-31">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="4495971456-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4495971456-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4495971456-36">}</span><span class="p" data-group-id="4495971456-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4495971456-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4495971456-38">(</span><span class="n">Data</span><span class="p" data-group-id="4495971456-38">)</span><span class="p" data-group-id="4495971456-37">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="9425870728-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9425870728-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9425870728-36">}</span><span class="p" data-group-id="9425870728-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9425870728-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="9425870728-38">(</span><span class="n">Data</span><span class="p" data-group-id="9425870728-38">)</span><span class="p" data-group-id="9425870728-37">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="4495971456-39">(</span><span class="n">Port</span><span class="p" data-group-id="4495971456-39">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="9425870728-39">(</span><span class="n">Port</span><span class="p" data-group-id="9425870728-39">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4495971456-40">{</span><span class="nf">self</span><span class="p" data-group-id="4495971456-41">(</span><span class="p" data-group-id="4495971456-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4495971456-40">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9425870728-40">{</span><span class="nf">self</span><span class="p" data-group-id="9425870728-41">(</span><span class="p" data-group-id="9425870728-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="9425870728-40">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="4495971456-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4495971456-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="4495971456-43">(</span><span class="ss">normal</span><span class="p" data-group-id="4495971456-43">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="9425870728-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="9425870728-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="9425870728-43">(</span><span class="ss">normal</span><span class="p" data-group-id="9425870728-43">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="4495971456-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4495971456-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="4495971456-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4495971456-45">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9425870728-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9425870728-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="9425870728-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="9425870728-45">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4495971456-46">(</span><span class="p" data-group-id="4495971456-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4495971456-47">}</span><span class="p" data-group-id="4495971456-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4495971456-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4495971456-48">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4495971456-49">(</span><span class="p" data-group-id="4495971456-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4495971456-50">}</span><span class="p" data-group-id="4495971456-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4495971456-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4495971456-51">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="9425870728-46">(</span><span class="p" data-group-id="9425870728-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9425870728-47">}</span><span class="p" data-group-id="9425870728-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9425870728-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9425870728-48">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="9425870728-49">(</span><span class="p" data-group-id="9425870728-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9425870728-50">}</span><span class="p" data-group-id="9425870728-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9425870728-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9425870728-51">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="4495971456-52">(</span><span class="p" data-group-id="4495971456-53">[</span><span class="n">Int</span><span class="p" data-group-id="4495971456-53">]</span><span class="p" data-group-id="4495971456-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="9425870728-52">(</span><span class="p" data-group-id="9425870728-53">[</span><span class="n">Int</span><span class="p" data-group-id="9425870728-53">]</span><span class="p" data-group-id="9425870728-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-program" class="section-heading">
│ │ │    <a href="#c-program" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">C Program</span>
│ │ │  </h2>
│ │ │  <p>On the C side, it is necessary to write functions for receiving and sending data
│ │ │  with 2 byte length indicators from/to Erlang. By default, the C program is to
│ │ │ @@ -333,25 +333,25 @@
│ │ │  and terminates.</p><h2 id="running-the-example" class="section-heading">
│ │ │    <a href="#running-the-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running the Example</span>
│ │ │  </h2>
│ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">$ gcc -o extprg complex.c erl_comm.c port.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="1477951203-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="1477951203-1">]</span><span class="w"> </span><span class="p" data-group-id="1477951203-2">[</span><span class="ss">source</span><span class="p" data-group-id="1477951203-2">]</span><span class="w"> </span><span class="p" data-group-id="1477951203-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="1477951203-3">]</span><span class="w"> </span><span class="p" data-group-id="1477951203-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1477951203-4">]</span><span class="w"> </span><span class="p" data-group-id="1477951203-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="1477951203-5">]</span><span class="w"> </span><span class="p" data-group-id="1477951203-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1477951203-6">]</span><span class="w"> </span><span class="p" data-group-id="1477951203-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="1477951203-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="3889927104-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="3889927104-1">]</span><span class="w"> </span><span class="p" data-group-id="3889927104-2">[</span><span class="ss">source</span><span class="p" data-group-id="3889927104-2">]</span><span class="w"> </span><span class="p" data-group-id="3889927104-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3889927104-3">]</span><span class="w"> </span><span class="p" data-group-id="3889927104-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3889927104-4">]</span><span class="w"> </span><span class="p" data-group-id="3889927104-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3889927104-5">]</span><span class="w"> </span><span class="p" data-group-id="3889927104-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3889927104-6">]</span><span class="w"> </span><span class="p" data-group-id="3889927104-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="3889927104-7">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="1477951203-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="1477951203-9">(</span><span class="p" data-group-id="1477951203-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="1477951203-8">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="1477951203-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="1477951203-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1477951203-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="1477951203-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2446757690-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="2446757690-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="3889927104-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3889927104-9">(</span><span class="p" data-group-id="3889927104-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3889927104-8">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="3889927104-10">(</span><span class="ss">complex1</span><span class="p" data-group-id="3889927104-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3889927104-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex1</span><span class="p" data-group-id="3889927104-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2170433128-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="2170433128-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="2446757690-2">(</span><span class="mi">3</span><span class="p" data-group-id="2446757690-2">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="2170433128-2">(</span><span class="mi">3</span><span class="p" data-group-id="2170433128-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="2446757690-3">(</span><span class="mi">5</span><span class="p" data-group-id="2446757690-3">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="2170433128-3">(</span><span class="mi">5</span><span class="p" data-group-id="2170433128-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2446757690-4">(</span><span class="p" data-group-id="2446757690-4">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">complex1</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2170433128-4">(</span><span class="p" data-group-id="2170433128-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="example.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/c_portdriver.html
│ │ │ @@ -151,112 +151,112 @@
│ │ │  <p>Like a port program, the port communicates with an Erlang process. All
│ │ │  communication goes through one Erlang process that is the <em>connected process</em> of
│ │ │  the port driver. Terminating this process closes the port driver.</p><p>Before the port is created, the driver must be loaded. This is done with the
│ │ │  function <a href="../../lib/kernel-10.2.7.2/doc/html/erl_ddll.html#load_driver/2"><code class="inline">erl_ddll:load_driver/2</code></a>, with the name of the shared library as
│ │ │  argument.</p><p>The port is then created using the BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#open_port/2"><code class="inline">open_port/2</code></a>, with the
│ │ │  tuple <code class="inline">{spawn, DriverName}</code> as the first argument. The string <code class="inline">SharedLib</code> is the
│ │ │  name of the port driver. The second argument is a list of options, none in this
│ │ │ -case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3232890570-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="3232890570-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3232890570-2">(</span><span class="p" data-group-id="3232890570-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3232890570-3">]</span><span class="p" data-group-id="3232890570-2">)</span><span class="p">.</span><span class="w">
│ │ │ +case:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0120575788-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="0120575788-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0120575788-2">(</span><span class="p" data-group-id="0120575788-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0120575788-3">]</span><span class="p" data-group-id="0120575788-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="3232890570-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="3232890570-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="3232890570-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="3232890570-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0120575788-4">(</span><span class="n">SharedLib</span><span class="p" data-group-id="0120575788-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="0120575788-5">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="0120575788-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3232890570-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="3232890570-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="3232890570-7">(</span><span class="p" data-group-id="3232890570-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="3232890570-8">}</span><span class="p" data-group-id="3232890570-7">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0120575788-6">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="0120575788-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0120575788-7">(</span><span class="p" data-group-id="0120575788-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="0120575788-8">}</span><span class="p" data-group-id="0120575788-7">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3232890570-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3232890570-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="3232890570-10">]</span><span class="p" data-group-id="3232890570-9">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0120575788-9">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0120575788-10">[</span><span class="n">SharedLib</span><span class="p" data-group-id="0120575788-10">]</span><span class="p" data-group-id="0120575788-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3232890570-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="3232890570-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nf">register</span><span class="p" data-group-id="3232890570-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3232890570-13">(</span><span class="p" data-group-id="3232890570-13">)</span><span class="p" data-group-id="3232890570-12">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="3232890570-14">(</span><span class="p" data-group-id="3232890570-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="3232890570-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3232890570-16">[</span><span class="p" data-group-id="3232890570-16">]</span><span class="p" data-group-id="3232890570-14">)</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">loop</span><span class="p" data-group-id="3232890570-17">(</span><span class="n">Port</span><span class="p" data-group-id="3232890570-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ -message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1730662957-1">(</span><span class="n">X</span><span class="p" data-group-id="1730662957-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="1730662957-2">(</span><span class="p" data-group-id="1730662957-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1730662957-3">}</span><span class="p" data-group-id="1730662957-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="1730662957-4">(</span><span class="n">Y</span><span class="p" data-group-id="1730662957-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="1730662957-5">(</span><span class="p" data-group-id="1730662957-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1730662957-6">}</span><span class="p" data-group-id="1730662957-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0120575788-11">(</span><span class="n">SharedLib</span><span class="p" data-group-id="0120575788-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nf">register</span><span class="p" data-group-id="0120575788-12">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0120575788-13">(</span><span class="p" data-group-id="0120575788-13">)</span><span class="p" data-group-id="0120575788-12">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0120575788-14">(</span><span class="p" data-group-id="0120575788-15">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="0120575788-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0120575788-16">[</span><span class="p" data-group-id="0120575788-16">]</span><span class="p" data-group-id="0120575788-14">)</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">loop</span><span class="p" data-group-id="0120575788-17">(</span><span class="n">Port</span><span class="p" data-group-id="0120575788-17">)</span><span class="p">.</span></code></pre><p>Now <code class="inline">complex5:foo/1</code> and <code class="inline">complex5:bar/1</code> can be implemented. Both send a
│ │ │ +message to the <code class="inline">complex</code> process and receive the following reply:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="4688908132-1">(</span><span class="n">X</span><span class="p" data-group-id="4688908132-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4688908132-2">(</span><span class="p" data-group-id="4688908132-3">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4688908132-3">}</span><span class="p" data-group-id="4688908132-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="4688908132-4">(</span><span class="n">Y</span><span class="p" data-group-id="4688908132-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="4688908132-5">(</span><span class="p" data-group-id="4688908132-6">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4688908132-6">}</span><span class="p" data-group-id="4688908132-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="1730662957-7">(</span><span class="n">Msg</span><span class="p" data-group-id="1730662957-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1730662957-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1730662957-9">(</span><span class="p" data-group-id="1730662957-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="1730662957-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="4688908132-7">(</span><span class="n">Msg</span><span class="p" data-group-id="4688908132-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4688908132-8">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4688908132-9">(</span><span class="p" data-group-id="4688908132-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4688908132-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1730662957-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1730662957-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4688908132-10">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4688908132-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Result</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3925225930-1">(</span><span class="n">Port</span><span class="p" data-group-id="3925225930-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">complex</code> process performs the following:</p><ul><li>Encodes the message into a sequence of bytes.</li><li>Sends it to the port.</li><li>Waits for a reply.</li><li>Decodes the reply.</li><li>Sends it back to the caller:</li></ul><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="4936207535-1">(</span><span class="n">Port</span><span class="p" data-group-id="4936207535-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3925225930-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="3925225930-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3925225930-3">{</span><span class="nf">self</span><span class="p" data-group-id="3925225930-4">(</span><span class="p" data-group-id="3925225930-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3925225930-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="3925225930-6">(</span><span class="n">Msg</span><span class="p" data-group-id="3925225930-6">)</span><span class="p" data-group-id="3925225930-5">}</span><span class="p" data-group-id="3925225930-3">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4936207535-2">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4936207535-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4936207535-3">{</span><span class="nf">self</span><span class="p" data-group-id="4936207535-4">(</span><span class="p" data-group-id="4936207535-4">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4936207535-5">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4936207535-6">(</span><span class="n">Msg</span><span class="p" data-group-id="4936207535-6">)</span><span class="p" data-group-id="4936207535-5">}</span><span class="p" data-group-id="4936207535-3">}</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="k">receive</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="3925225930-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3925225930-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3925225930-8">}</span><span class="p" data-group-id="3925225930-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3925225930-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="3925225930-10">(</span><span class="n">Data</span><span class="p" data-group-id="3925225930-10">)</span><span class="p" data-group-id="3925225930-9">}</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="4936207535-7">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4936207535-8">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4936207535-8">}</span><span class="p" data-group-id="4936207535-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4936207535-9">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4936207535-10">(</span><span class="n">Data</span><span class="p" data-group-id="4936207535-10">)</span><span class="p" data-group-id="4936207535-9">}</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="3925225930-11">(</span><span class="n">Port</span><span class="p" data-group-id="3925225930-11">)</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="4936207535-11">(</span><span class="n">Port</span><span class="p" data-group-id="4936207535-11">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Assuming that both the arguments and the results from the C functions are less
│ │ │  than 256, a simple encoding/decoding scheme is employed. In this scheme, <code class="inline">foo</code>
│ │ │  is represented by byte 1, <code class="inline">bar</code> is represented by 2, and the argument/result is
│ │ │ -represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="2677164773-1">(</span><span class="p" data-group-id="2677164773-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2677164773-2">}</span><span class="p" data-group-id="2677164773-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2677164773-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2677164773-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="2677164773-4">(</span><span class="p" data-group-id="2677164773-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2677164773-5">}</span><span class="p" data-group-id="2677164773-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2677164773-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2677164773-6">]</span><span class="p">.</span><span class="w">
│ │ │ +represented by a single byte as well:</p><pre><code class="makeup erlang" translate="no"><span class="nf">encode</span><span class="p" data-group-id="1787216457-1">(</span><span class="p" data-group-id="1787216457-2">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1787216457-2">}</span><span class="p" data-group-id="1787216457-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1787216457-3">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1787216457-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="1787216457-4">(</span><span class="p" data-group-id="1787216457-5">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1787216457-5">}</span><span class="p" data-group-id="1787216457-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1787216457-6">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1787216457-6">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="2677164773-7">(</span><span class="p" data-group-id="2677164773-8">[</span><span class="n">Int</span><span class="p" data-group-id="2677164773-8">]</span><span class="p" data-group-id="2677164773-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="1787216457-7">(</span><span class="p" data-group-id="1787216457-8">[</span><span class="n">Int</span><span class="p" data-group-id="1787216457-8">]</span><span class="p" data-group-id="1787216457-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>The resulting Erlang program, including functions for stopping the port and
│ │ │  detecting port failures, is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5296435157-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="5296435157-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5296435157-2">(</span><span class="p" data-group-id="5296435157-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5296435157-3">]</span><span class="p" data-group-id="5296435157-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5296435157-4">(</span><span class="p" data-group-id="5296435157-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5296435157-5">]</span><span class="p" data-group-id="5296435157-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9963376974-1">(</span><span class="ss">complex5</span><span class="p" data-group-id="9963376974-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9963376974-2">(</span><span class="p" data-group-id="9963376974-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9963376974-3">]</span><span class="p" data-group-id="9963376974-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9963376974-4">(</span><span class="p" data-group-id="9963376974-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9963376974-5">]</span><span class="p" data-group-id="9963376974-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="5296435157-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="5296435157-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="5296435157-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="5296435157-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9963376974-6">(</span><span class="n">SharedLib</span><span class="p" data-group-id="9963376974-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="9963376974-7">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="9963376974-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │  	</span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5296435157-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="5296435157-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="5296435157-9">(</span><span class="p" data-group-id="5296435157-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="5296435157-10">}</span><span class="p" data-group-id="5296435157-9">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9963376974-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="9963376974-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +	</span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="9963376974-9">(</span><span class="p" data-group-id="9963376974-10">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="9963376974-10">}</span><span class="p" data-group-id="9963376974-9">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="5296435157-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296435157-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="5296435157-12">]</span><span class="p" data-group-id="5296435157-11">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9963376974-11">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9963376974-12">[</span><span class="n">SharedLib</span><span class="p" data-group-id="9963376974-12">]</span><span class="p" data-group-id="9963376974-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5296435157-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="5296435157-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="5296435157-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5296435157-15">(</span><span class="p" data-group-id="5296435157-15">)</span><span class="p" data-group-id="5296435157-14">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="5296435157-16">(</span><span class="p" data-group-id="5296435157-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="5296435157-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296435157-18">[</span><span class="p" data-group-id="5296435157-18">]</span><span class="p" data-group-id="5296435157-16">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="5296435157-19">(</span><span class="n">Port</span><span class="p" data-group-id="5296435157-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9963376974-13">(</span><span class="n">SharedLib</span><span class="p" data-group-id="9963376974-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9963376974-14">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9963376974-15">(</span><span class="p" data-group-id="9963376974-15">)</span><span class="p" data-group-id="9963376974-14">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9963376974-16">(</span><span class="p" data-group-id="9963376974-17">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">SharedLib</span><span class="p" data-group-id="9963376974-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9963376974-18">[</span><span class="p" data-group-id="9963376974-18">]</span><span class="p" data-group-id="9963376974-16">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="9963376974-19">(</span><span class="n">Port</span><span class="p" data-group-id="9963376974-19">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="5296435157-20">(</span><span class="p" data-group-id="5296435157-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="9963376974-20">(</span><span class="p" data-group-id="9963376974-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="5296435157-21">(</span><span class="n">X</span><span class="p" data-group-id="5296435157-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="5296435157-22">(</span><span class="p" data-group-id="5296435157-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5296435157-23">}</span><span class="p" data-group-id="5296435157-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="5296435157-24">(</span><span class="n">Y</span><span class="p" data-group-id="5296435157-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="5296435157-25">(</span><span class="p" data-group-id="5296435157-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5296435157-26">}</span><span class="p" data-group-id="5296435157-25">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="9963376974-21">(</span><span class="n">X</span><span class="p" data-group-id="9963376974-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="9963376974-22">(</span><span class="p" data-group-id="9963376974-23">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9963376974-23">}</span><span class="p" data-group-id="9963376974-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="9963376974-24">(</span><span class="n">Y</span><span class="p" data-group-id="9963376974-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="9963376974-25">(</span><span class="p" data-group-id="9963376974-26">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9963376974-26">}</span><span class="p" data-group-id="9963376974-25">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="5296435157-27">(</span><span class="n">Msg</span><span class="p" data-group-id="5296435157-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5296435157-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5296435157-29">(</span><span class="p" data-group-id="5296435157-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5296435157-28">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="9963376974-27">(</span><span class="n">Msg</span><span class="p" data-group-id="9963376974-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9963376974-28">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9963376974-29">(</span><span class="p" data-group-id="9963376974-29">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9963376974-28">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5296435157-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5296435157-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9963376974-30">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9963376974-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="5296435157-31">(</span><span class="n">Port</span><span class="p" data-group-id="5296435157-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="9963376974-31">(</span><span class="n">Port</span><span class="p" data-group-id="9963376974-31">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5296435157-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5296435157-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5296435157-33">{</span><span class="nf">self</span><span class="p" data-group-id="5296435157-34">(</span><span class="p" data-group-id="5296435157-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296435157-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="5296435157-36">(</span><span class="n">Msg</span><span class="p" data-group-id="5296435157-36">)</span><span class="p" data-group-id="5296435157-35">}</span><span class="p" data-group-id="5296435157-33">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9963376974-32">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9963376974-32">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9963376974-33">{</span><span class="nf">self</span><span class="p" data-group-id="9963376974-34">(</span><span class="p" data-group-id="9963376974-34">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9963376974-35">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="9963376974-36">(</span><span class="n">Msg</span><span class="p" data-group-id="9963376974-36">)</span><span class="p" data-group-id="9963376974-35">}</span><span class="p" data-group-id="9963376974-33">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="5296435157-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296435157-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5296435157-38">}</span><span class="p" data-group-id="5296435157-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5296435157-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="5296435157-40">(</span><span class="n">Data</span><span class="p" data-group-id="5296435157-40">)</span><span class="p" data-group-id="5296435157-39">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="9963376974-37">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9963376974-38">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9963376974-38">}</span><span class="p" data-group-id="9963376974-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9963376974-39">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="9963376974-40">(</span><span class="n">Data</span><span class="p" data-group-id="9963376974-40">)</span><span class="p" data-group-id="9963376974-39">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="5296435157-41">(</span><span class="n">Port</span><span class="p" data-group-id="5296435157-41">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="9963376974-41">(</span><span class="n">Port</span><span class="p" data-group-id="9963376974-41">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5296435157-42">{</span><span class="nf">self</span><span class="p" data-group-id="5296435157-43">(</span><span class="p" data-group-id="5296435157-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="5296435157-42">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9963376974-42">{</span><span class="nf">self</span><span class="p" data-group-id="9963376974-43">(</span><span class="p" data-group-id="9963376974-43">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="9963376974-42">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="5296435157-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="5296435157-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="5296435157-45">(</span><span class="ss">normal</span><span class="p" data-group-id="5296435157-45">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="9963376974-44">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="9963376974-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="9963376974-45">(</span><span class="ss">normal</span><span class="p" data-group-id="9963376974-45">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5296435157-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5296435157-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5296435157-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5296435157-48">[</span><span class="n">Reason</span><span class="p" data-group-id="5296435157-48">]</span><span class="p" data-group-id="5296435157-47">)</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="5296435157-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="5296435157-49">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9963376974-46">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9963376974-46">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9963376974-47">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9963376974-48">[</span><span class="n">Reason</span><span class="p" data-group-id="9963376974-48">]</span><span class="p" data-group-id="9963376974-47">)</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="9963376974-49">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="9963376974-49">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="5296435157-50">(</span><span class="p" data-group-id="5296435157-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5296435157-51">}</span><span class="p" data-group-id="5296435157-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5296435157-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5296435157-52">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="5296435157-53">(</span><span class="p" data-group-id="5296435157-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5296435157-54">}</span><span class="p" data-group-id="5296435157-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5296435157-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5296435157-55">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="9963376974-50">(</span><span class="p" data-group-id="9963376974-51">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9963376974-51">}</span><span class="p" data-group-id="9963376974-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9963376974-52">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9963376974-52">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="9963376974-53">(</span><span class="p" data-group-id="9963376974-54">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9963376974-54">}</span><span class="p" data-group-id="9963376974-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9963376974-55">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9963376974-55">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="5296435157-56">(</span><span class="p" data-group-id="5296435157-57">[</span><span class="n">Int</span><span class="p" data-group-id="5296435157-57">]</span><span class="p" data-group-id="5296435157-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="9963376974-56">(</span><span class="p" data-group-id="9963376974-57">[</span><span class="n">Int</span><span class="p" data-group-id="9963376974-57">]</span><span class="p" data-group-id="9963376974-56">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><h2 id="c-driver" class="section-heading">
│ │ │    <a href="#c-driver" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">C Driver</span>
│ │ │  </h2>
│ │ │  <p>The C driver is a module that is compiled and linked into a shared library. It
│ │ │  uses a driver structure and includes the header file <code class="inline">erl_driver.h</code>.</p><p>The driver structure is filled with the driver name and function pointers. It is
│ │ │ @@ -347,25 +347,25 @@
│ │ │    <a href="#running-the-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running the Example</span>
│ │ │  </h2>
│ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o example_drv.so -fpic -shared complex.c port_driver.c
│ │ │  windows&gt; cl -LD -MD -Fe example_drv.dll complex.c port_driver.c</code></pre><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="2440412040-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="2440412040-1">]</span><span class="w"> </span><span class="p" data-group-id="2440412040-2">[</span><span class="ss">source</span><span class="p" data-group-id="2440412040-2">]</span><span class="w"> </span><span class="p" data-group-id="2440412040-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="2440412040-3">]</span><span class="w"> </span><span class="p" data-group-id="2440412040-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="2440412040-4">]</span><span class="w"> </span><span class="p" data-group-id="2440412040-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="2440412040-5">]</span><span class="w"> </span><span class="p" data-group-id="2440412040-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2440412040-6">]</span><span class="w"> </span><span class="p" data-group-id="2440412040-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="2440412040-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="0170800263-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="0170800263-1">]</span><span class="w"> </span><span class="p" data-group-id="0170800263-2">[</span><span class="ss">source</span><span class="p" data-group-id="0170800263-2">]</span><span class="w"> </span><span class="p" data-group-id="0170800263-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0170800263-3">]</span><span class="w"> </span><span class="p" data-group-id="0170800263-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0170800263-4">]</span><span class="w"> </span><span class="p" data-group-id="0170800263-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0170800263-5">]</span><span class="w"> </span><span class="p" data-group-id="0170800263-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0170800263-6">]</span><span class="w"> </span><span class="p" data-group-id="0170800263-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="0170800263-7">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="2440412040-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="2440412040-9">(</span><span class="p" data-group-id="2440412040-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="2440412040-8">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="2440412040-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="2440412040-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2440412040-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="2440412040-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2414493809-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="2414493809-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="0170800263-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="0170800263-9">(</span><span class="p" data-group-id="0170800263-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="0170800263-8">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="0170800263-10">(</span><span class="ss">complex5</span><span class="p" data-group-id="0170800263-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0170800263-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex5</span><span class="p" data-group-id="0170800263-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8152196685-1">(</span><span class="s">&quot;example_drv&quot;</span><span class="p" data-group-id="8152196685-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="2414493809-2">(</span><span class="mi">3</span><span class="p" data-group-id="2414493809-2">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="8152196685-2">(</span><span class="mi">3</span><span class="p" data-group-id="8152196685-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="2414493809-3">(</span><span class="mi">5</span><span class="p" data-group-id="2414493809-3">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="8152196685-3">(</span><span class="mi">5</span><span class="p" data-group-id="8152196685-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2414493809-4">(</span><span class="p" data-group-id="2414493809-4">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">complex5</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="8152196685-4">(</span><span class="p" data-group-id="8152196685-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="erl_interface.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/code_loading.html
│ │ │ @@ -122,16 +122,16 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Compilation</span>
│ │ │  </h2>
│ │ │  <p>Erlang programs must be <em>compiled</em> to object code. The compiler can generate a
│ │ │  new file that contains the object code. The current abstract machine, which runs
│ │ │  the object code, is called BEAM, therefore the object files get the suffix
│ │ │ -<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../lib/compiler-8.6.1.2/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="2006358278-1">(</span><span class="n">Module</span><span class="p" data-group-id="2006358278-1">)</span><span class="w">
│ │ │ -</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="2006358278-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="2006358278-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │ +<code class="inline">.beam</code>. The compiler can also generate a binary which can be loaded directly.</p><p>The compiler is located in the module <a href="../../lib/compiler-8.6.1.2/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><pre><code class="makeup erlang" translate="no"><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="5429017820-1">(</span><span class="n">Module</span><span class="p" data-group-id="5429017820-1">)</span><span class="w">
│ │ │ +</span><span class="nc">compile</span><span class="p">:</span><span class="nf">file</span><span class="p" data-group-id="5429017820-2">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="5429017820-2">)</span></code></pre><p>The Erlang shell understands the command <code class="inline">c(Module)</code>, which both compiles and
│ │ │  loads <code class="inline">Module</code>.</p><p>There is also a module <code class="inline">make</code>, which provides a set of functions similar to the
│ │ │  UNIX type Make functions, see module <a href="../../lib/tools-4.1.1/doc/html/make.html"><code class="inline">make</code></a> in Tools.</p><p>The compiler can also be accessed from the OS prompt using the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erl_cmd.html">erl</a> executable in ERTS.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -compile Module1...ModuleN</span><span class="w">
│ │ │  </span><span class="c1">% erl -make</span></code></pre><p>The <code class="inline">erlc</code> program provides way to compile modules from the OS
│ │ │  shell, see the <a href="../../erts-15.2.7.2/doc/html/erlc_cmd.html">erlc</a> executable in ERTS. It
│ │ │  understands a number of flags that can be used to define macros, add search
│ │ │  paths for include files, and more.</p><pre><code class="text">% erlc &lt;flags&gt; File1.erl...FileN.erl</code></pre><p><a href="" id="loading"></a></p><h2 id="code-loading" class="section-heading">
│ │ │ @@ -156,54 +156,54 @@
│ │ │  When a module is loaded into the system for the first time, the code becomes
│ │ │  'current'. If then a new instance of the module is loaded, the code of the
│ │ │  previous instance becomes 'old' and the new instance becomes 'current'.</p><p>Both old and current code is valid, and can be evaluated concurrently. Fully
│ │ │  qualified function calls always refer to current code. Old code can still be
│ │ │  evaluated because of processes lingering in the old code.</p><p>If a third instance of the module is loaded, the code server removes (purges)
│ │ │  the old code and any processes lingering in it is terminated. Then the third
│ │ │  instance becomes 'current' and the previously current code becomes 'old'.</p><p>To change from old code to current code, a process must make a fully qualified
│ │ │ -function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1452872707-1">(</span><span class="ss">m</span><span class="p" data-group-id="1452872707-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1452872707-2">(</span><span class="p" data-group-id="1452872707-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1452872707-3">]</span><span class="p" data-group-id="1452872707-2">)</span><span class="p">.</span><span class="w">
│ │ │ +function call.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6407278972-1">(</span><span class="ss">m</span><span class="p" data-group-id="6407278972-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6407278972-2">(</span><span class="p" data-group-id="6407278972-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6407278972-3">]</span><span class="p" data-group-id="6407278972-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="1452872707-4">(</span><span class="p" data-group-id="1452872707-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="6407278972-4">(</span><span class="p" data-group-id="6407278972-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">code_switch</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="1452872707-5">(</span><span class="p" data-group-id="1452872707-5">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nc">m</span><span class="p">:</span><span class="nf">loop</span><span class="p" data-group-id="6407278972-5">(</span><span class="p" data-group-id="6407278972-5">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">Msg</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="1452872707-6">(</span><span class="p" data-group-id="1452872707-6">)</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6407278972-6">(</span><span class="p" data-group-id="6407278972-6">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To make the process change code, send the message <code class="inline">code_switch</code> to it. The
│ │ │  process then makes a fully qualified call to <code class="inline">m:loop()</code> and changes to current
│ │ │  code. Notice that <code class="inline">m:loop/0</code> must be exported.</p><p>For code replacement of funs to work, use the syntax
│ │ │  <code class="inline">fun Module:FunctionName/Arity</code>.</p><p><a href="" id="on_load"></a></p><h2 id="running-a-function-when-a-module-is-loaded" class="section-heading">
│ │ │    <a href="#running-a-function-when-a-module-is-loaded" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running a Function When a Module is Loaded</span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">-on_load()</code> directive names a function that is to be run automatically when
│ │ │ -a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="2955922096-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="2955922096-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │ +a module is loaded.</p><p>Its syntax is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="7512165269-1">(</span><span class="n">Name</span><span class="o">/</span><span class="mi">0</span><span class="p" data-group-id="7512165269-1">)</span><span class="p">.</span></code></pre><p>It is not necessary to export the function. It is called in a freshly spawned
│ │ │  process (which terminates as soon as the function returns).</p><p>The function must return <code class="inline">ok</code> if the module is to become the new current code
│ │ │  for the module and become callable.</p><p>Returning any other value or generating an exception causes the new code to be
│ │ │  unloaded. If the return value is not an atom, a warning error report is sent to
│ │ │  the error logger.</p><p>If there already is current code for the module, that code will remain current
│ │ │  and can be called until the <code class="inline">on_load</code> function has returned. If the <code class="inline">on_load</code>
│ │ │  function fails, the current code (if any) will remain current. If there is no
│ │ │  current code for a module, any process that makes an external call to the module
│ │ │  before the <code class="inline">on_load</code> function has finished will be suspended until the <code class="inline">on_load</code>
│ │ │  function have finished.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, if the <code class="inline">on_load</code> function failed, any previously current
│ │ │  code would become old, essentially leaving the system without any working and
│ │ │  reachable instance of the module.</p></section><p>In embedded mode, first all modules are loaded. Then all <code class="inline">on_load</code> functions are
│ │ │  called. The system is terminated unless all of the <code class="inline">on_load</code> functions return
│ │ │ -<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0746380780-1">(</span><span class="ss">m</span><span class="p" data-group-id="0746380780-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="0746380780-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0746380780-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">ok</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6968642620-1">(</span><span class="ss">m</span><span class="p" data-group-id="6968642620-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="6968642620-2">(</span><span class="ss">load_my_nifs</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6968642620-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="0746380780-3">(</span><span class="p" data-group-id="0746380780-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">load_my_nifs</span><span class="p" data-group-id="6968642620-3">(</span><span class="p" data-group-id="6968642620-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NifPath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">    </span><span class="c1">%Set up the path to the NIF library.</span><span class="w">
│ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">       </span><span class="c1">%Initialize the Info term</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="0746380780-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="0746380780-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../erts-15.2.7.2/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="6968642620-4">(</span><span class="n">NifPath</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="6968642620-4">)</span><span class="p">.</span></code></pre><p>If the call to <a href="../../erts-15.2.7.2/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a> fails, the module is unloaded and a warning
│ │ │  report is sent to the error loader.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="distributed.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/commoncaveats.html
│ │ │ @@ -118,31 +118,31 @@
│ │ │  <p>This section lists a few constructs to watch out for.</p><h2 id="operator" class="section-heading">
│ │ │    <a href="#operator" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Operator <code class="inline">++</code></span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">++</code> operator copies its left-hand side operand. That is clearly
│ │ │ -seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="8426099195-1">(</span><span class="p" data-group-id="8426099195-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8426099195-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8426099195-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8426099195-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="8426099195-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8426099195-4">)</span><span class="p" data-group-id="8426099195-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="8426099195-5">(</span><span class="p" data-group-id="8426099195-6">[</span><span class="p" data-group-id="8426099195-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8426099195-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="5832762716-1">(</span><span class="p" data-group-id="5832762716-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5832762716-2">]</span><span class="p" data-group-id="5832762716-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="5832762716-3">(</span><span class="n">T</span><span class="p" data-group-id="5832762716-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="5832762716-4">[</span><span class="n">H</span><span class="p" data-group-id="5832762716-4">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">naive_reverse</span><span class="p" data-group-id="5832762716-5">(</span><span class="p" data-group-id="5832762716-6">[</span><span class="p" data-group-id="5832762716-6">]</span><span class="p" data-group-id="5832762716-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5832762716-7">[</span><span class="p" data-group-id="5832762716-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ -result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="0076739500-1">(</span><span class="n">List</span><span class="p" data-group-id="0076739500-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="0076739500-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0076739500-3">[</span><span class="p" data-group-id="0076739500-3">]</span><span class="p" data-group-id="0076739500-2">)</span><span class="p">.</span><span class="w">
│ │ │ +seen if we do our own implementation in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_plus_plus</span><span class="p" data-group-id="8903931968-1">(</span><span class="p" data-group-id="8903931968-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8903931968-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8903931968-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8903931968-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="8903931968-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8903931968-4">)</span><span class="p" data-group-id="8903931968-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">my_plus_plus</span><span class="p" data-group-id="8903931968-5">(</span><span class="p" data-group-id="8903931968-6">[</span><span class="p" data-group-id="8903931968-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8903931968-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>We must be careful how we use <code class="inline">++</code> in a loop. First is how not to use it:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_reverse</span><span class="p" data-group-id="6403593811-1">(</span><span class="p" data-group-id="6403593811-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6403593811-2">]</span><span class="p" data-group-id="6403593811-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">naive_reverse</span><span class="p" data-group-id="6403593811-3">(</span><span class="n">T</span><span class="p" data-group-id="6403593811-3">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6403593811-4">[</span><span class="n">H</span><span class="p" data-group-id="6403593811-4">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">naive_reverse</span><span class="p" data-group-id="6403593811-5">(</span><span class="p" data-group-id="6403593811-6">[</span><span class="p" data-group-id="6403593811-6">]</span><span class="p" data-group-id="6403593811-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6403593811-7">[</span><span class="p" data-group-id="6403593811-7">]</span><span class="p">.</span></code></pre><p>As the <code class="inline">++</code> operator copies its left-hand side operand, the growing
│ │ │ +result is copied repeatedly, leading to quadratic complexity.</p><p>On the other hand, using <code class="inline">++</code> in loop like this is perfectly fine:</p><p><strong>OK</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5638382805-1">(</span><span class="n">List</span><span class="p" data-group-id="5638382805-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5638382805-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5638382805-3">[</span><span class="p" data-group-id="5638382805-3">]</span><span class="p" data-group-id="5638382805-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="0076739500-4">(</span><span class="p" data-group-id="0076739500-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0076739500-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0076739500-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="0076739500-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0076739500-7">[</span><span class="n">H</span><span class="p" data-group-id="0076739500-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0076739500-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="0076739500-8">(</span><span class="p" data-group-id="0076739500-9">[</span><span class="p" data-group-id="0076739500-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="0076739500-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5638382805-4">(</span><span class="p" data-group-id="5638382805-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5638382805-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5638382805-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5638382805-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5638382805-7">[</span><span class="n">H</span><span class="p" data-group-id="5638382805-7">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5638382805-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">naive_but_ok_reverse</span><span class="p" data-group-id="5638382805-8">(</span><span class="p" data-group-id="5638382805-9">[</span><span class="p" data-group-id="5638382805-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5638382805-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>Each list element is copied only once. The growing result <code class="inline">Acc</code> is the right-hand
│ │ │ -side operand, which it is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="6322027661-1">(</span><span class="p" data-group-id="6322027661-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6322027661-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6322027661-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="6322027661-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6322027661-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="6322027661-4">]</span><span class="p" data-group-id="6322027661-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="6322027661-5">(</span><span class="p" data-group-id="6322027661-6">[</span><span class="p" data-group-id="6322027661-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6322027661-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +side operand, which it is <em>not</em> copied.</p><p>Experienced Erlang programmers would probably write as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">vanilla_reverse</span><span class="p" data-group-id="5015169984-1">(</span><span class="p" data-group-id="5015169984-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5015169984-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5015169984-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="5015169984-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5015169984-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="5015169984-4">]</span><span class="p" data-group-id="5015169984-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">vanilla_reverse</span><span class="p" data-group-id="5015169984-5">(</span><span class="p" data-group-id="5015169984-6">[</span><span class="p" data-group-id="5015169984-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5015169984-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">.</span></code></pre><p>In principle, this is slightly more efficient because the list element <code class="inline">[H]</code>
│ │ │  is not built before being copied and discarded. In practice, the compiler
│ │ │  rewrites <code class="inline">[H] ++ Acc</code> to <code class="inline">[H|Acc]</code>.</p><h2 id="timer-module" class="section-heading">
│ │ │    <a href="#timer-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Timer Module</span>
│ │ │ @@ -160,77 +160,77 @@
│ │ │  therefore harmless.</p><h2 id="accidental-copying-and-loss-of-sharing" class="section-heading">
│ │ │    <a href="#accidental-copying-and-loss-of-sharing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Accidental Copying and Loss of Sharing</span>
│ │ │  </h2>
│ │ │  <p>When spawning a new process using a fun, one can accidentally copy more data to
│ │ │ -the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="2477346607-1">(</span><span class="n">State</span><span class="p" data-group-id="2477346607-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2477346607-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2477346607-3">(</span><span class="p" data-group-id="2477346607-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2477346607-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2477346607-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="2477346607-5">]</span><span class="p" data-group-id="2477346607-4">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="2477346607-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │ +the process than intended. For example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental1</span><span class="p" data-group-id="4195814383-1">(</span><span class="n">State</span><span class="p" data-group-id="4195814383-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="4195814383-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4195814383-3">(</span><span class="p" data-group-id="4195814383-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4195814383-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4195814383-5">[</span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p" data-group-id="4195814383-5">]</span><span class="p" data-group-id="4195814383-4">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="4195814383-2">)</span><span class="p">.</span></code></pre><p>The code in the fun will extract one element from the record and print it. The
│ │ │  rest of the <code class="inline">state</code> record is not used. However, when the <a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn/1"><code class="inline">spawn/1</code></a>
│ │ │ -function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="1610069856-1">(</span><span class="n">State</span><span class="p" data-group-id="1610069856-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1610069856-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1610069856-3">(</span><span class="p" data-group-id="1610069856-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1610069856-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1610069856-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="1610069856-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1610069856-6">)</span><span class="p" data-group-id="1610069856-5">]</span><span class="p" data-group-id="1610069856-4">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="1610069856-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ -behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="9486202930-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9486202930-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9486202930-2">(</span><span class="p" data-group-id="9486202930-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9486202930-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9486202930-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ -map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="7740029342-1">(</span><span class="p" data-group-id="7740029342-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="7740029342-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7740029342-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="7740029342-3">)</span><span class="p" data-group-id="7740029342-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │ +function is executed, the entire record is copied to the newly created process.</p><p>The same kind of problem can happen with a map:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">accidental2</span><span class="p" data-group-id="3330455605-1">(</span><span class="n">State</span><span class="p" data-group-id="3330455605-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3330455605-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3330455605-3">(</span><span class="p" data-group-id="3330455605-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3330455605-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3330455605-5">[</span><span class="nf">map_get</span><span class="p" data-group-id="3330455605-6">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3330455605-6">)</span><span class="p" data-group-id="3330455605-5">]</span><span class="p" data-group-id="3330455605-4">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="3330455605-2">)</span><span class="p">.</span></code></pre><p>In the following example (part of a module implementing the <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │ +behavior) the created fun is sent to another process:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="9130130888-1">(</span><span class="ss">give_me_a_fun</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9130130888-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9130130888-2">(</span><span class="p" data-group-id="9130130888-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="nb">size</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9130130888-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9130130888-3">}</span><span class="p">.</span></code></pre><p>How bad that unnecessary copy is depends on the contents of the record or the
│ │ │ +map.</p><p>For example, if the <code class="inline">state</code> record is initialized like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init1</span><span class="p" data-group-id="0668337508-1">(</span><span class="p" data-group-id="0668337508-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0668337508-2">{</span><span class="ss">data</span><span class="o">=</span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="0668337508-3">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">10000</span><span class="p" data-group-id="0668337508-3">)</span><span class="p" data-group-id="0668337508-2">}</span><span class="p">.</span></code></pre><p>a list with 10000 elements (or about 20000 heap words) will be copied to the
│ │ │  newly created process.</p><p>An unnecessary copy of 10000 element list can be bad enough, but it can get even
│ │ │  worse if the <code class="inline">state</code> record contains <em>shared subterms</em>. Here is a simple example
│ │ │ -of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1447852393-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="1447852393-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ -the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="7799304323-1">(</span><span class="p" data-group-id="7799304323-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="7799304323-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7799304323-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="7799304323-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7799304323-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="7799304323-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7799304323-5">[</span><span class="mi">0</span><span class="p" data-group-id="7799304323-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7799304323-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="7799304323-6">)</span><span class="p" data-group-id="7799304323-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="7799304323-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">Shared</span><span class="p" data-group-id="7799304323-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │ +of a term with a shared subterm:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1985324602-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="1985324602-1">}</span></code></pre><p>When a term is copied to another process, sharing of subterms will be lost and
│ │ │ +the copied term can be many times larger than the original term. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init2</span><span class="p" data-group-id="1103719840-1">(</span><span class="p" data-group-id="1103719840-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SharedSubTerms</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="1103719840-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1103719840-3">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="1103719840-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1103719840-4">[</span><span class="n">A</span><span class="p">|</span><span class="n">A</span><span class="p" data-group-id="1103719840-4">]</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1103719840-5">[</span><span class="mi">0</span><span class="p" data-group-id="1103719840-5">]</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1103719840-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">15</span><span class="p" data-group-id="1103719840-6">)</span><span class="p" data-group-id="1103719840-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="1103719840-7">{</span><span class="ss">data</span><span class="o">=</span><span class="n">Shared</span><span class="p" data-group-id="1103719840-7">}</span><span class="p">.</span></code></pre><p>In the process that calls <code class="inline">init2/0</code>, the size of the <code class="inline">data</code> field in the <code class="inline">state</code>
│ │ │  record will be 32 heap words. When the record is copied to the newly created
│ │ │  process, sharing will be lost and the size of the copied <code class="inline">data</code> field will be
│ │ │  131070 heap words. More details about
│ │ │  <a href="eff_guide_processes.html#loss-of-sharing">loss off sharing</a> are found in a later
│ │ │  section.</p><p>To avoid the problem, outside of the fun extract only the fields of the record
│ │ │ -that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="3745366264-1">(</span><span class="n">State</span><span class="p" data-group-id="3745366264-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +that are actually used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental1</span><span class="p" data-group-id="9459298718-1">(</span><span class="n">State</span><span class="p" data-group-id="9459298718-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">info</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="3745366264-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3745366264-3">(</span><span class="p" data-group-id="3745366264-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3745366264-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745366264-5">[</span><span class="n">Info</span><span class="p" data-group-id="3745366264-5">]</span><span class="p" data-group-id="3745366264-4">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="3745366264-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ -used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="4584532137-1">(</span><span class="n">State</span><span class="p" data-group-id="4584532137-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="4584532137-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4584532137-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4584532137-3">(</span><span class="nf">fun</span><span class="p" data-group-id="4584532137-4">(</span><span class="p" data-group-id="4584532137-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4584532137-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4584532137-6">[</span><span class="n">Info</span><span class="p" data-group-id="4584532137-6">]</span><span class="p" data-group-id="4584532137-5">)</span><span class="w">
│ │ │ -          </span><span class="k">end</span><span class="p" data-group-id="4584532137-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1" class="section-heading">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9459298718-2">(</span><span class="nf">fun</span><span class="p" data-group-id="9459298718-3">(</span><span class="p" data-group-id="9459298718-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9459298718-4">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9459298718-5">[</span><span class="n">Info</span><span class="p" data-group-id="9459298718-5">]</span><span class="p" data-group-id="9459298718-4">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="9459298718-2">)</span><span class="p">.</span></code></pre><p>Similarly, outside of the fun extract only the map elements that are actually
│ │ │ +used:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">fixed_accidental2</span><span class="p" data-group-id="2752828152-1">(</span><span class="n">State</span><span class="p" data-group-id="2752828152-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">map_get</span><span class="p" data-group-id="2752828152-2">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2752828152-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2752828152-3">(</span><span class="nf">fun</span><span class="p" data-group-id="2752828152-4">(</span><span class="p" data-group-id="2752828152-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2752828152-5">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="s">\n&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2752828152-6">[</span><span class="n">Info</span><span class="p" data-group-id="2752828152-6">]</span><span class="p" data-group-id="2752828152-5">)</span><span class="w">
│ │ │ +          </span><span class="k">end</span><span class="p" data-group-id="2752828152-3">)</span><span class="p">.</span></code></pre><h2 id="list_to_atom-1" class="section-heading">
│ │ │    <a href="#list_to_atom-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">list_to_atom/1</span>
│ │ │  </h2>
│ │ │  <p>Atoms are not garbage-collected. Once an atom is created, it is never removed.
│ │ │  The emulator terminates if the limit for the number of atoms (1,048,576 by
│ │ │  default) is reached.</p><p>Therefore, converting arbitrary input strings to atoms can be dangerous in a
│ │ │  system that runs continuously. If only certain well-defined atoms are allowed as
│ │ │  input, <a href="../../erts-15.2.7.2/doc/html/erlang.html#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a> or
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_existing_atom/1"><code class="inline">binary_to_existing_atom/1</code></a> can be used
│ │ │  to guard against a denial-of-service attack. (All atoms that are allowed must
│ │ │  have been created earlier, for example, by using all of them in a module
│ │ │  and loading that module.)</p><p>Using <a href="../../erts-15.2.7.2/doc/html/erlang.html#list_to_atom/1"><code class="inline">list_to_atom/1</code></a> to construct an atom that
│ │ │ -is passed to <a href="../../erts-15.2.7.2/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="3851593230-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="3851593230-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="3851593230-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="3851593230-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │ +is passed to <a href="../../erts-15.2.7.2/doc/html/erlang.html#apply/3"><code class="inline">apply/3</code></a> is quite expensive.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">apply</span><span class="p" data-group-id="4680552661-1">(</span><span class="nf">list_to_atom</span><span class="p" data-group-id="4680552661-2">(</span><span class="s">&quot;some_prefix&quot;</span><span class="o">++</span><span class="n">Var</span><span class="p" data-group-id="4680552661-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4680552661-1">)</span></code></pre><h2 id="length-1" class="section-heading">
│ │ │    <a href="#length-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">length/1</span>
│ │ │  </h2>
│ │ │  <p>The time for calculating the length of a list is proportional to the length of
│ │ │  the list, as opposed to <a href="../../erts-15.2.7.2/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a>,
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#byte_size/1"><code class="inline">byte_size/1</code></a>, and <a href="../../erts-15.2.7.2/doc/html/erlang.html#bit_size/1"><code class="inline">bit_size/1</code></a>, which all
│ │ │  execute in constant time.</p><p>Normally, there is no need to worry about the speed of <a href="../../erts-15.2.7.2/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a>,
│ │ │  because it is efficiently implemented in C. In time-critical code, you might
│ │ │  want to avoid it if the input list could potentially be very long.</p><p>Some uses of <a href="../../erts-15.2.7.2/doc/html/erlang.html#length/1"><code class="inline">length/1</code></a> can be replaced by matching. For example,
│ │ │ -the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="5119764686-1">(</span><span class="n">L</span><span class="p" data-group-id="5119764686-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5119764686-2">(</span><span class="n">L</span><span class="p" data-group-id="5119764686-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="2047192661-1">(</span><span class="p" data-group-id="2047192661-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="2047192661-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="2047192661-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="3930256470-1">(</span><span class="n">L</span><span class="p" data-group-id="3930256470-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3930256470-2">(</span><span class="n">L</span><span class="p" data-group-id="3930256470-2">)</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="9442447619-1">(</span><span class="p" data-group-id="9442447619-2">[</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="9442447619-2">]</span><span class="o">=</span><span class="n">L</span><span class="p" data-group-id="9442447619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>One slight difference is that <a href="../../erts-15.2.7.2/doc/html/erlang.html#length/1"><code class="inline">length(L)</code></a> fails if <code class="inline">L</code> is an
│ │ │  improper list, while the pattern in the second code fragment accepts an improper
│ │ │  list.</p><h2 id="setelement-3" class="section-heading">
│ │ │    <a href="#setelement-3" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">setelement/3</span>
│ │ │ @@ -238,18 +238,18 @@
│ │ │  <p><a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> copies the tuple it modifies. Therefore,
│ │ │  updating a tuple in a loop using <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> creates a new
│ │ │  copy of the tuple every time.</p><p>There is one exception to the rule that the tuple is copied. If the compiler
│ │ │  clearly can see that destructively updating the tuple would give the same result
│ │ │  as if the tuple was copied, the call to <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> is
│ │ │  replaced with a special destructive <code class="inline">setelement</code> instruction. In the following
│ │ │  code sequence, the first <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call copies the tuple
│ │ │ -and modifies the ninth element:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="5957897222-1">(</span><span class="n">T0</span><span class="p" data-group-id="5957897222-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="5957897222-2">(</span><span class="n">T0</span><span class="p" data-group-id="5957897222-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="5957897222-3">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="5957897222-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="5957897222-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="5957897222-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">setelement</span><span class="p" data-group-id="5957897222-5">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="5957897222-5">)</span><span class="p">.</span></code></pre><p>The two following <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls modify the tuple in
│ │ │ +and modifies the ninth element:</p><pre><code class="makeup erlang" translate="no"><span class="nf">multiple_setelement</span><span class="p" data-group-id="8397002766-1">(</span><span class="n">T0</span><span class="p" data-group-id="8397002766-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="8397002766-2">(</span><span class="n">T0</span><span class="p" data-group-id="8397002766-2">)</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">9</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">T1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="8397002766-3">(</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p" data-group-id="8397002766-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">T2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="8397002766-4">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="ss">foobar</span><span class="p" data-group-id="8397002766-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">setelement</span><span class="p" data-group-id="8397002766-5">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p">,</span><span class="w"> </span><span class="ss">new_value</span><span class="p" data-group-id="8397002766-5">)</span><span class="p">.</span></code></pre><p>The two following <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> calls modify the tuple in
│ │ │  place.</p><p>For the optimization to be applied, <em>all</em> the following conditions must be true:</p><ul><li>The tuple argument must be known to be a tuple of a known size.</li><li>The indices must be integer literals, not variables or expressions.</li><li>The indices must be given in descending order.</li><li>There must be no calls to another function in between the calls to
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a>.</li><li>The tuple returned from one <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a> call must only be
│ │ │  used in the subsequent call to <a href="../../erts-15.2.7.2/doc/html/erlang.html#setelement/3"><code class="inline">setelement/3</code></a>.</li></ul><p>If the code cannot be structured as in the <code class="inline">multiple_setelement/1</code> example, the
│ │ │  best way to modify multiple elements in a large tuple is to convert the tuple to
│ │ │  a list, modify the list, and convert it back to a tuple.</p><h2 id="size-1" class="section-heading">
│ │ │    <a href="#size-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/conc_prog.html
│ │ │ @@ -132,107 +132,107 @@
│ │ │  threads of execution in an Erlang program and to allow these threads to
│ │ │  communicate with each other. In Erlang, each thread of execution is called a
│ │ │  <em>process</em>.</p><p>(Aside: the term &quot;process&quot; is usually used when the threads of execution share
│ │ │  no data with each other and the term &quot;thread&quot; when they share data in some way.
│ │ │  Threads of execution in Erlang share no data, that is why they are called
│ │ │  processes).</p><p>The Erlang BIF <code class="inline">spawn</code> is used to create a new process:
│ │ │  <code class="inline">spawn(Module, Exported_Function, List of Arguments)</code>. Consider the following
│ │ │ -module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1609821242-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="1609821242-1">)</span><span class="p">.</span><span class="w">
│ │ │ +module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0673587873-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="0673587873-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1609821242-2">(</span><span class="p" data-group-id="1609821242-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1609821242-3">]</span><span class="p" data-group-id="1609821242-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0673587873-2">(</span><span class="p" data-group-id="0673587873-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0673587873-3">]</span><span class="p" data-group-id="0673587873-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="1609821242-4">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="1609821242-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="0673587873-4">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0673587873-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">done</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">say_something</span><span class="p" data-group-id="1609821242-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="1609821242-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1609821242-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1609821242-7">[</span><span class="n">What</span><span class="p" data-group-id="1609821242-7">]</span><span class="p" data-group-id="1609821242-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">say_something</span><span class="p" data-group-id="1609821242-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1609821242-8">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="1609821242-9">(</span><span class="p" data-group-id="1609821242-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1609821242-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1609821242-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1609821242-11">]</span><span class="p" data-group-id="1609821242-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1609821242-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1609821242-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1609821242-13">]</span><span class="p" data-group-id="1609821242-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="0225082795-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="0225082795-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0225082795-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="0225082795-2">}</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="0225082795-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0225082795-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">say_something</span><span class="p" data-group-id="0673587873-5">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="p" data-group-id="0673587873-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0673587873-6">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0673587873-7">[</span><span class="n">What</span><span class="p" data-group-id="0673587873-7">]</span><span class="p" data-group-id="0673587873-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">say_something</span><span class="p" data-group-id="0673587873-8">(</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="n">Times</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0673587873-8">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="0673587873-9">(</span><span class="p" data-group-id="0673587873-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0673587873-10">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0673587873-11">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0673587873-11">]</span><span class="p" data-group-id="0673587873-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0673587873-12">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0673587873-13">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0673587873-13">]</span><span class="p" data-group-id="0673587873-12">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="8843939361-1">(</span><span class="ss">tut14</span><span class="p" data-group-id="8843939361-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8843939361-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut14</span><span class="p" data-group-id="8843939361-2">}</span><span class="gp unselectable">
│ │ │ +6&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">say_something</span><span class="p" data-group-id="8843939361-3">(</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8843939361-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">done</span></code></pre><p>As shown, the function <code class="inline">say_something</code> writes its first argument the number of
│ │ │  times specified by second argument. The function <code class="inline">start</code> starts two Erlang
│ │ │  processes, one that writes &quot;hello&quot; three times and one that writes &quot;goodbye&quot;
│ │ │  three times. Both processes use the function <code class="inline">say_something</code>. Notice that a
│ │ │  function used in this way by <code class="inline">spawn</code>, to start a process, must be exported from
│ │ │ -the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7452572045-1">(</span><span class="p" data-group-id="7452572045-1">)</span><span class="p">.</span><span class="w">
│ │ │ +the module (that is, in the <code class="inline">-export</code> at the start of the module).</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nc">tut14</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="3988479864-1">(</span><span class="p" data-group-id="3988479864-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.63</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span></code></pre><p>Notice that it did not write &quot;hello&quot; three times and then &quot;goodbye&quot; three times.
│ │ │  Instead, the first process wrote a &quot;hello&quot;, the second a &quot;goodbye&quot;, the first
│ │ │  another &quot;hello&quot; and so forth. But where did the <code class="inline">&lt;0.63.0&gt;</code> come from? The return
│ │ │  value of a function is the return value of the last &quot;thing&quot; in the function. The
│ │ │ -last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="0894288178-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0894288178-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0894288178-2">]</span><span class="p" data-group-id="0894288178-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │ +last thing in the function <code class="inline">start</code> is</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="8572512156-1">(</span><span class="ss">tut14</span><span class="p">,</span><span class="w"> </span><span class="ss">say_something</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8572512156-2">[</span><span class="ss">goodbye</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8572512156-2">]</span><span class="p" data-group-id="8572512156-1">)</span><span class="p">.</span></code></pre><p><code class="inline">spawn</code> returns a <em>process identifier</em>, or <em>pid</em>, which uniquely identifies the
│ │ │  process. So <code class="inline">&lt;0.63.0&gt;</code> is the pid of the <code class="inline">spawn</code> function call above. The next
│ │ │  example shows how to use pids.</p><p>Notice also that ~p is used instead of ~w in <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a>. To quote <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#tilde_p">the manual</a>:</p><blockquote><p>~p Writes the data with standard syntax in the same way as ~w, but breaks terms
│ │ │  whose printed representation is longer than one line into many lines and indents
│ │ │  each line sensibly. It also tries to detect flat lists of printable characters and
│ │ │  to output these as strings</p></blockquote><h2 id="message-passing" class="section-heading">
│ │ │    <a href="#message-passing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Message Passing</span>
│ │ │  </h2>
│ │ │  <p>In the following example two processes are created and they send messages to
│ │ │ -each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8169661786-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="8169661786-1">)</span><span class="p">.</span><span class="w">
│ │ │ +each other a number of times.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3535128225-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="3535128225-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8169661786-2">(</span><span class="p" data-group-id="8169661786-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8169661786-3">]</span><span class="p" data-group-id="8169661786-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3535128225-2">(</span><span class="p" data-group-id="3535128225-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3535128225-3">]</span><span class="p" data-group-id="3535128225-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8169661786-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="8169661786-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="3535128225-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3535128225-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8169661786-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8169661786-6">[</span><span class="p" data-group-id="8169661786-6">]</span><span class="p" data-group-id="8169661786-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3535128225-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3535128225-6">[</span><span class="p" data-group-id="3535128225-6">]</span><span class="p" data-group-id="3535128225-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="8169661786-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="8169661786-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8169661786-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8169661786-9">(</span><span class="p" data-group-id="8169661786-9">)</span><span class="p" data-group-id="8169661786-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="3535128225-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3535128225-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3535128225-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3535128225-9">(</span><span class="p" data-group-id="3535128225-9">)</span><span class="p" data-group-id="3535128225-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8169661786-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8169661786-11">[</span><span class="p" data-group-id="8169661786-11">]</span><span class="p" data-group-id="8169661786-10">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3535128225-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3535128225-11">[</span><span class="p" data-group-id="3535128225-11">]</span><span class="p" data-group-id="3535128225-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="8169661786-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="8169661786-12">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="3535128225-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3535128225-12">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="8169661786-13">(</span><span class="p" data-group-id="8169661786-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="3535128225-13">(</span><span class="p" data-group-id="3535128225-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8169661786-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8169661786-15">[</span><span class="p" data-group-id="8169661786-15">]</span><span class="p" data-group-id="8169661786-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8169661786-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8169661786-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8169661786-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8169661786-18">[</span><span class="p" data-group-id="8169661786-18">]</span><span class="p" data-group-id="8169661786-17">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3535128225-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3535128225-15">[</span><span class="p" data-group-id="3535128225-15">]</span><span class="p" data-group-id="3535128225-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3535128225-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="3535128225-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3535128225-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3535128225-18">[</span><span class="p" data-group-id="3535128225-18">]</span><span class="p" data-group-id="3535128225-17">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="8169661786-19">(</span><span class="p" data-group-id="8169661786-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="3535128225-19">(</span><span class="p" data-group-id="3535128225-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="8169661786-20">(</span><span class="p" data-group-id="8169661786-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8169661786-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8169661786-22">[</span><span class="p" data-group-id="8169661786-22">]</span><span class="p" data-group-id="8169661786-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="8169661786-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8169661786-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="8169661786-24">]</span><span class="p" data-group-id="8169661786-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="9707087768-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="9707087768-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9707087768-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="9707087768-2">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="w"> </span><span class="nf">start</span><span class="p" data-group-id="9707087768-3">(</span><span class="p" data-group-id="9707087768-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="3535128225-20">(</span><span class="p" data-group-id="3535128225-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="3535128225-21">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3535128225-22">[</span><span class="p" data-group-id="3535128225-22">]</span><span class="p" data-group-id="3535128225-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3535128225-23">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3535128225-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3535128225-24">]</span><span class="p" data-group-id="3535128225-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">c</span><span class="p" data-group-id="0050653001-1">(</span><span class="ss">tut15</span><span class="p" data-group-id="0050653001-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0050653001-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut15</span><span class="p" data-group-id="0050653001-2">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">tut15</span><span class="p">:</span><span class="w"> </span><span class="nf">start</span><span class="p" data-group-id="0050653001-3">(</span><span class="p" data-group-id="0050653001-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.36</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1065048370-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1065048370-2">[</span><span class="p" data-group-id="1065048370-2">]</span><span class="p" data-group-id="1065048370-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ -&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="0992048565-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0992048565-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="0992048565-2">]</span><span class="p" data-group-id="0992048565-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="1642528780-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="1642528780-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>The function <code class="inline">start</code> first creates a process, let us call it &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6265215163-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6265215163-2">[</span><span class="p" data-group-id="6265215163-2">]</span><span class="p" data-group-id="6265215163-1">)</span></code></pre><p>This process executes <code class="inline">tut15:pong()</code>. <code class="inline">Pong_PID</code> is the process identity of the
│ │ │ +&quot;pong&quot; process. The function <code class="inline">start</code> now creates another process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="7795483278-1">(</span><span class="ss">tut15</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7795483278-2">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7795483278-2">]</span><span class="p" data-group-id="7795483278-1">)</span><span class="p">,</span></code></pre><p>This process executes:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="6395269648-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="6395269648-1">)</span></code></pre><p><code class="inline">&lt;0.36.0&gt;</code> is the return value from the <code class="inline">start</code> function.</p><p>The process &quot;pong&quot; now does:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │      </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1917499504-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917499504-2">[</span><span class="p" data-group-id="1917499504-2">]</span><span class="p" data-group-id="1917499504-1">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1917499504-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1917499504-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1917499504-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1917499504-5">[</span><span class="p" data-group-id="1917499504-5">]</span><span class="p" data-group-id="1917499504-4">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8480716899-1">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8480716899-2">[</span><span class="p" data-group-id="8480716899-2">]</span><span class="p" data-group-id="8480716899-1">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8480716899-3">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8480716899-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8480716899-4">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8480716899-5">[</span><span class="p" data-group-id="8480716899-5">]</span><span class="p" data-group-id="8480716899-4">)</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">pong</span><span class="p" data-group-id="1917499504-6">(</span><span class="p" data-group-id="1917499504-6">)</span><span class="w">
│ │ │ +        </span><span class="nf">pong</span><span class="p" data-group-id="8480716899-6">(</span><span class="p" data-group-id="8480716899-6">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> construct is used to allow processes to wait for messages from
│ │ │  other processes. It has the following format:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │     </span><span class="ss">pattern1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │         </span><span class="ss">actions1</span><span class="p">;</span><span class="w">
│ │ │     </span><span class="ss">pattern2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │         </span><span class="ss">actions2</span><span class="p">;</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ @@ -253,84 +253,84 @@
│ │ │  queue (keeping the first message and any other messages in the queue). If the
│ │ │  second message does not match, the third message is tried, and so on, until the
│ │ │  end of the queue is reached. If the end of the queue is reached, the process
│ │ │  blocks (stops execution) and waits until a new message is received and this
│ │ │  procedure is repeated.</p><p>The Erlang implementation is &quot;clever&quot; and minimizes the number of times each
│ │ │  message is tested against the patterns in each <code class="inline">receive</code>.</p><p>Now back to the ping pong example.</p><p>&quot;Pong&quot; is waiting for messages. If the atom <code class="inline">finished</code> is received, &quot;pong&quot;
│ │ │  writes &quot;Pong finished&quot; to the output and, as it has nothing more to do,
│ │ │ -terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0087740308-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="0087740308-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │ +terminates. If it receives a message with the format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6082823256-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6082823256-1">}</span></code></pre><p>it writes &quot;Pong received ping&quot; to the output and sends the atom <code class="inline">pong</code> to the
│ │ │  process &quot;ping&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span></code></pre><p>Notice how the operator &quot;!&quot; is used to send messages. The syntax of &quot;!&quot; is:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Message</span></code></pre><p>That is, <code class="inline">Message</code> (any Erlang term) is sent to the process with identity <code class="inline">Pid</code>.</p><p>After sending the message <code class="inline">pong</code> to the process &quot;ping&quot;, &quot;pong&quot; calls the <code class="inline">pong</code>
│ │ │  function again, which causes it to get back to the <code class="inline">receive</code> again and wait for
│ │ │ -another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="4141536952-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="4141536952-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │ +another message.</p><p>Now let us look at the process &quot;ping&quot;. Recall that it was started by executing:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut15</span><span class="p">:</span><span class="nf">ping</span><span class="p" data-group-id="9532863206-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="9532863206-1">)</span></code></pre><p>Looking at the function <code class="inline">ping/2</code>, the second clause of <code class="inline">ping/2</code> is executed
│ │ │  since the value of the first argument is 3 (not 0) (first clause head is
│ │ │ -<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2191501230-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2191501230-2">(</span><span class="p" data-group-id="2191501230-2">)</span><span class="p" data-group-id="2191501230-1">}</span><span class="p">,</span></code></pre><p><a href="../../erts-15.2.7.2/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../erts-15.2.7.2/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │ +<code class="inline">ping(0,Pong_PID)</code>, second clause head is <code class="inline">ping(N,Pong_PID)</code>, so <code class="inline">N</code> becomes 3).</p><p>The second clause sends a message to &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8834272912-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8834272912-2">(</span><span class="p" data-group-id="8834272912-2">)</span><span class="p" data-group-id="8834272912-1">}</span><span class="p">,</span></code></pre><p><a href="../../erts-15.2.7.2/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the pid of the process that executes <a href="../../erts-15.2.7.2/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a>, in this case the
│ │ │  pid of &quot;ping&quot;. (Recall the code for &quot;pong&quot;, this lands up in the variable
│ │ │  <code class="inline">Ping_PID</code> in the <code class="inline">receive</code> previously explained.)</p><p>&quot;Ping&quot; now waits for a reply from &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4281191198-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4281191198-2">[</span><span class="p" data-group-id="4281191198-2">]</span><span class="p" data-group-id="4281191198-1">)</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8197428843-1">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8197428843-2">[</span><span class="p" data-group-id="8197428843-2">]</span><span class="p" data-group-id="8197428843-1">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><p>It writes &quot;Ping received pong&quot; when this reply arrives, after which &quot;ping&quot; calls
│ │ │ -the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="3722293925-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="3722293925-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ -occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="0996158648-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="0996158648-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the <code class="inline">ping</code> function again.</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="0231259169-1">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="0231259169-1">)</span></code></pre><p><code class="inline">N-1</code> causes the first argument to be decremented until it becomes 0. When this
│ │ │ +occurs, the first clause of <code class="inline">ping/2</code> is executed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">ping</span><span class="p" data-group-id="7948094000-1">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_PID</span><span class="p" data-group-id="7948094000-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Pong_PID</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0996158648-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0996158648-3">[</span><span class="p" data-group-id="0996158648-3">]</span><span class="p" data-group-id="0996158648-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7948094000-2">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7948094000-3">[</span><span class="p" data-group-id="7948094000-3">]</span><span class="p" data-group-id="7948094000-2">)</span><span class="p">;</span></code></pre><p>The atom <code class="inline">finished</code> is sent to &quot;pong&quot; (causing it to terminate as described
│ │ │  above) and &quot;ping finished&quot; is written to the output. &quot;Ping&quot; then terminates as
│ │ │  it has nothing left to do.</p><h2 id="registered-process-names" class="section-heading">
│ │ │    <a href="#registered-process-names" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Registered Process Names</span>
│ │ │  </h2>
│ │ │  <p>In the above example, &quot;pong&quot; was first created to be able to give the identity
│ │ │  of &quot;pong&quot; when &quot;ping&quot; was started. That is, in some way &quot;ping&quot; must be able to
│ │ │  know the identity of &quot;pong&quot; to be able to send a message to it. Sometimes
│ │ │  processes which need to know each other's identities are started independently
│ │ │  of each other. Erlang thus provides a mechanism for processes to be given names
│ │ │  so that these names can be used as identities instead of pids. This is done by
│ │ │ -using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="2633455821-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2633455821-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ -the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7831814267-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="7831814267-1">)</span><span class="p">.</span><span class="w">
│ │ │ +using the <code class="inline">register</code> BIF:</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="4457556872-1">(</span><span class="ss">some_atom</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="4457556872-1">)</span></code></pre><p>Let us now rewrite the ping pong example using this and give the name <code class="inline">pong</code> to
│ │ │ +the &quot;pong&quot; process:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2739129692-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="2739129692-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7831814267-2">(</span><span class="p" data-group-id="7831814267-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7831814267-3">]</span><span class="p" data-group-id="7831814267-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2739129692-2">(</span><span class="p" data-group-id="2739129692-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2739129692-3">]</span><span class="p" data-group-id="2739129692-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7831814267-4">(</span><span class="mi">0</span><span class="p" data-group-id="7831814267-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="2739129692-4">(</span><span class="mi">0</span><span class="p" data-group-id="2739129692-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7831814267-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831814267-6">[</span><span class="p" data-group-id="7831814267-6">]</span><span class="p" data-group-id="7831814267-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2739129692-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2739129692-6">[</span><span class="p" data-group-id="2739129692-6">]</span><span class="p" data-group-id="2739129692-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="7831814267-7">(</span><span class="n">N</span><span class="p" data-group-id="7831814267-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7831814267-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7831814267-9">(</span><span class="p" data-group-id="7831814267-9">)</span><span class="p" data-group-id="7831814267-8">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="2739129692-7">(</span><span class="n">N</span><span class="p" data-group-id="2739129692-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2739129692-8">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2739129692-9">(</span><span class="p" data-group-id="2739129692-9">)</span><span class="p" data-group-id="2739129692-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7831814267-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831814267-11">[</span><span class="p" data-group-id="7831814267-11">]</span><span class="p" data-group-id="7831814267-10">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2739129692-10">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2739129692-11">[</span><span class="p" data-group-id="2739129692-11">]</span><span class="p" data-group-id="2739129692-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="7831814267-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7831814267-12">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="2739129692-12">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2739129692-12">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="7831814267-13">(</span><span class="p" data-group-id="7831814267-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="2739129692-13">(</span><span class="p" data-group-id="2739129692-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7831814267-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831814267-15">[</span><span class="p" data-group-id="7831814267-15">]</span><span class="p" data-group-id="7831814267-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7831814267-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7831814267-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7831814267-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831814267-18">[</span><span class="p" data-group-id="7831814267-18">]</span><span class="p" data-group-id="7831814267-17">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2739129692-14">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2739129692-15">[</span><span class="p" data-group-id="2739129692-15">]</span><span class="p" data-group-id="2739129692-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2739129692-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2739129692-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2739129692-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2739129692-18">[</span><span class="p" data-group-id="2739129692-18">]</span><span class="p" data-group-id="2739129692-17">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="7831814267-19">(</span><span class="p" data-group-id="7831814267-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="2739129692-19">(</span><span class="p" data-group-id="2739129692-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="7831814267-20">(</span><span class="p" data-group-id="7831814267-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="7831814267-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7831814267-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831814267-23">[</span><span class="p" data-group-id="7831814267-23">]</span><span class="p" data-group-id="7831814267-22">)</span><span class="p" data-group-id="7831814267-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="7831814267-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831814267-25">[</span><span class="mi">3</span><span class="p" data-group-id="7831814267-25">]</span><span class="p" data-group-id="7831814267-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="2564010876-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="2564010876-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2564010876-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="2564010876-2">}</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2564010876-3">(</span><span class="p" data-group-id="2564010876-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2739129692-20">(</span><span class="p" data-group-id="2739129692-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="2739129692-21">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2739129692-22">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2739129692-23">[</span><span class="p" data-group-id="2739129692-23">]</span><span class="p" data-group-id="2739129692-22">)</span><span class="p" data-group-id="2739129692-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2739129692-24">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2739129692-25">[</span><span class="mi">3</span><span class="p" data-group-id="2739129692-25">]</span><span class="p" data-group-id="2739129692-24">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nf">c</span><span class="p" data-group-id="0205890845-1">(</span><span class="ss">tut16</span><span class="p" data-group-id="0205890845-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0205890845-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut16</span><span class="p" data-group-id="0205890845-2">}</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="nc">tut16</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0205890845-3">(</span><span class="p" data-group-id="0205890845-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.38</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span><span class="w">
│ │ │ -</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="9820883264-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9820883264-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9820883264-3">[</span><span class="p" data-group-id="9820883264-3">]</span><span class="p" data-group-id="9820883264-2">)</span><span class="p" data-group-id="9820883264-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ -process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4243704970-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4243704970-2">(</span><span class="p" data-group-id="4243704970-2">)</span><span class="p" data-group-id="4243704970-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │ +</span><span class="n">Pong</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>Here the <code class="inline">start/0</code> function,</p><pre><code class="makeup erlang" translate="no"><span class="nf">register</span><span class="p" data-group-id="6995948977-1">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6995948977-2">(</span><span class="ss">tut16</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6995948977-3">[</span><span class="p" data-group-id="6995948977-3">]</span><span class="p" data-group-id="6995948977-2">)</span><span class="p" data-group-id="6995948977-1">)</span><span class="p">,</span></code></pre><p>both spawns the &quot;pong&quot; process and gives it the name <code class="inline">pong</code>. In the &quot;ping&quot;
│ │ │ +process, messages can be sent to <code class="inline">pong</code> by:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pong</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1170105306-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1170105306-2">(</span><span class="p" data-group-id="1170105306-2">)</span><span class="p" data-group-id="1170105306-1">}</span><span class="p">,</span></code></pre><p><code class="inline">ping/2</code> now becomes <code class="inline">ping/1</code> as the argument <code class="inline">Pong_PID</code> is not needed.</p><h2 id="distributed-programming" class="section-heading">
│ │ │    <a href="#distributed-programming" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Distributed Programming</span>
│ │ │  </h2>
│ │ │  <p>Let us rewrite the ping pong program with &quot;ping&quot; and &quot;pong&quot; on different
│ │ │  computers. First a few things are needed to set up to get this to work. The
│ │ │ @@ -350,106 +350,106 @@
│ │ │  of the file. This is a requirement.</p><p>When you start an Erlang system that is going to talk to other Erlang systems,
│ │ │  you must give it a name, for example:</p><pre><code class="text">$ erl -sname my_name</code></pre><p>We will see more details of this later. If you want to experiment with
│ │ │  distributed Erlang, but you only have one computer to work on, you can start two
│ │ │  separate Erlang systems on the same computer but give them different names. Each
│ │ │  Erlang system running on a computer is called an <em>Erlang node</em>.</p><p>(Note: <code class="inline">erl -sname</code> assumes that all nodes are in the same IP domain and we can
│ │ │  use only the first component of the IP address, if we want to use nodes in
│ │ │  different domains we use <code class="inline">-name</code> instead, but then all IP address must be given
│ │ │ -in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9105633398-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="9105633398-1">)</span><span class="p">.</span><span class="w">
│ │ │ +in full.)</p><p>Here is the ping pong example modified to run on two separate nodes:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8741114684-1">(</span><span class="ss">tut17</span><span class="p" data-group-id="8741114684-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9105633398-2">(</span><span class="p" data-group-id="9105633398-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9105633398-3">]</span><span class="p" data-group-id="9105633398-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8741114684-2">(</span><span class="p" data-group-id="8741114684-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8741114684-3">]</span><span class="p" data-group-id="8741114684-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="9105633398-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9105633398-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9105633398-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9105633398-7">[</span><span class="p" data-group-id="9105633398-7">]</span><span class="p" data-group-id="9105633398-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="8741114684-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8741114684-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8741114684-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8741114684-7">[</span><span class="p" data-group-id="8741114684-7">]</span><span class="p" data-group-id="8741114684-6">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="9105633398-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9105633398-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9105633398-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9105633398-11">(</span><span class="p" data-group-id="9105633398-11">)</span><span class="p" data-group-id="9105633398-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="8741114684-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8741114684-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8741114684-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8741114684-11">(</span><span class="p" data-group-id="8741114684-11">)</span><span class="p" data-group-id="8741114684-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9105633398-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9105633398-13">[</span><span class="p" data-group-id="9105633398-13">]</span><span class="p" data-group-id="9105633398-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8741114684-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8741114684-13">[</span><span class="p" data-group-id="8741114684-13">]</span><span class="p" data-group-id="8741114684-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="9105633398-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="8741114684-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="9105633398-15">(</span><span class="p" data-group-id="9105633398-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="8741114684-15">(</span><span class="p" data-group-id="8741114684-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9105633398-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9105633398-17">[</span><span class="p" data-group-id="9105633398-17">]</span><span class="p" data-group-id="9105633398-16">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9105633398-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9105633398-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9105633398-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9105633398-20">[</span><span class="p" data-group-id="9105633398-20">]</span><span class="p" data-group-id="9105633398-19">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8741114684-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8741114684-17">[</span><span class="p" data-group-id="8741114684-17">]</span><span class="p" data-group-id="8741114684-16">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="8741114684-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="8741114684-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8741114684-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8741114684-20">[</span><span class="p" data-group-id="8741114684-20">]</span><span class="p" data-group-id="8741114684-19">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="9105633398-21">(</span><span class="p" data-group-id="9105633398-21">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="8741114684-21">(</span><span class="p" data-group-id="8741114684-21">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="9105633398-22">(</span><span class="p" data-group-id="9105633398-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="9105633398-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9105633398-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9105633398-25">[</span><span class="p" data-group-id="9105633398-25">]</span><span class="p" data-group-id="9105633398-24">)</span><span class="p" data-group-id="9105633398-23">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="8741114684-22">(</span><span class="p" data-group-id="8741114684-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="8741114684-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="8741114684-24">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8741114684-25">[</span><span class="p" data-group-id="8741114684-25">]</span><span class="p" data-group-id="8741114684-24">)</span><span class="p" data-group-id="8741114684-23">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="9105633398-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="9105633398-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9105633398-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="9105633398-28">]</span><span class="p" data-group-id="9105633398-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="8741114684-26">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8741114684-27">(</span><span class="ss">tut17</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8741114684-28">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="8741114684-28">]</span><span class="p" data-group-id="8741114684-27">)</span><span class="p">.</span></code></pre><p>Let us assume there are two computers called gollum and kosken. First a node is
│ │ │  started on kosken, called ping, and then a node on gollum, called pong.</p><p>On kosken (on a Linux/UNIX system):</p><pre><code class="text">kosken&gt; erl -sname ping
│ │ │  Erlang (BEAM) emulator version 5.2.3.7 [hipe] [threads:0]
│ │ │  
│ │ │  Eshell V5.2.3.7  (abort with ^G)
│ │ │  (ping@kosken)1&gt;</code></pre><p>On gollum:</p><pre><code class="text">gollum&gt; erl -sname pong
│ │ │  Erlang (BEAM) emulator version 5.2.3.7 [hipe] [threads:0]
│ │ │  
│ │ │  Eshell V5.2.3.7  (abort with ^G)
│ │ │ -(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="4812374104-1">(</span><span class="p" data-group-id="4812374104-1">)</span><span class="p">.</span><span class="w">
│ │ │ +(pong@gollum)1&gt;</code></pre><p>Now the &quot;pong&quot; process on gollum is started:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_pong</span><span class="p" data-group-id="5843634822-1">(</span><span class="p" data-group-id="5843634822-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><p>And the &quot;ping&quot; process on kosken is started (from the code above you can see
│ │ │  that a parameter of the <code class="inline">start_ping</code> function is the node name of the Erlang
│ │ │ -system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="7559980173-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="7559980173-1">)</span><span class="p">.</span><span class="w">
│ │ │ +system where &quot;pong&quot; is running):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(ping@kosken)1&gt; </span><span class="nc">tut17</span><span class="p">:</span><span class="nf">start_ping</span><span class="p" data-group-id="8626236257-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="8626236257-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.37</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="ss">ping</span><span class="w"> </span><span class="ss">finished</span></code></pre><p>As shown, the ping pong program has run. On the &quot;pong&quot; side:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)2&gt; </span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="nf">finished</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4717805101-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="4717805101-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │ +</span><span class="p" data-group-id="2288365780-1">(</span><span class="ss">pong@gollum</span><span class="p" data-group-id="2288365780-1">)</span><span class="mi">2</span><span class="o">&gt;</span><span class="w"> </span></code></pre><p>Looking at the <code class="inline">tut17</code> code, you see that the <code class="inline">pong</code> function itself is
│ │ │  unchanged, the following lines work in the same way irrespective of on which
│ │ │ -node the &quot;ping&quot; process is executes:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5444384579-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5444384579-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5444384579-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5444384579-3">[</span><span class="p" data-group-id="5444384579-3">]</span><span class="p" data-group-id="5444384579-2">)</span><span class="p">,</span><span class="w">
│ │ │ +node the &quot;ping&quot; process is executes:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7060094504-1">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="7060094504-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7060094504-2">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7060094504-3">[</span><span class="p" data-group-id="7060094504-3">]</span><span class="p" data-group-id="7060094504-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span></code></pre><p>Thus, Erlang pids contain information about where the process executes. So if
│ │ │  you know the pid of a process, the <code class="inline">!</code> operator can be used to send it a
│ │ │ -message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2073520035-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2073520035-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2073520035-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2073520035-3">(</span><span class="p" data-group-id="2073520035-3">)</span><span class="p" data-group-id="2073520035-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │ +message disregarding if the process is on the same node or on a different node.</p><p>A difference is how messages are sent to a registered process on another node:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0920274542-1">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0920274542-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0920274542-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0920274542-3">(</span><span class="p" data-group-id="0920274542-3">)</span><span class="p" data-group-id="0920274542-2">}</span><span class="p">,</span></code></pre><p>A tuple <code class="inline">{registered_name,node_name}</code> is used instead of just the
│ │ │  <code class="inline">registered_name</code>.</p><p>In the previous example, &quot;ping&quot; and &quot;pong&quot; were started from the shells of two
│ │ │  separate Erlang nodes. <code class="inline">spawn</code> can also be used to start processes in other
│ │ │  nodes.</p><p>The next example is the ping pong program, yet again, but this time &quot;ping&quot; is
│ │ │ -started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2575615212-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="2575615212-1">)</span><span class="p">.</span><span class="w">
│ │ │ +started in another node:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5710803130-1">(</span><span class="ss">tut18</span><span class="p" data-group-id="5710803130-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2575615212-2">(</span><span class="p" data-group-id="2575615212-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2575615212-3">]</span><span class="p" data-group-id="2575615212-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5710803130-2">(</span><span class="p" data-group-id="5710803130-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5710803130-3">]</span><span class="p" data-group-id="5710803130-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2575615212-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2575615212-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2575615212-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2575615212-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2575615212-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2575615212-7">[</span><span class="p" data-group-id="2575615212-7">]</span><span class="p" data-group-id="2575615212-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="5710803130-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5710803130-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5710803130-5">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5710803130-5">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">finished</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5710803130-6">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710803130-7">[</span><span class="p" data-group-id="5710803130-7">]</span><span class="p" data-group-id="5710803130-6">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="2575615212-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2575615212-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2575615212-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2575615212-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2575615212-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2575615212-11">(</span><span class="p" data-group-id="2575615212-11">)</span><span class="p" data-group-id="2575615212-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="5710803130-8">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5710803130-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5710803130-9">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5710803130-9">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5710803130-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5710803130-11">(</span><span class="p" data-group-id="5710803130-11">)</span><span class="p" data-group-id="5710803130-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2575615212-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2575615212-13">[</span><span class="p" data-group-id="2575615212-13">]</span><span class="p" data-group-id="2575615212-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5710803130-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710803130-13">[</span><span class="p" data-group-id="5710803130-13">]</span><span class="p" data-group-id="5710803130-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="2575615212-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="2575615212-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="5710803130-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="5710803130-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="2575615212-15">(</span><span class="p" data-group-id="2575615212-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="5710803130-15">(</span><span class="p" data-group-id="5710803130-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">finished</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2575615212-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2575615212-17">[</span><span class="p" data-group-id="2575615212-17">]</span><span class="p" data-group-id="2575615212-16">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2575615212-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="2575615212-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2575615212-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2575615212-20">[</span><span class="p" data-group-id="2575615212-20">]</span><span class="p" data-group-id="2575615212-19">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5710803130-16">(</span><span class="s">&quot;Pong finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710803130-17">[</span><span class="p" data-group-id="5710803130-17">]</span><span class="p" data-group-id="5710803130-16">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5710803130-18">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5710803130-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5710803130-19">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710803130-20">[</span><span class="p" data-group-id="5710803130-20">]</span><span class="p" data-group-id="5710803130-19">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="2575615212-21">(</span><span class="p" data-group-id="2575615212-21">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="5710803130-21">(</span><span class="p" data-group-id="5710803130-21">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2575615212-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="2575615212-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2575615212-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="2575615212-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2575615212-25">[</span><span class="p" data-group-id="2575615212-25">]</span><span class="p" data-group-id="2575615212-24">)</span><span class="p" data-group-id="2575615212-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2575615212-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2575615212-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="2575615212-28">(</span><span class="p" data-group-id="2575615212-28">)</span><span class="p" data-group-id="2575615212-27">]</span><span class="p" data-group-id="2575615212-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ -been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6381478500-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="6381478500-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="5710803130-22">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="5710803130-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="5710803130-23">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5710803130-24">(</span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710803130-25">[</span><span class="p" data-group-id="5710803130-25">]</span><span class="p" data-group-id="5710803130-24">)</span><span class="p" data-group-id="5710803130-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5710803130-26">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut18</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5710803130-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="5710803130-28">(</span><span class="p" data-group-id="5710803130-28">)</span><span class="p" data-group-id="5710803130-27">]</span><span class="p" data-group-id="5710803130-26">)</span><span class="p">.</span></code></pre><p>Assuming an Erlang system called ping (but not the &quot;ping&quot; process) has already
│ │ │ +been started on kosken, then on gollum this is done:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(pong@gollum)1&gt; </span><span class="nc">tut18</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2549643754-1">(</span><span class="ss">ping@kosken</span><span class="p" data-group-id="2549643754-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">3934.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │  </span><span class="n">Pong</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">ping</span><span class="w">
│ │ │  </span><span class="n">Ping</span><span class="w"> </span><span class="ss">received</span><span class="w"> </span><span class="ss">pong</span><span class="w">
│ │ │ @@ -516,188 +516,188 @@
│ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0741376386-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="0741376386-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0741376386-2">(</span><span class="p" data-group-id="0741376386-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0741376386-3">]</span><span class="p" data-group-id="0741376386-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9302710995-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="9302710995-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9302710995-2">(</span><span class="p" data-group-id="9302710995-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9302710995-3">]</span><span class="p" data-group-id="9302710995-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="0741376386-4">(</span><span class="p" data-group-id="0741376386-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="9302710995-4">(</span><span class="p" data-group-id="9302710995-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]</span><span class="w">
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="0741376386-5">(</span><span class="n">User_List</span><span class="p" data-group-id="0741376386-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="9302710995-5">(</span><span class="n">User_List</span><span class="p" data-group-id="9302710995-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0741376386-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="0741376386-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-7">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="0741376386-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="0741376386-8">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="0741376386-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="0741376386-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-10">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="0741376386-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="0741376386-11">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="0741376386-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-13">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0741376386-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-15">[</span><span class="n">User_List</span><span class="p" data-group-id="0741376386-15">]</span><span class="p" data-group-id="0741376386-14">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="0741376386-16">(</span><span class="n">User_List</span><span class="p" data-group-id="0741376386-16">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-6">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9302710995-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="9302710995-7">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9302710995-8">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9302710995-8">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-9">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="9302710995-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="9302710995-10">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-10">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9302710995-11">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9302710995-11">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-12">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9302710995-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-13">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9302710995-14">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-15">[</span><span class="n">User_List</span><span class="p" data-group-id="9302710995-15">]</span><span class="p" data-group-id="9302710995-14">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="9302710995-16">(</span><span class="n">User_List</span><span class="p" data-group-id="9302710995-16">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="0741376386-17">(</span><span class="p" data-group-id="0741376386-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="0741376386-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0741376386-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-20">[</span><span class="p" data-group-id="0741376386-21">[</span><span class="p" data-group-id="0741376386-21">]</span><span class="p" data-group-id="0741376386-20">]</span><span class="p" data-group-id="0741376386-19">)</span><span class="p" data-group-id="0741376386-18">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="9302710995-17">(</span><span class="p" data-group-id="9302710995-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="9302710995-18">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9302710995-19">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-20">[</span><span class="p" data-group-id="9302710995-21">[</span><span class="p" data-group-id="9302710995-21">]</span><span class="p" data-group-id="9302710995-20">]</span><span class="p" data-group-id="9302710995-19">)</span><span class="p" data-group-id="9302710995-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="0741376386-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="9302710995-22">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="0741376386-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="9302710995-23">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-23">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="0741376386-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-24">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="9302710995-24">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="0741376386-25">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0741376386-26">[</span><span class="p" data-group-id="0741376386-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0741376386-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-25">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="9302710995-25">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9302710995-26">[</span><span class="p" data-group-id="9302710995-27">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9302710995-27">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-26">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="0741376386-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="0741376386-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-29">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="9302710995-28">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="9302710995-29">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-29">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% Server transfers a message between user</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="0741376386-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="9302710995-30">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="0741376386-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9302710995-31">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-31">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="0741376386-32">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-33">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-34">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0741376386-34">}</span><span class="p" data-group-id="0741376386-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="0741376386-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-35">)</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-32">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9302710995-32">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-33">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-34">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9302710995-34">}</span><span class="p" data-group-id="9302710995-33">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9302710995-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-35">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="0741376386-36">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="9302710995-36">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="0741376386-37">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0741376386-37">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9302710995-37">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9302710995-37">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-38">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="0741376386-38">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-39">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-40">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="0741376386-40">}</span><span class="p" data-group-id="0741376386-39">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-41">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-41">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="0741376386-42">}</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-38">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="9302710995-38">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-39">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-40">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9302710995-40">}</span><span class="p" data-group-id="9302710995-39">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-41">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-41">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9302710995-42">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="0741376386-43">(</span><span class="n">Name</span><span class="p" data-group-id="0741376386-43">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="0741376386-44">(</span><span class="ss">mess_client</span><span class="p" data-group-id="0741376386-44">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="9302710995-43">(</span><span class="n">Name</span><span class="p" data-group-id="9302710995-43">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9302710995-44">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9302710995-44">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="0741376386-45">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="0741376386-46">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-47">[</span><span class="nf">server_node</span><span class="p" data-group-id="0741376386-48">(</span><span class="p" data-group-id="0741376386-48">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0741376386-47">]</span><span class="p" data-group-id="0741376386-46">)</span><span class="p" data-group-id="0741376386-45">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="9302710995-45">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="9302710995-46">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-47">[</span><span class="nf">server_node</span><span class="p" data-group-id="9302710995-48">(</span><span class="p" data-group-id="9302710995-48">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9302710995-47">]</span><span class="p" data-group-id="9302710995-46">)</span><span class="p" data-group-id="9302710995-45">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="0741376386-49">(</span><span class="p" data-group-id="0741376386-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="9302710995-49">(</span><span class="p" data-group-id="9302710995-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="0741376386-50">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="0741376386-51">(</span><span class="ss">mess_client</span><span class="p" data-group-id="0741376386-51">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="9302710995-50">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-50">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9302710995-51">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9302710995-51">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-52">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-52">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-52">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-52">}</span><span class="p">,</span><span class="w">
│ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% The client process which runs on each server node</span><span class="w">
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="0741376386-53">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0741376386-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0741376386-54">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="0741376386-54">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-55">{</span><span class="nf">self</span><span class="p" data-group-id="0741376386-56">(</span><span class="p" data-group-id="0741376386-56">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0741376386-55">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="0741376386-57">(</span><span class="p" data-group-id="0741376386-57">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="0741376386-58">(</span><span class="n">Server_Node</span><span class="p" data-group-id="0741376386-58">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9302710995-53">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9302710995-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9302710995-54">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9302710995-54">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-55">{</span><span class="nf">self</span><span class="p" data-group-id="9302710995-56">(</span><span class="p" data-group-id="9302710995-56">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9302710995-55">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="9302710995-57">(</span><span class="p" data-group-id="9302710995-57">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9302710995-58">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9302710995-58">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="0741376386-59">(</span><span class="n">Server_Node</span><span class="p" data-group-id="0741376386-59">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="9302710995-59">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9302710995-59">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0741376386-60">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="0741376386-60">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-61">{</span><span class="nf">self</span><span class="p" data-group-id="0741376386-62">(</span><span class="p" data-group-id="0741376386-62">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="0741376386-61">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="0741376386-63">(</span><span class="ss">normal</span><span class="p" data-group-id="0741376386-63">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-64">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-64">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0741376386-65">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="0741376386-65">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0741376386-66">{</span><span class="nf">self</span><span class="p" data-group-id="0741376386-67">(</span><span class="p" data-group-id="0741376386-67">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-66">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="0741376386-68">(</span><span class="p" data-group-id="0741376386-68">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-69">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-69">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0741376386-70">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-71">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0741376386-71">]</span><span class="p" data-group-id="0741376386-70">)</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9302710995-60">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9302710995-60">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-61">{</span><span class="nf">self</span><span class="p" data-group-id="9302710995-62">(</span><span class="p" data-group-id="9302710995-62">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p" data-group-id="9302710995-61">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9302710995-63">(</span><span class="ss">normal</span><span class="p" data-group-id="9302710995-63">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-64">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-64">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9302710995-65">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9302710995-65">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9302710995-66">{</span><span class="nf">self</span><span class="p" data-group-id="9302710995-67">(</span><span class="p" data-group-id="9302710995-67">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-66">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="9302710995-68">(</span><span class="p" data-group-id="9302710995-68">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-69">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-69">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9302710995-70">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-71">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9302710995-71">]</span><span class="p" data-group-id="9302710995-70">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="0741376386-72">(</span><span class="n">Server_Node</span><span class="p" data-group-id="0741376386-72">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="9302710995-72">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9302710995-72">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="0741376386-73">(</span><span class="p" data-group-id="0741376386-73">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="9302710995-73">(</span><span class="p" data-group-id="9302710995-73">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-74">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="0741376386-74">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0741376386-75">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-76">[</span><span class="n">Why</span><span class="p" data-group-id="0741376386-76">]</span><span class="p" data-group-id="0741376386-75">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="0741376386-77">(</span><span class="ss">normal</span><span class="p" data-group-id="0741376386-77">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0741376386-78">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="0741376386-78">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0741376386-79">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0741376386-80">[</span><span class="n">What</span><span class="p" data-group-id="0741376386-80">]</span><span class="p" data-group-id="0741376386-79">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-74">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="9302710995-74">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9302710995-75">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-76">[</span><span class="n">Why</span><span class="p" data-group-id="9302710995-76">]</span><span class="p" data-group-id="9302710995-75">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="9302710995-77">(</span><span class="ss">normal</span><span class="p" data-group-id="9302710995-77">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9302710995-78">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="9302710995-78">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9302710995-79">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9302710995-80">[</span><span class="n">What</span><span class="p" data-group-id="9302710995-80">]</span><span class="p" data-group-id="9302710995-79">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>To use this program, you need to:</p><ul><li>Configure the <code class="inline">server_node()</code> function.</li><li>Copy the compiled code (<code class="inline">messenger.beam</code>) to the directory on each computer
│ │ │  where you start Erlang.</li></ul><p>In the following example using this program, nodes are started on four different
│ │ │  computers. If you do not have that many machines available on your network, you
│ │ │  can start several nodes on the same machine.</p><p>Four Erlang nodes are started up: messenger@super, c1@bilbo, c2@kosken,
│ │ │ -c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="3308852413-1">(</span><span class="p" data-group-id="3308852413-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="8450345248-1">(</span><span class="ss">peter</span><span class="p" data-group-id="8450345248-1">)</span><span class="p">.</span><span class="w">
│ │ │ +c3@gollum.</p><p>First the server at messenger@super is started up:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(messenger@super)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">start_server</span><span class="p" data-group-id="0629020152-1">(</span><span class="p" data-group-id="0629020152-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">true</span></code></pre><p>Now Peter logs on at c1@bilbo:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="7112099595-1">(</span><span class="ss">peter</span><span class="p" data-group-id="7112099595-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="6610008448-1">(</span><span class="ss">james</span><span class="p" data-group-id="6610008448-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logged_on</span></code></pre><p>James logs on at c2@kosken:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="1696599961-1">(</span><span class="ss">james</span><span class="p" data-group-id="1696599961-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="0401596798-1">(</span><span class="ss">fred</span><span class="p" data-group-id="0401596798-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logged_on</span></code></pre><p>And Fred logs on at c3@gollum:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c3@gollum)1&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logon</span><span class="p" data-group-id="4322643341-1">(</span><span class="ss">fred</span><span class="p" data-group-id="4322643341-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │ -</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="1921207142-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1921207142-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logged_on</span></code></pre><p>Now Peter sends Fred a message:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c1@bilbo)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="7874708813-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7874708813-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="ss">sent</span></code></pre><p>Fred receives the message and sends a message to Peter and logs off:</p><pre><code class="makeup erlang" translate="no"><span class="n">Message</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="nc">peter</span><span class="p">:</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ -(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="2509403763-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="2509403763-1">)</span><span class="p">.</span><span class="w">
│ │ │ +(c3@gollum)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="7887726630-1">(</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;go away, I&#39;m busy&quot;</span><span class="p" data-group-id="7887726630-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="nf">sent</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2509403763-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="2509403763-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="2509403763-3">(</span><span class="p" data-group-id="2509403763-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="0342704926-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="0342704926-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7887726630-2">(</span><span class="ss">c3@gollum</span><span class="p" data-group-id="7887726630-2">)</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">logoff</span><span class="p" data-group-id="7887726630-3">(</span><span class="p" data-group-id="7887726630-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">logoff</span></code></pre><p>James now tries to send a message to Fred:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(c2@kosken)2&gt; </span><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="1143464058-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;peter doesn&#39;t like you&quot;</span><span class="p" data-group-id="1143464058-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="ss">receiver_not_found</span></code></pre><p>But this fails as Fred has already logged off.</p><p>First let us look at some of the new concepts that have been introduced.</p><p>There are two versions of the <code class="inline">server_transfer</code> function: one with four
│ │ │  arguments (<code class="inline">server_transfer/4</code>) and one with five (<code class="inline">server_transfer/5</code>). These
│ │ │  are regarded by Erlang as two separate functions.</p><p>Notice how to write the <code class="inline">server</code> function so that it calls itself, through
│ │ │  <code class="inline">server(User_List)</code>, and thus creates a loop. The Erlang compiler is &quot;clever&quot;
│ │ │  and optimizes the code so that this really is a sort of loop and not a proper
│ │ │  function call. But this only works if there is no code after the call.
│ │ │  Otherwise, the compiler expects the call to return and make a proper function
│ │ │  call. This would result in the process getting bigger and bigger for every loop.</p><p>Functions in the <code class="inline">lists</code> module are used. This is a very useful module and a
│ │ │  study of the manual page is recommended (<code class="inline">erl -man lists</code>).
│ │ │  <code class="inline">lists:keymember(Key,Position,Lists)</code> looks through a list of tuples and looks
│ │ │  at <code class="inline">Position</code> in each tuple to see if it is the same as <code class="inline">Key</code>. The first element
│ │ │  is position 1. If it finds a tuple where the element at <code class="inline">Position</code> is the same
│ │ │ -as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3074041624-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3074041624-2">[</span><span class="p" data-group-id="3074041624-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3074041624-3">}</span><span class="p">,</span><span class="p" data-group-id="3074041624-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3074041624-4">}</span><span class="p">,</span><span class="p" data-group-id="3074041624-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3074041624-5">}</span><span class="p">,</span><span class="p" data-group-id="3074041624-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3074041624-6">}</span><span class="p" data-group-id="3074041624-2">]</span><span class="p" data-group-id="3074041624-1">)</span><span class="p">.</span><span class="w">
│ │ │ +as <code class="inline">Key</code>, it returns <code class="inline">true</code>, otherwise <code class="inline">false</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="8129965553-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8129965553-2">[</span><span class="p" data-group-id="8129965553-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="8129965553-3">}</span><span class="p">,</span><span class="p" data-group-id="8129965553-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8129965553-4">}</span><span class="p">,</span><span class="p" data-group-id="8129965553-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8129965553-5">}</span><span class="p">,</span><span class="p" data-group-id="8129965553-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="8129965553-6">}</span><span class="p" data-group-id="8129965553-2">]</span><span class="p" data-group-id="8129965553-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="3074041624-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3074041624-8">[</span><span class="p" data-group-id="3074041624-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3074041624-9">}</span><span class="p">,</span><span class="p" data-group-id="3074041624-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3074041624-10">}</span><span class="p">,</span><span class="p" data-group-id="3074041624-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3074041624-11">}</span><span class="p">,</span><span class="p" data-group-id="3074041624-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3074041624-12">}</span><span class="p" data-group-id="3074041624-8">]</span><span class="p" data-group-id="3074041624-7">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="8129965553-7">(</span><span class="ss">p</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8129965553-8">[</span><span class="p" data-group-id="8129965553-9">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="8129965553-9">}</span><span class="p">,</span><span class="p" data-group-id="8129965553-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8129965553-10">}</span><span class="p">,</span><span class="p" data-group-id="8129965553-11">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8129965553-11">}</span><span class="p">,</span><span class="p" data-group-id="8129965553-12">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="8129965553-12">}</span><span class="p" data-group-id="8129965553-8">]</span><span class="p" data-group-id="8129965553-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><p><code class="inline">lists:keydelete</code> works in the same way but deletes the first tuple found (if
│ │ │ -any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="3079075789-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3079075789-2">[</span><span class="p" data-group-id="3079075789-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3079075789-3">}</span><span class="p">,</span><span class="p" data-group-id="3079075789-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3079075789-4">}</span><span class="p">,</span><span class="p" data-group-id="3079075789-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3079075789-5">}</span><span class="p">,</span><span class="p" data-group-id="3079075789-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3079075789-6">}</span><span class="p" data-group-id="3079075789-2">]</span><span class="p" data-group-id="3079075789-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3079075789-7">[</span><span class="p" data-group-id="3079075789-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="3079075789-8">}</span><span class="p">,</span><span class="p" data-group-id="3079075789-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3079075789-9">}</span><span class="p">,</span><span class="p" data-group-id="3079075789-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="3079075789-10">}</span><span class="p" data-group-id="3079075789-7">]</span></code></pre><p><code class="inline">lists:keysearch</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │ +any) and returns the remaining list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="1095930102-1">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1095930102-2">[</span><span class="p" data-group-id="1095930102-3">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1095930102-3">}</span><span class="p">,</span><span class="p" data-group-id="1095930102-4">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1095930102-4">}</span><span class="p">,</span><span class="p" data-group-id="1095930102-5">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1095930102-5">}</span><span class="p">,</span><span class="p" data-group-id="1095930102-6">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="1095930102-6">}</span><span class="p" data-group-id="1095930102-2">]</span><span class="p" data-group-id="1095930102-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1095930102-7">[</span><span class="p" data-group-id="1095930102-8">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="1095930102-8">}</span><span class="p">,</span><span class="p" data-group-id="1095930102-9">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1095930102-9">}</span><span class="p">,</span><span class="p" data-group-id="1095930102-10">{</span><span class="ss">q</span><span class="p">,</span><span class="ss">r</span><span class="p">,</span><span class="ss">s</span><span class="p" data-group-id="1095930102-10">}</span><span class="p" data-group-id="1095930102-7">]</span></code></pre><p><code class="inline">lists:keysearch</code> is like <code class="inline">lists:keymember</code>, but it returns
│ │ │  <code class="inline">{value,Tuple_Found}</code> or the atom <code class="inline">false</code>.</p><p>There are many very useful functions in the <code class="inline">lists</code> module.</p><p>An Erlang process (conceptually) runs until it does a <code class="inline">receive</code> and there is no
│ │ │  message which it wants to receive in the message queue. &quot;conceptually&quot; is used
│ │ │  here because the Erlang system shares the CPU time between the active processes
│ │ │  in the system.</p><p>A process terminates when there is nothing more for it to do, that is, the last
│ │ │  function it calls simply returns and does not call another function. Another way
│ │ │  for a process to terminate is for it to call <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a>. The argument
│ │ │  to <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a> has a special meaning, which is discussed later. In this
│ │ │  example, <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a> is done, which has the same effect as a
│ │ │  process running out of functions to call.</p><p>The BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#whereis/1"><code class="inline">whereis(RegisteredName)</code></a> checks if a registered process
│ │ │  of name <code class="inline">RegisteredName</code> exists. If it exists, the pid of that process is
│ │ │  returned. If it does not exist, the atom <code class="inline">undefined</code> is returned.</p><p>You should by now be able to understand most of the code in the
│ │ │  messenger-module. Let us study one case in detail: a message is sent from one
│ │ │ -user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="1717088505-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1717088505-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="9134836567-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9134836567-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3751114871-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3751114871-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3985532035-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="3985532035-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3985532035-2">{</span><span class="nf">self</span><span class="p" data-group-id="3985532035-3">(</span><span class="p" data-group-id="3985532035-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3985532035-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="5832769532-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="5832769532-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="8724666303-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8724666303-1">)</span></code></pre><p>If <code class="inline">keysearch</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ -sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9332522751-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9332522751-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │ +user to another.</p><p>The first user &quot;sends&quot; the message in the example above by:</p><pre><code class="makeup erlang" translate="no"><span class="nc">messenger</span><span class="p">:</span><span class="nf">message</span><span class="p" data-group-id="1812990375-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1812990375-1">)</span></code></pre><p>After testing that the client process exists:</p><pre><code class="makeup erlang" translate="no"><span class="nf">whereis</span><span class="p" data-group-id="5794306347-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5794306347-1">)</span></code></pre><p>And a message is sent to <code class="inline">mess_client</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2114254460-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2114254460-1">}</span></code></pre><p>The client sends the message to the server by:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8457896718-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="8457896718-1">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8457896718-2">{</span><span class="nf">self</span><span class="p" data-group-id="8457896718-3">(</span><span class="p" data-group-id="8457896718-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8457896718-2">}</span><span class="p">,</span></code></pre><p>And waits for a reply from the server.</p><p>The server receives this message and calls:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="1569156108-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="1569156108-1">)</span><span class="p">,</span></code></pre><p>This checks that the pid <code class="inline">From</code> is in the <code class="inline">User_List</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="3577296734-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="3577296734-1">)</span></code></pre><p>If <code class="inline">keysearch</code> returns the atom <code class="inline">false</code>, some error has occurred and the server
│ │ │ +sends back the message:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9281684692-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9281684692-1">}</span></code></pre><p>This is received by the client, which in turn does <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit(normal)</code></a>
│ │ │  and terminates. If <code class="inline">keysearch</code> returns <code class="inline">{value,{From,Name}}</code> it is certain that
│ │ │ -the user is logged on and that his name (peter) is in variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="2932546832-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2932546832-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │ +the user is logged on and that his name (peter) is in variable <code class="inline">Name</code>.</p><p>Let us now call:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server_transfer</span><span class="p" data-group-id="2614752672-1">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="2614752672-1">)</span></code></pre><p>Notice that as this is <code class="inline">server_transfer/5</code>, it is not the same as the previous
│ │ │  function <code class="inline">server_transfer/4</code>. Another <code class="inline">keysearch</code> is done on <code class="inline">User_List</code> to find
│ │ │ -the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="8466164919-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="8466164919-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │ +the pid of the client corresponding to fred:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7184918886-1">(</span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7184918886-1">)</span></code></pre><p>This time argument 2 is used, which is the second element in the tuple. If this
│ │ │  returns the atom <code class="inline">false</code>, fred is not logged on and the following message is
│ │ │ -sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7513799287-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="7513799287-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keysearch</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2757836914-1">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2757836914-2">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="2757836914-2">}</span><span class="p" data-group-id="2757836914-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3448211855-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3448211855-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6012638955-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="6012638955-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8138551649-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8138551649-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8138551649-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8138551649-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8138551649-3">]</span><span class="p" data-group-id="8138551649-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │ +sent:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9466853986-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="9466853986-1">}</span><span class="p">;</span></code></pre><p>This is received by the client.</p><p>If <code class="inline">keysearch</code> returns:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5459760800-1">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5459760800-2">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p" data-group-id="5459760800-2">}</span><span class="p" data-group-id="5459760800-1">}</span></code></pre><p>The following message is sent to fred's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8609377860-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="8609377860-1">}</span><span class="p">,</span></code></pre><p>The following message is sent to peter's client:</p><pre><code class="makeup erlang" translate="no"><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9015362970-1">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9015362970-1">}</span></code></pre><p>Fred's client receives the message and prints it:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9703052203-1">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9703052203-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9703052203-2">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9703052203-3">[</span><span class="ss">peter</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9703052203-3">]</span><span class="p" data-group-id="9703052203-2">)</span></code></pre><p>Peter's client receives the message in the <code class="inline">await_result</code> function.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="seq_prog.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/create_target.html
│ │ │ @@ -138,21 +138,21 @@
│ │ │    <span class="text">Creating a Target System</span>
│ │ │  </h2>
│ │ │  <p>It is assumed that you have a working Erlang/OTP system structured according to
│ │ │  the OTP design principles.</p><p><em>Step 1.</em> Create a <code class="inline">.rel</code> file (see the <a href="../../lib/sasl-4.2.2/doc/html/rel.html">rel(4)</a> manual page in
│ │ │  SASL), which specifies the ERTS version and lists all applications that are to
│ │ │  be included in the new basic target system. An example is the following
│ │ │  <code class="inline">mysystem.rel</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem.rel</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0731425466-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0731425466-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="0731425466-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0731425466-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="0731425466-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0731425466-4">[</span><span class="p" data-group-id="0731425466-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="0731425466-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0731425466-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="0731425466-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0731425466-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="0731425466-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0731425466-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="0731425466-8">}</span><span class="p" data-group-id="0731425466-4">]</span><span class="p" data-group-id="0731425466-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │ +</span><span class="p" data-group-id="4053001216-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4053001216-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;FIRST&quot;</span><span class="p" data-group-id="4053001216-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4053001216-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.10.4&quot;</span><span class="p" data-group-id="4053001216-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4053001216-4">[</span><span class="p" data-group-id="4053001216-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.16.4&quot;</span><span class="p" data-group-id="4053001216-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4053001216-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.19.4&quot;</span><span class="p" data-group-id="4053001216-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4053001216-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.3.4&quot;</span><span class="p" data-group-id="4053001216-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4053001216-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="4053001216-8">}</span><span class="p" data-group-id="4053001216-4">]</span><span class="p" data-group-id="4053001216-1">}</span><span class="p">.</span></code></pre><p>The listed applications are not only original Erlang/OTP applications but
│ │ │  possibly also new applications that you have written (here exemplified by the
│ │ │  application Pea (<code class="inline">pea</code>)).</p><p><em>Step 2.</em> Start Erlang/OTP from the directory where the <code class="inline">mysystem.rel</code> file
│ │ │  resides:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-1.0/ebin</code></pre><p>The <code class="inline">-pa</code> argument prepends the path to the <code class="inline">ebin</code> directory for
│ │ │  the Pea application to the code path.</p><p><em>Step 3.</em> Create the target system:</p><pre><code class="text">1&gt; target_system:create(&quot;mysystem&quot;).</code></pre><p>The function <code class="inline">target_system:create/1</code> performs the following:</p><ol><li><p>Reads the file <code class="inline">mysystem.rel</code> and creates a new file <code class="inline">plain.rel</code>.
│ │ │  The new file is identical to the original, except that it only
│ │ │  lists the Kernel and STDLIB applications.</p></li><li><p>From the files <code class="inline">mysystem.rel</code> and <code class="inline">plain.rel</code> creates the files
│ │ │  <code class="inline">mysystem.script</code>, <code class="inline">mysystem.boot</code>, <code class="inline">plain.script</code>, and <code class="inline">plain.boot</code>
│ │ │ @@ -242,25 +242,25 @@
│ │ │    <a href="#creating-the-next-version" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating the Next Version</span>
│ │ │  </h2>
│ │ │  <p>In this example the Pea application has been changed, and so are the
│ │ │  applications ERTS, Kernel, STDLIB and SASL.</p><p><em>Step 1.</em> Create the file <code class="inline">.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% mysystem2.rel</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8840689733-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8840689733-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="8840689733-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8840689733-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="8840689733-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8840689733-4">[</span><span class="p" data-group-id="8840689733-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="8840689733-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8840689733-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="8840689733-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8840689733-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="8840689733-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8840689733-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="8840689733-8">}</span><span class="p" data-group-id="8840689733-4">]</span><span class="p" data-group-id="8840689733-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │ +</span><span class="p" data-group-id="8576520457-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8576520457-2">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;SECOND&quot;</span><span class="p" data-group-id="8576520457-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8576520457-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;6.0&quot;</span><span class="p" data-group-id="8576520457-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8576520457-4">[</span><span class="p" data-group-id="8576520457-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;3.0&quot;</span><span class="p" data-group-id="8576520457-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8576520457-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="8576520457-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8576520457-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.4&quot;</span><span class="p" data-group-id="8576520457-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8576520457-8">{</span><span class="ss">pea</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="8576520457-8">}</span><span class="p" data-group-id="8576520457-4">]</span><span class="p" data-group-id="8576520457-1">}</span><span class="p">.</span></code></pre><p><em>Step 2.</em> Create the application upgrade file (see
│ │ │  <a href="../../lib/sasl-4.2.2/doc/html/appup.html">appup</a> in SASL) for Pea, for example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% pea.appup</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7409104893-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7409104893-2">[</span><span class="p" data-group-id="7409104893-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7409104893-4">[</span><span class="p" data-group-id="7409104893-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7409104893-5">}</span><span class="p" data-group-id="7409104893-4">]</span><span class="p" data-group-id="7409104893-3">}</span><span class="p" data-group-id="7409104893-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7409104893-6">[</span><span class="p" data-group-id="7409104893-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="7409104893-8">[</span><span class="p" data-group-id="7409104893-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="7409104893-9">}</span><span class="p" data-group-id="7409104893-8">]</span><span class="p" data-group-id="7409104893-7">}</span><span class="p" data-group-id="7409104893-6">]</span><span class="p" data-group-id="7409104893-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │ +</span><span class="p" data-group-id="5728661262-1">{</span><span class="s">&quot;2.0&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5728661262-2">[</span><span class="p" data-group-id="5728661262-3">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="5728661262-4">[</span><span class="p" data-group-id="5728661262-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="5728661262-5">}</span><span class="p" data-group-id="5728661262-4">]</span><span class="p" data-group-id="5728661262-3">}</span><span class="p" data-group-id="5728661262-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5728661262-6">[</span><span class="p" data-group-id="5728661262-7">{</span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="p" data-group-id="5728661262-8">[</span><span class="p" data-group-id="5728661262-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="ss">pea_lib</span><span class="p" data-group-id="5728661262-9">}</span><span class="p" data-group-id="5728661262-8">]</span><span class="p" data-group-id="5728661262-7">}</span><span class="p" data-group-id="5728661262-6">]</span><span class="p" data-group-id="5728661262-1">}</span><span class="p">.</span></code></pre><p><em>Step 3.</em> From the directory where the file <code class="inline">mysystem2.rel</code> resides, start the
│ │ │  Erlang/OTP system, giving the path to the new version of Pea:</p><pre><code class="text">% erl -pa /home/user/target_system/myapps/pea-2.0/ebin</code></pre><p><em>Step 4.</em> Create the release upgrade file (see <a href="../../lib/sasl-4.2.2/doc/html/relup.html">relup</a>
│ │ │  in SASL):</p><pre><code class="text">1&gt; systools:make_relup(&quot;mysystem2&quot;,[&quot;mysystem&quot;],[&quot;mysystem&quot;],
│ │ │      [{path,[&quot;/home/user/target_system/myapps/pea-1.0/ebin&quot;,
│ │ │      &quot;/my/old/erlang/lib/*/ebin&quot;]}]).</code></pre><p>Here <code class="inline">&quot;mysystem&quot;</code> is the base release and <code class="inline">&quot;mysystem2&quot;</code> is the release to
│ │ │  upgrade to.</p><p>The <code class="inline">path</code> option is used for pointing out the old version of all applications.
│ │ │  (The new versions are already in the code path - assuming of course that the
│ │ │  Erlang node on which this is executed is running the correct version of
│ │ │ @@ -292,21 +292,21 @@
│ │ │  {continue_after_restart,&quot;FIRST&quot;,[]}
│ │ │  heart: Tue Apr  1 12:15:10 2014: Erlang has closed.
│ │ │  heart: Tue Apr  1 12:15:11 2014: Executed &quot;/usr/local/erl-target/bin/start /usr/local/erl-target/releases/new_start_erl.data&quot; -&gt; 0. Terminating.
│ │ │  [End]</code></pre><p>The above return value and output after the call to
│ │ │  <a href="../../lib/sasl-4.2.2/doc/html/release_handler.html#install_release/1"><code class="inline">release_handler:install_release/1</code></a> means that the <code class="inline">release_handler</code> has
│ │ │  restarted the node by using <code class="inline">heart</code>. This is always done when the upgrade
│ │ │  involves a change of the applications ERTS, Kernel, STDLIB, or SASL. For more
│ │ │ -information, see <a href="upgrade.html">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="1303678576-1">(</span><span class="p" data-group-id="1303678576-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1303678576-2">[</span><span class="p" data-group-id="1303678576-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1303678576-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="1303678576-4">]</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">current</span><span class="p" data-group-id="1303678576-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1303678576-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1303678576-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="1303678576-6">]</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">permanent</span><span class="p" data-group-id="1303678576-5">}</span><span class="p" data-group-id="1303678576-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │ +information, see <a href="upgrade.html">Upgrade when Erlang/OTP has Changed</a>.</p><p>The node is accessible through a new pipe:</p><pre><code class="text">% /usr/local/erl-target/bin/to_erl /tmp/erlang.pipe.2</code></pre><p>List the available releases in the system:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">which_releases</span><span class="p" data-group-id="2178819676-1">(</span><span class="p" data-group-id="2178819676-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2178819676-2">[</span><span class="p" data-group-id="2178819676-3">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;SECOND&quot;</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="2178819676-4">[</span><span class="s">&quot;kernel-3.0&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-2.0&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-2.0&quot;</span><span class="p" data-group-id="2178819676-4">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">current</span><span class="p" data-group-id="2178819676-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="2178819676-5">{</span><span class="s">&quot;MYSYSTEM&quot;</span><span class="p">,</span><span class="s">&quot;FIRST&quot;</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="2178819676-6">[</span><span class="s">&quot;kernel-2.16.4&quot;</span><span class="p">,</span><span class="s">&quot;stdlib-1.19.4&quot;</span><span class="p">,</span><span class="s">&quot;sasl-2.3.4&quot;</span><span class="p">,</span><span class="s">&quot;pea-1.0&quot;</span><span class="p" data-group-id="2178819676-6">]</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">permanent</span><span class="p" data-group-id="2178819676-5">}</span><span class="p" data-group-id="2178819676-2">]</span></code></pre><p>Our new release, &quot;SECOND&quot;, is now the current release, but we can also see that
│ │ │  our &quot;FIRST&quot; release is still permanent. This means that if the node would be
│ │ │  restarted now, it would come up running the &quot;FIRST&quot; release again.</p><p><em>Step 3.</em> Make the new release permanent:</p><pre><code class="text">2&gt; release_handler:make_permanent(&quot;SECOND&quot;).</code></pre><p>Check the releases again:</p><pre><code class="c">3&gt; release_handler:which_releases().
│ │ │  [{&quot;MYSYSTEM&quot;,&quot;SECOND&quot;,
│ │ │    [&quot;kernel-3.0&quot;,&quot;stdlib-2.0&quot;,&quot;sasl-2.4&quot;,&quot;pea-2.0&quot;],
│ │ │    permanent},
│ │ │   {&quot;MYSYSTEM&quot;,&quot;FIRST&quot;,
│ │ │    [&quot;kernel-2.16.4&quot;,&quot;stdlib-1.19.4&quot;,&quot;sasl-2.3.4&quot;,&quot;pea-1.0&quot;],
│ │ │ @@ -315,268 +315,268 @@
│ │ │    <a href="#listing-of-target_system-erl" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Listing of target_system.erl</span>
│ │ │  </h2>
│ │ │  <p>This module can also be found in the <code class="inline">examples</code> directory of the SASL
│ │ │  application.</p><pre><code class="makeup erlang" translate="no"><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4174908662-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="4174908662-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4174908662-2">(</span><span class="p" data-group-id="4174908662-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4174908662-3">]</span><span class="p" data-group-id="4174908662-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7989307685-1">(</span><span class="ss">target_system</span><span class="p" data-group-id="7989307685-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7989307685-2">(</span><span class="p" data-group-id="7989307685-3">[</span><span class="ss">create</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">create</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">install</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7989307685-3">]</span><span class="p" data-group-id="7989307685-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Note: RelFileName below is the *stem* without trailing .rel,</span><span class="w">
│ │ │  </span><span class="c1">%% .script etc.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% create(RelFileName)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="4174908662-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">create</span><span class="p" data-group-id="4174908662-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="4174908662-6">[</span><span class="p" data-group-id="4174908662-6">]</span><span class="p" data-group-id="4174908662-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="7989307685-4">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">create</span><span class="p" data-group-id="7989307685-5">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="p" data-group-id="7989307685-6">[</span><span class="p" data-group-id="7989307685-6">]</span><span class="p" data-group-id="7989307685-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">create</span><span class="p" data-group-id="4174908662-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4174908662-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">create</span><span class="p" data-group-id="7989307685-7">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7989307685-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">RelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="4174908662-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-8">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="4174908662-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Dir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7989307685-8">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-8">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-9">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;plain&quot;</span><span class="p" data-group-id="7989307685-9">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">PlainRelFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PlainRelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="4174908662-11">]</span><span class="p" data-group-id="4174908662-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="4174908662-13">]</span><span class="p" data-group-id="4174908662-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="4174908662-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="4174908662-14">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="4174908662-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="4174908662-16">]</span><span class="p" data-group-id="4174908662-15">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4174908662-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="4174908662-18">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="4174908662-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="4174908662-19">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="n">AppVsns</span><span class="p" data-group-id="4174908662-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4174908662-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="4174908662-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="4174908662-21">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="4174908662-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="4174908662-22">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="4174908662-23">(</span><span class="nf">fun</span><span class="p" data-group-id="4174908662-24">(</span><span class="p" data-group-id="4174908662-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4174908662-25">}</span><span class="p" data-group-id="4174908662-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-10">(</span><span class="s">&quot;Reading file: ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-11">[</span><span class="n">RelFile</span><span class="p" data-group-id="7989307685-11">]</span><span class="p" data-group-id="7989307685-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-13">[</span><span class="n">RelSpec</span><span class="p" data-group-id="7989307685-13">]</span><span class="p" data-group-id="7989307685-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">consult</span><span class="p" data-group-id="7989307685-14">(</span><span class="n">RelFile</span><span class="p" data-group-id="7989307685-14">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-15">(</span><span class="s">&quot;Creating file: ~ts from ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="7989307685-16">[</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="n">RelFile</span><span class="p" data-group-id="7989307685-16">]</span><span class="p" data-group-id="7989307685-15">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-17">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7989307685-18">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7989307685-18">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7989307685-19">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="7989307685-19">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="n">AppVsns</span><span class="p" data-group-id="7989307685-17">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelSpec</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">PlainRelSpec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7989307685-20">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="7989307685-21">{</span><span class="n">RelName</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7989307685-21">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="7989307685-22">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p" data-group-id="7989307685-22">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="7989307685-23">(</span><span class="nf">fun</span><span class="p" data-group-id="7989307685-24">(</span><span class="p" data-group-id="7989307685-25">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7989307685-25">}</span><span class="p" data-group-id="7989307685-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="4174908662-26">(</span><span class="p" data-group-id="4174908662-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4174908662-27">}</span><span class="p" data-group-id="4174908662-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="7989307685-26">(</span><span class="p" data-group-id="7989307685-27">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7989307685-27">}</span><span class="p" data-group-id="7989307685-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                           </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="4174908662-28">(</span><span class="p">_</span><span class="p" data-group-id="4174908662-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="7989307685-28">(</span><span class="p">_</span><span class="p" data-group-id="7989307685-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                           </span><span class="ss">false</span><span class="w">
│ │ │ -                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="4174908662-23">)</span><span class="w">
│ │ │ -                   </span><span class="p" data-group-id="4174908662-20">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4174908662-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4174908662-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-31">[</span><span class="ss">write</span><span class="p" data-group-id="4174908662-31">]</span><span class="p" data-group-id="4174908662-30">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="4174908662-33">]</span><span class="p" data-group-id="4174908662-32">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="4174908662-34">(</span><span class="n">Fd</span><span class="p" data-group-id="4174908662-34">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="p" data-group-id="4174908662-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="4174908662-36">]</span><span class="p" data-group-id="4174908662-35">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="4174908662-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4174908662-37">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="4174908662-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-39">]</span><span class="p" data-group-id="4174908662-38">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">make_script</span><span class="p" data-group-id="4174908662-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4174908662-40">)</span><span class="p">,</span><span class="w">
│ │ │ +                                 </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsns</span><span class="p" data-group-id="7989307685-23">)</span><span class="w">
│ │ │ +                   </span><span class="p" data-group-id="7989307685-20">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7989307685-29">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7989307685-30">(</span><span class="n">PlainRelFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-31">[</span><span class="ss">write</span><span class="p" data-group-id="7989307685-31">]</span><span class="p" data-group-id="7989307685-30">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-32">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-33">[</span><span class="n">PlainRelSpec</span><span class="p" data-group-id="7989307685-33">]</span><span class="p" data-group-id="7989307685-32">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7989307685-34">(</span><span class="n">Fd</span><span class="p" data-group-id="7989307685-34">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-35">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="p" data-group-id="7989307685-36">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">PlainRelFileName</span><span class="p" data-group-id="7989307685-36">]</span><span class="p" data-group-id="7989307685-35">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="7989307685-37">(</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7989307685-37">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-38">(</span><span class="s">&quot;Making \&quot;~ts.script\&quot; and \&quot;~ts.boot\&quot; files ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="7989307685-39">[</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-39">]</span><span class="p" data-group-id="7989307685-38">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">make_script</span><span class="p" data-group-id="7989307685-40">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7989307685-40">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │      </span><span class="n">TarFileName</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="4174908662-42">]</span><span class="p" data-group-id="4174908662-41">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">make_tar</span><span class="p" data-group-id="4174908662-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="4174908662-43">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-41">(</span><span class="s">&quot;Creating tar file ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-42">[</span><span class="n">TarFileName</span><span class="p" data-group-id="7989307685-42">]</span><span class="p" data-group-id="7989307685-41">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">make_tar</span><span class="p" data-group-id="7989307685-43">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">SystoolsOpts</span><span class="p" data-group-id="7989307685-43">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="4174908662-44">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4174908662-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-46">]</span><span class="p" data-group-id="4174908662-45">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="4174908662-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-47">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-49">]</span><span class="p" data-group-id="4174908662-48">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="4174908662-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-50">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-51">(</span><span class="p" data-group-id="4174908662-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4174908662-52">]</span><span class="p" data-group-id="4174908662-51">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-53">(</span><span class="p" data-group-id="4174908662-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4174908662-54">]</span><span class="p" data-group-id="4174908662-53">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="4174908662-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="4174908662-56">]</span><span class="p" data-group-id="4174908662-55">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="4174908662-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-58">(</span><span class="p" data-group-id="4174908662-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="4174908662-59">]</span><span class="p" data-group-id="4174908662-58">)</span><span class="p" data-group-id="4174908662-57">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="4174908662-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-61">(</span><span class="p" data-group-id="4174908662-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="4174908662-62">]</span><span class="p" data-group-id="4174908662-61">)</span><span class="p" data-group-id="4174908662-60">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="4174908662-64">]</span><span class="p" data-group-id="4174908662-63">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="4174908662-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="4174908662-65">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="4174908662-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-68">(</span><span class="p" data-group-id="4174908662-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="4174908662-69">]</span><span class="p" data-group-id="4174908662-68">)</span><span class="p" data-group-id="4174908662-67">]</span><span class="p" data-group-id="4174908662-66">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-71">(</span><span class="p" data-group-id="4174908662-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="4174908662-72">]</span><span class="p" data-group-id="4174908662-71">)</span><span class="p" data-group-id="4174908662-70">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">TmpDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-44">(</span><span class="n">Dir</span><span class="p">,</span><span class="s">&quot;tmp&quot;</span><span class="p" data-group-id="7989307685-44">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-45">(</span><span class="s">&quot;Creating directory ~tp ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7989307685-46">[</span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-46">]</span><span class="p" data-group-id="7989307685-45">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7989307685-47">(</span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-47">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-48">(</span><span class="s">&quot;Extracting ~ts into directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-49">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-49">]</span><span class="p" data-group-id="7989307685-48">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="7989307685-50">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-50">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="n">TmpBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-51">(</span><span class="p" data-group-id="7989307685-52">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7989307685-52">]</span><span class="p" data-group-id="7989307685-51">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-53">(</span><span class="p" data-group-id="7989307685-54">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7989307685-54">]</span><span class="p" data-group-id="7989307685-53">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-55">(</span><span class="s">&quot;Deleting \&quot;erl\&quot; and \&quot;start\&quot; in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="7989307685-56">[</span><span class="n">ErtsBinDir</span><span class="p" data-group-id="7989307685-56">]</span><span class="p" data-group-id="7989307685-55">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7989307685-57">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-58">(</span><span class="p" data-group-id="7989307685-59">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erl&quot;</span><span class="p" data-group-id="7989307685-59">]</span><span class="p" data-group-id="7989307685-58">)</span><span class="p" data-group-id="7989307685-57">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7989307685-60">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-61">(</span><span class="p" data-group-id="7989307685-62">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="7989307685-62">]</span><span class="p" data-group-id="7989307685-61">)</span><span class="p" data-group-id="7989307685-60">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-63">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-64">[</span><span class="n">TmpBinDir</span><span class="p" data-group-id="7989307685-64">]</span><span class="p" data-group-id="7989307685-63">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7989307685-65">(</span><span class="n">TmpBinDir</span><span class="p" data-group-id="7989307685-65">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-66">(</span><span class="s">&quot;Copying file \&quot;~ts.boot\&quot; to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="7989307685-67">[</span><span class="n">PlainRelFileName</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-68">(</span><span class="p" data-group-id="7989307685-69">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="7989307685-69">]</span><span class="p" data-group-id="7989307685-68">)</span><span class="p" data-group-id="7989307685-67">]</span><span class="p" data-group-id="7989307685-66">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-70">(</span><span class="n">PlainRelFileName</span><span class="o">++</span><span class="s">&quot;.boot&quot;</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-71">(</span><span class="p" data-group-id="7989307685-72">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start.boot&quot;</span><span class="p" data-group-id="7989307685-72">]</span><span class="p" data-group-id="7989307685-71">)</span><span class="p" data-group-id="7989307685-70">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-73">(</span><span class="s">&quot;Copying files \&quot;epmd\&quot;, \&quot;run_erl\&quot; and \&quot;to_erl\&quot; from \n&quot;</span><span class="w">
│ │ │                </span><span class="s">&quot;~ts to ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="4174908662-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="4174908662-74">]</span><span class="p" data-group-id="4174908662-73">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-76">(</span><span class="p" data-group-id="4174908662-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="4174908662-77">]</span><span class="p" data-group-id="4174908662-76">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-78">(</span><span class="p" data-group-id="4174908662-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="4174908662-79">]</span><span class="p" data-group-id="4174908662-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="4174908662-80">]</span><span class="p" data-group-id="4174908662-75">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-82">(</span><span class="p" data-group-id="4174908662-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="4174908662-83">]</span><span class="p" data-group-id="4174908662-82">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-84">(</span><span class="p" data-group-id="4174908662-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="4174908662-85">]</span><span class="p" data-group-id="4174908662-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="4174908662-86">]</span><span class="p" data-group-id="4174908662-81">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-88">(</span><span class="p" data-group-id="4174908662-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="4174908662-89">]</span><span class="p" data-group-id="4174908662-88">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-90">(</span><span class="p" data-group-id="4174908662-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="4174908662-91">]</span><span class="p" data-group-id="4174908662-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="4174908662-92">]</span><span class="p" data-group-id="4174908662-87">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="7989307685-74">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">TmpBinDir</span><span class="p" data-group-id="7989307685-74">]</span><span class="p" data-group-id="7989307685-73">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-75">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-76">(</span><span class="p" data-group-id="7989307685-77">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="7989307685-77">]</span><span class="p" data-group-id="7989307685-76">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-78">(</span><span class="p" data-group-id="7989307685-79">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;epmd&quot;</span><span class="p" data-group-id="7989307685-79">]</span><span class="p" data-group-id="7989307685-78">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-80">[</span><span class="ss">preserve</span><span class="p" data-group-id="7989307685-80">]</span><span class="p" data-group-id="7989307685-75">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-81">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-82">(</span><span class="p" data-group-id="7989307685-83">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="7989307685-83">]</span><span class="p" data-group-id="7989307685-82">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-84">(</span><span class="p" data-group-id="7989307685-85">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;run_erl&quot;</span><span class="p" data-group-id="7989307685-85">]</span><span class="p" data-group-id="7989307685-84">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-86">[</span><span class="ss">preserve</span><span class="p" data-group-id="7989307685-86">]</span><span class="p" data-group-id="7989307685-81">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-87">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-88">(</span><span class="p" data-group-id="7989307685-89">[</span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="7989307685-89">]</span><span class="p" data-group-id="7989307685-88">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-90">(</span><span class="p" data-group-id="7989307685-91">[</span><span class="n">TmpBinDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;to_erl&quot;</span><span class="p" data-group-id="7989307685-91">]</span><span class="p" data-group-id="7989307685-90">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-92">[</span><span class="ss">preserve</span><span class="p" data-group-id="7989307685-92">]</span><span class="p" data-group-id="7989307685-87">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │      </span><span class="c1">%% This is needed if &#39;start&#39; script created from &#39;start.src&#39; shall</span><span class="w">
│ │ │      </span><span class="c1">%% be used as it points out this directory as log dir for &#39;run_erl&#39;</span><span class="w">
│ │ │ -    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-93">(</span><span class="p" data-group-id="4174908662-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="4174908662-94">]</span><span class="p" data-group-id="4174908662-93">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="4174908662-96">]</span><span class="p" data-group-id="4174908662-95">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="4174908662-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="4174908662-97">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-98">(</span><span class="p" data-group-id="4174908662-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="4174908662-99">]</span><span class="p" data-group-id="4174908662-98">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="4174908662-101">]</span><span class="p" data-group-id="4174908662-100">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="4174908662-103">]</span><span class="p" data-group-id="4174908662-102">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="4174908662-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="4174908662-104">)</span><span class="p">,</span><span class="w">
│ │ │ -
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="p" data-group-id="4174908662-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-106">]</span><span class="p" data-group-id="4174908662-105">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="4174908662-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4174908662-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="4174908662-109">]</span><span class="p" data-group-id="4174908662-108">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">TmpLogDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-93">(</span><span class="p" data-group-id="7989307685-94">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="7989307685-94">]</span><span class="p" data-group-id="7989307685-93">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-95">(</span><span class="s">&quot;Creating temporary directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-96">[</span><span class="n">TmpLogDir</span><span class="p" data-group-id="7989307685-96">]</span><span class="p" data-group-id="7989307685-95">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">make_dir</span><span class="p" data-group-id="7989307685-97">(</span><span class="n">TmpLogDir</span><span class="p" data-group-id="7989307685-97">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-98">(</span><span class="p" data-group-id="7989307685-99">[</span><span class="n">TmpDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="7989307685-99">]</span><span class="p" data-group-id="7989307685-98">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-100">(</span><span class="s">&quot;Creating ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-101">[</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="7989307685-101">]</span><span class="p" data-group-id="7989307685-100">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">StartErlData</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">io_lib</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-102">(</span><span class="s">&quot;</span><span class="si">~s</span><span class="s"> </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-103">[</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w"> </span><span class="n">RelVsn</span><span class="p" data-group-id="7989307685-103">]</span><span class="p" data-group-id="7989307685-102">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="7989307685-104">(</span><span class="n">StartErlDataFile</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="7989307685-104">)</span><span class="p">,</span><span class="w">
│ │ │ +
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-105">(</span><span class="s">&quot;Recreating tar file ~ts from contents in directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="p" data-group-id="7989307685-106">[</span><span class="n">TarFileName</span><span class="p">,</span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-106">]</span><span class="p" data-group-id="7989307685-105">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-107">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tar</span><span class="p" data-group-id="7989307685-107">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7989307685-108">(</span><span class="n">TarFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-109">[</span><span class="ss">write</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="7989307685-109">]</span><span class="p" data-group-id="7989307685-108">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% {ok, Cwd} = file:get_cwd(),</span><span class="w">
│ │ │      </span><span class="c1">%% file:set_cwd(&quot;tmp&quot;),</span><span class="w">
│ │ │      </span><span class="n">ErtsDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="o">++</span><span class="n">ErtsVsn</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4174908662-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4174908662-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-112">[</span><span class="p" data-group-id="4174908662-112">]</span><span class="p" data-group-id="4174908662-110">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4174908662-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="4174908662-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-115">[</span><span class="p" data-group-id="4174908662-115">]</span><span class="p" data-group-id="4174908662-113">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4174908662-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="4174908662-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-118">[</span><span class="p" data-group-id="4174908662-118">]</span><span class="p" data-group-id="4174908662-116">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4174908662-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="4174908662-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-121">[</span><span class="p" data-group-id="4174908662-121">]</span><span class="p" data-group-id="4174908662-119">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="4174908662-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="4174908662-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-124">[</span><span class="p" data-group-id="4174908662-124">]</span><span class="p" data-group-id="4174908662-122">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="4174908662-125">(</span><span class="n">Tar</span><span class="p" data-group-id="4174908662-125">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7989307685-110">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-111">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7989307685-111">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-112">[</span><span class="p" data-group-id="7989307685-112">]</span><span class="p" data-group-id="7989307685-110">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7989307685-113">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-114">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="n">ErtsDir</span><span class="p" data-group-id="7989307685-114">)</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsDir</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-115">[</span><span class="p" data-group-id="7989307685-115">]</span><span class="p" data-group-id="7989307685-113">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7989307685-116">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-117">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;releases&quot;</span><span class="p" data-group-id="7989307685-117">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-118">[</span><span class="p" data-group-id="7989307685-118">]</span><span class="p" data-group-id="7989307685-116">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7989307685-119">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-120">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;lib&quot;</span><span class="p" data-group-id="7989307685-120">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;lib&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-121">[</span><span class="p" data-group-id="7989307685-121">]</span><span class="p" data-group-id="7989307685-119">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="7989307685-122">(</span><span class="n">Tar</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-123">(</span><span class="n">TmpDir</span><span class="p">,</span><span class="s">&quot;log&quot;</span><span class="p" data-group-id="7989307685-123">)</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;log&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-124">[</span><span class="p" data-group-id="7989307685-124">]</span><span class="p" data-group-id="7989307685-122">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7989307685-125">(</span><span class="n">Tar</span><span class="p" data-group-id="7989307685-125">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% file:set_cwd(Cwd),</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4174908662-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-127">]</span><span class="p" data-group-id="4174908662-126">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="4174908662-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="4174908662-128">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-126">(</span><span class="s">&quot;Removing directory ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7989307685-127">[</span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-127">]</span><span class="p" data-group-id="7989307685-126">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="7989307685-128">(</span><span class="n">TmpDir</span><span class="p" data-group-id="7989307685-128">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │ -</span><span class="nf">install</span><span class="p" data-group-id="4174908662-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4174908662-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">install</span><span class="p" data-group-id="7989307685-129">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7989307685-129">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">TarFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.tar.gz&quot;</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="4174908662-131">]</span><span class="p" data-group-id="4174908662-130">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">extract_tar</span><span class="p" data-group-id="4174908662-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4174908662-132">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-133">(</span><span class="p" data-group-id="4174908662-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="4174908662-134">]</span><span class="p" data-group-id="4174908662-133">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="4174908662-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="4174908662-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="4174908662-136">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4174908662-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="4174908662-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="4174908662-138">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-139">(</span><span class="p" data-group-id="4174908662-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4174908662-140">]</span><span class="p" data-group-id="4174908662-139">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-141">(</span><span class="p" data-group-id="4174908662-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="4174908662-142">]</span><span class="p" data-group-id="4174908662-141">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ -              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="4174908662-143">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="4174908662-144">(</span><span class="p" data-group-id="4174908662-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="4174908662-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ -                      </span><span class="p" data-group-id="4174908662-146">[</span><span class="p" data-group-id="4174908662-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4174908662-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="4174908662-148">}</span><span class="p" data-group-id="4174908662-146">]</span><span class="p">,</span><span class="w">
│ │ │ -                      </span><span class="p" data-group-id="4174908662-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="4174908662-149">]</span><span class="p" data-group-id="4174908662-144">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-130">(</span><span class="s">&quot;Extracting ~ts ...</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-131">[</span><span class="n">TarFile</span><span class="p" data-group-id="7989307685-131">]</span><span class="p" data-group-id="7989307685-130">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">extract_tar</span><span class="p" data-group-id="7989307685-132">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7989307685-132">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">StartErlDataFile</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-133">(</span><span class="p" data-group-id="7989307685-134">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl.data&quot;</span><span class="p" data-group-id="7989307685-134">]</span><span class="p" data-group-id="7989307685-133">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-135">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">StartErlData</span><span class="p" data-group-id="7989307685-135">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="7989307685-136">(</span><span class="n">StartErlDataFile</span><span class="p" data-group-id="7989307685-136">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-137">[</span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">RelVsn</span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7989307685-137">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">string</span><span class="p">:</span><span class="nf">tokens</span><span class="p" data-group-id="7989307685-138">(</span><span class="n">StartErlData</span><span class="p">,</span><span class="w"> </span><span class="s">&quot; \n&quot;</span><span class="p" data-group-id="7989307685-138">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ErtsBinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-139">(</span><span class="p" data-group-id="7989307685-140">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;erts-&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">ErlVsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7989307685-140">]</span><span class="p" data-group-id="7989307685-139">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">BinDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-141">(</span><span class="p" data-group-id="7989307685-142">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;bin&quot;</span><span class="p" data-group-id="7989307685-142">]</span><span class="p" data-group-id="7989307685-141">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-143">(</span><span class="s">&quot;Substituting in erl.src, start.src and start_erl.src to &quot;</span><span class="w">
│ │ │ +              </span><span class="s">&quot;form erl, start and start_erl ...\n&quot;</span><span class="p" data-group-id="7989307685-143">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="7989307685-144">(</span><span class="p" data-group-id="7989307685-145">[</span><span class="s">&quot;erl&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="7989307685-145">]</span><span class="p">,</span><span class="w"> </span><span class="n">ErtsBinDir</span><span class="p">,</span><span class="w"> </span><span class="n">BinDir</span><span class="p">,</span><span class="w">
│ │ │ +                      </span><span class="p" data-group-id="7989307685-146">[</span><span class="p" data-group-id="7989307685-147">{</span><span class="s">&quot;FINAL_ROOTDIR&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7989307685-147">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-148">{</span><span class="s">&quot;EMU&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;beam&quot;</span><span class="p" data-group-id="7989307685-148">}</span><span class="p" data-group-id="7989307685-146">]</span><span class="p">,</span><span class="w">
│ │ │ +                      </span><span class="p" data-group-id="7989307685-149">[</span><span class="ss">preserve</span><span class="p" data-group-id="7989307685-149">]</span><span class="p" data-group-id="7989307685-144">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%%! Workaround for pre OTP 17.0: start.src and start_erl.src did</span><span class="w">
│ │ │      </span><span class="c1">%%! not have correct permissions, so the above &#39;preserve&#39; option did not help</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="4174908662-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="4174908662-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="4174908662-150">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="4174908662-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="4174908662-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="4174908662-152">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="7989307685-150">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-151">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start&quot;</span><span class="p" data-group-id="7989307685-151">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="7989307685-150">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">change_mode</span><span class="p" data-group-id="7989307685-152">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-153">(</span><span class="n">BinDir</span><span class="p">,</span><span class="s">&quot;start_erl&quot;</span><span class="p" data-group-id="7989307685-153">)</span><span class="p">,</span><span class="mi">8#0755</span><span class="p" data-group-id="7989307685-152">)</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="4174908662-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="4174908662-154">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="4174908662-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-156">(</span><span class="p" data-group-id="4174908662-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ -					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="4174908662-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-158">)</span><span class="p" data-group-id="4174908662-157">]</span><span class="p" data-group-id="4174908662-156">)</span><span class="p" data-group-id="4174908662-155">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">fwrite</span><span class="p" data-group-id="7989307685-154">(</span><span class="s">&quot;Creating the RELEASES file ...\n&quot;</span><span class="p" data-group-id="7989307685-154">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7989307685-155">(</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-156">(</span><span class="p" data-group-id="7989307685-157">[</span><span class="n">RootDir</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;releases&quot;</span><span class="p">,</span><span class="w">
│ │ │ +					    </span><span class="nc">filename</span><span class="p">:</span><span class="nf">basename</span><span class="p" data-group-id="7989307685-158">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-158">)</span><span class="p" data-group-id="7989307685-157">]</span><span class="p" data-group-id="7989307685-156">)</span><span class="p" data-group-id="7989307685-155">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% LOCALS</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% make_script(RelFileName,Opts)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">make_script</span><span class="p" data-group-id="4174908662-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="4174908662-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="4174908662-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ -				       </span><span class="p" data-group-id="4174908662-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="4174908662-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-163">)</span><span class="p" data-group-id="4174908662-162">}</span><span class="w">
│ │ │ -				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="4174908662-161">]</span><span class="p" data-group-id="4174908662-160">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">make_script</span><span class="p" data-group-id="7989307685-159">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="7989307685-159">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7989307685-160">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-161">[</span><span class="ss">no_module_tests</span><span class="p">,</span><span class="w">
│ │ │ +				       </span><span class="p" data-group-id="7989307685-162">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7989307685-163">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-163">)</span><span class="p" data-group-id="7989307685-162">}</span><span class="w">
│ │ │ +				       </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="7989307685-161">]</span><span class="p" data-group-id="7989307685-160">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% make_tar(RelFileName,Opts)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">make_tar</span><span class="p" data-group-id="4174908662-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="4174908662-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="4174908662-165">(</span><span class="p" data-group-id="4174908662-165">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="4174908662-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-167">[</span><span class="p" data-group-id="4174908662-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="4174908662-168">}</span><span class="p">,</span><span class="w">
│ │ │ -				    </span><span class="p" data-group-id="4174908662-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="4174908662-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-170">)</span><span class="p" data-group-id="4174908662-169">}</span><span class="w">
│ │ │ -				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="4174908662-167">]</span><span class="p" data-group-id="4174908662-166">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">make_tar</span><span class="p" data-group-id="7989307685-164">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="n">Opts</span><span class="p" data-group-id="7989307685-164">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">RootDir</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">code</span><span class="p">:</span><span class="nf">root_dir</span><span class="p" data-group-id="7989307685-165">(</span><span class="p" data-group-id="7989307685-165">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7989307685-166">(</span><span class="n">RelFileName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-167">[</span><span class="p" data-group-id="7989307685-168">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">RootDir</span><span class="p" data-group-id="7989307685-168">}</span><span class="p">,</span><span class="w">
│ │ │ +				    </span><span class="p" data-group-id="7989307685-169">{</span><span class="ss">outdir</span><span class="p">,</span><span class="nc">filename</span><span class="p">:</span><span class="nf">dirname</span><span class="p" data-group-id="7989307685-170">(</span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-170">)</span><span class="p" data-group-id="7989307685-169">}</span><span class="w">
│ │ │ +				    </span><span class="p">|</span><span class="n">Opts</span><span class="p" data-group-id="7989307685-167">]</span><span class="p" data-group-id="7989307685-166">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% extract_tar(TarFile, DestDir)</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">extract_tar</span><span class="p" data-group-id="4174908662-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="4174908662-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="4174908662-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-173">[</span><span class="p" data-group-id="4174908662-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="4174908662-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="4174908662-173">]</span><span class="p" data-group-id="4174908662-172">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">extract_tar</span><span class="p" data-group-id="7989307685-171">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="7989307685-171">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erl_tar</span><span class="p">:</span><span class="nf">extract</span><span class="p" data-group-id="7989307685-172">(</span><span class="n">TarFile</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-173">[</span><span class="p" data-group-id="7989307685-174">{</span><span class="ss">cwd</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p" data-group-id="7989307685-174">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compressed</span><span class="p" data-group-id="7989307685-173">]</span><span class="p" data-group-id="7989307685-172">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="4174908662-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="4174908662-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="4174908662-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="4174908662-176">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7989307685-175">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="p" data-group-id="7989307685-175">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">create_RELEASES</span><span class="p" data-group-id="7989307685-176">(</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">RelFileName</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.rel&quot;</span><span class="p" data-group-id="7989307685-176">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="4174908662-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="4174908662-178">(</span><span class="nf">fun</span><span class="p" data-group-id="4174908662-179">(</span><span class="n">Script</span><span class="p" data-group-id="4174908662-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="4174908662-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ -                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-180">)</span><span class="w">
│ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="4174908662-178">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">subst_src_script</span><span class="p" data-group-id="4174908662-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_file</span><span class="p" data-group-id="4174908662-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-183">(</span><span class="p" data-group-id="4174908662-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="4174908662-184">]</span><span class="p" data-group-id="4174908662-183">)</span><span class="p">,</span><span class="w">
│ │ │ -               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-185">(</span><span class="p" data-group-id="4174908662-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="4174908662-186">]</span><span class="p" data-group-id="4174908662-185">)</span><span class="p">,</span><span class="w">
│ │ │ -               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-182">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">subst_file</span><span class="p" data-group-id="4174908662-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="4174908662-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="4174908662-189">(</span><span class="n">Src</span><span class="p" data-group-id="4174908662-189">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="4174908662-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="4174908662-190">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">write_file</span><span class="p" data-group-id="4174908662-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="4174908662-191">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="4174908662-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">subst_src_scripts</span><span class="p" data-group-id="7989307685-177">(</span><span class="n">Scripts</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-177">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7989307685-178">(</span><span class="nf">fun</span><span class="p" data-group-id="7989307685-179">(</span><span class="n">Script</span><span class="p" data-group-id="7989307685-179">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                          </span><span class="nf">subst_src_script</span><span class="p" data-group-id="7989307685-180">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w">
│ │ │ +                                           </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-180">)</span><span class="w">
│ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Scripts</span><span class="p" data-group-id="7989307685-178">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">subst_src_script</span><span class="p" data-group-id="7989307685-181">(</span><span class="n">Script</span><span class="p">,</span><span class="w"> </span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-181">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_file</span><span class="p" data-group-id="7989307685-182">(</span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-183">(</span><span class="p" data-group-id="7989307685-184">[</span><span class="n">SrcDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;.src&quot;</span><span class="p" data-group-id="7989307685-184">]</span><span class="p" data-group-id="7989307685-183">)</span><span class="p">,</span><span class="w">
│ │ │ +               </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-185">(</span><span class="p" data-group-id="7989307685-186">[</span><span class="n">DestDir</span><span class="p">,</span><span class="w"> </span><span class="n">Script</span><span class="p" data-group-id="7989307685-186">]</span><span class="p" data-group-id="7989307685-185">)</span><span class="p">,</span><span class="w">
│ │ │ +               </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-182">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">subst_file</span><span class="p" data-group-id="7989307685-187">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-187">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-188">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="7989307685-188">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">read_txt_file</span><span class="p" data-group-id="7989307685-189">(</span><span class="n">Src</span><span class="p" data-group-id="7989307685-189">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">NConts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">subst</span><span class="p" data-group-id="7989307685-190">(</span><span class="n">Conts</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7989307685-190">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">write_file</span><span class="p" data-group-id="7989307685-191">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">NConts</span><span class="p" data-group-id="7989307685-191">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="7989307685-192">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-192">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4174908662-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4174908662-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="4174908662-194">(</span><span class="n">Src</span><span class="p" data-group-id="4174908662-194">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="4174908662-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4174908662-195">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7989307685-193">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7989307685-193">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="7989307685-194">(</span><span class="n">Src</span><span class="p" data-group-id="7989307685-194">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="7989307685-195">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7989307685-195">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% subst(Str, Vars)</span><span class="w">
│ │ │  </span><span class="c1">%% Vars = [{Var, Val}]</span><span class="w">
│ │ │  </span><span class="c1">%% Var = Val = string()</span><span class="w">
│ │ │  </span><span class="c1">%% Substitute all occurrences of %Var% for Val in Str, using the list</span><span class="w">
│ │ │  </span><span class="c1">%% of variables in Vars.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="4174908662-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="4174908662-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="4174908662-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-198">[</span><span class="p" data-group-id="4174908662-198">]</span><span class="p" data-group-id="4174908662-197">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="7989307685-196">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7989307685-196">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="7989307685-197">(</span><span class="n">Str</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-198">[</span><span class="p" data-group-id="7989307685-198">]</span><span class="p" data-group-id="7989307685-197">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="4174908662-199">(</span><span class="p" data-group-id="4174908662-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-201">(</span><span class="p" data-group-id="4174908662-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-203">[</span><span class="p" data-group-id="4174908662-203">]</span><span class="p" data-group-id="4174908662-201">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="4174908662-204">(</span><span class="p" data-group-id="4174908662-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-206">(</span><span class="p" data-group-id="4174908662-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-208">[</span><span class="p" data-group-id="4174908662-208">]</span><span class="p" data-group-id="4174908662-206">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="4174908662-209">(</span><span class="p" data-group-id="4174908662-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-211">(</span><span class="p" data-group-id="4174908662-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-213">[</span><span class="p" data-group-id="4174908662-213">]</span><span class="p" data-group-id="4174908662-211">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="4174908662-214">(</span><span class="p" data-group-id="4174908662-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="4174908662-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-217">]</span><span class="p" data-group-id="4174908662-216">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst</span><span class="p" data-group-id="4174908662-218">(</span><span class="p" data-group-id="4174908662-219">[</span><span class="p" data-group-id="4174908662-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4174908662-220">(</span><span class="n">Result</span><span class="p" data-group-id="4174908662-220">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-221">(</span><span class="p" data-group-id="4174908662-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4174908662-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4174908662-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="4174908662-223">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="4174908662-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="4174908662-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4174908662-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="4174908662-226">}</span><span class="p" data-group-id="4174908662-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="4174908662-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="4174908662-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-228">)</span><span class="p" data-group-id="4174908662-227">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="7989307685-199">(</span><span class="p" data-group-id="7989307685-200">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-200">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-199">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$Z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-201">(</span><span class="p" data-group-id="7989307685-202">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-202">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-203">[</span><span class="p" data-group-id="7989307685-203">]</span><span class="p" data-group-id="7989307685-201">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="7989307685-204">(</span><span class="p" data-group-id="7989307685-205">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-205">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-204">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-206">(</span><span class="p" data-group-id="7989307685-207">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-207">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-208">[</span><span class="p" data-group-id="7989307685-208">]</span><span class="p" data-group-id="7989307685-206">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="7989307685-209">(</span><span class="p" data-group-id="7989307685-210">[</span><span class="sc">$%</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-210">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-209">)</span><span class="w"> </span><span class="k">when</span><span class="w">  </span><span class="n">C</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="sc">$_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-211">(</span><span class="p" data-group-id="7989307685-212">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-212">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-213">[</span><span class="p" data-group-id="7989307685-213">]</span><span class="p" data-group-id="7989307685-211">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="7989307685-214">(</span><span class="p" data-group-id="7989307685-215">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-215">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-214">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="7989307685-216">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-217">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-217">]</span><span class="p" data-group-id="7989307685-216">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst</span><span class="p" data-group-id="7989307685-218">(</span><span class="p" data-group-id="7989307685-219">[</span><span class="p" data-group-id="7989307685-219">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-218">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7989307685-220">(</span><span class="n">Result</span><span class="p" data-group-id="7989307685-220">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-221">(</span><span class="p" data-group-id="7989307685-222">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-222">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7989307685-221">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7989307685-223">(</span><span class="n">VarAcc</span><span class="p" data-group-id="7989307685-223">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7989307685-224">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p" data-group-id="7989307685-224">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7989307685-225">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-226">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7989307685-226">}</span><span class="p" data-group-id="7989307685-225">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="7989307685-227">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="7989307685-228">(</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-228">)</span><span class="p" data-group-id="7989307685-227">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">subst</span><span class="p" data-group-id="4174908662-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4174908662-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-231">]</span><span class="p" data-group-id="4174908662-230">]</span><span class="p" data-group-id="4174908662-229">)</span><span class="w">
│ │ │ +            </span><span class="nf">subst</span><span class="p" data-group-id="7989307685-229">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-230">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7989307685-231">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-231">]</span><span class="p" data-group-id="7989307685-230">]</span><span class="p" data-group-id="7989307685-229">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-232">(</span><span class="p" data-group-id="4174908662-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="4174908662-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4174908662-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4174908662-235">]</span><span class="p" data-group-id="4174908662-234">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">subst_var</span><span class="p" data-group-id="4174908662-236">(</span><span class="p" data-group-id="4174908662-237">[</span><span class="p" data-group-id="4174908662-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="4174908662-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">subst</span><span class="p" data-group-id="4174908662-238">(</span><span class="p" data-group-id="4174908662-239">[</span><span class="p" data-group-id="4174908662-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="4174908662-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4174908662-241">]</span><span class="p" data-group-id="4174908662-240">]</span><span class="p" data-group-id="4174908662-238">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="4174908662-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-244">[</span><span class="p" data-group-id="4174908662-244">]</span><span class="p" data-group-id="4174908662-243">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">copy_file</span><span class="p" data-group-id="4174908662-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4174908662-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="4174908662-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="4174908662-247">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="4174908662-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4174908662-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-232">(</span><span class="p" data-group-id="7989307685-233">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7989307685-233">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7989307685-232">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-234">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-235">[</span><span class="n">C</span><span class="p">|</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7989307685-235">]</span><span class="p" data-group-id="7989307685-234">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">subst_var</span><span class="p" data-group-id="7989307685-236">(</span><span class="p" data-group-id="7989307685-237">[</span><span class="p" data-group-id="7989307685-237">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p">,</span><span class="w"> </span><span class="n">VarAcc</span><span class="p" data-group-id="7989307685-236">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">subst</span><span class="p" data-group-id="7989307685-238">(</span><span class="p" data-group-id="7989307685-239">[</span><span class="p" data-group-id="7989307685-239">]</span><span class="p">,</span><span class="w"> </span><span class="n">Vars</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-240">[</span><span class="n">VarAcc</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7989307685-241">[</span><span class="sc">$%</span><span class="p">|</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7989307685-241">]</span><span class="p" data-group-id="7989307685-240">]</span><span class="p" data-group-id="7989307685-238">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-242">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="7989307685-242">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-243">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-244">[</span><span class="p" data-group-id="7989307685-244">]</span><span class="p" data-group-id="7989307685-243">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">copy_file</span><span class="p" data-group-id="7989307685-245">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-245">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-246">{</span><span class="ss">ok</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7989307685-246">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">copy</span><span class="p" data-group-id="7989307685-247">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dest</span><span class="p" data-group-id="7989307685-247">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="7989307685-248">(</span><span class="ss">preserve</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7989307685-248">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="4174908662-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4174908662-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="4174908662-250">(</span><span class="n">Src</span><span class="p" data-group-id="4174908662-250">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="4174908662-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="4174908662-251">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7989307685-249">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7989307685-249">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file_info</span><span class="p" data-group-id="7989307685-250">(</span><span class="n">Src</span><span class="p" data-group-id="7989307685-250">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">file</span><span class="p">:</span><span class="nf">write_file_info</span><span class="p" data-group-id="7989307685-251">(</span><span class="n">Dest</span><span class="p">,</span><span class="w"> </span><span class="n">FileInfo</span><span class="p" data-group-id="7989307685-251">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">write_file</span><span class="p" data-group-id="4174908662-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="4174908662-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="4174908662-253">(</span><span class="p" data-group-id="4174908662-253">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="4174908662-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="4174908662-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-256">[</span><span class="ss">write</span><span class="p" data-group-id="4174908662-256">]</span><span class="p" data-group-id="4174908662-255">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="4174908662-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="4174908662-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="4174908662-258">)</span><span class="p" data-group-id="4174908662-257">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="4174908662-259">(</span><span class="n">Fd</span><span class="p" data-group-id="4174908662-259">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">read_txt_file</span><span class="p" data-group-id="4174908662-260">(</span><span class="n">File</span><span class="p" data-group-id="4174908662-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="4174908662-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="4174908662-262">(</span><span class="n">File</span><span class="p" data-group-id="4174908662-262">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4174908662-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="4174908662-264">(</span><span class="n">Bin</span><span class="p" data-group-id="4174908662-264">)</span><span class="p" data-group-id="4174908662-263">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="4174908662-265">(</span><span class="n">Dir</span><span class="p" data-group-id="4174908662-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="4174908662-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4174908662-267">[</span><span class="n">Dir</span><span class="p" data-group-id="4174908662-267">]</span><span class="p" data-group-id="4174908662-266">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">remove_all_files</span><span class="p" data-group-id="4174908662-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="4174908662-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="4174908662-269">(</span><span class="nf">fun</span><span class="p" data-group-id="4174908662-270">(</span><span class="n">File</span><span class="p" data-group-id="4174908662-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="4174908662-271">(</span><span class="p" data-group-id="4174908662-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="4174908662-272">]</span><span class="p" data-group-id="4174908662-271">)</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="4174908662-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="4174908662-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">write_file</span><span class="p" data-group-id="7989307685-252">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="n">Conts</span><span class="p" data-group-id="7989307685-252">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Enc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">native_name_encoding</span><span class="p" data-group-id="7989307685-253">(</span><span class="p" data-group-id="7989307685-253">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-254">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7989307685-254">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7989307685-255">(</span><span class="n">FName</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-256">[</span><span class="ss">write</span><span class="p" data-group-id="7989307685-256">]</span><span class="p" data-group-id="7989307685-255">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">write</span><span class="p" data-group-id="7989307685-257">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="nc">unicode</span><span class="p">:</span><span class="nf">characters_to_binary</span><span class="p" data-group-id="7989307685-258">(</span><span class="n">Conts</span><span class="p">,</span><span class="n">Enc</span><span class="p">,</span><span class="n">Enc</span><span class="p" data-group-id="7989307685-258">)</span><span class="p" data-group-id="7989307685-257">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="7989307685-259">(</span><span class="n">Fd</span><span class="p" data-group-id="7989307685-259">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">read_txt_file</span><span class="p" data-group-id="7989307685-260">(</span><span class="n">File</span><span class="p" data-group-id="7989307685-260">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-261">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Bin</span><span class="p" data-group-id="7989307685-261">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read_file</span><span class="p" data-group-id="7989307685-262">(</span><span class="n">File</span><span class="p" data-group-id="7989307685-262">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7989307685-263">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_list</span><span class="p" data-group-id="7989307685-264">(</span><span class="n">Bin</span><span class="p" data-group-id="7989307685-264">)</span><span class="p" data-group-id="7989307685-263">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">remove_dir_tree</span><span class="p" data-group-id="7989307685-265">(</span><span class="n">Dir</span><span class="p" data-group-id="7989307685-265">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">remove_all_files</span><span class="p" data-group-id="7989307685-266">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7989307685-267">[</span><span class="n">Dir</span><span class="p" data-group-id="7989307685-267">]</span><span class="p" data-group-id="7989307685-266">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">remove_all_files</span><span class="p" data-group-id="7989307685-268">(</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="7989307685-268">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="7989307685-269">(</span><span class="nf">fun</span><span class="p" data-group-id="7989307685-270">(</span><span class="n">File</span><span class="p" data-group-id="7989307685-270">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                          </span><span class="n">FilePath</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">filename</span><span class="p">:</span><span class="nf">join</span><span class="p" data-group-id="7989307685-271">(</span><span class="p" data-group-id="7989307685-272">[</span><span class="n">Dir</span><span class="p">,</span><span class="w"> </span><span class="n">File</span><span class="p" data-group-id="7989307685-272">]</span><span class="p" data-group-id="7989307685-271">)</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="k">case</span><span class="w"> </span><span class="nc">filelib</span><span class="p">:</span><span class="nf">is_dir</span><span class="p" data-group-id="7989307685-273">(</span><span class="n">FilePath</span><span class="p" data-group-id="7989307685-273">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │                                </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                  </span><span class="p" data-group-id="4174908662-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="4174908662-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="4174908662-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="4174908662-275">)</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="4174908662-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="4174908662-276">)</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="4174908662-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="4174908662-277">)</span><span class="p">;</span><span class="w">
│ │ │ +                                  </span><span class="p" data-group-id="7989307685-274">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="7989307685-274">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">list_dir</span><span class="p" data-group-id="7989307685-275">(</span><span class="n">FilePath</span><span class="p" data-group-id="7989307685-275">)</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="nf">remove_all_files</span><span class="p" data-group-id="7989307685-276">(</span><span class="n">FilePath</span><span class="p">,</span><span class="w"> </span><span class="n">DirFiles</span><span class="p" data-group-id="7989307685-276">)</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">del_dir</span><span class="p" data-group-id="7989307685-277">(</span><span class="n">FilePath</span><span class="p" data-group-id="7989307685-277">)</span><span class="p">;</span><span class="w">
│ │ │                                </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="4174908662-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="4174908662-278">)</span><span class="w">
│ │ │ +                                  </span><span class="nc">file</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="7989307685-278">(</span><span class="n">FilePath</span><span class="p" data-group-id="7989307685-278">)</span><span class="w">
│ │ │                            </span><span class="k">end</span><span class="w">
│ │ │ -                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="4174908662-269">)</span><span class="p">.</span></code></pre>
│ │ │ +                  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Files</span><span class="p" data-group-id="7989307685-269">)</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="error_logging.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/data_types.html
│ │ │ @@ -192,18 +192,18 @@
│ │ │    </a>
│ │ │    <span class="text">Representation of Floating Point Numbers</span>
│ │ │  </h3>
│ │ │  <p>When working with floats you may not see what you expect when printing or doing
│ │ │  arithmetic operations. This is because floats are represented by a fixed number
│ │ │  of bits in a base-2 system while printed floats are represented with a base-10
│ │ │  system. Erlang uses 64-bit floats. Here are examples of this phenomenon:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5392440629-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="5392440629-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5392440629-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5392440629-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │ +</span><span class="mf">0.30000000000000004</span></code></pre><p>The real numbers <code class="inline">0.1</code> and <code class="inline">0.2</code> cannot be represented exactly as floats.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4191745936-1">{</span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963968</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963968.0</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="mf">36028797018963970.0</span><span class="p">,</span><span class="w"> </span><span class="mi">36028797018963970</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mf">36028797018963970.0</span><span class="p" data-group-id="4191745936-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4191745936-2">{</span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="mf">3.602879701896397e16</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="4191745936-2">}</span><span class="p">.</span></code></pre><p>The value <code class="inline">36028797018963968</code> can be represented exactly as a float value but
│ │ │  Erlang's pretty printer rounds <code class="inline">36028797018963968.0</code> to <code class="inline">3.602879701896397e16</code>
│ │ │  (<code class="inline">=36028797018963970.0</code>) as all values in the range
│ │ │  <code class="inline">[36028797018963966.0, 36028797018963972.0]</code> are represented by
│ │ │  <code class="inline">36028797018963968.0</code>.</p><p>For more information about floats and issues with them see:</p><ul><li><a href="https://floating-point-gui.de/">What Every Programmer Should Know About Floating-Point Arithmetic</a></li><li><a href="https://0.30000000000000004.com/">0.30000000000000004.com/</a></li><li><a href="https://docs.python.org/3/tutorial/floatingpoint.html">Floating Point Arithmetic: Issues and Limitations</a></li></ul><p>If you need to work with exact decimal fractions, for instance to represent
│ │ │  money, it is recommended to use a library that handles that, or work in
│ │ │  cents instead of dollars or euros so that decimal fractions are not needed.</p><p>Also note that Erlang's floats do not exactly match IEEE 754 floats,
│ │ │  in that neither <em>Inf</em> nor <em>NaN</em> are supported in Erlang. Any
│ │ │ @@ -237,52 +237,52 @@
│ │ │  by eight are called <em>binaries</em>.</p><p><em>Examples:</em></p><pre><code class="text">1&gt; &lt;&lt;10,20&gt;&gt;.
│ │ │  &lt;&lt;10,20&gt;&gt;
│ │ │  2&gt; &lt;&lt;&quot;ABC&quot;&gt;&gt;.
│ │ │  &lt;&lt;&quot;ABC&quot;&gt;&gt;
│ │ │  3&gt; &lt;&lt;1:1,0:1&gt;&gt;.
│ │ │  &lt;&lt;2:2&gt;&gt;</code></pre><p>The <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_bitstring/1"><code class="inline">is_bitstring/1</code></a> BIF tests whether a
│ │ │  term is a bit string, and the <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_binary/1"><code class="inline">is_binary/1</code></a>
│ │ │ -BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="4843641039-1">(</span><span class="p" data-group-id="4843641039-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4843641039-2">&gt;&gt;</span><span class="p" data-group-id="4843641039-1">)</span><span class="p">.</span><span class="w">
│ │ │ +BIF tests whether a term is a binary.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">is_bitstring</span><span class="p" data-group-id="3390430524-1">(</span><span class="p" data-group-id="3390430524-2">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3390430524-2">&gt;&gt;</span><span class="p" data-group-id="3390430524-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="4843641039-3">(</span><span class="p" data-group-id="4843641039-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4843641039-4">&gt;&gt;</span><span class="p" data-group-id="4843641039-3">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="3390430524-3">(</span><span class="p" data-group-id="3390430524-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3390430524-4">&gt;&gt;</span><span class="p" data-group-id="3390430524-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="4843641039-5">(</span><span class="p" data-group-id="4843641039-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="4843641039-6">&gt;&gt;</span><span class="p" data-group-id="4843641039-5">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nf">is_binary</span><span class="p" data-group-id="3390430524-5">(</span><span class="p" data-group-id="3390430524-6">&lt;&lt;</span><span class="mi">42</span><span class="p" data-group-id="3390430524-6">&gt;&gt;</span><span class="p" data-group-id="3390430524-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="w">
│ │ │  </span></code></pre><p>For more examples, see <a href="../../doc/system/bit_syntax.html">Programming Examples</a>.</p><h2 id="reference" class="section-heading">
│ │ │    <a href="#reference" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Reference</span>
│ │ │  </h2>
│ │ │  <p>A term that is <a href="../../doc/system/system_limits.html#unique_references">unique</a>
│ │ │  among connected nodes. A reference is created by calling the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#make_ref/0"><code class="inline">make_ref/0</code></a> BIF. The
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_reference/1"><code class="inline">is_reference/1</code></a> BIF tests whether a term
│ │ │ -is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="8674937556-1">(</span><span class="p" data-group-id="8674937556-1">)</span><span class="p">.</span><span class="w">
│ │ │ +is a reference.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="6372973122-1">(</span><span class="p" data-group-id="6372973122-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.76482849</span><span class="p">.</span><span class="mf">3801088007.198204</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="8674937556-2">(</span><span class="n">Ref</span><span class="p" data-group-id="8674937556-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nf">is_reference</span><span class="p" data-group-id="6372973122-2">(</span><span class="n">Ref</span><span class="p" data-group-id="6372973122-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h2 id="fun" class="section-heading">
│ │ │    <a href="#fun" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Fun</span>
│ │ │  </h2>
│ │ │  <p>A fun is a functional object. Funs make it possible to create an anonymous
│ │ │  function and pass the function itself — not its name — as argument to other
│ │ │ -functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9681708771-1">(</span><span class="n">X</span><span class="p" data-group-id="9681708771-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +functions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3630484291-1">(</span><span class="n">X</span><span class="p" data-group-id="3630484291-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="9681708771-2">(</span><span class="mi">2</span><span class="p" data-group-id="9681708771-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="3630484291-2">(</span><span class="mi">2</span><span class="p" data-group-id="3630484291-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre><p>The <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> and <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_function/2"><code class="inline">is_function/2</code></a>
│ │ │ -BIFs tests whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1043131429-1">(</span><span class="p" data-group-id="1043131429-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +BIFs tests whether a term is a fun.</p><p><em>Examples</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9633989763-1">(</span><span class="p" data-group-id="9633989763-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.105768164</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="1043131429-2">(</span><span class="n">F</span><span class="p" data-group-id="1043131429-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="9633989763-2">(</span><span class="n">F</span><span class="p" data-group-id="9633989763-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="1043131429-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="1043131429-3">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="9633989763-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9633989763-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="1043131429-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1043131429-4">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nf">is_function</span><span class="p" data-group-id="9633989763-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9633989763-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><p>Read more about funs in <a href="expressions.html#fun-expressions">Fun Expressions</a>. For more
│ │ │  examples, see <a href="../../doc/system/funs.html">Programming Examples</a>.</p><h2 id="port-identifier" class="section-heading">
│ │ │    <a href="#port-identifier" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Port Identifier</span>
│ │ │  </h2>
│ │ │ @@ -300,94 +300,94 @@
│ │ │  for a new process after a while.</p><p>The BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#self/0"><code class="inline">self/0</code></a> returns the Pid of the calling process. When
│ │ │  <a href="ref_man_processes.html#process-creation">creating a new process</a>, the parent
│ │ │  process will be able to get the Pid of the child process either via the return
│ │ │  value, as is the case when calling the <a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn/3"><code class="inline">spawn/3</code></a> BIF, or via
│ │ │  a message, which is the case when calling the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/5</code></a> BIF. A Pid is typically used when
│ │ │  when sending a process a <a href="ref_man_processes.html#signals">signal</a>. The
│ │ │ -<a href="../../erts-15.2.7.2/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9612057595-1">(</span><span class="ss">m</span><span class="p" data-group-id="9612057595-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9612057595-2">(</span><span class="p" data-group-id="9612057595-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9612057595-3">]</span><span class="p" data-group-id="9612057595-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="../../erts-15.2.7.2/doc/html/erlang.html#is_pid/1"><code class="inline">is_pid/1</code></a> BIF tests whether a term is a Pid.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6103374766-1">(</span><span class="ss">m</span><span class="p" data-group-id="6103374766-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6103374766-2">(</span><span class="p" data-group-id="6103374766-3">[</span><span class="ss">loop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6103374766-3">]</span><span class="p" data-group-id="6103374766-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="9612057595-4">(</span><span class="p" data-group-id="9612057595-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="6103374766-4">(</span><span class="p" data-group-id="6103374766-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">who_are_you</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9612057595-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9612057595-6">[</span><span class="nf">self</span><span class="p" data-group-id="9612057595-7">(</span><span class="p" data-group-id="9612057595-7">)</span><span class="p" data-group-id="9612057595-6">]</span><span class="p" data-group-id="9612057595-5">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="9612057595-8">(</span><span class="p" data-group-id="9612057595-8">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6103374766-5">(</span><span class="s">&quot;I am </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6103374766-6">[</span><span class="nf">self</span><span class="p" data-group-id="6103374766-7">(</span><span class="p" data-group-id="6103374766-7">)</span><span class="p" data-group-id="6103374766-6">]</span><span class="p" data-group-id="6103374766-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="6103374766-8">(</span><span class="p" data-group-id="6103374766-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9612057595-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9612057595-10">[</span><span class="p" data-group-id="9612057595-10">]</span><span class="p" data-group-id="9612057595-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="6103374766-9">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">loop</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6103374766-10">[</span><span class="p" data-group-id="6103374766-10">]</span><span class="p" data-group-id="6103374766-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">who_are_you</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">I</span><span class="w"> </span><span class="ss">am</span><span class="w"> </span><span class="o">&lt;</span><span class="mf">0.58</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="ss">who_are_you</span></code></pre><p>Read more about processes in <a href="ref_man_processes.html">Processes</a>.</p><h2 id="tuple" class="section-heading">
│ │ │    <a href="#tuple" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Tuple</span>
│ │ │  </h2>
│ │ │  <p>A tuple is a compound data type with a fixed number of terms:</p><pre><code class="text">{Term1,...,TermN}</code></pre><p>Each term <code class="inline">Term</code> in the tuple is called an <em>element</em>. The number of elements is
│ │ │ -said to be the <em>size</em> of the tuple.</p><p>There exists a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7160797621-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="7160797621-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7160797621-2">}</span><span class="p" data-group-id="7160797621-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7160797621-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="7160797621-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7160797621-4">}</span><span class="p" data-group-id="7160797621-3">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">element</span><span class="p" data-group-id="7160797621-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="7160797621-5">)</span><span class="p">.</span><span class="w">
│ │ │ +said to be the <em>size</em> of the tuple.</p><p>There exists a number of BIFs to manipulate tuples.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6181508653-1">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="6181508653-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6181508653-2">}</span><span class="p" data-group-id="6181508653-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6181508653-3">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">24</span><span class="p">,</span><span class="p" data-group-id="6181508653-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6181508653-4">}</span><span class="p" data-group-id="6181508653-3">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nf">element</span><span class="p" data-group-id="6181508653-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="6181508653-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">adam</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nf">element</span><span class="p" data-group-id="7160797621-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="7160797621-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7160797621-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7160797621-7">}</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="7160797621-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="7160797621-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7160797621-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="7160797621-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="7160797621-10">}</span><span class="p" data-group-id="7160797621-9">}</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="7160797621-11">(</span><span class="n">P</span><span class="p" data-group-id="7160797621-11">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nf">element</span><span class="p" data-group-id="6181508653-6">(</span><span class="mi">3</span><span class="p">,</span><span class="n">P</span><span class="p" data-group-id="6181508653-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6181508653-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6181508653-7">}</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">setelement</span><span class="p" data-group-id="6181508653-8">(</span><span class="mi">2</span><span class="p">,</span><span class="n">P</span><span class="p">,</span><span class="mi">25</span><span class="p" data-group-id="6181508653-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6181508653-9">{</span><span class="ss">adam</span><span class="p">,</span><span class="mi">25</span><span class="p">,</span><span class="p" data-group-id="6181508653-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="6181508653-10">}</span><span class="p" data-group-id="6181508653-9">}</span><span class="gp unselectable">
│ │ │ +5&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="6181508653-11">(</span><span class="n">P</span><span class="p" data-group-id="6181508653-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="7160797621-12">(</span><span class="p" data-group-id="7160797621-13">{</span><span class="p" data-group-id="7160797621-13">}</span><span class="p" data-group-id="7160797621-12">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="6181508653-12">(</span><span class="p" data-group-id="6181508653-13">{</span><span class="p" data-group-id="6181508653-13">}</span><span class="p" data-group-id="6181508653-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="7160797621-14">(</span><span class="p" data-group-id="7160797621-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="7160797621-15">}</span><span class="p" data-group-id="7160797621-14">)</span><span class="p">.</span><span class="w">
│ │ │ +7&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="6181508653-14">(</span><span class="p" data-group-id="6181508653-15">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6181508653-15">}</span><span class="p" data-group-id="6181508653-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h2 id="map" class="section-heading">
│ │ │    <a href="#map" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Map</span>
│ │ │  </h2>
│ │ │  <p>A map is a compound data type with a variable number of key-value associations:</p><pre><code class="text">#{Key1 =&gt; Value1, ..., KeyN =&gt; ValueN}</code></pre><p>Each key-value association in the map is called an <em>association pair</em>. The key
│ │ │  and value parts of the pair are called <em>elements</em>. The number of association
│ │ │ -pairs is said to be the <em>size</em> of the map.</p><p>There exists a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5161991255-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5161991255-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5161991255-2">}</span><span class="p" data-group-id="5161991255-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5161991255-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5161991255-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5161991255-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="5161991255-3">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="5161991255-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="5161991255-5">)</span><span class="p">.</span><span class="w">
│ │ │ +pairs is said to be the <em>size</em> of the map.</p><p>There exists a number of BIFs to manipulate maps.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9150022371-1">#{</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="w"> </span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9150022371-2">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9150022371-2">}</span><span class="p" data-group-id="9150022371-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9150022371-3">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">24</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9150022371-4">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9150022371-4">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="9150022371-3">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="9150022371-5">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="9150022371-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">adam</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="5161991255-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="5161991255-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5161991255-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5161991255-7">}</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="5161991255-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="5161991255-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5161991255-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5161991255-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="5161991255-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="5161991255-9">}</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="5161991255-11">(</span><span class="n">M</span><span class="p" data-group-id="5161991255-11">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">maps</span><span class="p">:</span><span class="nf">get</span><span class="p" data-group-id="9150022371-6">(</span><span class="ss">date</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="9150022371-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9150022371-7">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9150022371-7">}</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="9150022371-8">(</span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="9150022371-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9150022371-9">#{</span><span class="ss">age</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">25</span><span class="p">,</span><span class="ss">date</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9150022371-10">{</span><span class="ss">july</span><span class="p">,</span><span class="mi">29</span><span class="p" data-group-id="9150022371-10">}</span><span class="p">,</span><span class="ss">name</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">adam</span><span class="p" data-group-id="9150022371-9">}</span><span class="gp unselectable">
│ │ │ +5&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="9150022371-11">(</span><span class="n">M</span><span class="p" data-group-id="9150022371-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="5161991255-12">(</span><span class="p" data-group-id="5161991255-13">#{</span><span class="p" data-group-id="5161991255-13">}</span><span class="p" data-group-id="5161991255-12">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="9150022371-12">(</span><span class="p" data-group-id="9150022371-13">#{</span><span class="p" data-group-id="9150022371-13">}</span><span class="p" data-group-id="9150022371-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span></code></pre><p>A collection of maps processing functions are found in module <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html"><code class="inline">maps</code></a>
│ │ │  in STDLIB.</p><p>Read more about maps in <a href="expressions.html#map-expressions">Map Expressions</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Maps were introduced as an experimental feature in Erlang/OTP R17. Their
│ │ │  functionality was extended and became fully supported in Erlang/OTP 18.</p></section><h2 id="list" class="section-heading">
│ │ │    <a href="#list" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">List</span>
│ │ │  </h2>
│ │ │  <p>A list is a compound data type with a variable number of terms.</p><pre><code class="text">[Term1,...,TermN]</code></pre><p>Each term <code class="inline">Term</code> in the list is called an <em>element</em>. The number of elements is
│ │ │  said to be the <em>length</em> of the list.</p><p>Formally, a list is either the empty list <code class="inline">[]</code> or consists of a <em>head</em> (first
│ │ │  element) and a <em>tail</em> (remainder of the list). The <em>tail</em> is also a list. The
│ │ │  latter can be expressed as <code class="inline">[H|T]</code>. The notation <code class="inline">[Term1,...,TermN]</code> above is
│ │ │  equivalent with the list <code class="inline">[Term1|[...|[TermN|[]]]]</code>.</p><p><em>Example:</em></p><p><code class="inline">[]</code> is a list, thus<br/><code class="inline">[c|[]]</code> is a list, thus<br/><code class="inline">[b|[c|[]]]</code> is a list, thus<br/><code class="inline">[a|[b|[c|[]]]]</code> is a list, or in short <code class="inline">[a,b,c]</code></p><p>A list where the tail is a list is sometimes called a <em>proper list</em>. It is
│ │ │  allowed to have a list where the tail is not a list, for example, <code class="inline">[a|b]</code>.
│ │ │ -However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9648099333-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9648099333-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9648099333-2">}</span><span class="p" data-group-id="9648099333-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9648099333-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9648099333-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9648099333-4">}</span><span class="p" data-group-id="9648099333-3">]</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="9648099333-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9648099333-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9648099333-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9648099333-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9648099333-7">}</span><span class="p" data-group-id="9648099333-6">]</span><span class="gp unselectable">
│ │ │ +However, this type of list is of little practical use.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4095109674-1">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4095109674-2">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4095109674-2">}</span><span class="p" data-group-id="4095109674-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4095109674-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4095109674-4">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4095109674-4">}</span><span class="p" data-group-id="4095109674-3">]</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="4095109674-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4095109674-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4095109674-6">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4095109674-7">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4095109674-7">}</span><span class="p" data-group-id="4095109674-6">]</span><span class="gp unselectable">
│ │ │  3&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">a</span><span class="gp unselectable">
│ │ │  4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9648099333-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9648099333-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9648099333-9">}</span><span class="p" data-group-id="9648099333-8">]</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9648099333-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9648099333-10">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9648099333-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="9648099333-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9648099333-12">}</span><span class="p" data-group-id="9648099333-11">]</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nf">length</span><span class="p" data-group-id="9648099333-13">(</span><span class="n">L1</span><span class="p" data-group-id="9648099333-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4095109674-8">[</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4095109674-9">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4095109674-9">}</span><span class="p" data-group-id="4095109674-8">]</span><span class="gp unselectable">
│ │ │ +5&gt; </span><span class="n">L2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4095109674-10">[</span><span class="ss">d</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4095109674-10">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4095109674-11">[</span><span class="ss">d</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="4095109674-12">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="4095109674-12">}</span><span class="p" data-group-id="4095109674-11">]</span><span class="gp unselectable">
│ │ │ +6&gt; </span><span class="nf">length</span><span class="p" data-group-id="4095109674-13">(</span><span class="n">L1</span><span class="p" data-group-id="4095109674-13">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nf">length</span><span class="p" data-group-id="9648099333-14">(</span><span class="p" data-group-id="9648099333-15">[</span><span class="p" data-group-id="9648099333-15">]</span><span class="p" data-group-id="9648099333-14">)</span><span class="p">.</span><span class="w">
│ │ │ +7&gt; </span><span class="nf">length</span><span class="p" data-group-id="4095109674-14">(</span><span class="p" data-group-id="4095109674-15">[</span><span class="p" data-group-id="4095109674-15">]</span><span class="p" data-group-id="4095109674-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span></code></pre><p>A collection of list processing functions are found in module
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html"><code class="inline">lists</code></a> in STDLIB.</p><h2 id="string" class="section-heading">
│ │ │    <a href="#string" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">String</span>
│ │ │  </h2>
│ │ │ @@ -507,41 +507,41 @@
│ │ │    <span class="text">Record</span>
│ │ │  </h2>
│ │ │  <p>A record is a data structure for storing a fixed number of elements. It has
│ │ │  named fields and is similar to a struct in C. However, a record is not a true
│ │ │  data type. Instead, record expressions are translated to tuple expressions
│ │ │  during compilation. Therefore, record expressions are not understood by the
│ │ │  shell unless special actions are taken. For details, see module <a href="../../lib/stdlib-6.2.2.2/doc/html/shell.html"><code class="inline">shell</code></a>
│ │ │ -in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4387540929-1">(</span><span class="ss">person</span><span class="p" data-group-id="4387540929-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4387540929-2">(</span><span class="p" data-group-id="4387540929-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4387540929-3">]</span><span class="p" data-group-id="4387540929-2">)</span><span class="p">.</span><span class="w">
│ │ │ +in STDLIB.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2441479248-1">(</span><span class="ss">person</span><span class="p" data-group-id="2441479248-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2441479248-2">(</span><span class="p" data-group-id="2441479248-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2441479248-3">]</span><span class="p" data-group-id="2441479248-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4387540929-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4387540929-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="4387540929-5">}</span><span class="p" data-group-id="4387540929-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2441479248-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2441479248-5">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="2441479248-5">}</span><span class="p" data-group-id="2441479248-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="4387540929-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="4387540929-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="4387540929-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="4387540929-7">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="2441479248-6">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="2441479248-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2441479248-7">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="o">=</span><span class="n">Age</span><span class="p" data-group-id="2441479248-7">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4387540929-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="4387540929-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4387540929-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="4387540929-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.html">Records</a>. More examples are
│ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nc">person</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="2441479248-8">(</span><span class="ss">ernie</span><span class="p">,</span><span class="w"> </span><span class="mi">44</span><span class="p" data-group-id="2441479248-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2441479248-9">{</span><span class="ss">person</span><span class="p">,</span><span class="ss">ernie</span><span class="p">,</span><span class="mi">44</span><span class="p" data-group-id="2441479248-9">}</span></code></pre><p>Read more about records in <a href="ref_man_records.html">Records</a>. More examples are
│ │ │  found in <a href="../../doc/system/prog_ex_records.html">Programming Examples</a>.</p><h2 id="boolean" class="section-heading">
│ │ │    <a href="#boolean" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Boolean</span>
│ │ │  </h2>
│ │ │  <p>There is no Boolean data type in Erlang. Instead the atoms <code class="inline">true</code> and <code class="inline">false</code>
│ │ │  are used to denote Boolean values. The <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_boolean/1"><code class="inline">is_boolean/1</code></a>
│ │ │  BIF tests whether a term is a boolean.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">2</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="ss">true</span><span class="w"> </span><span class="ow">or</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="7659878221-1">(</span><span class="ss">true</span><span class="p" data-group-id="7659878221-1">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="2481056931-1">(</span><span class="ss">true</span><span class="p" data-group-id="2481056931-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="7659878221-2">(</span><span class="ss">false</span><span class="p" data-group-id="7659878221-2">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="2481056931-2">(</span><span class="ss">false</span><span class="p" data-group-id="2481056931-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="7659878221-3">(</span><span class="ss">ok</span><span class="p" data-group-id="7659878221-3">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nf">is_boolean</span><span class="p" data-group-id="2481056931-3">(</span><span class="ss">ok</span><span class="p" data-group-id="2481056931-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><h2 id="escape-sequences" class="section-heading">
│ │ │    <a href="#escape-sequences" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Escape Sequences</span>
│ │ │  </h2>
│ │ │  <p>Within strings (<code class="inline">&quot;</code>-delimited), quoted atoms, and the content of
│ │ │ @@ -559,47 +559,47 @@
│ │ │  <a href="data_types.html#sigil"><code class="inline">~b</code> or <code class="inline">~s</code> sigils </a>the escape sequences for normal
│ │ │  strings, above, are used.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Triple-quoted strings and sigils were introduced in Erlang/OTP 27.</p></section><h2 id="type-conversions" class="section-heading">
│ │ │    <a href="#type-conversions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Conversions</span>
│ │ │  </h2>
│ │ │ -<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="0705998128-1">(</span><span class="ss">hello</span><span class="p" data-group-id="0705998128-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>There are a number of BIFs for type conversions.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="1297811585-1">(</span><span class="ss">hello</span><span class="p" data-group-id="1297811585-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="0705998128-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0705998128-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="1297811585-2">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1297811585-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="0705998128-3">(</span><span class="p" data-group-id="0705998128-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0705998128-4">&gt;&gt;</span><span class="p" data-group-id="0705998128-3">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1297811585-3">(</span><span class="p" data-group-id="1297811585-4">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1297811585-4">&gt;&gt;</span><span class="p" data-group-id="1297811585-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="0705998128-5">(</span><span class="p" data-group-id="0705998128-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="0705998128-6">&gt;&gt;</span><span class="p" data-group-id="0705998128-5">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nf">binary_to_list</span><span class="p" data-group-id="1297811585-5">(</span><span class="p" data-group-id="1297811585-6">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1297811585-6">&gt;&gt;</span><span class="p" data-group-id="1297811585-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="0705998128-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="0705998128-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="0705998128-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="0705998128-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="0705998128-9">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="1297811585-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1297811585-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-8">&lt;&lt;</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1297811585-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +6&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1297811585-9">(</span><span class="mf">7.0</span><span class="p" data-group-id="1297811585-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="0705998128-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="0705998128-10">)</span><span class="p">.</span><span class="w">
│ │ │ +7&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="1297811585-10">(</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="1297811585-10">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">7.0</span><span class="gp unselectable">
│ │ │ -8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="0705998128-11">(</span><span class="mi">77</span><span class="p" data-group-id="0705998128-11">)</span><span class="p">.</span><span class="w">
│ │ │ +8&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="1297811585-11">(</span><span class="mi">77</span><span class="p" data-group-id="1297811585-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;77&quot;</span><span class="gp unselectable">
│ │ │ -9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="0705998128-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="0705998128-12">)</span><span class="p">.</span><span class="w">
│ │ │ +9&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1297811585-12">(</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1297811585-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">77</span><span class="gp unselectable">
│ │ │ -10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="0705998128-13">(</span><span class="p" data-group-id="0705998128-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0705998128-14">}</span><span class="p" data-group-id="0705998128-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0705998128-15">]</span><span class="gp unselectable">
│ │ │ -11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="0705998128-16">(</span><span class="p" data-group-id="0705998128-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0705998128-17">]</span><span class="p" data-group-id="0705998128-16">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0705998128-18">}</span><span class="gp unselectable">
│ │ │ -12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="0705998128-19">(</span><span class="p" data-group-id="0705998128-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0705998128-20">}</span><span class="p" data-group-id="0705998128-19">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="0705998128-21">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="0705998128-22">(</span><span class="p" data-group-id="0705998128-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="0705998128-23">&gt;&gt;</span><span class="p" data-group-id="0705998128-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0705998128-24">}</span><span class="gp unselectable">
│ │ │ -14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="0705998128-25">(</span><span class="p" data-group-id="0705998128-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="0705998128-26">&gt;&gt;</span><span class="p" data-group-id="0705998128-25">)</span><span class="p">.</span><span class="w">
│ │ │ +10&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="1297811585-13">(</span><span class="p" data-group-id="1297811585-14">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1297811585-14">}</span><span class="p" data-group-id="1297811585-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-15">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1297811585-15">]</span><span class="gp unselectable">
│ │ │ +11&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="1297811585-16">(</span><span class="p" data-group-id="1297811585-17">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1297811585-17">]</span><span class="p" data-group-id="1297811585-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-18">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1297811585-18">}</span><span class="gp unselectable">
│ │ │ +12&gt; </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1297811585-19">(</span><span class="p" data-group-id="1297811585-20">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1297811585-20">}</span><span class="p" data-group-id="1297811585-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-21">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1297811585-21">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +13&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1297811585-22">(</span><span class="p" data-group-id="1297811585-23">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">97</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1297811585-23">&gt;&gt;</span><span class="p" data-group-id="1297811585-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-24">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1297811585-24">}</span><span class="gp unselectable">
│ │ │ +14&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="1297811585-25">(</span><span class="p" data-group-id="1297811585-26">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1297811585-26">&gt;&gt;</span><span class="p" data-group-id="1297811585-25">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">77</span><span class="gp unselectable">
│ │ │ -15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="0705998128-27">(</span><span class="mi">77</span><span class="p" data-group-id="0705998128-27">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="0705998128-28">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="0705998128-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="0705998128-29">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0705998128-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="0705998128-30">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="0705998128-31">(</span><span class="p" data-group-id="0705998128-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="0705998128-32">&gt;&gt;</span><span class="p" data-group-id="0705998128-31">)</span><span class="p">.</span><span class="w">
│ │ │ +15&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="1297811585-27">(</span><span class="mi">77</span><span class="p" data-group-id="1297811585-27">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-28">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="1297811585-28">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +16&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="1297811585-29">(</span><span class="mf">7.0</span><span class="p" data-group-id="1297811585-29">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1297811585-30">&lt;&lt;</span><span class="s">&quot;7.00000000000000000000e+00&quot;</span><span class="p" data-group-id="1297811585-30">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +17&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="1297811585-31">(</span><span class="p" data-group-id="1297811585-32">&lt;&lt;</span><span class="s">&quot;7.000e+00&quot;</span><span class="p" data-group-id="1297811585-32">&gt;&gt;</span><span class="p" data-group-id="1297811585-31">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">7.0</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="character_set.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/design_principles.html
│ │ │ @@ -152,135 +152,135 @@
│ │ │  the code for a process in a generic part (a behaviour module) and a specific
│ │ │  part (a <em>callback module</em>).</p><p>The behaviour module is part of Erlang/OTP. To implement a process such as a
│ │ │  supervisor, the user only needs to implement the callback module, which is to
│ │ │  export a pre-defined set of functions, the <em>callback functions</em>.</p><p>The following example illustrate how code can be divided into a generic and a
│ │ │  specific part. Consider the following code (written in plain Erlang) for a
│ │ │  simple server, which keeps track of a number of &quot;channels&quot;. Other processes can
│ │ │  allocate and free the channels by calling the functions <code class="inline">alloc/0</code> and <code class="inline">free/1</code>,
│ │ │ -respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0045897728-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="0045897728-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0045897728-2">(</span><span class="p" data-group-id="0045897728-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0045897728-3">]</span><span class="p" data-group-id="0045897728-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0045897728-4">(</span><span class="p" data-group-id="0045897728-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0045897728-5">]</span><span class="p" data-group-id="0045897728-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0045897728-6">(</span><span class="p" data-group-id="0045897728-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0045897728-7">]</span><span class="p" data-group-id="0045897728-6">)</span><span class="p">.</span><span class="w">
│ │ │ +respectively.</p><p><a href="" id="ch1"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2405049082-1">(</span><span class="ss">ch1</span><span class="p" data-group-id="2405049082-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2405049082-2">(</span><span class="p" data-group-id="2405049082-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2405049082-3">]</span><span class="p" data-group-id="2405049082-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2405049082-4">(</span><span class="p" data-group-id="2405049082-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2405049082-5">]</span><span class="p" data-group-id="2405049082-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2405049082-6">(</span><span class="p" data-group-id="2405049082-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2405049082-7">]</span><span class="p" data-group-id="2405049082-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="0045897728-8">(</span><span class="p" data-group-id="0045897728-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="0045897728-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0045897728-10">[</span><span class="p" data-group-id="0045897728-10">]</span><span class="p" data-group-id="0045897728-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2405049082-8">(</span><span class="p" data-group-id="2405049082-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2405049082-9">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2405049082-10">[</span><span class="p" data-group-id="2405049082-10">]</span><span class="p" data-group-id="2405049082-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="0045897728-11">(</span><span class="p" data-group-id="0045897728-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0045897728-12">{</span><span class="nf">self</span><span class="p" data-group-id="0045897728-13">(</span><span class="p" data-group-id="0045897728-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="0045897728-12">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="2405049082-11">(</span><span class="p" data-group-id="2405049082-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2405049082-12">{</span><span class="nf">self</span><span class="p" data-group-id="2405049082-13">(</span><span class="p" data-group-id="2405049082-13">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2405049082-12">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0045897728-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="0045897728-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2405049082-14">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2405049082-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Res</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="0045897728-15">(</span><span class="n">Ch</span><span class="p" data-group-id="0045897728-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0045897728-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0045897728-16">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="2405049082-15">(</span><span class="n">Ch</span><span class="p" data-group-id="2405049082-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch1</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2405049082-16">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2405049082-16">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0045897728-17">(</span><span class="p" data-group-id="0045897728-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="0045897728-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0045897728-19">(</span><span class="p" data-group-id="0045897728-19">)</span><span class="p" data-group-id="0045897728-18">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="0045897728-20">(</span><span class="p" data-group-id="0045897728-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="0045897728-21">(</span><span class="n">Chs</span><span class="p" data-group-id="0045897728-21">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2405049082-17">(</span><span class="p" data-group-id="2405049082-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="2405049082-18">(</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2405049082-19">(</span><span class="p" data-group-id="2405049082-19">)</span><span class="p" data-group-id="2405049082-18">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="2405049082-20">(</span><span class="p" data-group-id="2405049082-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2405049082-21">(</span><span class="n">Chs</span><span class="p" data-group-id="2405049082-21">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="0045897728-22">(</span><span class="n">Chs</span><span class="p" data-group-id="0045897728-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="2405049082-22">(</span><span class="n">Chs</span><span class="p" data-group-id="2405049082-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0045897728-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="0045897728-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0045897728-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0045897728-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="0045897728-25">(</span><span class="n">Chs</span><span class="p" data-group-id="0045897728-25">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0045897728-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0045897728-26">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="0045897728-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="0045897728-27">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0045897728-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="0045897728-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="0045897728-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0045897728-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="0045897728-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="0045897728-30">)</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2089599919-1">(</span><span class="ss">server</span><span class="p" data-group-id="2089599919-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2089599919-2">(</span><span class="p" data-group-id="2089599919-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2089599919-3">]</span><span class="p" data-group-id="2089599919-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2089599919-4">(</span><span class="p" data-group-id="2089599919-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2089599919-5">]</span><span class="p" data-group-id="2089599919-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2089599919-6">(</span><span class="p" data-group-id="2089599919-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2089599919-7">]</span><span class="p" data-group-id="2089599919-6">)</span><span class="p">.</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2405049082-23">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2405049082-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2405049082-24">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2405049082-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="2405049082-25">(</span><span class="n">Chs</span><span class="p" data-group-id="2405049082-25">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2405049082-26">{</span><span class="ss">ch1</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2405049082-26">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2405049082-27">(</span><span class="n">Chs2</span><span class="p" data-group-id="2405049082-27">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2405049082-28">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2405049082-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2405049082-29">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2405049082-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2405049082-30">(</span><span class="n">Chs2</span><span class="p" data-group-id="2405049082-30">)</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>The code for the server can be rewritten into a generic part <code class="inline">server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2285818378-1">(</span><span class="ss">server</span><span class="p" data-group-id="2285818378-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2285818378-2">(</span><span class="p" data-group-id="2285818378-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2285818378-3">]</span><span class="p" data-group-id="2285818378-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2285818378-4">(</span><span class="p" data-group-id="2285818378-5">[</span><span class="ss">call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2285818378-5">]</span><span class="p" data-group-id="2285818378-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2285818378-6">(</span><span class="p" data-group-id="2285818378-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2285818378-7">]</span><span class="p" data-group-id="2285818378-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="2089599919-8">(</span><span class="n">Mod</span><span class="p" data-group-id="2089599919-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2089599919-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2089599919-10">[</span><span class="n">Mod</span><span class="p" data-group-id="2089599919-10">]</span><span class="p" data-group-id="2089599919-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2285818378-8">(</span><span class="n">Mod</span><span class="p" data-group-id="2285818378-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="2285818378-9">(</span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2285818378-10">[</span><span class="n">Mod</span><span class="p" data-group-id="2285818378-10">]</span><span class="p" data-group-id="2285818378-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="2089599919-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2089599919-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2089599919-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2089599919-13">(</span><span class="p" data-group-id="2089599919-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2089599919-12">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="2285818378-11">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2285818378-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2285818378-12">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2285818378-13">(</span><span class="p" data-group-id="2285818378-13">)</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2285818378-12">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2089599919-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2089599919-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2285818378-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2285818378-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Res</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">cast</span><span class="p" data-group-id="2089599919-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2089599919-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2089599919-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2089599919-16">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">cast</span><span class="p" data-group-id="2285818378-15">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2285818378-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Name</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2285818378-16">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2285818378-16">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="2089599919-17">(</span><span class="n">Mod</span><span class="p" data-group-id="2089599919-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="2089599919-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2089599919-19">(</span><span class="p" data-group-id="2089599919-19">)</span><span class="p" data-group-id="2089599919-18">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="2089599919-20">(</span><span class="p" data-group-id="2089599919-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="2089599919-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2089599919-21">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2285818378-17">(</span><span class="n">Mod</span><span class="p" data-group-id="2285818378-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="2285818378-18">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2285818378-19">(</span><span class="p" data-group-id="2285818378-19">)</span><span class="p" data-group-id="2285818378-18">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">init</span><span class="p" data-group-id="2285818378-20">(</span><span class="p" data-group-id="2285818378-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2285818378-21">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2285818378-21">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="2089599919-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2089599919-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="2285818378-22">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2285818378-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2089599919-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2089599919-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2089599919-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2089599919-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="2089599919-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2089599919-25">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2089599919-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2089599919-26">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="2089599919-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2089599919-27">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2089599919-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2089599919-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="2089599919-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2089599919-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="2089599919-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2089599919-30">)</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5036073058-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="5036073058-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5036073058-2">(</span><span class="p" data-group-id="5036073058-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5036073058-3">]</span><span class="p" data-group-id="5036073058-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5036073058-4">(</span><span class="p" data-group-id="5036073058-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5036073058-5">]</span><span class="p" data-group-id="5036073058-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5036073058-6">(</span><span class="p" data-group-id="5036073058-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5036073058-7">]</span><span class="p" data-group-id="5036073058-6">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="5036073058-8">(</span><span class="p" data-group-id="5036073058-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5036073058-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="5036073058-9">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="5036073058-10">(</span><span class="p" data-group-id="5036073058-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="5036073058-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="5036073058-11">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="5036073058-12">(</span><span class="n">Ch</span><span class="p" data-group-id="5036073058-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="5036073058-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5036073058-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5036073058-14">}</span><span class="p" data-group-id="5036073058-13">)</span><span class="p">.</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2285818378-23">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2285818378-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2285818378-24">{</span><span class="n">Res</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2285818378-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_call</span><span class="p" data-group-id="2285818378-25">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2285818378-25">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2285818378-26">{</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2285818378-26">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2285818378-27">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2285818378-27">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2285818378-28">{</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="n">Req</span><span class="p" data-group-id="2285818378-28">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">State2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Mod</span><span class="p">:</span><span class="nf">handle_cast</span><span class="p" data-group-id="2285818378-29">(</span><span class="n">Req</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2285818378-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="2285818378-30">(</span><span class="n">Mod</span><span class="p">,</span><span class="w"> </span><span class="n">State2</span><span class="p" data-group-id="2285818378-30">)</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>And a callback module <code class="inline">ch2.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2487441429-1">(</span><span class="ss">ch2</span><span class="p" data-group-id="2487441429-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2487441429-2">(</span><span class="p" data-group-id="2487441429-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2487441429-3">]</span><span class="p" data-group-id="2487441429-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2487441429-4">(</span><span class="p" data-group-id="2487441429-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2487441429-5">]</span><span class="p" data-group-id="2487441429-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2487441429-6">(</span><span class="p" data-group-id="2487441429-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2487441429-7">]</span><span class="p" data-group-id="2487441429-6">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="2487441429-8">(</span><span class="p" data-group-id="2487441429-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="2487441429-9">(</span><span class="ss">ch2</span><span class="p" data-group-id="2487441429-9">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="2487441429-10">(</span><span class="p" data-group-id="2487441429-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2487441429-11">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2487441429-11">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="2487441429-12">(</span><span class="n">Ch</span><span class="p" data-group-id="2487441429-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2487441429-13">(</span><span class="ss">ch2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2487441429-14">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2487441429-14">}</span><span class="p" data-group-id="2487441429-13">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="5036073058-15">(</span><span class="p" data-group-id="5036073058-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">channels</span><span class="p" data-group-id="5036073058-16">(</span><span class="p" data-group-id="5036073058-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2487441429-15">(</span><span class="p" data-group-id="2487441429-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">channels</span><span class="p" data-group-id="2487441429-16">(</span><span class="p" data-group-id="2487441429-16">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="5036073058-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5036073058-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">alloc</span><span class="p" data-group-id="5036073058-18">(</span><span class="n">Chs</span><span class="p" data-group-id="5036073058-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="2487441429-17">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2487441429-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">alloc</span><span class="p" data-group-id="2487441429-18">(</span><span class="n">Chs</span><span class="p" data-group-id="2487441429-18">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; {Ch,Chs2}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="5036073058-19">(</span><span class="p" data-group-id="5036073058-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5036073058-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5036073058-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">free</span><span class="p" data-group-id="5036073058-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5036073058-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="2487441429-19">(</span><span class="p" data-group-id="2487441429-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2487441429-20">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2487441429-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">free</span><span class="p" data-group-id="2487441429-21">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2487441429-21">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% =&gt; Chs2</span></code></pre><p>Notice the following:</p><ul><li>The code in <code class="inline">server</code> can be reused to build many different servers.</li><li>The server name, in this example the atom <code class="inline">ch2</code>, is hidden from the users of
│ │ │  the client functions. This means that the name can be changed without
│ │ │  affecting them.</li><li>The protocol (messages sent to and received from the server) is also hidden.
│ │ │  This is good programming practice and allows one to change the protocol
│ │ │  without changing the code using the interface functions.</li><li>The functionality of <code class="inline">server</code> can be extended without having to change <code class="inline">ch2</code>
│ │ │  or any other callback module.</li></ul><p>In <code class="inline">ch1.erl</code> and <code class="inline">ch2.erl</code> above, the implementation of <code class="inline">channels/0</code>, <code class="inline">alloc/1</code>,
│ │ │  and <code class="inline">free/2</code> has been intentionally left out, as it is not relevant to the
│ │ │  example. For completeness, one way to write these functions is given below. This
│ │ │  is an example only, a realistic implementation must be able to handle situations
│ │ │ -like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="3001895046-1">(</span><span class="p" data-group-id="3001895046-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="3001895046-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3001895046-3">[</span><span class="p" data-group-id="3001895046-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="3001895046-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="3001895046-4">)</span><span class="p" data-group-id="3001895046-2">}</span><span class="p">.</span><span class="w">
│ │ │ +like running out of channels to allocate, and so on.</p><p><a href="" id="channels-implementation"></a></p><pre><code class="makeup erlang" translate="no"><span class="nf">channels</span><span class="p" data-group-id="0773632774-1">(</span><span class="p" data-group-id="0773632774-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0773632774-2">{</span><span class="p">_</span><span class="n">Allocated</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0773632774-3">[</span><span class="p" data-group-id="0773632774-3">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="0773632774-4">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="0773632774-4">)</span><span class="p" data-group-id="0773632774-2">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="3001895046-5">(</span><span class="p" data-group-id="3001895046-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3001895046-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3001895046-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="3001895046-6">}</span><span class="p" data-group-id="3001895046-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="3001895046-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3001895046-9">{</span><span class="p" data-group-id="3001895046-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="3001895046-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3001895046-9">}</span><span class="p" data-group-id="3001895046-8">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="0773632774-5">(</span><span class="p" data-group-id="0773632774-6">{</span><span class="n">Allocated</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0773632774-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0773632774-7">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">_</span><span class="n">Free</span><span class="p" data-group-id="0773632774-6">}</span><span class="p" data-group-id="0773632774-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="0773632774-8">{</span><span class="n">H</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0773632774-9">{</span><span class="p" data-group-id="0773632774-10">[</span><span class="n">H</span><span class="p">|</span><span class="n">Allocated</span><span class="p" data-group-id="0773632774-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0773632774-9">}</span><span class="p" data-group-id="0773632774-8">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="3001895046-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3001895046-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="3001895046-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="3001895046-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="3001895046-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="3001895046-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="0773632774-11">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0773632774-12">{</span><span class="n">Alloc</span><span class="p">,</span><span class="w"> </span><span class="n">Free</span><span class="p" data-group-id="0773632774-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Channels</span><span class="p" data-group-id="0773632774-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">member</span><span class="p" data-group-id="0773632774-13">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0773632774-13">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │        </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="3001895046-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="3001895046-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="3001895046-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3001895046-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="3001895046-16">]</span><span class="p" data-group-id="3001895046-14">}</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="0773632774-14">{</span><span class="nc">lists</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="0773632774-15">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="0773632774-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0773632774-16">[</span><span class="n">Ch</span><span class="p">|</span><span class="n">Free</span><span class="p" data-group-id="0773632774-16">]</span><span class="p" data-group-id="0773632774-14">}</span><span class="p">;</span><span class="w">
│ │ │        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │           </span><span class="n">Channels</span><span class="w">
│ │ │     </span><span class="k">end</span><span class="p">.</span></code></pre><p>Code written without using behaviours can be more efficient, but the increased
│ │ │  efficiency is at the expense of generality. The ability to manage all
│ │ │  applications in the system in a consistent manner is important.</p><p>Using behaviours also makes it easier to read and understand code written by
│ │ │  other programmers. Improvised programming structures, while possibly more
│ │ │  efficient, are always more difficult to understand.</p><p>The <code class="inline">server</code> module corresponds, greatly simplified, to the Erlang/OTP behaviour
│ │ │  <code class="inline">gen_server</code>.</p><p>The standard Erlang/OTP behaviours are:</p><ul><li><p><a href="gen_server_concepts.html">gen_server</a></p><p>For implementing the server of a client-server relation</p></li><li><p><a href="statem.html">gen_statem</a></p><p>For implementing state machines</p></li><li><p><a href="events.html">gen_event</a></p><p>For implementing event handling functionality</p></li><li><p><a href="sup_princ.html">supervisor</a></p><p>For implementing a supervisor in a supervision tree</p></li></ul><p>The compiler understands the module attribute <code class="inline">-behaviour(Behaviour)</code> and issues
│ │ │ -warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9098375068-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="9098375068-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9098375068-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="9098375068-2">)</span><span class="p">.</span><span class="w">
│ │ │ +warnings about missing callback functions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3999926435-1">(</span><span class="ss">chs3</span><span class="p" data-group-id="3999926435-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3999926435-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="3999926435-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="9098375068-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="9098375068-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="3999926435-3">(</span><span class="ss">chs3</span><span class="p" data-group-id="3999926435-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="o">/</span><span class="ss">chs3</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">10</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">undefined</span><span class="w"> </span><span class="ss">call</span><span class="o">-</span><span class="ss">back</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9098375068-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="9098375068-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │ +</span><span class="p" data-group-id="3999926435-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">chs3</span><span class="p" data-group-id="3999926435-4">}</span></code></pre><h2 id="applications" class="section-heading">
│ │ │    <a href="#applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Applications</span>
│ │ │  </h2>
│ │ │  <p>Erlang/OTP comes with a number of components, each implementing some specific
│ │ │  functionality. Components are with Erlang/OTP terminology called <em>applications</em>.
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/distributed.html
│ │ │ @@ -142,25 +142,25 @@
│ │ │  </h2>
│ │ │  <p>A <em>node</em> is an executing Erlang runtime system that has been given a name, using
│ │ │  the command-line flag <a href="../../erts-15.2.7.2/doc/html/erl_cmd.html#name"><code class="inline">-name</code></a> (long names) or
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erl_cmd.html#sname"><code class="inline">-sname</code></a> (short names).</p><p>The format of the node name is an atom <code class="inline">name@host</code>. <code class="inline">name</code> is the name given by
│ │ │  the user. <code class="inline">host</code> is the full host name if long names are used, or the first part
│ │ │  of the host name if short names are used. Function <a href="../../erts-15.2.7.2/doc/html/erlang.html#node/0"><code class="inline">node()</code></a>
│ │ │  returns the name of the node.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -name dilbert</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5968084187-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="5968084187-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="5968084187-2">(</span><span class="p" data-group-id="5968084187-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9133953666-1">(</span><span class="ss">dilbert@uab</span><span class="p">.</span><span class="ss">ericsson</span><span class="p">.</span><span class="ss">se</span><span class="p" data-group-id="9133953666-1">)</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">node</span><span class="p" data-group-id="9133953666-2">(</span><span class="p" data-group-id="9133953666-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">&#39;dilbert@uab.ericsson.se&#39;</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">% erl -sname dilbert</span><span class="gp unselectable">
│ │ │ -(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="5968084187-3">(</span><span class="p" data-group-id="5968084187-3">)</span><span class="p">.</span><span class="w">
│ │ │ +(dilbert@uab)1&gt; </span><span class="nf">node</span><span class="p" data-group-id="9133953666-3">(</span><span class="p" data-group-id="9133953666-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">dilbert@uab</span></code></pre><p>The node name can also be given in runtime by calling <a href="../../lib/kernel-10.2.7.2/doc/html/net_kernel.html#start/1"><code class="inline">net_kernel:start/1</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nf">node</span><span class="p" data-group-id="0178379083-1">(</span><span class="p" data-group-id="0178379083-1">)</span><span class="p">.</span><span class="w">
│ │ │ +1&gt; </span><span class="nf">node</span><span class="p" data-group-id="7469004697-1">(</span><span class="p" data-group-id="7469004697-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">nonode@nohost</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0178379083-2">(</span><span class="p" data-group-id="0178379083-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="0178379083-3">]</span><span class="p" data-group-id="0178379083-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0178379083-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0178379083-4">}</span><span class="gp unselectable">
│ │ │ -(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="0178379083-5">(</span><span class="p" data-group-id="0178379083-5">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nc">net_kernel</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7469004697-2">(</span><span class="p" data-group-id="7469004697-3">[</span><span class="ss">dilbert</span><span class="p">,</span><span class="ss">shortnames</span><span class="p" data-group-id="7469004697-3">]</span><span class="p" data-group-id="7469004697-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7469004697-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.102</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="7469004697-4">}</span><span class="gp unselectable">
│ │ │ +(dilbert@uab)3&gt; </span><span class="nf">node</span><span class="p" data-group-id="7469004697-5">(</span><span class="p" data-group-id="7469004697-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">dilbert@uab</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>A node with a long node name cannot communicate with a node with a short node
│ │ │  name.</p></section><h2 id="node-connections" class="section-heading">
│ │ │    <a href="#node-connections" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Node Connections</span>
│ │ │  </h2>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/distributed_applications.html
│ │ │ @@ -150,36 +150,36 @@
│ │ │  (within the time-out specified by <code class="inline">sync_nodes_timeout</code>).</li><li><p><code class="inline">sync_nodes_timeout = integer() | infinity</code> - Specifies how many milliseconds
│ │ │  to wait for the other nodes to start.</p></li></ul><p>When started, the node waits for all nodes specified by <code class="inline">sync_nodes_mandatory</code>
│ │ │  and <code class="inline">sync_nodes_optional</code> to come up. When all nodes are up, or when all
│ │ │  mandatory nodes are up and the time specified by <code class="inline">sync_nodes_timeout</code> has
│ │ │  elapsed, all applications start. If not all mandatory nodes are up, the node
│ │ │  terminates.</p><p><em>Example:</em></p><p>An application <code class="inline">myapp</code> is to run at the node <code class="inline">cp1@cave</code>. If this node goes down,
│ │ │  <code class="inline">myapp</code> is to be restarted at <code class="inline">cp2@cave</code> or <code class="inline">cp3@cave</code>. A system configuration
│ │ │ -file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1851359458-1">[</span><span class="p" data-group-id="1851359458-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1851359458-3">[</span><span class="p" data-group-id="1851359458-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1851359458-5">[</span><span class="p" data-group-id="1851359458-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1851359458-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1851359458-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="1851359458-8">}</span><span class="p" data-group-id="1851359458-7">]</span><span class="p" data-group-id="1851359458-6">}</span><span class="p" data-group-id="1851359458-5">]</span><span class="p" data-group-id="1851359458-4">}</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1851359458-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1851359458-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="1851359458-10">]</span><span class="p" data-group-id="1851359458-9">}</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1851359458-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="1851359458-11">}</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1851359458-3">]</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1851359458-2">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1851359458-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │ +file <code class="inline">cp1.config</code> for <code class="inline">cp1@cave</code> can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1399420099-1">[</span><span class="p" data-group-id="1399420099-2">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1399420099-3">[</span><span class="p" data-group-id="1399420099-4">{</span><span class="ss">distributed</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1399420099-5">[</span><span class="p" data-group-id="1399420099-6">{</span><span class="ss">myapp</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1399420099-7">[</span><span class="ss">cp1@cave</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1399420099-8">{</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="1399420099-8">}</span><span class="p" data-group-id="1399420099-7">]</span><span class="p" data-group-id="1399420099-6">}</span><span class="p" data-group-id="1399420099-5">]</span><span class="p" data-group-id="1399420099-4">}</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="1399420099-9">{</span><span class="ss">sync_nodes_mandatory</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1399420099-10">[</span><span class="ss">cp2@cave</span><span class="p">,</span><span class="w"> </span><span class="ss">cp3@cave</span><span class="p" data-group-id="1399420099-10">]</span><span class="p" data-group-id="1399420099-9">}</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="1399420099-11">{</span><span class="ss">sync_nodes_timeout</span><span class="p">,</span><span class="w"> </span><span class="mi">5000</span><span class="p" data-group-id="1399420099-11">}</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1399420099-3">]</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1399420099-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1399420099-1">]</span><span class="p">.</span></code></pre><p>The system configuration files for <code class="inline">cp2@cave</code> and <code class="inline">cp3@cave</code> are identical,
│ │ │  except for the list of mandatory nodes, which is to be <code class="inline">[cp1@cave, cp3@cave]</code>
│ │ │  for <code class="inline">cp2@cave</code> and <code class="inline">[cp1@cave, cp2@cave]</code> for <code class="inline">cp3@cave</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>All involved nodes must have the same value for <code class="inline">distributed</code> and
│ │ │  <code class="inline">sync_nodes_timeout</code>. Otherwise the system behavior is undefined.</p></section><h2 id="starting-and-stopping-distributed-applications" class="section-heading">
│ │ │    <a href="#starting-and-stopping-distributed-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting and Stopping Distributed Applications</span>
│ │ │  </h2>
│ │ │  <p>When all involved (mandatory) nodes have been started, the distributed
│ │ │  application can be started by calling <code class="inline">application:start(Application)</code> at <em>all
│ │ │  of these nodes.</em></p><p>A boot script (see <a href="release_structure.html">Releases</a>) can be used that
│ │ │  automatically starts the application.</p><p>The application is started at the first operational node that is listed in the
│ │ │  list of nodes in the <code class="inline">distributed</code> configuration parameter. The application is
│ │ │  started as usual. That is, an application master is created and calls the
│ │ │ -application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8039805397-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="8039805397-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │ +application callback function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1812061565-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="1812061565-1">)</span></code></pre><p>Example:</p><p>Continuing the example from the previous section, the three nodes are started,
│ │ │  specifying the system configuration file:</p><pre><code class="text">&gt; erl -sname cp1 -config cp1
│ │ │  &gt; erl -sname cp2 -config cp2
│ │ │  &gt; erl -sname cp3 -config cp3</code></pre><p>When all nodes are operational, <code class="inline">myapp</code> can be started. This is achieved by
│ │ │  calling <code class="inline">application:start(myapp)</code> at all three nodes. It is then started at
│ │ │  <code class="inline">cp1</code>, as shown in the following figure:</p><p><a href="" id="dist1"></a></p><p><img src="assets/dist1.gif" alt="Application myapp - Situation 1" title="Application myapp - Situation 1"/></p><p>Similarly, the application must be stopped by calling
│ │ │  <code class="inline">application:stop(Application)</code> at all involved nodes.</p><h2 id="failover" class="section-heading">
│ │ │    <a href="#failover" class="hover-link">
│ │ │ @@ -187,30 +187,30 @@
│ │ │    </a>
│ │ │    <span class="text">Failover</span>
│ │ │  </h2>
│ │ │  <p>If the node where the application is running goes down, the application is
│ │ │  restarted (after the specified time-out) at the first operational node that is
│ │ │  listed in the list of nodes in the <code class="inline">distributed</code> configuration parameter. This
│ │ │  is called a <em>failover</em>.</p><p>The application is started the normal way at the new node, that is, by the
│ │ │ -application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4427656978-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="4427656978-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │ +application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1021954580-1">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="1021954580-1">)</span></code></pre><p>An exception is if the application has the <code class="inline">start_phases</code> key defined (see
│ │ │  <a href="included_applications.html">Included Applications</a>). The application is then
│ │ │ -instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6858009361-1">(</span><span class="p" data-group-id="6858009361-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="6858009361-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="6858009361-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │ +instead started by calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="4747823107-1">(</span><span class="p" data-group-id="4747823107-2">{</span><span class="ss">failover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="4747823107-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="4747823107-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the terminated node.</p><p><em>Example:</em></p><p>If <code class="inline">cp1</code> goes down, the system checks which one of the other nodes, <code class="inline">cp2</code> or
│ │ │  <code class="inline">cp3</code>, has the least number of running applications, but waits for 5 seconds for
│ │ │  <code class="inline">cp1</code> to restart. If <code class="inline">cp1</code> does not restart and <code class="inline">cp2</code> runs fewer applications
│ │ │  than <code class="inline">cp3</code>, <code class="inline">myapp</code> is restarted on <code class="inline">cp2</code>.</p><p><a href="" id="dist2"></a></p><p><img src="assets/dist2.gif" alt="Application myapp - Situation 2" title="Application myapp - Situation 2"/></p><p>Suppose now that <code class="inline">cp2</code> goes also down and does not restart within 5 seconds.
│ │ │  <code class="inline">myapp</code> is now restarted on <code class="inline">cp3</code>.</p><p><a href="" id="dist3"></a></p><p><img src="assets/dist3.gif" alt="Application myapp - Situation 3" title="Application myapp - Situation 3"/></p><h2 id="takeover" class="section-heading">
│ │ │    <a href="#takeover" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Takeover</span>
│ │ │  </h2>
│ │ │  <p>If a node is started, which has higher priority according to <code class="inline">distributed</code> than
│ │ │  the node where a distributed application is running, the application is
│ │ │  restarted at the new node and stopped at the old node. This is called a
│ │ │ -<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="7789350471-1">(</span><span class="p" data-group-id="7789350471-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="7789350471-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="7789350471-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │ +<em>takeover</em>.</p><p>The application is started by the application master calling:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9779190345-1">(</span><span class="p" data-group-id="9779190345-2">{</span><span class="ss">takeover</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="9779190345-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">StartArgs</span><span class="p" data-group-id="9779190345-1">)</span></code></pre><p>Here <code class="inline">Node</code> is the old node.</p><p><em>Example:</em></p><p>If <code class="inline">myapp</code> is running at <code class="inline">cp3</code>, and if <code class="inline">cp2</code> now restarts, it does not restart
│ │ │  <code class="inline">myapp</code>, as the order between the <code class="inline">cp2</code> and <code class="inline">cp3</code> nodes is undefined.</p><p><a href="" id="dist4"></a></p><p><img src="assets/dist4.gif" alt="Application myapp - Situation 4" title="Application myapp - Situation 4"/></p><p>However, if <code class="inline">cp1</code> also restarts, the function <a href="../../lib/kernel-10.2.7.2/doc/html/application.html#takeover/2"><code class="inline">application:takeover/2</code></a> moves
│ │ │  <code class="inline">myapp</code> to <code class="inline">cp1</code>, as <code class="inline">cp1</code> has a higher priority than <code class="inline">cp3</code> for this
│ │ │  application. In this case, <code class="inline">Module:start({takeover, cp3@cave}, StartArgs)</code> is
│ │ │  executed at <code class="inline">cp1</code> to start the application.</p><p><a href="" id="dist5"></a></p><p><img src="assets/dist5.gif" alt="Application myapp - Situation 5" title="Application myapp - Situation 5"/></p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/documentation.html
│ │ │ @@ -112,23 +112,23 @@
│ │ │        </a>
│ │ │  
│ │ │  
│ │ │      <span>Documentation</span>
│ │ │    </h1>
│ │ │  
│ │ │  <p>Documentation in Erlang is done through the <code class="inline">-moduledoc</code> and <code class="inline">-doc</code>
│ │ │ -<a href="modules.html#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5813938129-1">(</span><span class="ss">arith</span><span class="p" data-group-id="5813938129-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="modules.html#module-attributes">attributes</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2299464486-1">(</span><span class="ss">arith</span><span class="p" data-group-id="2299464486-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  A module for basic arithmetic.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5813938129-2">(</span><span class="p" data-group-id="5813938129-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5813938129-3">]</span><span class="p" data-group-id="5813938129-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2299464486-2">(</span><span class="p" data-group-id="2299464486-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2299464486-3">]</span><span class="p" data-group-id="2299464486-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5813938129-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5813938129-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="2299464486-4">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="2299464486-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The <code class="inline">-moduledoc</code> attribute has to be located before the first <code class="inline">-doc</code> attribute
│ │ │  or function declaration. It documents the overall purpose of the module.</p><p>The <code class="inline">-doc</code> attribute always precedes the <a href="ref_man_functions.html">function</a> or
│ │ │  <a href="modules.html#module-attributes">attribute</a> it documents. The
│ │ │  attributes that can be documented are
│ │ │  <a href="typespec.html#type-declarations-of-user-defined-types">user-defined types</a>
│ │ │  (<code class="inline">-type</code> and <code class="inline">-opaque</code>) and
│ │ │  <a href="modules.html#behaviour-module-attribute">behaviour module attributes</a>
│ │ │  (<code class="inline">-callback</code>).</p><p>By default the format used for documentation attributes is
│ │ │ @@ -140,55 +140,55 @@
│ │ │  <a href="modules.html#documentation-attributes">Documentation Attributes</a>.</p><p><code class="inline">-doc</code> attributes have been available since Erlang/OTP 27.</p><h2 id="documentation-metadata" class="section-heading">
│ │ │    <a href="#documentation-metadata" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documentation metadata</span>
│ │ │  </h2>
│ │ │  <p>It is possible to add metadata to the documentation entry. You do this by adding
│ │ │ -a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5530224731-1">(</span><span class="ss">arith</span><span class="p" data-group-id="5530224731-1">)</span><span class="p">.</span><span class="w">
│ │ │ +a <code class="inline">-moduledoc</code> or <code class="inline">-doc</code> attribute with a map as argument. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9836932907-1">(</span><span class="ss">arith</span><span class="p" data-group-id="9836932907-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  A module for basic arithmetic.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="5530224731-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="5530224731-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="9836932907-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="9836932907-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5530224731-3">(</span><span class="p" data-group-id="5530224731-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5530224731-4">]</span><span class="p" data-group-id="5530224731-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9836932907-3">(</span><span class="p" data-group-id="9836932907-4">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9836932907-4">]</span><span class="p" data-group-id="9836932907-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="5530224731-5">(</span><span class="p" data-group-id="5530224731-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="5530224731-6">}</span><span class="p" data-group-id="5530224731-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5530224731-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5530224731-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="9836932907-5">(</span><span class="p" data-group-id="9836932907-6">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p" data-group-id="9836932907-6">}</span><span class="p" data-group-id="9836932907-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9836932907-7">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9836932907-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>The metadata is used by documentation tools to provide extra information to the
│ │ │  user. There can be multiple metadata documentation entries, in which case the
│ │ │  maps will be merged with the latest taking precedence if there are duplicate
│ │ │  keys. Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;Adds two numbers.&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="9303450786-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="9303450786-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="9303450786-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="9303450786-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="9303450786-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9303450786-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="3509514628-1">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;1.0&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">author</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p" data-group-id="3509514628-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="3509514628-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;2.0&quot;</span><span class="p" data-group-id="3509514628-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="3509514628-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3509514628-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><p>This will result in a metadata entry of <code class="inline">#{since =&gt; &quot;2.0&quot;, author =&gt; &quot;Joe&quot;}</code>.</p><p>The keys and values in the metadata map can be any type, but it is recommended
│ │ │  that only <a href="data_types.html#atom">atoms</a> are used for keys and
│ │ │  <a href="data_types.html#string">strings</a> for the values.</p><h2 id="external-documentation-files" class="section-heading">
│ │ │    <a href="#external-documentation-files" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">External documentation files</span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">-moduledoc</code> and <code class="inline">-doc</code> can also be placed in external files. To do so use
│ │ │  <code class="inline">-doc {file, &quot;path/to/doc.md&quot;}</code> to point to the documentation. The path used is
│ │ │  relative to the file where the <code class="inline">-doc</code> attribute is located. For example:</p><pre><code class="markdown">%% doc/add.md
│ │ │  Adds two numbers.</code></pre><p>and</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% src/arith.erl</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="5203239741-1">(</span><span class="p" data-group-id="5203239741-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="5203239741-2">}</span><span class="p" data-group-id="5203239741-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5203239741-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5203239741-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="8598055421-1">(</span><span class="p" data-group-id="8598055421-2">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/add.md&quot;</span><span class="p" data-group-id="8598055421-2">}</span><span class="p" data-group-id="8598055421-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="8598055421-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="8598055421-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span></code></pre><h2 id="documenting-a-module" class="section-heading">
│ │ │    <a href="#documenting-a-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documenting a module</span>
│ │ │  </h2>
│ │ │  <p>The module description should include details on how to use the API and examples
│ │ │  of the different functions working together. Here is a good place to use images
│ │ │  and other diagrams to better show the usage of the module. Instead of writing a
│ │ │  long text in the <code class="inline">moduledoc</code> attribute, it could be better to break it out into
│ │ │  an external page.</p><p>The <code class="inline">moduledoc</code> attribute should start with a short paragraph describing the
│ │ │ -module and then go into greater details. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0088783739-1">(</span><span class="ss">arith</span><span class="p" data-group-id="0088783739-1">)</span><span class="p">.</span><span class="w">
│ │ │ +module and then go into greater details. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3536238104-1">(</span><span class="ss">arith</span><span class="p" data-group-id="3536238104-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │     A module for basic arithmetic.
│ │ │  
│ │ │     This module can be used to add and subtract values. For example:
│ │ │  
│ │ │     ```erlang
│ │ │     1&gt; arith:substract(arith:add(2, 3), 1).
│ │ │ @@ -203,94 +203,94 @@
│ │ │  <p>There are three reserved metadata keys for <code class="inline">-moduledoc</code>:</p><ul><li><code class="inline">since</code> - Shows in which version of the application the module was added.
│ │ │  If this is added, all functions, types, and callbacks within will also receive
│ │ │  the same <code class="inline">since</code> value unless specified in the metadata of the function, type
│ │ │  or callback.</li><li><code class="inline">deprecated</code> - Shows a text in the documentation explaining that it is
│ │ │  deprecated and what to use instead.</li><li><code class="inline">format</code> - The format to use for all documentation in this module. The
│ │ │  default is <code class="inline">text/markdown</code>. It should be written using the
│ │ │  <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types">mime type</a>
│ │ │ -of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="8436027139-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="8436027139-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="8436027139-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="8436027139-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="8436027139-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="8436027139-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │ +of the format.</li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="2106491539-1">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;../doc/arith.asciidoc&quot;</span><span class="p" data-group-id="2106491539-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="2106491539-2">#{</span><span class="ss">since</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;0.1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">format</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;text/asciidoc&quot;</span><span class="p" data-group-id="2106491539-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">moduledoc</span><span class="w"> </span><span class="p" data-group-id="2106491539-3">#{</span><span class="ss">deprecated</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;Use the Erlang arithmetic operators instead.&quot;</span><span class="p" data-group-id="2106491539-3">}</span><span class="p">.</span></code></pre><h2 id="documenting-functions-user-defined-types-and-callbacks" class="section-heading">
│ │ │    <a href="#documenting-functions-user-defined-types-and-callbacks" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documenting functions, user-defined types, and callbacks</span>
│ │ │  </h2>
│ │ │  <p>Functions, types, and callbacks can be documented using the <code class="inline">-doc</code> attribute.
│ │ │  Each entry should start with a short paragraph describing the purpose of entity,
│ │ │  and then go into greater detail in needed.</p><p>It is not recommended to include images or diagrams in this documentation as it
│ │ │  is used by IDEs and <a href="../../lib/stdlib-6.2.2.2/doc/html/c.html#h/1"><code class="inline">c:h/1</code></a> to show the documentation to the user.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  A number that can be used by the arith module.
│ │ │  
│ │ │  We use a special number here so that we know
│ │ │  that this number comes from this module.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="6053383249-1">(</span><span class="p" data-group-id="6053383249-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="6053383249-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="6053383249-3">(</span><span class="p" data-group-id="6053383249-3">)</span><span class="p" data-group-id="6053383249-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0680063125-1">(</span><span class="p" data-group-id="0680063125-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0680063125-2">{</span><span class="ss">arith</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">number</span><span class="p" data-group-id="0680063125-3">(</span><span class="p" data-group-id="0680063125-3">)</span><span class="p" data-group-id="0680063125-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  Adds two numbers.
│ │ │  
│ │ │  ### Example:
│ │ │  
│ │ │  ```
│ │ │  1&gt; arith:add(arith:number(1), arith:number(2)). {number, 3}
│ │ │  ```
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="6053383249-4">(</span><span class="nf">number</span><span class="p" data-group-id="6053383249-5">(</span><span class="p" data-group-id="6053383249-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="6053383249-6">(</span><span class="p" data-group-id="6053383249-6">)</span><span class="p" data-group-id="6053383249-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="6053383249-7">(</span><span class="p" data-group-id="6053383249-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="6053383249-8">(</span><span class="p" data-group-id="6053383249-9">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="6053383249-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6053383249-10">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="6053383249-10">}</span><span class="p" data-group-id="6053383249-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6053383249-11">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="6053383249-11">}</span><span class="p">.</span></code></pre><h3 id="doc-metadata" class="section-heading">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="0680063125-4">(</span><span class="nf">number</span><span class="p" data-group-id="0680063125-5">(</span><span class="p" data-group-id="0680063125-5">)</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0680063125-6">(</span><span class="p" data-group-id="0680063125-6">)</span><span class="p" data-group-id="0680063125-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0680063125-7">(</span><span class="p" data-group-id="0680063125-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="0680063125-8">(</span><span class="p" data-group-id="0680063125-9">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="p" data-group-id="0680063125-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0680063125-10">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="0680063125-10">}</span><span class="p" data-group-id="0680063125-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0680063125-11">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="0680063125-11">}</span><span class="p">.</span></code></pre><h3 id="doc-metadata" class="section-heading">
│ │ │    <a href="#doc-metadata" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Doc metadata</span>
│ │ │  </h3>
│ │ │  <p>There are four reserved metadata keys for <code class="inline">-doc</code>:</p><ul><li><p><code class="inline">since =&gt; unicode:chardata()</code> - Shows which version of the application the
│ │ │  module was added.</p></li><li><p><code class="inline">deprecated =&gt; unicode:chardata()</code> - Shows a text in the documentation
│ │ │  explaining that it is deprecated and what to use instead. The compiler will
│ │ │  automatically insert this key if there is a <code class="inline">-deprecated</code> attribute marking a
│ │ │  function as deprecated.</p></li><li><p><code class="inline">equiv =&gt; unicode:chardata() | F/A | F(...)</code> - Notes that this function is equivalent to
│ │ │  another function in this module. The equivalence can be described using either
│ │ │ -<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../lib/stdlib-6.2.2.2/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="9102670365-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="9102670365-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="9102670365-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9102670365-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9102670365-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9102670365-4">[</span><span class="p" data-group-id="9102670365-4">]</span><span class="p" data-group-id="9102670365-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="9102670365-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="9102670365-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="5712308371-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="5712308371-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5712308371-3">[</span><span class="p" data-group-id="5712308371-3">]</span><span class="p" data-group-id="5712308371-2">)</span><span class="p" data-group-id="5712308371-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="5712308371-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5712308371-5">(</span><span class="p" data-group-id="5712308371-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5712308371-6">(</span><span class="p" data-group-id="5712308371-6">)</span><span class="p" data-group-id="5712308371-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="5712308371-7">(</span><span class="p" data-group-id="5712308371-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5712308371-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="5712308371-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="5712308371-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5712308371-10">[</span><span class="p" data-group-id="5712308371-10">]</span><span class="p" data-group-id="5712308371-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5712308371-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="5712308371-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../lib/kernel-10.2.7.2/doc/html/eep48_chapter.html">EEP-48</a> doc chunk metadata is
│ │ │ +<code class="inline">Func/Arity</code>, <code class="inline">Func(Args)</code> or a <a href="../../lib/stdlib-6.2.2.2/doc/html/unicode.html#t:chardata/0">unicode string</a>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="7226505388-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7226505388-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7226505388-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="7226505388-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="7226505388-3">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7226505388-4">[</span><span class="p" data-group-id="7226505388-4">]</span><span class="p" data-group-id="7226505388-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7226505388-5">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="7226505388-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="p" data-group-id="9571510651-1">#{</span><span class="ss">equiv</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9571510651-2">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9571510651-3">[</span><span class="p" data-group-id="9571510651-3">]</span><span class="p" data-group-id="9571510651-2">)</span><span class="p" data-group-id="9571510651-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9571510651-4">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9571510651-5">(</span><span class="p" data-group-id="9571510651-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9571510651-6">(</span><span class="p" data-group-id="9571510651-6">)</span><span class="p" data-group-id="9571510651-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="9571510651-7">(</span><span class="p" data-group-id="9571510651-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9571510651-8">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="9571510651-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">add</span><span class="p" data-group-id="9571510651-9">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9571510651-10">[</span><span class="p" data-group-id="9571510651-10">]</span><span class="p" data-group-id="9571510651-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="9571510651-11">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="9571510651-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The entry into the <a href="../../lib/kernel-10.2.7.2/doc/html/eep48_chapter.html">EEP-48</a> doc chunk metadata is
│ │ │  the value converted to a string.</p></li><li><p><code class="inline">exported =&gt; boolean()</code> - A <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a> signifying if the entry is <code class="inline">exported</code>
│ │ │  or not. This value is automatically set by the compiler and should not be set
│ │ │  by the user.</p></li></ul><h3 id="doc-signatures" class="section-heading">
│ │ │    <a href="#doc-signatures" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Doc signatures</span>
│ │ │  </h3>
│ │ │  <p>The doc signature is a short text shown to describe the function and its arguments.
│ │ │  By default it is determined by looking at the names of the arguments in the
│ │ │ -<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="3747073292-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="3747073292-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">-spec</code> or function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add</span><span class="p" data-group-id="4247115420-1">(</span><span class="n">One</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="p" data-group-id="4247115420-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">One</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Two</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="3747073292-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3747073292-3">(</span><span class="p" data-group-id="3747073292-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3747073292-4">(</span><span class="p" data-group-id="3747073292-4">)</span><span class="p" data-group-id="3747073292-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3747073292-5">(</span><span class="p" data-group-id="3747073292-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">sub</span><span class="p" data-group-id="3747073292-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="3747073292-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ -specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0413718700-1">(</span><span class="n">Value</span><span class="p" data-group-id="0413718700-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0413718700-2">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0413718700-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">sub</span><span class="p" data-group-id="4247115420-2">(</span><span class="n">One</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4247115420-3">(</span><span class="p" data-group-id="4247115420-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Two</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4247115420-4">(</span><span class="p" data-group-id="4247115420-4">)</span><span class="p" data-group-id="4247115420-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="4247115420-5">(</span><span class="p" data-group-id="4247115420-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">sub</span><span class="p" data-group-id="4247115420-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4247115420-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>will have a signature of <code class="inline">add(One, Two)</code> and <code class="inline">sub(One, Two)</code>.</p><p>For types or callbacks, the signature is derived from the type or callback
│ │ │ +specification. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2108747512-1">(</span><span class="n">Value</span><span class="p" data-group-id="2108747512-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2108747512-2">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="2108747512-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `number(Value)`</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0413718700-3">(</span><span class="p" data-group-id="0413718700-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0413718700-4">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0413718700-5">(</span><span class="p" data-group-id="0413718700-5">)</span><span class="p" data-group-id="0413718700-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2108747512-3">(</span><span class="p" data-group-id="2108747512-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2108747512-4">{</span><span class="ss">number</span><span class="p">,</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2108747512-5">(</span><span class="p" data-group-id="2108747512-5">)</span><span class="p" data-group-id="2108747512-4">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `number()`</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="0413718700-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0413718700-7">(</span><span class="p" data-group-id="0413718700-7">)</span><span class="p" data-group-id="0413718700-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="2108747512-6">(</span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2108747512-7">(</span><span class="p" data-group-id="2108747512-7">)</span><span class="p" data-group-id="2108747512-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `increment(In)`</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="0413718700-8">(</span><span class="n">In</span><span class="p" data-group-id="0413718700-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="0413718700-9">(</span><span class="p" data-group-id="0413718700-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">increment</span><span class="p" data-group-id="2108747512-8">(</span><span class="n">In</span><span class="p" data-group-id="2108747512-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Out</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="2108747512-9">(</span><span class="p" data-group-id="2108747512-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% signature will be `increment(In)`</span></code></pre><p>If it is not possible to &quot;easily&quot; figure out a nice signature from the code, the
│ │ │  MFA syntax is used instead. For example: <code class="inline">add/2</code>, <code class="inline">number/1</code>, <code class="inline">increment/1</code></p><p>It is possible to supply a custom signature by placing it as the first line of the
│ │ │  <code class="inline">-doc</code> attribute. The provided signature must be in the form of a function
│ │ │  declaration up until the <code class="inline">-&gt;</code>. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;&quot;
│ │ │  add(One, Two)
│ │ │  
│ │ │  Adds two numbers.
│ │ │  &quot;&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="5658428380-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5658428380-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>Will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="7669967460-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7669967460-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">.</span></code></pre><p>Will create the signature <code class="inline">add(One, Two)</code>. The signature will be removed from the
│ │ │  documentation string, so in the example above only the text <code class="inline">&quot;Adds two numbers&quot;</code>
│ │ │  will be part of the documentation. This works for functions, types, and
│ │ │  callbacks.</p><h2 id="links-in-markdown" class="section-heading">
│ │ │    <a href="#links-in-markdown" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Links in Markdown</span>
│ │ │ @@ -328,28 +328,28 @@
│ │ │  modules. That is, modules that should be used by other applications and modules
│ │ │  that should not. By default all modules in an application are visible, but by
│ │ │  setting <code class="inline">-moduledoc false.</code> specific modules can be hidden from being listed as
│ │ │  part of the available API.</p><p>An Erlang <a href="modules.html">module</a> consists of public and private functions and type
│ │ │  attributes. By default, all exported functions, exported types and callbacks are
│ │ │  considered visible and part of the modules public API. In addition, any
│ │ │  non-exported type that is referred to by any other visible type attribute is
│ │ │ -also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9214701544-1">(</span><span class="p" data-group-id="9214701544-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9214701544-2">]</span><span class="p" data-group-id="9214701544-1">)</span><span class="p">.</span><span class="w">
│ │ │ +also visible, but not considered to be part of the public API. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0170805624-1">(</span><span class="p" data-group-id="0170805624-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0170805624-2">]</span><span class="p" data-group-id="0170805624-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="9214701544-3">(</span><span class="p" data-group-id="9214701544-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="9214701544-4">(</span><span class="p" data-group-id="9214701544-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="9214701544-5">(</span><span class="p" data-group-id="9214701544-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="9214701544-6">(</span><span class="p" data-group-id="9214701544-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>in the above code, the function <code class="inline">example/0</code> is exported and it referenced the
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="0170805624-3">(</span><span class="p" data-group-id="0170805624-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="0170805624-4">(</span><span class="p" data-group-id="0170805624-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="0170805624-5">(</span><span class="p" data-group-id="0170805624-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="0170805624-6">(</span><span class="p" data-group-id="0170805624-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>in the above code, the function <code class="inline">example/0</code> is exported and it referenced the
│ │ │  un-exported type <code class="inline">private/0</code>. Therefore both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be
│ │ │  marked as visible. The <code class="inline">private/0</code> type will have the metadata field <code class="inline">exported</code>
│ │ │  set to <code class="inline">false</code> to show that it is not part of the public API.</p><p>If you want to make a visible entity hidden you need to set the <code class="inline">-doc</code> attribute
│ │ │ -to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8821318198-1">(</span><span class="p" data-group-id="8821318198-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8821318198-2">]</span><span class="p" data-group-id="8821318198-1">)</span><span class="p">.</span><span class="w">
│ │ │ +to <code class="inline">false</code>. Let us revisit our previous example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5471382768-1">(</span><span class="p" data-group-id="5471382768-2">[</span><span class="ss">example</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5471382768-2">]</span><span class="p" data-group-id="5471382768-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="8821318198-3">(</span><span class="p" data-group-id="8821318198-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="8821318198-4">(</span><span class="p" data-group-id="8821318198-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="8821318198-5">(</span><span class="p" data-group-id="8821318198-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="5471382768-3">(</span><span class="p" data-group-id="5471382768-3">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">example</span><span class="p" data-group-id="5471382768-4">(</span><span class="p" data-group-id="5471382768-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">private</span><span class="p" data-group-id="5471382768-5">(</span><span class="p" data-group-id="5471382768-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="ss">false</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="8821318198-6">(</span><span class="p" data-group-id="8821318198-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="5471382768-6">(</span><span class="p" data-group-id="5471382768-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">one</span><span class="p">.</span></code></pre><p>The function <code class="inline">example/0</code> is exported but explicitly marked as hidden; therefore
│ │ │  both <code class="inline">example/0</code> and <code class="inline">private/0</code> will be hidden.</p><p>Any documentation added to an automatically hidden entity (non-exported function
│ │ │  or type) is ignored and will generate a warning. Such functions can be
│ │ │  documented using comments.</p><h2 id="compiling-and-getting-documentation" class="section-heading">
│ │ │    <a href="#compiling-and-getting-documentation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Compiling and getting documentation</span>
│ │ │ @@ -375,21 +375,21 @@
│ │ │    <span class="text">Using ExDoc to generate HTML/ePub documentation</span>
│ │ │  </h2>
│ │ │  <p><a href="https://hexdocs.pm/ex_doc/">ExDoc</a> has built-in support to generate
│ │ │  documentation from Markdown. The simplest way is by using the
│ │ │  <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> plugin. To set up a
│ │ │  rebar3 project to use <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate
│ │ │  documentation add the following to your <code class="inline">rebar3.config</code>.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Enable the plugin</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9448157509-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9448157509-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="9448157509-2">]</span><span class="p" data-group-id="9448157509-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3238954537-1">{</span><span class="ss">plugins</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3238954537-2">[</span><span class="ss">rebar3_ex_doc</span><span class="p" data-group-id="3238954537-2">]</span><span class="p" data-group-id="3238954537-1">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="9448157509-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9448157509-4">[</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9448157509-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9448157509-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="9448157509-6">]</span><span class="p" data-group-id="9448157509-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9448157509-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="9448157509-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9448157509-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="9448157509-8">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9448157509-4">]</span><span class="p" data-group-id="9448157509-3">}</span><span class="p">.</span></code></pre><p>When configured you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │ +</span><span class="p" data-group-id="3238954537-3">{</span><span class="ss">ex_doc</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3238954537-4">[</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3238954537-5">{</span><span class="ss">extras</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3238954537-6">[</span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="3238954537-6">]</span><span class="p" data-group-id="3238954537-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3238954537-7">{</span><span class="ss">main</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;README.md&quot;</span><span class="p" data-group-id="3238954537-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3238954537-8">{</span><span class="ss">source_url</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;https://github.com/namespace/your_app&quot;</span><span class="p" data-group-id="3238954537-8">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3238954537-4">]</span><span class="p" data-group-id="3238954537-3">}</span><span class="p">.</span></code></pre><p>When configured you can run <code class="inline">rebar3 ex_doc</code> to generate the
│ │ │  documentation to <code class="inline">doc/index.html</code>. For more details and options see
│ │ │  the <a href="https://hexdocs.pm/rebar3_ex_doc">rebar3_ex_doc</a> documentation.</p><p>You can also download the
│ │ │  <a href="https://github.com/elixir/ex_doc/releases/latest">release escript bundle</a> from
│ │ │  github and run it from the command line. The documentation for using the escript
│ │ │  is found by running <code class="inline">ex_doc --help</code>.</p><p>If you are writing documentation that will be using
│ │ │  <a href="https://hexdocs.pm/ex_doc/">ExDoc</a> to generate HTML/ePub it is highly
│ │ │  recommended to read its documentation.</p>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/drivers.html
│ │ │ @@ -122,23 +122,23 @@
│ │ │    <span class="text">Drivers and Concurrency</span>
│ │ │  </h2>
│ │ │  <p>The runtime system always takes a lock before running any code in a driver.</p><p>By default, that lock is at the driver level, that is, if several ports have
│ │ │  been opened to the same driver, only code for one port at the same time can be
│ │ │  running.</p><p>A driver can be configured to have one lock for each port instead.</p><p>If a driver is used in a functional way (that is, holds no state, but only does
│ │ │  some heavy calculation and returns a result), several ports with registered
│ │ │  names can be opened beforehand, and the port to be used can be chosen based on
│ │ │ -the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8186101049-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="8186101049-2">(</span><span class="p" data-group-id="8186101049-2">)</span><span class="p">,</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="8186101049-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │ +the scheduler ID as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2132034997-1">(</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="2132034997-2">(</span><span class="p" data-group-id="2132034997-2">)</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="2132034997-3">{</span><span class="ss">some_driver_01</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_02</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_03</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_04</span><span class="p">,</span><span class="w">
│ │ │  	 </span><span class="ss">some_driver_05</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_06</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_07</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_08</span><span class="p">,</span><span class="w">
│ │ │  	 </span><span class="ss">some_driver_09</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_10</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_11</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_12</span><span class="p">,</span><span class="w">
│ │ │ -	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="8186101049-3">}</span><span class="p" data-group-id="8186101049-1">)</span><span class="p">.</span><span class="w">
│ │ │ +	 </span><span class="ss">some_driver_13</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_14</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_15</span><span class="p">,</span><span class="w"> </span><span class="ss">some_driver_16</span><span class="p" data-group-id="2132034997-3">}</span><span class="p" data-group-id="2132034997-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client_port</span><span class="p" data-group-id="8186101049-4">(</span><span class="p" data-group-id="8186101049-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="8186101049-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="8186101049-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="8186101049-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="8186101049-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="8186101049-8">(</span><span class="p" data-group-id="8186101049-8">)</span><span class="p" data-group-id="8186101049-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="8186101049-9">(</span><span class="p" data-group-id="8186101049-9">)</span><span class="p" data-group-id="8186101049-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │ +</span><span class="nf">client_port</span><span class="p" data-group-id="2132034997-4">(</span><span class="p" data-group-id="2132034997-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="2132034997-5">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="2132034997-6">(</span><span class="ss">scheduler_id</span><span class="p" data-group-id="2132034997-6">)</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="nf">tuple_size</span><span class="p" data-group-id="2132034997-7">(</span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="2132034997-8">(</span><span class="p" data-group-id="2132034997-8">)</span><span class="p" data-group-id="2132034997-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="o">?</span><span class="n">PORT_NAMES</span><span class="p" data-group-id="2132034997-9">(</span><span class="p" data-group-id="2132034997-9">)</span><span class="p" data-group-id="2132034997-5">)</span><span class="p">.</span></code></pre><p>As long as there are no more than 16 schedulers, there will never be any lock
│ │ │  contention on the port lock for the driver.</p><h2 id="avoiding-copying-binaries-when-calling-a-driver" class="section-heading">
│ │ │    <a href="#avoiding-copying-binaries-when-calling-a-driver" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Avoiding Copying Binaries When Calling a Driver</span>
│ │ │  </h2>
│ │ │  <p>There are basically two ways to avoid copying a binary that is sent to a driver:</p><ul><li><p>If the <code class="inline">Data</code> argument for <a href="../../erts-15.2.7.2/doc/html/erlang.html#port_control/3"><code class="inline">port_control/3</code></a> is a
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/eff_guide_functions.html
│ │ │ @@ -122,67 +122,67 @@
│ │ │    <span class="text">Pattern Matching</span>
│ │ │  </h2>
│ │ │  <p>Pattern matching in function head as well as in <code class="inline">case</code> and <code class="inline">receive</code> clauses are
│ │ │  optimized by the compiler. With a few exceptions, there is nothing to gain by
│ │ │  rearranging clauses.</p><p>One exception is pattern matching of binaries. The compiler does not rearrange
│ │ │  clauses that match binaries. Placing the clause that matches against the empty
│ │ │  binary <em>last</em> is usually slightly faster than placing it <em>first</em>.</p><p>The following is a rather unnatural example to show another exception where
│ │ │ -rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-1">(</span><span class="ss">one</span><span class="p" data-group-id="9180062113-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-2">(</span><span class="ss">two</span><span class="p" data-group-id="9180062113-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-3">(</span><span class="ss">three</span><span class="p" data-group-id="9180062113-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-4">(</span><span class="n">Int</span><span class="p" data-group-id="9180062113-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9180062113-5">(</span><span class="n">Int</span><span class="p" data-group-id="9180062113-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-6">(</span><span class="ss">four</span><span class="p" data-group-id="9180062113-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-7">(</span><span class="ss">five</span><span class="p" data-group-id="9180062113-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map1</span><span class="p" data-group-id="9180062113-8">(</span><span class="ss">six</span><span class="p" data-group-id="9180062113-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │ +rearranging clauses is beneficial:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-1">(</span><span class="ss">one</span><span class="p" data-group-id="8362468346-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-2">(</span><span class="ss">two</span><span class="p" data-group-id="8362468346-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-3">(</span><span class="ss">three</span><span class="p" data-group-id="8362468346-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-4">(</span><span class="n">Int</span><span class="p" data-group-id="8362468346-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8362468346-5">(</span><span class="n">Int</span><span class="p" data-group-id="8362468346-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-6">(</span><span class="ss">four</span><span class="p" data-group-id="8362468346-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-7">(</span><span class="ss">five</span><span class="p" data-group-id="8362468346-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map1</span><span class="p" data-group-id="8362468346-8">(</span><span class="ss">six</span><span class="p" data-group-id="8362468346-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>The problem is the clause with the variable <code class="inline">Int</code>. As a variable can match
│ │ │  anything, including the atoms <code class="inline">four</code>, <code class="inline">five</code>, and <code class="inline">six</code>, which the following
│ │ │  clauses also match, the compiler must generate suboptimal code that executes as
│ │ │  follows:</p><ul><li>First, the input value is compared to <code class="inline">one</code>, <code class="inline">two</code>, and <code class="inline">three</code> (using a
│ │ │  single instruction that does a binary search; thus, quite efficient even if
│ │ │  there are many values) to select which one of the first three clauses to
│ │ │  execute (if any).</li><li>If none of the first three clauses match, the fourth clause match as a
│ │ │  variable always matches.</li><li>If the guard test <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(Int)</code></a> succeeds, the fourth
│ │ │  clause is executed.</li><li>If the guard test fails, the input value is compared to <code class="inline">four</code>, <code class="inline">five</code>, and
│ │ │  <code class="inline">six</code>, and the appropriate clause is selected. (There is a <code class="inline">function_clause</code>
│ │ │ -exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-1">(</span><span class="ss">one</span><span class="p" data-group-id="9174193828-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-2">(</span><span class="ss">two</span><span class="p" data-group-id="9174193828-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-3">(</span><span class="ss">three</span><span class="p" data-group-id="9174193828-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-4">(</span><span class="ss">four</span><span class="p" data-group-id="9174193828-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-5">(</span><span class="ss">five</span><span class="p" data-group-id="9174193828-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-6">(</span><span class="ss">six</span><span class="p" data-group-id="9174193828-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map2</span><span class="p" data-group-id="9174193828-7">(</span><span class="n">Int</span><span class="p" data-group-id="9174193828-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9174193828-8">(</span><span class="n">Int</span><span class="p" data-group-id="9174193828-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-1">(</span><span class="n">Int</span><span class="p" data-group-id="4868933163-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4868933163-2">(</span><span class="n">Int</span><span class="p" data-group-id="4868933163-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-3">(</span><span class="ss">one</span><span class="p" data-group-id="4868933163-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-4">(</span><span class="ss">two</span><span class="p" data-group-id="4868933163-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-5">(</span><span class="ss">three</span><span class="p" data-group-id="4868933163-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-6">(</span><span class="ss">four</span><span class="p" data-group-id="4868933163-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-7">(</span><span class="ss">five</span><span class="p" data-group-id="4868933163-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">atom_map3</span><span class="p" data-group-id="4868933163-8">(</span><span class="ss">six</span><span class="p" data-group-id="4868933163-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="8689161640-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8689161640-2">[</span><span class="p" data-group-id="8689161640-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="8689161640-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +exception if none of the values matched.)</li></ul><p>Rewriting to either:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-1">(</span><span class="ss">one</span><span class="p" data-group-id="7666557876-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-2">(</span><span class="ss">two</span><span class="p" data-group-id="7666557876-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-3">(</span><span class="ss">three</span><span class="p" data-group-id="7666557876-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-4">(</span><span class="ss">four</span><span class="p" data-group-id="7666557876-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-5">(</span><span class="ss">five</span><span class="p" data-group-id="7666557876-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-6">(</span><span class="ss">six</span><span class="p" data-group-id="7666557876-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map2</span><span class="p" data-group-id="7666557876-7">(</span><span class="n">Int</span><span class="p" data-group-id="7666557876-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7666557876-8">(</span><span class="n">Int</span><span class="p" data-group-id="7666557876-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>or:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-1">(</span><span class="n">Int</span><span class="p" data-group-id="6125010908-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="6125010908-2">(</span><span class="n">Int</span><span class="p" data-group-id="6125010908-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-3">(</span><span class="ss">one</span><span class="p" data-group-id="6125010908-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-4">(</span><span class="ss">two</span><span class="p" data-group-id="6125010908-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-5">(</span><span class="ss">three</span><span class="p" data-group-id="6125010908-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-6">(</span><span class="ss">four</span><span class="p" data-group-id="6125010908-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-7">(</span><span class="ss">five</span><span class="p" data-group-id="6125010908-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">atom_map3</span><span class="p" data-group-id="6125010908-8">(</span><span class="ss">six</span><span class="p" data-group-id="6125010908-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span></code></pre><p>gives slightly more efficient matching code.</p><p>Another example:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs1</span><span class="p" data-group-id="2890069318-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2890069318-2">[</span><span class="p" data-group-id="2890069318-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="2890069318-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="8689161640-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8689161640-4">[</span><span class="p" data-group-id="8689161640-4">]</span><span class="p" data-group-id="8689161640-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="2890069318-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2890069318-4">[</span><span class="p" data-group-id="2890069318-4">]</span><span class="p" data-group-id="2890069318-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs1</span><span class="p" data-group-id="8689161640-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8689161640-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="8689161640-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8689161640-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="8689161640-7">]</span><span class="p" data-group-id="8689161640-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8689161640-8">[</span><span class="n">Map</span><span class="p" data-group-id="8689161640-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8689161640-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="8689161640-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="8689161640-10">)</span><span class="p" data-group-id="8689161640-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │ +</span><span class="nf">map_pairs1</span><span class="p" data-group-id="2890069318-5">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2890069318-6">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="2890069318-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2890069318-7">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="2890069318-7">]</span><span class="p" data-group-id="2890069318-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2890069318-8">[</span><span class="n">Map</span><span class="p" data-group-id="2890069318-9">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2890069318-9">)</span><span class="p">|</span><span class="nf">map_pairs1</span><span class="p" data-group-id="2890069318-10">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="2890069318-10">)</span><span class="p" data-group-id="2890069318-8">]</span><span class="p">.</span></code></pre><p>The first argument is <em>not</em> a problem. It is variable, but it is a variable in
│ │ │  all clauses. The problem is the variable in the second argument, <code class="inline">Xs</code>, in the
│ │ │  middle clause. Because the variable can match anything, the compiler is not
│ │ │  allowed to rearrange the clauses, but must generate code that matches them in
│ │ │  the order written.</p><p>If the function is rewritten as follows, the compiler is free to rearrange the
│ │ │ -clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="4000054565-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4000054565-2">[</span><span class="p" data-group-id="4000054565-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="4000054565-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +clauses:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">map_pairs2</span><span class="p" data-group-id="8123045877-1">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123045877-2">[</span><span class="p" data-group-id="8123045877-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="8123045877-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Ys</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="4000054565-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4000054565-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="4000054565-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4000054565-5">[</span><span class="p" data-group-id="4000054565-5">]</span><span class="w"> </span><span class="p" data-group-id="4000054565-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="8123045877-3">(</span><span class="p">_</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123045877-4">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="8123045877-4">]</span><span class="o">=</span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123045877-5">[</span><span class="p" data-group-id="8123045877-5">]</span><span class="w"> </span><span class="p" data-group-id="8123045877-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Xs</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map_pairs2</span><span class="p" data-group-id="4000054565-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4000054565-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="4000054565-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4000054565-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="4000054565-8">]</span><span class="p" data-group-id="4000054565-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4000054565-9">[</span><span class="n">Map</span><span class="p" data-group-id="4000054565-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4000054565-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="4000054565-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="4000054565-11">)</span><span class="p" data-group-id="4000054565-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="5955725528-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="5955725528-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">map_pairs2</span><span class="p" data-group-id="8123045877-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123045877-7">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="8123045877-7">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8123045877-8">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="8123045877-8">]</span><span class="p" data-group-id="8123045877-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8123045877-9">[</span><span class="n">Map</span><span class="p" data-group-id="8123045877-10">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8123045877-10">)</span><span class="p">|</span><span class="nf">map_pairs2</span><span class="p" data-group-id="8123045877-11">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="8123045877-11">)</span><span class="p" data-group-id="8123045877-9">]</span><span class="p">.</span></code></pre><p>The compiler will generate code similar to this:</p><p><strong>DO NOT (already done by the compiler)</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="2742535574-1">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs0</span><span class="p">,</span><span class="w"> </span><span class="n">Ys0</span><span class="p" data-group-id="2742535574-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Xs0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5955725528-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="5955725528-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="2742535574-2">[</span><span class="n">X</span><span class="p">|</span><span class="n">Xs</span><span class="p" data-group-id="2742535574-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="k">case</span><span class="w"> </span><span class="n">Ys0</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="5955725528-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="5955725528-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="p" data-group-id="5955725528-4">[</span><span class="n">Map</span><span class="p" data-group-id="5955725528-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5955725528-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="5955725528-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="5955725528-6">)</span><span class="p" data-group-id="5955725528-4">]</span><span class="p">;</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="5955725528-7">[</span><span class="p" data-group-id="5955725528-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="2742535574-3">[</span><span class="n">Y</span><span class="p">|</span><span class="n">Ys</span><span class="p" data-group-id="2742535574-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="p" data-group-id="2742535574-4">[</span><span class="n">Map</span><span class="p" data-group-id="2742535574-5">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2742535574-5">)</span><span class="p">|</span><span class="nf">explicit_map_pairs</span><span class="p" data-group-id="2742535574-6">(</span><span class="n">Map</span><span class="p">,</span><span class="w"> </span><span class="n">Xs</span><span class="p">,</span><span class="w"> </span><span class="n">Ys</span><span class="p" data-group-id="2742535574-6">)</span><span class="p" data-group-id="2742535574-4">]</span><span class="p">;</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="2742535574-7">[</span><span class="p" data-group-id="2742535574-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  		    </span><span class="n">Xs0</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="5955725528-8">[</span><span class="p" data-group-id="5955725528-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="2742535574-8">[</span><span class="p" data-group-id="2742535574-8">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Ys0</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>This is slightly faster for probably the most common case that the input lists
│ │ │  are not empty or very short. (Another advantage is that Dialyzer can deduce a
│ │ │  better type for the <code class="inline">Xs</code> variable.)</p><h2 id="function-calls" class="section-heading">
│ │ │    <a href="#function-calls" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/eff_guide_processes.html
│ │ │ @@ -119,45 +119,45 @@
│ │ │    <a href="#creating-an-erlang-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating an Erlang Process</span>
│ │ │  </h2>
│ │ │  <p>An Erlang process is lightweight compared to threads and processes in operating
│ │ │  systems.</p><p>A newly spawned Erlang process uses 327 words of memory. The size can be found
│ │ │ -as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="9386970833-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="9386970833-1">]</span><span class="w"> </span><span class="p" data-group-id="9386970833-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="9386970833-2">]</span><span class="w"> </span><span class="p" data-group-id="9386970833-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9386970833-3">]</span><span class="w"> </span><span class="p" data-group-id="9386970833-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="9386970833-4">]</span><span class="w"> </span><span class="p" data-group-id="9386970833-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="9386970833-5">]</span><span class="w"> </span><span class="p" data-group-id="9386970833-6">[</span><span class="ss">jit</span><span class="p" data-group-id="9386970833-6">]</span><span class="w">
│ │ │ +as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="1823955936-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p">.</span><span class="mi">3</span><span class="p" data-group-id="1823955936-1">]</span><span class="w"> </span><span class="p" data-group-id="1823955936-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="1823955936-2">]</span><span class="w"> </span><span class="p" data-group-id="1823955936-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1823955936-3">]</span><span class="w"> </span><span class="p" data-group-id="1823955936-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="1823955936-4">]</span><span class="w"> </span><span class="p" data-group-id="1823955936-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1823955936-5">]</span><span class="w"> </span><span class="p" data-group-id="1823955936-6">[</span><span class="ss">jit</span><span class="p" data-group-id="1823955936-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="9386970833-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="9386970833-8">(</span><span class="p" data-group-id="9386970833-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="9386970833-7">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9386970833-9">(</span><span class="p" data-group-id="9386970833-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mf">2.3</span><span class="w"> </span><span class="p" data-group-id="1823955936-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="1823955936-8">(</span><span class="p" data-group-id="1823955936-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="1823955936-7">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1823955936-9">(</span><span class="p" data-group-id="1823955936-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="ss">infinity</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">43.39164016</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="9386970833-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="9386970833-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="9386970833-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="9386970833-12">(</span><span class="n">Fun</span><span class="p" data-group-id="9386970833-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="9386970833-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9386970833-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="9386970833-13">}</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="9386970833-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="9386970833-14">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="p" data-group-id="1823955936-10">{</span><span class="p">_</span><span class="p">,</span><span class="n">Bytes</span><span class="p" data-group-id="1823955936-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">process_info</span><span class="p" data-group-id="1823955936-11">(</span><span class="nf">spawn</span><span class="p" data-group-id="1823955936-12">(</span><span class="n">Fun</span><span class="p" data-group-id="1823955936-12">)</span><span class="p">,</span><span class="w"> </span><span class="nb">memory</span><span class="p" data-group-id="1823955936-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1823955936-13">{</span><span class="nb">memory</span><span class="p">,</span><span class="mi">2616</span><span class="p" data-group-id="1823955936-13">}</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="n">Bytes</span><span class="w"> </span><span class="ow">div</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="1823955936-14">(</span><span class="ss">wordsize</span><span class="p" data-group-id="1823955936-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">327</span></code></pre><p>The size includes 233 words for the heap area (which includes the stack). The
│ │ │  garbage collector increases the heap as needed.</p><p>The main (outer) loop for a process <em>must</em> be tail-recursive. Otherwise, the
│ │ │ -stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="5383562944-1">(</span><span class="p" data-group-id="5383562944-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +stack grows until the process terminates.</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="8032337539-1">(</span><span class="p" data-group-id="8032337539-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │    </span><span class="k">receive</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5383562944-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5383562944-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="5383562944-3">(</span><span class="n">Msg</span><span class="p" data-group-id="5383562944-3">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="5383562944-4">(</span><span class="p" data-group-id="5383562944-4">)</span><span class="p">;</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5383562944-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5383562944-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="5383562944-6">(</span><span class="n">Msg</span><span class="p" data-group-id="5383562944-6">)</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="8032337539-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8032337539-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="8032337539-3">(</span><span class="n">Msg</span><span class="p" data-group-id="8032337539-3">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="8032337539-4">(</span><span class="p" data-group-id="8032337539-4">)</span><span class="p">;</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="8032337539-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8032337539-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +          </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="8032337539-6">(</span><span class="n">Msg</span><span class="p" data-group-id="8032337539-6">)</span><span class="p">,</span><span class="w">
│ │ │            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="nf">loop</span><span class="p" data-group-id="5383562944-7">(</span><span class="p" data-group-id="5383562944-7">)</span><span class="w">
│ │ │ +          </span><span class="nf">loop</span><span class="p" data-group-id="8032337539-7">(</span><span class="p" data-group-id="8032337539-7">)</span><span class="w">
│ │ │    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5383562944-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5383562944-9">[</span><span class="p" data-group-id="5383562944-9">]</span><span class="p" data-group-id="5383562944-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8032337539-8">(</span><span class="s">&quot;Message is processed</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8032337539-9">[</span><span class="p" data-group-id="8032337539-9">]</span><span class="p" data-group-id="8032337539-8">)</span><span class="p">.</span></code></pre><p>The call to <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> will never be executed, but a return address will
│ │ │  still be pushed to the stack each time <code class="inline">loop/0</code> is called recursively. The
│ │ │ -correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2110187574-1">(</span><span class="p" data-group-id="2110187574-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +correct tail-recursive version of the function looks as follows:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="9489878772-1">(</span><span class="p" data-group-id="9489878772-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │     </span><span class="k">receive</span><span class="w">
│ │ │ -      </span><span class="p" data-group-id="2110187574-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2110187574-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="2110187574-3">(</span><span class="n">Msg</span><span class="p" data-group-id="2110187574-3">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="2110187574-4">(</span><span class="p" data-group-id="2110187574-4">)</span><span class="p">;</span><span class="w">
│ │ │ -      </span><span class="p" data-group-id="2110187574-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="2110187574-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2110187574-6">(</span><span class="n">Msg</span><span class="p" data-group-id="2110187574-6">)</span><span class="p">,</span><span class="w">
│ │ │ +      </span><span class="p" data-group-id="9489878772-2">{</span><span class="ss">sys</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9489878772-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="nf">handle_sys_msg</span><span class="p" data-group-id="9489878772-3">(</span><span class="n">Msg</span><span class="p" data-group-id="9489878772-3">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="9489878772-4">(</span><span class="p" data-group-id="9489878772-4">)</span><span class="p">;</span><span class="w">
│ │ │ +      </span><span class="p" data-group-id="9489878772-5">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9489878772-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="n">Reply</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9489878772-6">(</span><span class="n">Msg</span><span class="p" data-group-id="9489878772-6">)</span><span class="p">,</span><span class="w">
│ │ │           </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Reply</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">loop</span><span class="p" data-group-id="2110187574-7">(</span><span class="p" data-group-id="2110187574-7">)</span><span class="w">
│ │ │ +         </span><span class="nf">loop</span><span class="p" data-group-id="9489878772-7">(</span><span class="p" data-group-id="9489878772-7">)</span><span class="w">
│ │ │   </span><span class="k">end</span><span class="p">.</span></code></pre><h3 id="initial-heap-size" class="section-heading">
│ │ │    <a href="#initial-heap-size" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Initial Heap Size</span>
│ │ │  </h3>
│ │ │  <p>The default initial heap size of 233 words is quite conservative to support
│ │ │ @@ -189,30 +189,30 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Receiving messages</span>
│ │ │  </h2>
│ │ │  <p>The cost of receiving messages depends on how complicated the <code class="inline">receive</code>
│ │ │  expression is. A simple expression that matches any message is very cheap
│ │ │  because it retrieves the first message in the message queue:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2954640523-1">(</span><span class="n">Message</span><span class="p" data-group-id="2954640523-1">)</span><span class="w">
│ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9124962462-1">(</span><span class="n">Message</span><span class="p" data-group-id="9124962462-1">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>However, this is not always convenient: we can receive a message that we do not
│ │ │  know how to handle at this point, so it is common to only match the messages we
│ │ │  expect:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4744239037-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="4744239037-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="4744239037-2">(</span><span class="n">Message</span><span class="p" data-group-id="4744239037-2">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7428728241-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7428728241-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="7428728241-2">(</span><span class="n">Message</span><span class="p" data-group-id="7428728241-2">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>While this is convenient it means that the entire message queue must be searched
│ │ │  until it finds a matching message. This is very expensive for processes with
│ │ │  long message queues, so there is an optimization for the common case of
│ │ │ -sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="4590460247-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="4590460247-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4590460247-2">{</span><span class="nf">self</span><span class="p" data-group-id="4590460247-3">(</span><span class="p" data-group-id="4590460247-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="4590460247-2">}</span><span class="p">,</span><span class="w">
│ │ │ +sending a request and waiting for a response shortly after:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="1242674138-1">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="1242674138-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1242674138-2">{</span><span class="nf">self</span><span class="p" data-group-id="1242674138-3">(</span><span class="p" data-group-id="1242674138-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1242674138-2">}</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4590460247-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="4590460247-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="4590460247-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4590460247-6">[</span><span class="ss">flush</span><span class="p" data-group-id="4590460247-6">]</span><span class="p" data-group-id="4590460247-5">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="4590460247-7">(</span><span class="n">Reply</span><span class="p" data-group-id="4590460247-7">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4590460247-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4590460247-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nf">handle_error</span><span class="p" data-group-id="4590460247-9">(</span><span class="n">Reason</span><span class="p" data-group-id="4590460247-9">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1242674138-4">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="1242674138-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="1242674138-5">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1242674138-6">[</span><span class="ss">flush</span><span class="p" data-group-id="1242674138-6">]</span><span class="p" data-group-id="1242674138-5">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="1242674138-7">(</span><span class="n">Reply</span><span class="p" data-group-id="1242674138-7">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1242674138-8">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1242674138-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">handle_error</span><span class="p" data-group-id="1242674138-9">(</span><span class="n">Reason</span><span class="p" data-group-id="1242674138-9">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p>Since the compiler knows that the reference created by
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a> cannot exist before the call (since it is a globally
│ │ │  unique identifier), and that the <code class="inline">receive</code> only matches messages that contain
│ │ │  said reference, it will tell the emulator to search only the messages that
│ │ │  arrived after the call to <a href="../../erts-15.2.7.2/doc/html/erlang.html#monitor/2"><code class="inline">monitor/2</code></a>.</p><p>The above is a simple example where one is but guaranteed that the optimization
│ │ │  will take, but what about more complicated code?</p><p><a href="" id="recv_opt_info"></a></p><h3 id="option-recv_opt_info" class="section-heading">
│ │ │    <a href="#option-recv_opt_info" class="hover-link">
│ │ │ @@ -228,101 +228,101 @@
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">200</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">NOT</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">do</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">suitable</span><span class="w"> </span><span class="ss">reference</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">mark</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">message</span><span class="w"> </span><span class="ss">queue</span><span class="w"> </span><span class="ss">position</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">208</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="nb">monitor</span><span class="p">/</span><span class="mi">2</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">206</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">219</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">INFO</span><span class="p">:</span><span class="w"> </span><span class="ss">passing</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">created</span><span class="w"> </span><span class="ss">by</span><span class="w"> </span><span class="ss">make_ref</span><span class="p">/</span><span class="mi">0</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">218</span><span class="w">
│ │ │  </span><span class="ss">efficiency_guide</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">222</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="n">OPTIMIZED</span><span class="p">:</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">clauses</span><span class="w"> </span><span class="ss">match</span><span class="w"> </span><span class="ss">reference</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">function</span><span class="w"> </span><span class="ss">parameter</span><span class="w"> </span><span class="mi">1</span></code></pre><p>To make it clearer exactly what code the warnings refer to, the warnings in the
│ │ │  following examples are inserted as comments after the clause they refer to, for
│ │ │  example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">simple_receive</span><span class="p" data-group-id="9481411068-1">(</span><span class="p" data-group-id="9481411068-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">simple_receive</span><span class="p" data-group-id="2411083556-1">(</span><span class="p" data-group-id="2411083556-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% efficiency_guide.erl:194: Warning: INFO: not a selective receive, this is always fast</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9481411068-2">(</span><span class="n">Message</span><span class="p" data-group-id="9481411068-2">)</span><span class="w">
│ │ │ +    </span><span class="n">Message</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2411083556-2">(</span><span class="n">Message</span><span class="p" data-group-id="2411083556-2">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO NOT, unless Tag is known to be a suitable reference: see</span><span class="w">
│ │ │  </span><span class="c1">%% cross_function_receive/0 further down.</span><span class="w">
│ │ │ -</span><span class="nf">selective_receive</span><span class="p" data-group-id="9481411068-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9481411068-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">selective_receive</span><span class="p" data-group-id="2411083556-3">(</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="2411083556-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% efficiency_guide.erl:200: Warning: NOT OPTIMIZED: all clauses do not match a suitable reference</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9481411068-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9481411068-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9481411068-5">(</span><span class="n">Message</span><span class="p" data-group-id="9481411068-5">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2411083556-4">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="2411083556-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2411083556-5">(</span><span class="n">Message</span><span class="p" data-group-id="2411083556-5">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">optimized_receive</span><span class="p" data-group-id="9481411068-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9481411068-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">optimized_receive</span><span class="p" data-group-id="2411083556-6">(</span><span class="n">Process</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="2411083556-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% efficiency_guide.erl:206: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ -    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="9481411068-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="9481411068-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9481411068-8">{</span><span class="nf">self</span><span class="p" data-group-id="9481411068-9">(</span><span class="p" data-group-id="9481411068-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="9481411068-8">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">MRef</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="2411083556-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">Process</span><span class="p" data-group-id="2411083556-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Process</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2411083556-8">{</span><span class="nf">self</span><span class="p" data-group-id="2411083556-9">(</span><span class="p" data-group-id="2411083556-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="2411083556-8">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:208: Warning: OPTIMIZED: matches reference created by monitor/2 at efficiency_guide.erl:206</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9481411068-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="9481411068-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="9481411068-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9481411068-12">[</span><span class="ss">flush</span><span class="p" data-group-id="9481411068-12">]</span><span class="p" data-group-id="9481411068-11">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">handle_reply</span><span class="p" data-group-id="9481411068-13">(</span><span class="n">Reply</span><span class="p" data-group-id="9481411068-13">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9481411068-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9481411068-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">handle_error</span><span class="p" data-group-id="9481411068-15">(</span><span class="n">Reason</span><span class="p" data-group-id="9481411068-15">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2411083556-10">{</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="p" data-group-id="2411083556-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">demonitor</span><span class="p" data-group-id="2411083556-11">(</span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2411083556-12">[</span><span class="ss">flush</span><span class="p" data-group-id="2411083556-12">]</span><span class="p" data-group-id="2411083556-11">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nf">handle_reply</span><span class="p" data-group-id="2411083556-13">(</span><span class="n">Reply</span><span class="p" data-group-id="2411083556-13">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2411083556-14">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2411083556-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">handle_error</span><span class="p" data-group-id="2411083556-15">(</span><span class="n">Reason</span><span class="p" data-group-id="2411083556-15">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% DO</span><span class="w">
│ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9481411068-16">(</span><span class="p" data-group-id="9481411068-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="2411083556-16">(</span><span class="p" data-group-id="2411083556-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:218: Warning: OPTIMIZED: reference used to mark a message queue position</span><span class="w">
│ │ │ -    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="9481411068-17">(</span><span class="p" data-group-id="9481411068-17">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Ref</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="2411083556-17">(</span><span class="p" data-group-id="2411083556-17">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:219: Warning: INFO: passing reference created by make_ref/0 at efficiency_guide.erl:218</span><span class="w">
│ │ │ -    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9481411068-18">(</span><span class="n">Ref</span><span class="p" data-group-id="9481411068-18">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">cross_function_receive</span><span class="p" data-group-id="2411083556-18">(</span><span class="n">Ref</span><span class="p" data-group-id="2411083556-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="9481411068-19">(</span><span class="n">Ref</span><span class="p" data-group-id="9481411068-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">cross_function_receive</span><span class="p" data-group-id="2411083556-19">(</span><span class="n">Ref</span><span class="p" data-group-id="2411083556-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% efficiency_guide.erl:222: Warning: OPTIMIZED: all clauses match reference in function parameter 1</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9481411068-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9481411068-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="9481411068-21">(</span><span class="n">Message</span><span class="p" data-group-id="9481411068-21">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2411083556-20">{</span><span class="n">Ref</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="2411083556-20">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_msg</span><span class="p" data-group-id="2411083556-21">(</span><span class="n">Message</span><span class="p" data-group-id="2411083556-21">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="literal-pool" class="section-heading">
│ │ │    <a href="#literal-pool" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Literal Pool</span>
│ │ │  </h2>
│ │ │  <p>Constant Erlang terms (hereafter called <em>literals</em>) are kept in <em>literal pools</em>;
│ │ │  each loaded module has its own pool. The following function does not build the
│ │ │  tuple every time it is called (only to have it discarded the next time the
│ │ │  garbage collector was run), but the tuple is located in the module's literal
│ │ │ -pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="6860118010-1">(</span><span class="n">M</span><span class="p" data-group-id="6860118010-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="6860118010-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6860118010-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="6860118010-3">}</span><span class="p" data-group-id="6860118010-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │ +pool:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">days_in_month</span><span class="p" data-group-id="3759020556-1">(</span><span class="n">M</span><span class="p" data-group-id="3759020556-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="3759020556-2">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3759020556-3">{</span><span class="mi">31</span><span class="p">,</span><span class="mi">28</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">31</span><span class="p" data-group-id="3759020556-3">}</span><span class="p" data-group-id="3759020556-2">)</span><span class="p">.</span></code></pre><p>If a literal, or a term that contains a literal, is inserted into an Ets table,
│ │ │  it is <em>copied</em>. The reason is that the module containing the literal can be
│ │ │  unloaded in the future.</p><p>When a literal is sent to another process, it is <em>not</em> copied. When a module
│ │ │  holding a literal is unloaded, the literal will be copied to the heap of all
│ │ │  processes that hold references to that literal.</p><p>There also exists a global literal pool that is managed by the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/persistent_term.html"><code class="inline">persistent_term</code></a> module.</p><p>By default, 1 GB of virtual address space is reserved for all literal pools (in
│ │ │  BEAM code and persistent terms). The amount of virtual address space reserved
│ │ │  for literals can be changed by using the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erts_alloc.html#MIscs"><code class="inline">+MIscs option</code></a> when starting the emulator.</p><p>Here is an example how the reserved virtual address space for literals can be
│ │ │  raised to 2 GB (2048 MB):</p><pre><code class="text">erl +MIscs 2048</code></pre><h2 id="loss-of-sharing" class="section-heading">
│ │ │    <a href="#loss-of-sharing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Loss of Sharing</span>
│ │ │  </h2>
│ │ │ -<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4663825127-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="4663825127-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ -subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="6659161265-1">(</span><span class="p" data-group-id="6659161265-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="6659161265-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6659161265-3">[</span><span class="mi">42</span><span class="p" data-group-id="6659161265-3">]</span><span class="p" data-group-id="6659161265-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>An Erlang term can have shared subterms. Here is a simple example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6797448818-1">{</span><span class="n">SubTerm</span><span class="p">,</span><span class="w"> </span><span class="n">SubTerm</span><span class="p" data-group-id="6797448818-1">}</span></code></pre><p>Shared subterms are <em>not</em> preserved in the following cases:</p><ul><li>When a term is sent to another process</li><li>When a term is passed as the initial process arguments in the <code class="inline">spawn</code> call</li><li>When a term is stored in an Ets table</li></ul><p>That is an optimization. Most applications do not send messages with shared
│ │ │ +subterms.</p><p>The following example shows how a shared subterm can be created:</p><pre><code class="makeup erlang" translate="no"><span class="nf">kilo_byte</span><span class="p" data-group-id="9659032818-1">(</span><span class="p" data-group-id="9659032818-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="9659032818-2">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9659032818-3">[</span><span class="mi">42</span><span class="p" data-group-id="9659032818-3">]</span><span class="p" data-group-id="9659032818-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="6659161265-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6659161265-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9659032818-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9659032818-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">kilo_byte</span><span class="p" data-group-id="6659161265-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="6659161265-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="6659161265-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6659161265-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="6659161265-7">]</span><span class="p" data-group-id="6659161265-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../erts-15.2.7.2/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │ +</span><span class="nf">kilo_byte</span><span class="p" data-group-id="9659032818-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9659032818-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">kilo_byte</span><span class="p" data-group-id="9659032818-6">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9659032818-7">[</span><span class="n">Acc</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="9659032818-7">]</span><span class="p" data-group-id="9659032818-6">)</span><span class="p">.</span></code></pre><p><code class="inline">kilo_byte/1</code> creates a deep list. If <a href="../../erts-15.2.7.2/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a>
│ │ │  is called, the deep list can be converted to a binary of 1024 bytes:</p><pre><code class="text">1&gt; byte_size(list_to_binary(efficiency_guide:kilo_byte())).
│ │ │  1024</code></pre><p>Using the <code class="inline">erts_debug:size/1</code> BIF, it can be seen that the deep list only
│ │ │ -requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="3924431095-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="3924431095-2">(</span><span class="p" data-group-id="3924431095-2">)</span><span class="p" data-group-id="3924431095-1">)</span><span class="p">.</span><span class="w">
│ │ │ +requires 22 words of heap space:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="5791317371-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="5791317371-2">(</span><span class="p" data-group-id="5791317371-2">)</span><span class="p" data-group-id="5791317371-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">22</span></code></pre><p>Using the <code class="inline">erts_debug:flat_size/1</code> BIF, the size of the deep list can be
│ │ │  calculated if sharing is ignored. It becomes the size of the list when it has
│ │ │ -been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="0721914008-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="0721914008-2">(</span><span class="p" data-group-id="0721914008-2">)</span><span class="p" data-group-id="0721914008-1">)</span><span class="p">.</span><span class="w">
│ │ │ +been sent to another process or stored in an Ets table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="7995192065-1">(</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="7995192065-2">(</span><span class="p" data-group-id="7995192065-2">)</span><span class="p" data-group-id="7995192065-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4094</span></code></pre><p>It can be verified that sharing will be lost if the data is inserted into an Ets
│ │ │ -table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1496213195-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1496213195-2">[</span><span class="p" data-group-id="1496213195-2">]</span><span class="p" data-group-id="1496213195-1">)</span><span class="p">.</span><span class="w">
│ │ │ +table:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1384119218-1">(</span><span class="ss">tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1384119218-2">[</span><span class="p" data-group-id="1384119218-2">]</span><span class="p" data-group-id="1384119218-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.1662103692</span><span class="p">.</span><span class="mf">2407923716.214181</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="1496213195-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1496213195-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="1496213195-5">(</span><span class="p" data-group-id="1496213195-5">)</span><span class="p" data-group-id="1496213195-4">}</span><span class="p" data-group-id="1496213195-3">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">ets</span><span class="p">:</span><span class="nf">insert</span><span class="p" data-group-id="1384119218-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1384119218-4">{</span><span class="ss">key</span><span class="p">,</span><span class="nc">efficiency_guide</span><span class="p">:</span><span class="nf">kilo_byte</span><span class="p" data-group-id="1384119218-5">(</span><span class="p" data-group-id="1384119218-5">)</span><span class="p" data-group-id="1384119218-4">}</span><span class="p" data-group-id="1384119218-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="1496213195-6">(</span><span class="nf">element</span><span class="p" data-group-id="1496213195-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="1496213195-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1496213195-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="1496213195-9">)</span><span class="p" data-group-id="1496213195-8">)</span><span class="p" data-group-id="1496213195-7">)</span><span class="p" data-group-id="1496213195-6">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">size</span><span class="p" data-group-id="1384119218-6">(</span><span class="nf">element</span><span class="p" data-group-id="1384119218-7">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="1384119218-8">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1384119218-9">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="1384119218-9">)</span><span class="p" data-group-id="1384119218-8">)</span><span class="p" data-group-id="1384119218-7">)</span><span class="p" data-group-id="1384119218-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4094</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="1496213195-10">(</span><span class="nf">element</span><span class="p" data-group-id="1496213195-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="1496213195-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1496213195-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="1496213195-13">)</span><span class="p" data-group-id="1496213195-12">)</span><span class="p" data-group-id="1496213195-11">)</span><span class="p" data-group-id="1496213195-10">)</span><span class="p">.</span><span class="w">
│ │ │ +7&gt; </span><span class="nc">erts_debug</span><span class="p">:</span><span class="nf">flat_size</span><span class="p" data-group-id="1384119218-10">(</span><span class="nf">element</span><span class="p" data-group-id="1384119218-11">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="nf">hd</span><span class="p" data-group-id="1384119218-12">(</span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="1384119218-13">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="ss">key</span><span class="p" data-group-id="1384119218-13">)</span><span class="p" data-group-id="1384119218-12">)</span><span class="p" data-group-id="1384119218-11">)</span><span class="p" data-group-id="1384119218-10">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4094</span></code></pre><p>When the data has passed through an Ets table, <code class="inline">erts_debug:size/1</code> and
│ │ │  <code class="inline">erts_debug:flat_size/1</code> return the same value. Sharing has been lost.</p><p>It is possible to build an <em>experimental</em> variant of the runtime system that
│ │ │  will preserve sharing when copying terms by giving the
│ │ │  <code class="inline">--enable-sharing-preserving</code> option to the <code class="inline">configure</code> script.</p><h2 id="smp-run-time-system" class="section-heading">
│ │ │    <a href="#smp-run-time-system" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/erl_interface.html
│ │ │ @@ -120,119 +120,119 @@
│ │ │  to read the port example in <a href="c_port.html">Ports</a> before reading this section.</p><h2 id="erlang-program" class="section-heading">
│ │ │    <a href="#erlang-program" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Erlang Program</span>
│ │ │  </h2>
│ │ │  <p>The following example shows an Erlang program communicating with a C program
│ │ │ -over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4968468829-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="4968468829-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4968468829-2">(</span><span class="p" data-group-id="4968468829-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4968468829-3">]</span><span class="p" data-group-id="4968468829-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4968468829-4">(</span><span class="p" data-group-id="4968468829-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4968468829-5">]</span><span class="p" data-group-id="4968468829-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="4968468829-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4968468829-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4968468829-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4968468829-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="4968468829-8">]</span><span class="p" data-group-id="4968468829-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4968468829-9">(</span><span class="p" data-group-id="4968468829-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +over a plain port with home made encoding:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5366020020-1">(</span><span class="ss">complex1</span><span class="p" data-group-id="5366020020-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5366020020-2">(</span><span class="p" data-group-id="5366020020-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5366020020-3">]</span><span class="p" data-group-id="5366020020-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5366020020-4">(</span><span class="p" data-group-id="5366020020-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5366020020-5">]</span><span class="p" data-group-id="5366020020-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="5366020020-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="5366020020-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5366020020-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5366020020-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="5366020020-8">]</span><span class="p" data-group-id="5366020020-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="5366020020-9">(</span><span class="p" data-group-id="5366020020-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="4968468829-10">(</span><span class="n">X</span><span class="p" data-group-id="4968468829-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4968468829-11">(</span><span class="p" data-group-id="4968468829-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4968468829-12">}</span><span class="p" data-group-id="4968468829-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="4968468829-13">(</span><span class="n">Y</span><span class="p" data-group-id="4968468829-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="4968468829-14">(</span><span class="p" data-group-id="4968468829-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4968468829-15">}</span><span class="p" data-group-id="4968468829-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="5366020020-10">(</span><span class="n">X</span><span class="p" data-group-id="5366020020-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="5366020020-11">(</span><span class="p" data-group-id="5366020020-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5366020020-12">}</span><span class="p" data-group-id="5366020020-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="5366020020-13">(</span><span class="n">Y</span><span class="p" data-group-id="5366020020-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="5366020020-14">(</span><span class="p" data-group-id="5366020020-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5366020020-15">}</span><span class="p" data-group-id="5366020020-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="4968468829-16">(</span><span class="n">Msg</span><span class="p" data-group-id="4968468829-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4968468829-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4968468829-18">(</span><span class="p" data-group-id="4968468829-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4968468829-17">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="5366020020-16">(</span><span class="n">Msg</span><span class="p" data-group-id="5366020020-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5366020020-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5366020020-18">(</span><span class="p" data-group-id="5366020020-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5366020020-17">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="4968468829-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="4968468829-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="5366020020-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5366020020-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4968468829-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="4968468829-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="4968468829-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="4968468829-22">(</span><span class="p" data-group-id="4968468829-22">)</span><span class="p" data-group-id="4968468829-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="4968468829-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4968468829-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="4968468829-24">(</span><span class="p" data-group-id="4968468829-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="4968468829-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4968468829-26">[</span><span class="p" data-group-id="4968468829-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4968468829-27">}</span><span class="p" data-group-id="4968468829-26">]</span><span class="p" data-group-id="4968468829-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="4968468829-28">(</span><span class="n">Port</span><span class="p" data-group-id="4968468829-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="5366020020-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="5366020020-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="5366020020-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5366020020-22">(</span><span class="p" data-group-id="5366020020-22">)</span><span class="p" data-group-id="5366020020-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="5366020020-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5366020020-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="5366020020-24">(</span><span class="p" data-group-id="5366020020-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="5366020020-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5366020020-26">[</span><span class="p" data-group-id="5366020020-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5366020020-27">}</span><span class="p" data-group-id="5366020020-26">]</span><span class="p" data-group-id="5366020020-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="5366020020-28">(</span><span class="n">Port</span><span class="p" data-group-id="5366020020-28">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="4968468829-29">(</span><span class="n">Port</span><span class="p" data-group-id="4968468829-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="5366020020-29">(</span><span class="n">Port</span><span class="p" data-group-id="5366020020-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="4968468829-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="4968468829-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4968468829-31">{</span><span class="nf">self</span><span class="p" data-group-id="4968468829-32">(</span><span class="p" data-group-id="4968468829-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4968468829-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="4968468829-34">(</span><span class="n">Msg</span><span class="p" data-group-id="4968468829-34">)</span><span class="p" data-group-id="4968468829-33">}</span><span class="p" data-group-id="4968468829-31">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="5366020020-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="5366020020-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5366020020-31">{</span><span class="nf">self</span><span class="p" data-group-id="5366020020-32">(</span><span class="p" data-group-id="5366020020-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5366020020-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="5366020020-34">(</span><span class="n">Msg</span><span class="p" data-group-id="5366020020-34">)</span><span class="p" data-group-id="5366020020-33">}</span><span class="p" data-group-id="5366020020-31">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="4968468829-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4968468829-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4968468829-36">}</span><span class="p" data-group-id="4968468829-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4968468829-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="4968468829-38">(</span><span class="n">Data</span><span class="p" data-group-id="4968468829-38">)</span><span class="p" data-group-id="4968468829-37">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="5366020020-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5366020020-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5366020020-36">}</span><span class="p" data-group-id="5366020020-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5366020020-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="5366020020-38">(</span><span class="n">Data</span><span class="p" data-group-id="5366020020-38">)</span><span class="p" data-group-id="5366020020-37">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="4968468829-39">(</span><span class="n">Port</span><span class="p" data-group-id="4968468829-39">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="5366020020-39">(</span><span class="n">Port</span><span class="p" data-group-id="5366020020-39">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="4968468829-40">{</span><span class="nf">self</span><span class="p" data-group-id="4968468829-41">(</span><span class="p" data-group-id="4968468829-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="4968468829-40">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5366020020-40">{</span><span class="nf">self</span><span class="p" data-group-id="5366020020-41">(</span><span class="p" data-group-id="5366020020-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="5366020020-40">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="4968468829-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="4968468829-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="4968468829-43">(</span><span class="ss">normal</span><span class="p" data-group-id="4968468829-43">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="5366020020-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="5366020020-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="5366020020-43">(</span><span class="ss">normal</span><span class="p" data-group-id="5366020020-43">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="4968468829-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4968468829-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="4968468829-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="4968468829-45">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="5366020020-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5366020020-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="5366020020-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="5366020020-45">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4968468829-46">(</span><span class="p" data-group-id="4968468829-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4968468829-47">}</span><span class="p" data-group-id="4968468829-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4968468829-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4968468829-48">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">encode</span><span class="p" data-group-id="4968468829-49">(</span><span class="p" data-group-id="4968468829-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4968468829-50">}</span><span class="p" data-group-id="4968468829-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4968468829-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4968468829-51">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="5366020020-46">(</span><span class="p" data-group-id="5366020020-47">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5366020020-47">}</span><span class="p" data-group-id="5366020020-46">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5366020020-48">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="5366020020-48">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">encode</span><span class="p" data-group-id="5366020020-49">(</span><span class="p" data-group-id="5366020020-50">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5366020020-50">}</span><span class="p" data-group-id="5366020020-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5366020020-51">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5366020020-51">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">decode</span><span class="p" data-group-id="4968468829-52">(</span><span class="p" data-group-id="4968468829-53">[</span><span class="n">Int</span><span class="p" data-group-id="4968468829-53">]</span><span class="p" data-group-id="4968468829-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │ +</span><span class="nf">decode</span><span class="p" data-group-id="5366020020-52">(</span><span class="p" data-group-id="5366020020-53">[</span><span class="n">Int</span><span class="p" data-group-id="5366020020-53">]</span><span class="p" data-group-id="5366020020-52">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Int</span><span class="p">.</span></code></pre><p>There are two differences when using Erl_Interface on the C side compared to the
│ │ │  example in <a href="c_port.html">Ports</a>, using only the plain port:</p><ul><li>As Erl_Interface operates on the Erlang external term format, the port must be
│ │ │  set to use binaries.</li><li>Instead of inventing an encoding/decoding scheme, the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#term_to_binary/1"><code class="inline">term_to_binary/1</code></a> and
│ │ │ -<a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="5005822637-1">(</span><span class="p" data-group-id="5005822637-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="5005822637-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5005822637-3">[</span><span class="p" data-group-id="5005822637-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5005822637-4">}</span><span class="p" data-group-id="5005822637-3">]</span><span class="p" data-group-id="5005822637-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="8789702972-1">(</span><span class="p" data-group-id="8789702972-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="8789702972-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8789702972-3">[</span><span class="p" data-group-id="8789702972-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8789702972-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="8789702972-3">]</span><span class="p" data-group-id="8789702972-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1156607091-1">{</span><span class="nf">self</span><span class="p" data-group-id="1156607091-2">(</span><span class="p" data-group-id="1156607091-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1156607091-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="1156607091-4">(</span><span class="n">Msg</span><span class="p" data-group-id="1156607091-4">)</span><span class="p" data-group-id="1156607091-3">}</span><span class="p" data-group-id="1156607091-1">}</span><span class="p">,</span><span class="w">
│ │ │ +<a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> BIFs are to be used.</li></ul><p>That is:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="1582828926-1">(</span><span class="p" data-group-id="1582828926-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="1582828926-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1582828926-3">[</span><span class="p" data-group-id="1582828926-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1582828926-4">}</span><span class="p" data-group-id="1582828926-3">]</span><span class="p" data-group-id="1582828926-1">)</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open_port</span><span class="p" data-group-id="8146491676-1">(</span><span class="p" data-group-id="8146491676-2">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="8146491676-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8146491676-3">[</span><span class="p" data-group-id="8146491676-4">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8146491676-4">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="8146491676-3">]</span><span class="p" data-group-id="8146491676-1">)</span></code></pre><p>And:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3263555905-1">{</span><span class="nf">self</span><span class="p" data-group-id="3263555905-2">(</span><span class="p" data-group-id="3263555905-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3263555905-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">encode</span><span class="p" data-group-id="3263555905-4">(</span><span class="n">Msg</span><span class="p" data-group-id="3263555905-4">)</span><span class="p" data-group-id="3263555905-3">}</span><span class="p" data-group-id="3263555905-1">}</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1156607091-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1156607091-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1156607091-6">}</span><span class="p" data-group-id="1156607091-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1156607091-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="1156607091-8">(</span><span class="n">Data</span><span class="p" data-group-id="1156607091-8">)</span><span class="p" data-group-id="1156607091-7">}</span><span class="w">
│ │ │ -</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3179838443-1">{</span><span class="nf">self</span><span class="p" data-group-id="3179838443-2">(</span><span class="p" data-group-id="3179838443-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3179838443-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="3179838443-4">(</span><span class="n">Msg</span><span class="p" data-group-id="3179838443-4">)</span><span class="p" data-group-id="3179838443-3">}</span><span class="p" data-group-id="3179838443-1">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3263555905-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3263555905-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3263555905-6">}</span><span class="p" data-group-id="3263555905-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3263555905-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">decode</span><span class="p" data-group-id="3263555905-8">(</span><span class="n">Data</span><span class="p" data-group-id="3263555905-8">)</span><span class="p" data-group-id="3263555905-7">}</span><span class="w">
│ │ │ +</span><span class="k">end</span></code></pre><p>is replaced with:</p><pre><code class="makeup erlang" translate="no"><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3095466919-1">{</span><span class="nf">self</span><span class="p" data-group-id="3095466919-2">(</span><span class="p" data-group-id="3095466919-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3095466919-3">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="3095466919-4">(</span><span class="n">Msg</span><span class="p" data-group-id="3095466919-4">)</span><span class="p" data-group-id="3095466919-3">}</span><span class="p" data-group-id="3095466919-1">}</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3179838443-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3179838443-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3179838443-6">}</span><span class="p" data-group-id="3179838443-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3179838443-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3179838443-8">(</span><span class="n">Data</span><span class="p" data-group-id="3179838443-8">)</span><span class="p" data-group-id="3179838443-7">}</span><span class="w">
│ │ │ -</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9274295053-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="9274295053-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9274295053-2">(</span><span class="p" data-group-id="9274295053-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9274295053-3">]</span><span class="p" data-group-id="9274295053-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9274295053-4">(</span><span class="p" data-group-id="9274295053-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9274295053-5">]</span><span class="p" data-group-id="9274295053-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="9274295053-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9274295053-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="9274295053-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9274295053-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="9274295053-8">]</span><span class="p" data-group-id="9274295053-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="9274295053-9">(</span><span class="p" data-group-id="9274295053-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3095466919-5">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3095466919-6">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3095466919-6">}</span><span class="p" data-group-id="3095466919-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3095466919-7">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3095466919-8">(</span><span class="n">Data</span><span class="p" data-group-id="3095466919-8">)</span><span class="p" data-group-id="3095466919-7">}</span><span class="w">
│ │ │ +</span><span class="k">end</span></code></pre><p>The resulting Erlang program is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8657330870-1">(</span><span class="ss">complex2</span><span class="p" data-group-id="8657330870-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8657330870-2">(</span><span class="p" data-group-id="8657330870-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8657330870-3">]</span><span class="p" data-group-id="8657330870-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8657330870-4">(</span><span class="p" data-group-id="8657330870-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8657330870-5">]</span><span class="p" data-group-id="8657330870-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="8657330870-6">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="8657330870-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="8657330870-7">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8657330870-8">[</span><span class="n">ExtPrg</span><span class="p" data-group-id="8657330870-8">]</span><span class="p" data-group-id="8657330870-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="8657330870-9">(</span><span class="p" data-group-id="8657330870-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">stop</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="9274295053-10">(</span><span class="n">X</span><span class="p" data-group-id="9274295053-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="9274295053-11">(</span><span class="p" data-group-id="9274295053-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9274295053-12">}</span><span class="p" data-group-id="9274295053-11">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="9274295053-13">(</span><span class="n">Y</span><span class="p" data-group-id="9274295053-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">call_port</span><span class="p" data-group-id="9274295053-14">(</span><span class="p" data-group-id="9274295053-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9274295053-15">}</span><span class="p" data-group-id="9274295053-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="8657330870-10">(</span><span class="n">X</span><span class="p" data-group-id="8657330870-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="8657330870-11">(</span><span class="p" data-group-id="8657330870-12">{</span><span class="ss">foo</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8657330870-12">}</span><span class="p" data-group-id="8657330870-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="8657330870-13">(</span><span class="n">Y</span><span class="p" data-group-id="8657330870-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">call_port</span><span class="p" data-group-id="8657330870-14">(</span><span class="p" data-group-id="8657330870-15">{</span><span class="ss">bar</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8657330870-15">}</span><span class="p" data-group-id="8657330870-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">call_port</span><span class="p" data-group-id="9274295053-16">(</span><span class="n">Msg</span><span class="p" data-group-id="9274295053-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9274295053-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9274295053-18">(</span><span class="p" data-group-id="9274295053-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9274295053-17">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">call_port</span><span class="p" data-group-id="8657330870-16">(</span><span class="n">Msg</span><span class="p" data-group-id="8657330870-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">complex</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8657330870-17">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8657330870-18">(</span><span class="p" data-group-id="8657330870-18">)</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8657330870-17">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="9274295053-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="9274295053-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="8657330870-19">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="8657330870-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9274295053-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="9274295053-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="9274295053-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9274295053-22">(</span><span class="p" data-group-id="9274295053-22">)</span><span class="p" data-group-id="9274295053-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="9274295053-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9274295053-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9274295053-24">(</span><span class="p" data-group-id="9274295053-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="9274295053-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9274295053-26">[</span><span class="p" data-group-id="9274295053-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9274295053-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="9274295053-26">]</span><span class="p" data-group-id="9274295053-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="9274295053-28">(</span><span class="n">Port</span><span class="p" data-group-id="9274295053-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8657330870-20">(</span><span class="n">ExtPrg</span><span class="p" data-group-id="8657330870-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="8657330870-21">(</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8657330870-22">(</span><span class="p" data-group-id="8657330870-22">)</span><span class="p" data-group-id="8657330870-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="8657330870-23">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="8657330870-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="8657330870-24">(</span><span class="p" data-group-id="8657330870-25">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="n">ExtPrg</span><span class="p" data-group-id="8657330870-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8657330870-26">[</span><span class="p" data-group-id="8657330870-27">{</span><span class="ss">packet</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8657330870-27">}</span><span class="p">,</span><span class="w"> </span><span class="ss">binary</span><span class="p" data-group-id="8657330870-26">]</span><span class="p" data-group-id="8657330870-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="8657330870-28">(</span><span class="n">Port</span><span class="p" data-group-id="8657330870-28">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="9274295053-29">(</span><span class="n">Port</span><span class="p" data-group-id="9274295053-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="8657330870-29">(</span><span class="n">Port</span><span class="p" data-group-id="8657330870-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="9274295053-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="9274295053-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9274295053-31">{</span><span class="nf">self</span><span class="p" data-group-id="9274295053-32">(</span><span class="p" data-group-id="9274295053-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9274295053-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="9274295053-34">(</span><span class="n">Msg</span><span class="p" data-group-id="9274295053-34">)</span><span class="p" data-group-id="9274295053-33">}</span><span class="p" data-group-id="9274295053-31">}</span><span class="p">,</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="8657330870-30">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="n">Caller</span><span class="p">,</span><span class="w"> </span><span class="n">Msg</span><span class="p" data-group-id="8657330870-30">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8657330870-31">{</span><span class="nf">self</span><span class="p" data-group-id="8657330870-32">(</span><span class="p" data-group-id="8657330870-32">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8657330870-33">{</span><span class="ss">command</span><span class="p">,</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="8657330870-34">(</span><span class="n">Msg</span><span class="p" data-group-id="8657330870-34">)</span><span class="p" data-group-id="8657330870-33">}</span><span class="p" data-group-id="8657330870-31">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="9274295053-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9274295053-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9274295053-36">}</span><span class="p" data-group-id="9274295053-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9274295053-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9274295053-38">(</span><span class="n">Data</span><span class="p" data-group-id="9274295053-38">)</span><span class="p" data-group-id="9274295053-37">}</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="8657330870-35">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8657330870-36">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8657330870-36">}</span><span class="p" data-group-id="8657330870-35">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="n">Caller</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8657330870-37">{</span><span class="ss">complex</span><span class="p">,</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="8657330870-38">(</span><span class="n">Data</span><span class="p" data-group-id="8657330870-38">)</span><span class="p" data-group-id="8657330870-37">}</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">loop</span><span class="p" data-group-id="9274295053-39">(</span><span class="n">Port</span><span class="p" data-group-id="9274295053-39">)</span><span class="p">;</span><span class="w">
│ │ │ +	    </span><span class="nf">loop</span><span class="p" data-group-id="8657330870-39">(</span><span class="n">Port</span><span class="p" data-group-id="8657330870-39">)</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">stop</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9274295053-40">{</span><span class="nf">self</span><span class="p" data-group-id="9274295053-41">(</span><span class="p" data-group-id="9274295053-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="9274295053-40">}</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="n">Port</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8657330870-40">{</span><span class="nf">self</span><span class="p" data-group-id="8657330870-41">(</span><span class="p" data-group-id="8657330870-41">)</span><span class="p">,</span><span class="w"> </span><span class="ss">close</span><span class="p" data-group-id="8657330870-40">}</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="k">receive</span><span class="w">
│ │ │ -		</span><span class="p" data-group-id="9274295053-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="9274295053-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -		    </span><span class="nf">exit</span><span class="p" data-group-id="9274295053-43">(</span><span class="ss">normal</span><span class="p" data-group-id="9274295053-43">)</span><span class="w">
│ │ │ +		</span><span class="p" data-group-id="8657330870-42">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="ss">closed</span><span class="p" data-group-id="8657330870-42">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +		    </span><span class="nf">exit</span><span class="p" data-group-id="8657330870-43">(</span><span class="ss">normal</span><span class="p" data-group-id="8657330870-43">)</span><span class="w">
│ │ │  	    </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="9274295053-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9274295053-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="nf">exit</span><span class="p" data-group-id="9274295053-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="9274295053-45">)</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="8657330870-44">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="8657330870-44">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	    </span><span class="nf">exit</span><span class="p" data-group-id="8657330870-45">(</span><span class="ss">port_terminated</span><span class="p" data-group-id="8657330870-45">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Notice that calling <code class="inline">complex2:foo/1</code> and <code class="inline">complex2:bar/1</code> results in the tuple
│ │ │  <code class="inline">{foo,X}</code> or <code class="inline">{bar,Y}</code> being sent to the <code class="inline">complex</code> process, which codes them as
│ │ │  binaries and sends them to the port. This means that the C program must be able
│ │ │  to handle these two tuples.</p><h2 id="c-program" class="section-heading">
│ │ │    <a href="#c-program" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -362,27 +362,27 @@
│ │ │      -L/usr/local/otp/lib/erl_interface-3.9.2/lib \
│ │ │      complex.c erl_comm.c ei.c -lei -lpthread</code></pre><p>In Erlang/OTP R5B and later versions of OTP, the <code class="inline">include</code> and <code class="inline">lib</code> directories
│ │ │  are situated under <code class="inline">$OTPROOT/lib/erl_interface-VSN</code>, where <code class="inline">$OTPROOT</code> is the
│ │ │  root directory of the OTP installation (<code class="inline">/usr/local/otp</code> in the recent example)
│ │ │  and <code class="inline">VSN</code> is the version of the Erl_interface application (3.2.1 in the recent
│ │ │  example).</p><p>In R4B and earlier versions of OTP, <code class="inline">include</code> and <code class="inline">lib</code> are situated under
│ │ │  <code class="inline">$OTPROOT/usr</code>.</p><p><em>Step 2.</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="3828003632-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="3828003632-1">]</span><span class="w"> </span><span class="p" data-group-id="3828003632-2">[</span><span class="ss">source</span><span class="p" data-group-id="3828003632-2">]</span><span class="w"> </span><span class="p" data-group-id="3828003632-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="3828003632-3">]</span><span class="w"> </span><span class="p" data-group-id="3828003632-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3828003632-4">]</span><span class="w"> </span><span class="p" data-group-id="3828003632-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="3828003632-5">]</span><span class="w"> </span><span class="p" data-group-id="3828003632-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="3828003632-6">]</span><span class="w"> </span><span class="p" data-group-id="3828003632-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="3828003632-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="p" data-group-id="5869568532-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">14.2</span><span class="p" data-group-id="5869568532-1">]</span><span class="w"> </span><span class="p" data-group-id="5869568532-2">[</span><span class="ss">source</span><span class="p" data-group-id="5869568532-2">]</span><span class="w"> </span><span class="p" data-group-id="5869568532-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="5869568532-3">]</span><span class="w"> </span><span class="p" data-group-id="5869568532-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="5869568532-4">]</span><span class="w"> </span><span class="p" data-group-id="5869568532-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="5869568532-5">]</span><span class="w"> </span><span class="p" data-group-id="5869568532-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5869568532-6">]</span><span class="w"> </span><span class="p" data-group-id="5869568532-7">[</span><span class="nc">jit</span><span class="p">:</span><span class="ss">ns</span><span class="p" data-group-id="5869568532-7">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="3828003632-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="3828003632-9">(</span><span class="p" data-group-id="3828003632-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="3828003632-8">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="3828003632-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="3828003632-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3828003632-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="3828003632-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="6873749247-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="6873749247-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V14</span><span class="p">.</span><span class="mi">2</span><span class="w"> </span><span class="p" data-group-id="5869568532-8">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="5869568532-9">(</span><span class="p" data-group-id="5869568532-9">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="5869568532-8">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="5869568532-10">(</span><span class="ss">complex2</span><span class="p" data-group-id="5869568532-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5869568532-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex2</span><span class="p" data-group-id="5869568532-11">}</span></code></pre><p><em>Step 3.</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="0062701031-1">(</span><span class="s">&quot;./extprg&quot;</span><span class="p" data-group-id="0062701031-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.34</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="6873749247-2">(</span><span class="mi">3</span><span class="p" data-group-id="6873749247-2">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="0062701031-2">(</span><span class="mi">3</span><span class="p" data-group-id="0062701031-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="6873749247-3">(</span><span class="mi">5</span><span class="p" data-group-id="6873749247-3">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="0062701031-3">(</span><span class="mi">5</span><span class="p" data-group-id="0062701031-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="6873749247-4">(</span><span class="mi">352</span><span class="p" data-group-id="6873749247-4">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="0062701031-4">(</span><span class="mi">352</span><span class="p" data-group-id="0062701031-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">704</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6873749247-5">(</span><span class="p" data-group-id="6873749247-5">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nc">complex2</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="0062701031-5">(</span><span class="p" data-group-id="0062701031-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">stop</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="c_port.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/error_logging.html
│ │ │ @@ -143,39 +143,39 @@
│ │ │  reports and other error and information reports are by default logged through
│ │ │  the log handler which is set up when the Kernel application is started.</p><p>Prior to Erlang/OTP 21.0, supervisor, crash, and progress reports were only
│ │ │  logged when the SASL application was running. This behaviour can, for backwards
│ │ │  compatibility, be enabled by setting the Kernel configuration parameter
│ │ │  <a href="../../lib/kernel-10.2.7.2/doc/html/kernel_app.html#logger_sasl_compatible"><code class="inline">logger_sasl_compatible</code></a> to
│ │ │  <code class="inline">true</code>. For more information, see
│ │ │  <a href="../../lib/sasl-4.2.2/doc/html/error_logging.html">SASL Error Logging</a> in the SASL User's Guide.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -kernel logger_level info</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">21</span><span class="w"> </span><span class="p" data-group-id="8852695614-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">10.0</span><span class="p" data-group-id="8852695614-1">]</span><span class="w"> </span><span class="p" data-group-id="8852695614-2">[</span><span class="ss">source</span><span class="o">-</span><span class="mi">13</span><span class="ss">c50db</span><span class="p" data-group-id="8852695614-2">]</span><span class="w"> </span><span class="p" data-group-id="8852695614-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="8852695614-3">]</span><span class="w"> </span><span class="p" data-group-id="8852695614-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="8852695614-4">]</span><span class="w"> </span><span class="p" data-group-id="8852695614-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="8852695614-5">]</span><span class="w"> </span><span class="p" data-group-id="8852695614-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="8852695614-6">]</span><span class="w"> </span><span class="p" data-group-id="8852695614-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="8852695614-7">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">21</span><span class="w"> </span><span class="p" data-group-id="0039183344-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">10.0</span><span class="p" data-group-id="0039183344-1">]</span><span class="w"> </span><span class="p" data-group-id="0039183344-2">[</span><span class="ss">source</span><span class="o">-</span><span class="mi">13</span><span class="ss">c50db</span><span class="p" data-group-id="0039183344-2">]</span><span class="w"> </span><span class="p" data-group-id="0039183344-3">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0039183344-3">]</span><span class="w"> </span><span class="p" data-group-id="0039183344-4">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="0039183344-4">]</span><span class="w"> </span><span class="p" data-group-id="0039183344-5">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0039183344-5">]</span><span class="w"> </span><span class="p" data-group-id="0039183344-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="0039183344-6">]</span><span class="w"> </span><span class="p" data-group-id="0039183344-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="0039183344-7">]</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.916404</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │      </span><span class="nc">application</span><span class="p">:</span><span class="w"> </span><span class="ss">kernel</span><span class="w">
│ │ │      </span><span class="nc">started_at</span><span class="p">:</span><span class="w"> </span><span class="ss">nonode@nohost</span><span class="w">
│ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.922908</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │      </span><span class="nc">application</span><span class="p">:</span><span class="w"> </span><span class="ss">stdlib</span><span class="w">
│ │ │      </span><span class="nc">started_at</span><span class="p">:</span><span class="w"> </span><span class="ss">nonode@nohost</span><span class="w">
│ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.925755</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8852695614-8">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="8852695614-8">}</span><span class="w">
│ │ │ -    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8852695614-9">[</span><span class="p" data-group-id="8852695614-10">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.74</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="8852695614-10">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-11">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_sup</span><span class="p" data-group-id="8852695614-11">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-12">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="8852695614-13">{</span><span class="ss">disk_log_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="8852695614-14">[</span><span class="p" data-group-id="8852695614-14">]</span><span class="p" data-group-id="8852695614-13">}</span><span class="p" data-group-id="8852695614-12">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-15">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="8852695614-15">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-16">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">1000</span><span class="p" data-group-id="8852695614-16">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-17">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">supervisor</span><span class="p" data-group-id="8852695614-17">}</span><span class="p" data-group-id="8852695614-9">]</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0039183344-8">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="0039183344-8">}</span><span class="w">
│ │ │ +    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0039183344-9">[</span><span class="p" data-group-id="0039183344-10">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.74</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0039183344-10">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-11">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_sup</span><span class="p" data-group-id="0039183344-11">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-12">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="0039183344-13">{</span><span class="ss">disk_log_sup</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="0039183344-14">[</span><span class="p" data-group-id="0039183344-14">]</span><span class="p" data-group-id="0039183344-13">}</span><span class="p" data-group-id="0039183344-12">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-15">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="0039183344-15">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-16">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">1000</span><span class="p" data-group-id="0039183344-16">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-17">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">supervisor</span><span class="p" data-group-id="0039183344-17">}</span><span class="p" data-group-id="0039183344-9">]</span><span class="w">
│ │ │  </span><span class="o">=</span><span class="n">PROGRESS</span><span class="w"> </span><span class="n">REPORT</span><span class="o">==</span><span class="o">==</span><span class="w"> </span><span class="mi">8</span><span class="o">-</span><span class="n">Jun</span><span class="o">-</span><span class="mi">2018</span><span class="p">:</span><span class="p">:</span><span class="mi">16</span><span class="p">:</span><span class="mi">54</span><span class="p">:</span><span class="mf">19.926056</span><span class="w"> </span><span class="o">==</span><span class="o">=</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8852695614-18">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="8852695614-18">}</span><span class="w">
│ │ │ -    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8852695614-19">[</span><span class="p" data-group-id="8852695614-20">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.75</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="8852695614-20">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-21">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_server</span><span class="p" data-group-id="8852695614-21">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-22">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="8852695614-23">{</span><span class="ss">disk_log_server</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="8852695614-24">[</span><span class="p" data-group-id="8852695614-24">]</span><span class="p" data-group-id="8852695614-23">}</span><span class="p" data-group-id="8852695614-22">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-25">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="8852695614-25">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-26">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">2000</span><span class="p" data-group-id="8852695614-26">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="8852695614-27">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">worker</span><span class="p" data-group-id="8852695614-27">}</span><span class="p" data-group-id="8852695614-19">]</span><span class="w">
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V10</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="8852695614-28">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="8852695614-28">)</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0039183344-18">{</span><span class="ss">local</span><span class="p">,</span><span class="ss">kernel_safe_sup</span><span class="p" data-group-id="0039183344-18">}</span><span class="w">
│ │ │ +    </span><span class="nc">started</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0039183344-19">[</span><span class="p" data-group-id="0039183344-20">{</span><span class="ss">pid</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.75</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0039183344-20">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-21">{</span><span class="ss">id</span><span class="p">,</span><span class="ss">disk_log_server</span><span class="p" data-group-id="0039183344-21">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-22">{</span><span class="ss">mfargs</span><span class="p">,</span><span class="p" data-group-id="0039183344-23">{</span><span class="ss">disk_log_server</span><span class="p">,</span><span class="ss">start_link</span><span class="p">,</span><span class="p" data-group-id="0039183344-24">[</span><span class="p" data-group-id="0039183344-24">]</span><span class="p" data-group-id="0039183344-23">}</span><span class="p" data-group-id="0039183344-22">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-25">{</span><span class="ss">restart_type</span><span class="p">,</span><span class="ss">permanent</span><span class="p" data-group-id="0039183344-25">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-26">{</span><span class="ss">shutdown</span><span class="p">,</span><span class="mi">2000</span><span class="p" data-group-id="0039183344-26">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0039183344-27">{</span><span class="ss">child_type</span><span class="p">,</span><span class="ss">worker</span><span class="p" data-group-id="0039183344-27">}</span><span class="p" data-group-id="0039183344-19">]</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V10</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="0039183344-28">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="0039183344-28">)</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="o">&gt;</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="system_principles.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/errors.html
│ │ │ @@ -151,22 +151,22 @@
│ │ │  classes, with different origins. The <a href="expressions.html#try">try</a> expression can
│ │ │  distinguish between the different classes, whereas the
│ │ │  <a href="expressions.html#catch-and-throw">catch</a> expression cannot. <code class="inline">try</code> and <code class="inline">catch</code> are described
│ │ │  in <a href="expressions.html">Expressions</a>.</p><table><thead><tr><th style="text-align: left;"><em>Class</em></th><th style="text-align: left;"><em>Origin</em></th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">error</code></td><td style="text-align: left;">Run-time error, for example, <code class="inline">1+a</code>, or the process called <a href="../../erts-15.2.7.2/doc/html/erlang.html#error/1"><code class="inline">error/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">exit</code></td><td style="text-align: left;">The process called <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit/1</code></a></td></tr><tr><td style="text-align: left;"><code class="inline">throw</code></td><td style="text-align: left;">The process called <a href="../../erts-15.2.7.2/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a></td></tr></tbody></table><p><em>Table: Exception Classes.</em></p><p>All of the above exceptions can also be generated by calling <a href="../../erts-15.2.7.2/doc/html/erlang.html#raise/3"><code class="inline">erlang:raise/3</code></a>.</p><p>An exception consists of its class, an exit reason (see
│ │ │  <a href="errors.html#exit_reasons">Exit Reason</a>), and a stack trace (which aids in finding
│ │ │  the code location of the exception).</p><p>The stack trace can be bound to a variable from within a <code class="inline">try</code> expression for
│ │ │  any exception class, or as part of the exit reason when a run-time error is
│ │ │ -caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="6989212217-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6989212217-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="6989212217-2">}</span><span class="p" data-group-id="6989212217-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6989212217-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="6989212217-4">(</span><span class="ss">test</span><span class="p" data-group-id="6989212217-4">)</span><span class="p" data-group-id="6989212217-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6989212217-5">[</span><span class="p" data-group-id="6989212217-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="6989212217-7">[</span><span class="p" data-group-id="6989212217-7">]</span><span class="p" data-group-id="6989212217-6">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6989212217-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="6989212217-9">[</span><span class="p" data-group-id="6989212217-9">]</span><span class="p" data-group-id="6989212217-8">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6989212217-5">]</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="6989212217-10">(</span><span class="ss">test</span><span class="p" data-group-id="6989212217-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6989212217-11">[</span><span class="p" data-group-id="6989212217-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="6989212217-13">[</span><span class="p" data-group-id="6989212217-13">]</span><span class="p" data-group-id="6989212217-12">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6989212217-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="6989212217-15">[</span><span class="p" data-group-id="6989212217-15">]</span><span class="p" data-group-id="6989212217-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6989212217-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-back-trace-stacktrace" class="section-heading">
│ │ │ +caught by a <code class="inline">catch</code>. Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="0734335525-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="0734335525-2">{</span><span class="ss">test</span><span class="p">,</span><span class="n">Stacktrace</span><span class="p" data-group-id="0734335525-2">}</span><span class="p" data-group-id="0734335525-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0734335525-3">(</span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="0734335525-4">(</span><span class="ss">test</span><span class="p" data-group-id="0734335525-4">)</span><span class="p" data-group-id="0734335525-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Stacktrace</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0734335525-5">[</span><span class="p" data-group-id="0734335525-6">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="0734335525-7">[</span><span class="p" data-group-id="0734335525-7">]</span><span class="p" data-group-id="0734335525-6">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0734335525-8">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="0734335525-9">[</span><span class="p" data-group-id="0734335525-9">]</span><span class="p" data-group-id="0734335525-8">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0734335525-5">]</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="k">try</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="0734335525-10">(</span><span class="ss">test</span><span class="p" data-group-id="0734335525-10">)</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="n">Class</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stacktrace</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Stacktrace</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0734335525-11">[</span><span class="p" data-group-id="0734335525-12">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="0734335525-13">[</span><span class="p" data-group-id="0734335525-13">]</span><span class="p" data-group-id="0734335525-12">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0734335525-14">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="0734335525-15">[</span><span class="p" data-group-id="0734335525-15">]</span><span class="p" data-group-id="0734335525-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0734335525-11">]</span></code></pre><p><a href="" id="stacktrace"></a></p><h3 id="the-call-stack-back-trace-stacktrace" class="section-heading">
│ │ │    <a href="#the-call-stack-back-trace-stacktrace" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The call-stack back trace (stacktrace)</span>
│ │ │  </h3>
│ │ │  <p>The stack back-trace (<a href="../../erts-15.2.7.2/doc/html/erlang.html#t:stacktrace/0"><em>stacktrace</em></a>) is a list that
│ │ │  contains <code class="inline">{Module, Function, Arity, ExtraInfo}</code> and/or <code class="inline">{Fun, Arity, ExtraInfo}</code>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/events.html
│ │ │ @@ -135,43 +135,43 @@
│ │ │  event handler.</p><h2 id="example" class="section-heading">
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │  <p>The callback module for the event handler writing error messages to the terminal
│ │ │ -can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8801268211-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="8801268211-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8801268211-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="8801268211-2">)</span><span class="p">.</span><span class="w">
│ │ │ +can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0409046796-1">(</span><span class="ss">terminal_logger</span><span class="p" data-group-id="0409046796-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0409046796-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="0409046796-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8801268211-3">(</span><span class="p" data-group-id="8801268211-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8801268211-4">]</span><span class="p" data-group-id="8801268211-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0409046796-3">(</span><span class="p" data-group-id="0409046796-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0409046796-4">]</span><span class="p" data-group-id="0409046796-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8801268211-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8801268211-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8801268211-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8801268211-7">[</span><span class="p" data-group-id="8801268211-7">]</span><span class="p" data-group-id="8801268211-6">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="0409046796-5">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="0409046796-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0409046796-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0409046796-7">[</span><span class="p" data-group-id="0409046796-7">]</span><span class="p" data-group-id="0409046796-6">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="8801268211-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8801268211-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8801268211-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8801268211-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="8801268211-10">]</span><span class="p" data-group-id="8801268211-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8801268211-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="8801268211-11">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0409046796-8">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0409046796-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0409046796-9">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0409046796-10">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="0409046796-10">]</span><span class="p" data-group-id="0409046796-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0409046796-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0409046796-11">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="8801268211-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="8801268211-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="0409046796-12">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="0409046796-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback module for the event handler writing error messages to a file can
│ │ │ -look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0821396548-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="0821396548-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0821396548-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="0821396548-2">)</span><span class="p">.</span><span class="w">
│ │ │ +look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8271284389-1">(</span><span class="ss">file_logger</span><span class="p" data-group-id="8271284389-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8271284389-2">(</span><span class="ss">gen_event</span><span class="p" data-group-id="8271284389-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0821396548-3">(</span><span class="p" data-group-id="0821396548-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0821396548-4">]</span><span class="p" data-group-id="0821396548-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8271284389-3">(</span><span class="p" data-group-id="8271284389-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8271284389-4">]</span><span class="p" data-group-id="8271284389-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="0821396548-5">(</span><span class="n">File</span><span class="p" data-group-id="0821396548-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0821396548-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0821396548-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="0821396548-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="0821396548-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0821396548-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0821396548-8">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="0821396548-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0821396548-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0821396548-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0821396548-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="0821396548-11">]</span><span class="p" data-group-id="0821396548-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0821396548-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0821396548-12">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8271284389-5">(</span><span class="n">File</span><span class="p" data-group-id="8271284389-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8271284389-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8271284389-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="8271284389-7">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="8271284389-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8271284389-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8271284389-8">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8271284389-9">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8271284389-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8271284389-10">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8271284389-11">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="8271284389-11">]</span><span class="p" data-group-id="8271284389-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8271284389-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8271284389-12">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="0821396548-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="0821396548-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="0821396548-14">(</span><span class="n">Fd</span><span class="p" data-group-id="0821396548-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="8271284389-13">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8271284389-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="8271284389-14">(</span><span class="n">Fd</span><span class="p" data-group-id="8271284389-14">)</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><p><a href="" id="mgr"></a></p><h2 id="starting-an-event-manager" class="section-heading">
│ │ │    <a href="#starting-an-event-manager" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting an Event Manager</span>
│ │ │  </h2>
│ │ │  <p>To start an event manager for handling errors, as described in the previous
│ │ │  example, call the following function:</p><pre><code class="text">gen_event:start_link({local, error_man})</code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_event.html#start_link/1"><code class="inline">gen_event:start_link/1</code></a> spawns and links to a new event manager process.</p><p>The argument, <code class="inline">{local, error_man}</code>, specifies the name under which the
│ │ │ @@ -184,57 +184,57 @@
│ │ │  manager that is not part of a supervision tree.</p><h2 id="adding-an-event-handler" class="section-heading">
│ │ │    <a href="#adding-an-event-handler" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding an Event Handler</span>
│ │ │  </h2>
│ │ │  <p>The following example shows how to start an event manager and add an event
│ │ │ -handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="1813549444-1">(</span><span class="p" data-group-id="1813549444-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="1813549444-2">}</span><span class="p" data-group-id="1813549444-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1813549444-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1813549444-3">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="1813549444-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1813549444-5">[</span><span class="p" data-group-id="1813549444-5">]</span><span class="p" data-group-id="1813549444-4">)</span><span class="p">.</span><span class="w">
│ │ │ +handler to it by using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="5913993968-1">(</span><span class="p" data-group-id="5913993968-2">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="5913993968-2">}</span><span class="p" data-group-id="5913993968-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5913993968-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.31</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5913993968-3">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">add_handler</span><span class="p" data-group-id="5913993968-4">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5913993968-5">[</span><span class="p" data-group-id="5913993968-5">]</span><span class="p" data-group-id="5913993968-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │  telling it to add the event handler <code class="inline">terminal_logger</code>. The event manager calls
│ │ │  the callback function <code class="inline">terminal_logger:init([])</code>, where the argument <code class="inline">[]</code> is the
│ │ │  third argument to <code class="inline">add_handler</code>. <code class="inline">init/1</code> is expected to return <code class="inline">{ok, State}</code>,
│ │ │ -where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4247841373-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4247841373-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4247841373-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4247841373-3">[</span><span class="p" data-group-id="4247841373-3">]</span><span class="p" data-group-id="4247841373-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │ +where <code class="inline">State</code> is the internal state of the event handler.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="8490095818-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="8490095818-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8490095818-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8490095818-3">[</span><span class="p" data-group-id="8490095818-3">]</span><span class="p" data-group-id="8490095818-2">}</span><span class="p">.</span></code></pre><p>Here, <code class="inline">init/1</code> does not need any input data and ignores its argument. For
│ │ │  <code class="inline">terminal_logger</code>, the internal state is not used. For <code class="inline">file_logger</code>, the
│ │ │ -internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1768055367-1">(</span><span class="n">File</span><span class="p" data-group-id="1768055367-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1768055367-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1768055367-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1768055367-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="1768055367-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1768055367-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1768055367-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │ +internal state is used to save the open file descriptor.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7374405212-1">(</span><span class="n">File</span><span class="p" data-group-id="7374405212-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7374405212-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7374405212-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="7374405212-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">read</span><span class="p" data-group-id="7374405212-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7374405212-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="7374405212-4">}</span><span class="p">.</span></code></pre><h2 id="notifying-about-events" class="section-heading">
│ │ │    <a href="#notifying-about-events" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Notifying about Events</span>
│ │ │  </h2>
│ │ │  <pre><code class="text">3&gt; gen_event:notify(error_man, no_reply).
│ │ │  ***Error*** no_reply
│ │ │  ok</code></pre><p><code class="inline">error_man</code> is the name of the event manager and <code class="inline">no_reply</code> is the event.</p><p>The event is made into a message and sent to the event manager. When the event
│ │ │  is received, the event manager calls <code class="inline">handle_event(Event, State)</code> for each
│ │ │  installed event handler, in the same order as they were added. The function is
│ │ │  expected to return a tuple <code class="inline">{ok,State1}</code>, where <code class="inline">State1</code> is a new value for the
│ │ │ -state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="3212152081-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3212152081-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3212152081-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3212152081-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="3212152081-3">]</span><span class="p" data-group-id="3212152081-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3212152081-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="3212152081-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="8500053184-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8500053184-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8500053184-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8500053184-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="8500053184-3">]</span><span class="p" data-group-id="8500053184-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8500053184-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8500053184-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │ +state of the event handler.</p><p>In <code class="inline">terminal_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="9628994210-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9628994210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9628994210-2">(</span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9628994210-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="9628994210-3">]</span><span class="p" data-group-id="9628994210-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9628994210-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9628994210-4">}</span><span class="p">.</span></code></pre><p>In <code class="inline">file_logger</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_event</span><span class="p" data-group-id="1856374019-1">(</span><span class="n">ErrorMsg</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1856374019-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1856374019-2">(</span><span class="n">Fd</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;***Error*** </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1856374019-3">[</span><span class="n">ErrorMsg</span><span class="p" data-group-id="1856374019-3">]</span><span class="p" data-group-id="1856374019-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1856374019-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1856374019-4">}</span><span class="p">.</span></code></pre><h2 id="deleting-an-event-handler" class="section-heading">
│ │ │    <a href="#deleting-an-event-handler" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deleting an Event Handler</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="6897527365-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6897527365-2">[</span><span class="p" data-group-id="6897527365-2">]</span><span class="p" data-group-id="6897527365-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">delete_handler</span><span class="p" data-group-id="3834980521-1">(</span><span class="ss">error_man</span><span class="p">,</span><span class="w"> </span><span class="ss">terminal_logger</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3834980521-2">[</span><span class="p" data-group-id="3834980521-2">]</span><span class="p" data-group-id="3834980521-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>This function sends a message to the event manager registered as <code class="inline">error_man</code>,
│ │ │  telling it to delete the event handler <code class="inline">terminal_logger</code>. The event manager
│ │ │  calls the callback function <code class="inline">terminal_logger:terminate([], State)</code>, where the
│ │ │  argument <code class="inline">[]</code> is the third argument to <code class="inline">delete_handler</code>. <code class="inline">terminate/2</code> is to be
│ │ │  the opposite of <code class="inline">init/1</code> and do any necessary cleaning up. Its return value is
│ │ │ -ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="7865020101-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="7865020101-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="9154298942-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="9154298942-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9154298942-2">(</span><span class="n">Fd</span><span class="p" data-group-id="9154298942-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │ +ignored.</p><p>For <code class="inline">terminal_logger</code>, no cleaning up is necessary:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="3647569232-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p" data-group-id="3647569232-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>For <code class="inline">file_logger</code>, the file descriptor opened in <code class="inline">init</code> must be closed:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="1585134126-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1585134126-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1585134126-2">(</span><span class="n">Fd</span><span class="p" data-group-id="1585134126-2">)</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │    <a href="#stopping" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stopping</span>
│ │ │  </h2>
│ │ │  <p>When an event manager is stopped, it gives each of the installed event handlers
│ │ │  the chance to clean up by calling <code class="inline">terminate/2</code>, the same way as when deleting a
│ │ │ @@ -249,33 +249,33 @@
│ │ │  this is done is defined by a <a href="sup_princ.html#shutdown">shutdown strategy</a> set in
│ │ │  the supervisor.</p><h3 id="standalone-event-managers" class="section-heading">
│ │ │    <a href="#standalone-event-managers" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standalone Event Managers</span>
│ │ │  </h3>
│ │ │ -<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="9419831238-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="9419831238-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>An event manager can also be stopped by calling:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">gen_event</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2330868120-1">(</span><span class="ss">error_man</span><span class="p" data-group-id="2330868120-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><h2 id="handling-other-messages" class="section-heading">
│ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling Other Messages</span>
│ │ │  </h2>
│ │ │  <p>If the <code class="inline">gen_event</code> process is to be able to receive other messages
│ │ │  than events, the callback function <code class="inline">handle_info(Info, State)</code> must be
│ │ │  implemented to handle them. Examples of other messages are exit
│ │ │  messages if the event manager is linked to other processes than the
│ │ │  supervisor (for example via <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_event.html#add_sup_handler/3"><code class="inline">gen_event:add_sup_handler/3</code></a>) and is
│ │ │ -trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="2350512884-1">(</span><span class="p" data-group-id="2350512884-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2350512884-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2350512884-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="9396577466-1">(</span><span class="p" data-group-id="9396577466-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9396577466-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9396577466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2350512884-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="2350512884-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="4981082157-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4981082157-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9396577466-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="9396577466-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="1444475907-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="1444475907-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4981082157-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="4981082157-2">}</span><span class="p">.</span></code></pre>
│ │ │ +    </span><span class="p" data-group-id="1444475907-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="1444475907-2">}</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="statem.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/example.html
│ │ │ @@ -131,15 +131,15 @@
│ │ │  
│ │ │  int bar(int y) {
│ │ │    return y*2;
│ │ │  }</code></pre><p>The functions are deliberately kept as simple as possible, for readability
│ │ │  reasons.</p><p>From an Erlang perspective, it is preferable to be able to call <code class="inline">foo</code> and <code class="inline">bar</code>
│ │ │  without having to bother about that they are C functions:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% Erlang code</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="1002828395-1">(</span><span class="n">X</span><span class="p" data-group-id="1002828395-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">complex</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="2010275129-1">(</span><span class="n">X</span><span class="p" data-group-id="2010275129-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Here, the communication with C is hidden in the implementation of <code class="inline">complex.erl</code>.
│ │ │  In the following sections, it is shown how this module can be implemented using
│ │ │  the different interoperability mechanisms.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/expressions.html
│ │ │ @@ -151,81 +151,81 @@
│ │ │  </span><span class="n">Phone_number</span><span class="w">
│ │ │  </span><span class="p">_</span><span class="w">
│ │ │  </span><span class="p">_</span><span class="n">Height</span><span class="w">
│ │ │  </span><span class="ss">name@node</span></code></pre><p>Variables are bound to values using <a href="patterns.html">pattern matching</a>. Erlang uses
│ │ │  <em>single assignment</em>, that is, a variable can only be bound once.</p><p>The <em>anonymous variable</em> is denoted by underscore (_) and can be used when a
│ │ │  variable is required but its value can be ignored.</p><p><em>Example:</em></p><pre><code class="text">[H|_] = [1,2,3]</code></pre><p>Variables starting with underscore (<code class="inline">_</code>), for example, <code class="inline">_Height</code>, are normal
│ │ │  variables, not anonymous. However, they are ignored by the compiler in the sense
│ │ │ -that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="6560435105-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6560435105-2">[</span><span class="p" data-group-id="6560435105-2">]</span><span class="p" data-group-id="6560435105-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6560435105-3">[</span><span class="p" data-group-id="6560435105-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="2719691681-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2719691681-2">[</span><span class="p" data-group-id="2719691681-2">]</span><span class="p" data-group-id="2719691681-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2719691681-3">[</span><span class="p" data-group-id="2719691681-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ -the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="0348909720-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0348909720-2">[</span><span class="p" data-group-id="0348909720-2">]</span><span class="p" data-group-id="0348909720-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0348909720-3">[</span><span class="p" data-group-id="0348909720-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ -following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9013078034-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9013078034-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9013078034-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9013078034-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5973134954-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="5973134954-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5973134954-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5973134954-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │ +that they do not generate warnings.</p><p><em>Example:</em></p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="1864182421-1">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1864182421-2">[</span><span class="p" data-group-id="1864182421-2">]</span><span class="p" data-group-id="1864182421-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1864182421-3">[</span><span class="p" data-group-id="1864182421-3">]</span><span class="p">.</span></code></pre><p>can be rewritten to be more readable:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="8140982773-1">(</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8140982773-2">[</span><span class="p" data-group-id="8140982773-2">]</span><span class="p" data-group-id="8140982773-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8140982773-3">[</span><span class="p" data-group-id="8140982773-3">]</span><span class="p">.</span></code></pre><p>This causes a warning for an unused variable, <code class="inline">Elem</code>. To avoid the warning,
│ │ │ +the code can be rewritten to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">member</span><span class="p" data-group-id="1767073621-1">(</span><span class="p">_</span><span class="n">Elem</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1767073621-2">[</span><span class="p" data-group-id="1767073621-2">]</span><span class="p" data-group-id="1767073621-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1767073621-3">[</span><span class="p" data-group-id="1767073621-3">]</span><span class="p">.</span></code></pre><p>Notice that since variables starting with an underscore are not anonymous, the
│ │ │ +following example matches:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9850353343-1">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9850353343-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9850353343-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9850353343-2">}</span></code></pre><p>But this example fails:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7787459833-1">{</span><span class="p">_</span><span class="n">N</span><span class="p">,</span><span class="p">_</span><span class="n">N</span><span class="p" data-group-id="7787459833-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7787459833-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7787459833-2">}</span></code></pre><p>The scope for a variable is its function clause. Variables bound in a branch of
│ │ │  an <code class="inline">if</code>, <code class="inline">case</code>, or <code class="inline">receive</code> expression must be bound in all branches to have a
│ │ │  value outside the expression. Otherwise they are regarded as unsafe outside
│ │ │  the expression.</p><p>For the <code class="inline">try</code> expression variable scoping is limited so that variables bound in
│ │ │  the expression are always unsafe outside the expression.</p><h2 id="patterns" class="section-heading">
│ │ │    <a href="#patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Patterns</span>
│ │ │  </h2>
│ │ │  <p>A pattern has the same structure as a term but can contain unbound variables.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">Name1</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3213169006-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3213169006-1">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3213169006-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="3213169006-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.html#case">case expressions</a>,
│ │ │ +</span><span class="p" data-group-id="8263375096-1">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8263375096-1">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8263375096-2">{</span><span class="ss">error</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="8263375096-2">}</span></code></pre><p>Patterns are allowed in clause heads, <a href="expressions.html#case">case expressions</a>,
│ │ │  <a href="expressions.html#receive">receive expressions</a>, and
│ │ │  <a href="expressions.html#the-match-operator">match expressions</a>.</p><h3 id="the-compound-pattern-operator" class="section-heading">
│ │ │    <a href="#the-compound-pattern-operator" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The Compound Pattern Operator</span>
│ │ │  </h3>
│ │ │  <p>If <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are valid patterns, the following is also a valid
│ │ │  pattern:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span></code></pre><p>When matched against a term, both <code class="inline">Pattern1</code> and <code class="inline">Pattern2</code> are matched against
│ │ │ -the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4265496963-1">(</span><span class="p" data-group-id="4265496963-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="4265496963-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4265496963-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4265496963-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="4265496963-3">}</span><span class="p">,</span><span class="w">
│ │ │ +the term. The idea behind this feature is to avoid reconstruction of terms.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7056969896-1">(</span><span class="p" data-group-id="7056969896-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="7056969896-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7056969896-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Signal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7056969896-3">{</span><span class="ss">connect</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="n">Number</span><span class="p">,</span><span class="n">Options</span><span class="p" data-group-id="7056969896-3">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="4265496963-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="4265496963-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="9647756345-1">(</span><span class="p" data-group-id="9647756345-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9647756345-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9647756345-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="7056969896-4">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7056969896-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>can instead be written as</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1415153703-1">(</span><span class="p" data-group-id="1415153703-2">{</span><span class="ss">connect</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="n">To</span><span class="p">,</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1415153703-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1415153703-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="9647756345-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9647756345-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="1415153703-3">(</span><span class="n">Signal</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="1415153703-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ignore</span><span class="p">.</span></code></pre><p>The compound pattern operator does not imply that its operands are matched in
│ │ │  any particular order. That means that it is not legal to bind a variable in
│ │ │  <code class="inline">Pattern1</code> and use it in <code class="inline">Pattern2</code>, or vice versa.</p><h3 id="string-prefix-in-patterns" class="section-heading">
│ │ │    <a href="#string-prefix-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">String Prefix in Patterns</span>
│ │ │  </h3>
│ │ │ -<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7370479830-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="7370479830-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="5669243206-1">(</span><span class="p" data-group-id="5669243206-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="5669243206-2">]</span><span class="p" data-group-id="5669243206-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │ +<p>When matching strings, the following is a valid pattern:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="5733717939-1">(</span><span class="s">&quot;prefix&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="5733717939-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This is syntactic sugar for the equivalent, but harder to read:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4010905920-1">(</span><span class="p" data-group-id="4010905920-2">[</span><span class="sc">$p</span><span class="p">,</span><span class="sc">$r</span><span class="p">,</span><span class="sc">$e</span><span class="p">,</span><span class="sc">$f</span><span class="p">,</span><span class="sc">$i</span><span class="p">,</span><span class="sc">$x</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Str</span><span class="p" data-group-id="4010905920-2">]</span><span class="p" data-group-id="4010905920-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h3 id="expressions-in-patterns" class="section-heading">
│ │ │    <a href="#expressions-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Expressions in Patterns</span>
│ │ │  </h3>
│ │ │  <p>An arithmetic expression can be used within a pattern if it meets both of the
│ │ │ -following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when complied.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="7787633041-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="7787633041-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7787633041-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="7787633041-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │ +following two conditions:</p><ul><li>It uses only numeric or bitwise operators.</li><li>Its value can be evaluated to a constant when complied.</li></ul><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="p" data-group-id="3465105712-1">{</span><span class="n">Value</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="3465105712-1">}</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3465105712-2">{</span><span class="o">?</span><span class="n">THRESHOLD</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="3465105712-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="the-match-operator" class="section-heading">
│ │ │    <a href="#the-match-operator" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The Match Operator</span>
│ │ │  </h2>
│ │ │  <p>The following matches <code class="inline">Pattern</code> against <code class="inline">Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>If the matching succeeds, any unbound variable in the pattern becomes bound and
│ │ │  the value of <code class="inline">Expr</code> is returned.</p><p>If multiple match operators are applied in sequence, they will be evaluated from
│ │ │ -right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7523487115-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="7523487115-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7523487115-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7523487115-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7523487115-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7523487115-3">}</span><span class="gp unselectable">
│ │ │ +right to left.</p><p>If the matching fails, a <code class="inline">badmatch</code> run-time error occurs.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8403244836-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8403244836-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8403244836-2">{</span><span class="ss">answer</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="8403244836-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8403244836-3">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8403244836-3">}</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">answer</span><span class="gp unselectable">
│ │ │  3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │  4&gt; </span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7523487115-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7523487115-4">}</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="p" data-group-id="7523487115-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="7523487115-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7523487115-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7523487115-6">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8403244836-4">{</span><span class="ss">answer</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="8403244836-4">}</span><span class="gp unselectable">
│ │ │ +5&gt; </span><span class="p" data-group-id="8403244836-5">{</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="8403244836-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8403244836-6">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8403244836-6">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right-hand side value [1,2]</span></code></pre><p>Because multiple match operators are evaluated from right to left, it means
│ │ │  that:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span></code></pre><p>is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="n">Temporary</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expression</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">PatternN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Pattern2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Temporary</span><span class="p">,</span><span class="w">
│ │ │ @@ -239,30 +239,30 @@
│ │ │  can safely be skipped on a first reading.</p></section><p>The <code class="inline">=</code> character is used to denote two similar but distinct operators: the
│ │ │  match operator and the compound pattern operator. Which one is meant is
│ │ │  determined by context.</p><p>The <em>compound pattern operator</em> is used to construct a compound pattern from two
│ │ │  patterns. Compound patterns are accepted everywhere a pattern is accepted. A
│ │ │  compound pattern matches if all of its constituent patterns match. It is not
│ │ │  legal for a pattern that is part of a compound pattern to use variables (as keys
│ │ │  in map patterns or sizes in binary patterns) bound in other sub patterns of the
│ │ │ -same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="3192382974-1">(</span><span class="p" data-group-id="3192382974-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="3192382974-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3192382974-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="3192382974-3">}</span><span class="p" data-group-id="3192382974-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +same compound pattern.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">fun</span><span class="p" data-group-id="1609433449-1">(</span><span class="p" data-group-id="1609433449-2">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="1609433449-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1609433449-3">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="1609433449-3">}</span><span class="p" data-group-id="1609433449-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:7: variable &#39;Key&#39; is unbound</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3192382974-4">(</span><span class="p" data-group-id="3192382974-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3192382974-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="3192382974-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3192382974-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3192382974-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3192382974-7">(</span><span class="p" data-group-id="3192382974-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3192382974-8">}</span><span class="p" data-group-id="3192382974-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3192382974-9">{</span><span class="p" data-group-id="3192382974-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3192382974-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3192382974-9">}</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3192382974-11">(</span><span class="p" data-group-id="3192382974-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="3192382974-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3192382974-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="3192382974-13">&gt;&gt;</span><span class="p" data-group-id="3192382974-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3192382974-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="3192382974-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="3192382974-15">(</span><span class="p" data-group-id="3192382974-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="3192382974-16">&gt;&gt;</span><span class="p" data-group-id="3192382974-15">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3192382974-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="3192382974-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │ +2&gt; </span><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1609433449-4">(</span><span class="p" data-group-id="1609433449-5">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1609433449-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="1609433449-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1609433449-6">{</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="1609433449-6">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1609433449-7">(</span><span class="p" data-group-id="1609433449-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1609433449-8">}</span><span class="p" data-group-id="1609433449-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1609433449-9">{</span><span class="p" data-group-id="1609433449-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1609433449-10">}</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1609433449-9">}</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="n">G</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1609433449-11">(</span><span class="p" data-group-id="1609433449-12">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="n">B</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1609433449-12">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1609433449-13">&lt;&lt;</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1609433449-13">&gt;&gt;</span><span class="p" data-group-id="1609433449-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1609433449-14">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="1609433449-14">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">G</span><span class="p" data-group-id="1609433449-15">(</span><span class="p" data-group-id="1609433449-16">&lt;&lt;</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p" data-group-id="1609433449-16">&gt;&gt;</span><span class="p" data-group-id="1609433449-15">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1609433449-17">{</span><span class="mi">42</span><span class="p">,</span><span class="mi">43</span><span class="p">,</span><span class="mi">10795</span><span class="p" data-group-id="1609433449-17">}</span></code></pre><p>The <em>match operator</em> is allowed everywhere an expression is allowed. It is used
│ │ │  to match the value of an expression to a pattern. If multiple match operators
│ │ │ -are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0173422378-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="0173422378-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0173422378-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="0173422378-2">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">f</span><span class="p" data-group-id="0173422378-3">(</span><span class="n">Key</span><span class="p" data-group-id="0173422378-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0173422378-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0173422378-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0173422378-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="0173422378-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ +are applied in sequence, they will be evaluated from right to left.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7201536388-1">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="7201536388-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7201536388-2">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">key2</span><span class="p">,</span><span class="ss">key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="7201536388-2">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nf">f</span><span class="p" data-group-id="7201536388-3">(</span><span class="n">Key</span><span class="p" data-group-id="7201536388-3">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7201536388-4">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7201536388-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7201536388-5">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="7201536388-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">value</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nf">f</span><span class="p" data-group-id="0173422378-6">(</span><span class="n">Key</span><span class="p" data-group-id="0173422378-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0173422378-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0173422378-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0173422378-8">(</span><span class="p" data-group-id="0173422378-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="0173422378-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="0173422378-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nf">f</span><span class="p" data-group-id="7201536388-6">(</span><span class="n">Key</span><span class="p" data-group-id="7201536388-6">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7201536388-7">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7201536388-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7201536388-8">(</span><span class="p" data-group-id="7201536388-9">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="7201536388-9">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="7201536388-8">)</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">value</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nf">f</span><span class="p" data-group-id="0173422378-10">(</span><span class="n">Key</span><span class="p" data-group-id="0173422378-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0173422378-11">(</span><span class="p" data-group-id="0173422378-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="0173422378-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0173422378-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="0173422378-13">}</span><span class="p" data-group-id="0173422378-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nf">f</span><span class="p" data-group-id="7201536388-10">(</span><span class="n">Key</span><span class="p" data-group-id="7201536388-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7201536388-11">(</span><span class="p" data-group-id="7201536388-12">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="7201536388-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7201536388-13">#{</span><span class="ss">key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="7201536388-13">}</span><span class="p" data-group-id="7201536388-11">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="n">Value</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:12: variable &#39;Key&#39; is unbound</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="p" data-group-id="0173422378-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="0173422378-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0173422378-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0173422378-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="p" data-group-id="7201536388-14">&lt;&lt;</span><span class="n">X</span><span class="p">:</span><span class="n">Y</span><span class="p" data-group-id="7201536388-14">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">begin</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7201536388-15">&lt;&lt;</span><span class="mi">42</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="7201536388-15">&gt;&gt;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span></code></pre><p>The expression at prompt <code class="inline">2&gt;</code> first matches the value of variable <code class="inline">M</code> against
│ │ │  pattern <code class="inline">#{key := Key}</code>, binding variable <code class="inline">Key</code>. It then matches the value of
│ │ │  <code class="inline">M</code> against pattern <code class="inline">#{Key := Value}</code> using variable <code class="inline">Key</code> as the key, binding
│ │ │  variable <code class="inline">Value</code>.</p><p>The expression at prompt <code class="inline">3&gt;</code> matches expression <code class="inline">(#{key := Key} = M)</code> against
│ │ │  pattern <code class="inline">#{Key := Value}</code>. The expression inside the parentheses is evaluated
│ │ │  first. That is, <code class="inline">M</code> is matched against <code class="inline">#{key := Key}</code>, and then the value of
│ │ │  <code class="inline">M</code> is matched against pattern <code class="inline">#{Key := Value}</code>. That is the same evaluation
│ │ │ @@ -276,30 +276,30 @@
│ │ │  binding variable <code class="inline">Y</code> and creating a binary. The binary is then matched against
│ │ │  pattern <code class="inline">&lt;&lt;X:Y&gt;&gt;</code> using the value of <code class="inline">Y</code> as the size of the segment.</p><h2 id="function-calls" class="section-heading">
│ │ │    <a href="#function-calls" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Function Calls</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="n">ExprF</span><span class="p" data-group-id="2304886977-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="2304886977-1">)</span><span class="w">
│ │ │ -</span><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="2304886977-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="2304886977-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="n">ExprF</span><span class="p" data-group-id="5559490015-1">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="5559490015-1">)</span><span class="w">
│ │ │ +</span><span class="n">ExprM</span><span class="p">:</span><span class="n">ExprF</span><span class="p" data-group-id="5559490015-2">(</span><span class="n">Expr1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ExprN</span><span class="p" data-group-id="5559490015-2">)</span></code></pre><p>In the first form of function calls, <code class="inline">ExprM:ExprF(Expr1,...,ExprN)</code>, each of
│ │ │  <code class="inline">ExprM</code> and <code class="inline">ExprF</code> must be an atom or an expression that evaluates to an atom.
│ │ │  The function is said to be called by using the <em>fully qualified function name</em>.
│ │ │ -This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="7188388954-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7188388954-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │ +This is often referred to as a <em>remote</em> or <em>external function call</em>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="7651762058-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7651762058-1">)</span></code></pre><p>In the second form of function calls, <code class="inline">ExprF(Expr1,...,ExprN)</code>, <code class="inline">ExprF</code> must be
│ │ │  an atom or evaluate to a fun.</p><p>If <code class="inline">ExprF</code> is an atom, the function is said to be called by using the
│ │ │  <em>implicitly qualified function name</em>. If the function <code class="inline">ExprF</code> is locally
│ │ │  defined, it is called. Alternatively, if <code class="inline">ExprF</code> is explicitly imported from the
│ │ │  <code class="inline">M</code> module, <code class="inline">M:ExprF(Expr1,...,ExprN)</code> is called. If <code class="inline">ExprF</code> is neither declared
│ │ │  locally nor explicitly imported, <code class="inline">ExprF</code> must be the name of an automatically
│ │ │ -imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="2254776752-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2254776752-1">)</span><span class="w">
│ │ │ -</span><span class="nf">spawn</span><span class="p" data-group-id="2254776752-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2254776752-3">[</span><span class="p" data-group-id="2254776752-3">]</span><span class="p" data-group-id="2254776752-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6547647906-1">(</span><span class="n">X</span><span class="p" data-group-id="6547647906-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Fun1</span><span class="p" data-group-id="6547647906-2">(</span><span class="mi">3</span><span class="p" data-group-id="6547647906-2">)</span><span class="p">.</span><span class="w">
│ │ │ +imported BIF.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="9172599243-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9172599243-1">)</span><span class="w">
│ │ │ +</span><span class="nf">spawn</span><span class="p" data-group-id="9172599243-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9172599243-3">[</span><span class="p" data-group-id="9172599243-3">]</span><span class="p" data-group-id="9172599243-2">)</span></code></pre><p><em>Examples</em> where <code class="inline">ExprF</code> is a fun:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0381129553-1">(</span><span class="n">X</span><span class="p" data-group-id="0381129553-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Fun1</span><span class="p" data-group-id="0381129553-2">(</span><span class="mi">3</span><span class="p" data-group-id="0381129553-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6547647906-3">(</span><span class="p" data-group-id="6547647906-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6547647906-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6547647906-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6547647906-5">]</span><span class="p" data-group-id="6547647906-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6547647906-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6547647906-6">]</span><span class="w">
│ │ │ +2&gt; </span><span class="k">fun</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="ss">append</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0381129553-3">(</span><span class="p" data-group-id="0381129553-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0381129553-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0381129553-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0381129553-5">]</span><span class="p" data-group-id="0381129553-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0381129553-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0381129553-6">]</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="o">&gt;</span></code></pre><p>Notice that when calling a local function, there is a difference between using
│ │ │  the implicitly or fully qualified function name. The latter always refers to the
│ │ │  latest version of the module. See
│ │ │  <a href="code_loading.html">Compilation and Code Loading </a>and
│ │ │  <a href="ref_man_functions.html#eval">Function Evaluation</a>.</p><h3 id="local-function-names-clashing-with-auto-imported-bifs" class="section-heading">
│ │ │    <a href="#local-function-names-clashing-with-auto-imported-bifs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -316,40 +316,40 @@
│ │ │  called instead. This is to avoid that future additions to the set of
│ │ │  auto-imported BIFs do not silently change the behavior of old code.</p></section><p>However, to avoid that old (pre R14) code changed its behavior when compiled
│ │ │  with Erlang/OTP version R14A or later, the following restriction applies: If you
│ │ │  override the name of a BIF that was auto-imported in OTP versions prior to R14A
│ │ │  (ERTS version 5.8) and have an implicitly qualified call to that function in
│ │ │  your code, you either need to explicitly remove the auto-import using a compiler
│ │ │  directive, or replace the call with a fully qualified function call. Otherwise
│ │ │ -you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9832326640-1">(</span><span class="p" data-group-id="9832326640-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9832326640-2">]</span><span class="p" data-group-id="9832326640-1">)</span><span class="p">.</span><span class="w">
│ │ │ +you get a compilation error. See the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6400858953-1">(</span><span class="p" data-group-id="6400858953-2">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6400858953-2">]</span><span class="p" data-group-id="6400858953-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="9832326640-3">(</span><span class="p" data-group-id="9832326640-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="9832326640-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9832326640-5">]</span><span class="p" data-group-id="9832326640-4">}</span><span class="p" data-group-id="9832326640-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6400858953-3">(</span><span class="p" data-group-id="6400858953-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="6400858953-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6400858953-5">]</span><span class="p" data-group-id="6400858953-4">}</span><span class="p" data-group-id="6400858953-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="9832326640-6">(</span><span class="p" data-group-id="9832326640-7">[</span><span class="p" data-group-id="9832326640-7">]</span><span class="p" data-group-id="9832326640-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="6400858953-6">(</span><span class="p" data-group-id="6400858953-7">[</span><span class="p" data-group-id="6400858953-7">]</span><span class="p" data-group-id="6400858953-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">length</span><span class="p" data-group-id="9832326640-8">(</span><span class="p" data-group-id="9832326640-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9832326640-9">]</span><span class="p" data-group-id="9832326640-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9832326640-10">(</span><span class="n">T</span><span class="p" data-group-id="9832326640-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │ +</span><span class="nf">length</span><span class="p" data-group-id="6400858953-8">(</span><span class="p" data-group-id="6400858953-9">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6400858953-9">]</span><span class="p" data-group-id="6400858953-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="6400858953-10">(</span><span class="n">T</span><span class="p" data-group-id="6400858953-10">)</span><span class="p">.</span><span class="w"> </span><span class="c1">%% Calls the local function length/1</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="9832326640-11">(</span><span class="n">X</span><span class="p" data-group-id="9832326640-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="9832326640-12">(</span><span class="n">X</span><span class="p" data-group-id="9832326640-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="6400858953-11">(</span><span class="n">X</span><span class="p" data-group-id="6400858953-11">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="6400858953-12">(</span><span class="n">X</span><span class="p" data-group-id="6400858953-12">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │                                    </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │      </span><span class="ss">long</span><span class="p">.</span></code></pre><p>The same logic applies to explicitly imported functions from other modules, as
│ │ │  to locally defined functions. It is not allowed to both import a function from
│ │ │ -another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1484495366-1">(</span><span class="p" data-group-id="1484495366-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1484495366-2">]</span><span class="p" data-group-id="1484495366-1">)</span><span class="p">.</span><span class="w">
│ │ │ +another module and have the function declared in the module at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8172391993-1">(</span><span class="p" data-group-id="8172391993-2">[</span><span class="ss">f</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8172391993-2">]</span><span class="p" data-group-id="8172391993-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="1484495366-3">(</span><span class="p" data-group-id="1484495366-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="1484495366-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1484495366-5">]</span><span class="p" data-group-id="1484495366-4">}</span><span class="p" data-group-id="1484495366-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="8172391993-3">(</span><span class="p" data-group-id="8172391993-4">{</span><span class="ss">no_auto_import</span><span class="p">,</span><span class="p" data-group-id="8172391993-5">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8172391993-5">]</span><span class="p" data-group-id="8172391993-4">}</span><span class="p" data-group-id="8172391993-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% erlang:length/1 no longer autoimported</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="1484495366-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="1484495366-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1484495366-7">]</span><span class="p" data-group-id="1484495366-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="8172391993-6">(</span><span class="ss">mod</span><span class="p">,</span><span class="p" data-group-id="8172391993-7">[</span><span class="nb">length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8172391993-7">]</span><span class="p" data-group-id="8172391993-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="1484495366-8">(</span><span class="n">X</span><span class="p" data-group-id="1484495366-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="1484495366-9">(</span><span class="n">X</span><span class="p" data-group-id="1484495366-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="8172391993-8">(</span><span class="n">X</span><span class="p" data-group-id="8172391993-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="8172391993-9">(</span><span class="n">X</span><span class="p" data-group-id="8172391993-9">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">33</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">%% Calls erlang:length/1,</span><span class="w">
│ │ │                                     </span><span class="c1">%% which is allowed in guards</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="1484495366-10">(</span><span class="n">X</span><span class="p" data-group-id="1484495366-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">length</span><span class="p" data-group-id="8172391993-10">(</span><span class="n">X</span><span class="p" data-group-id="8172391993-10">)</span><span class="p">;</span><span class="w">              </span><span class="c1">%% Explicit call to erlang:length in body</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="1484495366-11">(</span><span class="n">X</span><span class="p" data-group-id="1484495366-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">length</span><span class="p" data-group-id="1484495366-12">(</span><span class="n">X</span><span class="p" data-group-id="1484495366-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="8172391993-11">(</span><span class="n">X</span><span class="p" data-group-id="8172391993-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">length</span><span class="p" data-group-id="8172391993-12">(</span><span class="n">X</span><span class="p" data-group-id="8172391993-12">)</span><span class="p">.</span><span class="w">                     </span><span class="c1">%% mod:length/1 is called</span></code></pre><p>For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the
│ │ │  name with a local function or explicit import is always allowed. However, if the
│ │ │  <code class="inline">-compile({no_auto_import,[F/A])</code> directive is not used, the compiler issues a
│ │ │  warning whenever the function is called in the module using the implicitly
│ │ │  qualified function name.</p><h2 id="if" class="section-heading">
│ │ │    <a href="#if" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -361,40 +361,40 @@
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">GuardSeqN</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The branches of an <code class="inline">if</code>-expression are scanned sequentially until a guard
│ │ │  sequence <code class="inline">GuardSeq</code> that evaluates to true is found. Then the corresponding
│ │ │  <code class="inline">Body</code> (a sequence of expressions separated by <code class="inline">,</code>) is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">if</code> expression.</p><p>If no guard sequence is evaluated as true, an <code class="inline">if_clause</code> run-time error occurs.
│ │ │  If necessary, the guard expression <code class="inline">true</code> can be used in the last branch, as
│ │ │ -that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="2119117909-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2119117909-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +that guard sequence is always true.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_greater_than</span><span class="p" data-group-id="7329540985-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7329540985-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% works as an &#39;else&#39; branch</span><span class="w">
│ │ │              </span><span class="ss">false</span><span class="w">
│ │ │      </span><span class="k">end</span></code></pre><h2 id="case" class="section-heading">
│ │ │    <a href="#case" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Case</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Expr</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="7916927780-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="7916927780-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="5382189222-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5382189222-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="7916927780-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="7916927780-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="5382189222-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="5382189222-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The expression <code class="inline">Expr</code> is evaluated and the patterns <code class="inline">Pattern</code> are sequentially
│ │ │  matched against the result. If a match succeeds and the optional guard sequence
│ │ │  <code class="inline">GuardSeq</code> is true, the corresponding <code class="inline">Body</code> is evaluated.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">case</code> expression.</p><p>If there is no matching pattern with a true guard sequence, a <code class="inline">case_clause</code>
│ │ │ -run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="5920222108-1">(</span><span class="n">Signal</span><span class="p" data-group-id="5920222108-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +run-time error occurs.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_valid_signal</span><span class="p" data-group-id="4944979619-1">(</span><span class="n">Signal</span><span class="p" data-group-id="4944979619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Signal</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5920222108-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5920222108-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4944979619-2">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="4944979619-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5920222108-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="5920222108-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="4944979619-3">{</span><span class="ss">signal</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">What</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">To</span><span class="p" data-group-id="4944979619-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="n">Else</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">false</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="maybe" class="section-heading">
│ │ │    <a href="#maybe" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -412,57 +412,57 @@
│ │ │  the top-level of a <code class="inline">maybe</code> block. It matches the pattern <code class="inline">Expr1</code> against
│ │ │  <code class="inline">Expr2</code>. If the matching succeeds, any unbound variable in the pattern becomes
│ │ │  bound. If the expression is the last expression in the <code class="inline">maybe</code> block, it also
│ │ │  returns the value of <code class="inline">Expr2</code>. If the matching is unsuccessful, the rest of the
│ │ │  expressions in the <code class="inline">maybe</code> block are skipped and the return value of the <code class="inline">maybe</code>
│ │ │  block is <code class="inline">Expr2</code>.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the code that
│ │ │  follows the block.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8489543519-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8489543519-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="8489543519-2">(</span><span class="p" data-group-id="8489543519-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0045830146-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0045830146-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="0045830146-2">(</span><span class="p" data-group-id="0045830146-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8489543519-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8489543519-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="8489543519-4">(</span><span class="p" data-group-id="8489543519-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0045830146-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0045830146-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="0045830146-4">(</span><span class="p" data-group-id="0045830146-4">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Let us first assume that <code class="inline">a()</code> returns <code class="inline">{ok,42}</code> and <code class="inline">b()</code> returns <code class="inline">{ok,58}</code>.
│ │ │  With those return values, all of the match operators will succeed, and the
│ │ │  return value of the <code class="inline">maybe</code> block is <code class="inline">A + B</code>, which is equal to <code class="inline">42 + 58 = 100</code>.</p><p>Now let us assume that <code class="inline">a()</code> returns <code class="inline">error</code>. The conditional match operator in
│ │ │  <code class="inline">{ok, A} ?= a()</code> fails to match, and the return value of the <code class="inline">maybe</code> block is
│ │ │  the value of the expression that failed to match, namely <code class="inline">error</code>. Similarly, if
│ │ │  <code class="inline">b()</code> returns <code class="inline">wrong</code>, the return value of the <code class="inline">maybe</code> block is <code class="inline">wrong</code>.</p><p>Finally, let us assume that <code class="inline">a()</code> returns <code class="inline">{ok,-1}</code>. Because <code class="inline">true = A &gt;= 0</code> uses
│ │ │  the match operator <code class="inline">=</code>, a <code class="inline">{badmatch,false}</code> run-time error occurs when the
│ │ │ -expression fails to match the pattern.</p><p>The example can be written in a less succient way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="0003501258-1">(</span><span class="p" data-group-id="0003501258-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0003501258-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0003501258-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +expression fails to match the pattern.</p><p>The example can be written in a less succient way using nested case expressions:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="0402680739-1">(</span><span class="p" data-group-id="0402680739-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0402680739-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0402680739-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="0003501258-3">(</span><span class="p" data-group-id="0003501258-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0003501258-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0003501258-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="0402680739-3">(</span><span class="p" data-group-id="0402680739-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0402680739-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0402680739-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="n">Other1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Other1</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Other2</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Other2</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">maybe</code> block can be augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │      </span><span class="n">Expr1</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">ExprN</span><span class="w">
│ │ │  </span><span class="k">else</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="9234206257-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9234206257-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2135187293-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2135187293-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="9234206257-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="9234206257-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2135187293-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2135187293-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>If a conditional match operator fails, the failed expression is matched against
│ │ │  the patterns in all clauses between the <code class="inline">else</code> and <code class="inline">end</code> keywords. If a match
│ │ │  succeeds and the optional guard sequence <code class="inline">GuardSeq</code> is true, the corresponding
│ │ │  <code class="inline">Body</code> is evaluated. The value returned from the body is the return value of the
│ │ │  <code class="inline">maybe</code> block.</p><p>If there is no matching pattern with a true guard sequence, an <code class="inline">else_clause</code>
│ │ │  run-time error occurs.</p><p>None of the variables bound in a <code class="inline">maybe</code> block must be used in the <code class="inline">else</code>
│ │ │  clauses. None of the variables bound in the <code class="inline">else</code> clauses must be used in the
│ │ │  code that follows the <code class="inline">maybe</code> block.</p><p>Here is the previous example augmented with <code class="inline">else</code> clauses:</p><pre><code class="makeup erlang" translate="no"><span class="k">maybe</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5079261118-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5079261118-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="5079261118-2">(</span><span class="p" data-group-id="5079261118-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5363900443-1">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5363900443-1">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">a</span><span class="p" data-group-id="5363900443-2">(</span><span class="p" data-group-id="5363900443-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5079261118-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5079261118-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="5079261118-4">(</span><span class="p" data-group-id="5079261118-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5363900443-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="5363900443-3">}</span><span class="w"> </span><span class="o">?</span><span class="o">=</span><span class="w"> </span><span class="nf">b</span><span class="p" data-group-id="5363900443-4">(</span><span class="p" data-group-id="5363900443-4">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w">
│ │ │  </span><span class="k">else</span><span class="w">
│ │ │      </span><span class="ss">error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">wrong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">else</code> clauses translate the failing value from the conditional match
│ │ │  operators to the value <code class="inline">error</code>. If the failing value is not one of the
│ │ │  recognized values, a <code class="inline">else_clause</code> run-time error occurs.</p><h2 id="send" class="section-heading">
│ │ │ @@ -481,75 +481,75 @@
│ │ │  <code class="inline">{Name,Node}</code> (or a pid located at another node), also never fails.</li></ul><h2 id="receive" class="section-heading">
│ │ │    <a href="#receive" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Receive</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4828884276-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4828884276-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="1422052522-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="1422052522-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4828884276-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4828884276-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="1422052522-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="1422052522-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Fetches a received message present in the message queue of the process. The
│ │ │  first message in the message queue is matched sequentially against the patterns
│ │ │  from top to bottom. If no match was found, the matching sequence is repeated for
│ │ │  the second message in the queue, and so on. Messages are queued in the
│ │ │  <a href="ref_man_processes.html#message-queue-order">order they were received</a>. If a match
│ │ │  succeeds, that is, if the <code class="inline">Pattern</code> matches and the optional guard sequence
│ │ │  <code class="inline">GuardSeq</code> is true, then the message is removed from the message queue and the
│ │ │  corresponding <code class="inline">Body</code> is evaluated. All other messages in the message queue
│ │ │  remain unchanged.</p><p>The return value of <code class="inline">Body</code> is the return value of the <code class="inline">receive</code> expression.</p><p><code class="inline">receive</code> never fails. The execution is suspended, possibly indefinitely, until
│ │ │  a message arrives that matches one of the patterns and with a true guard
│ │ │ -sequence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="6367729235-1">(</span><span class="p" data-group-id="6367729235-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +sequence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="3212964766-1">(</span><span class="p" data-group-id="3212964766-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="6367729235-2">(</span><span class="p" data-group-id="6367729235-2">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="6367729235-3">(</span><span class="p" data-group-id="6367729235-3">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6367729235-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6367729235-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6367729235-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6367729235-6">(</span><span class="p" data-group-id="6367729235-6">)</span><span class="p" data-group-id="6367729235-5">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="6367729235-7">(</span><span class="p" data-group-id="6367729235-7">)</span><span class="w">
│ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="3212964766-2">(</span><span class="p" data-group-id="3212964766-2">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="3212964766-3">(</span><span class="p" data-group-id="3212964766-3">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3212964766-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3212964766-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3212964766-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3212964766-6">(</span><span class="p" data-group-id="3212964766-6">)</span><span class="p" data-group-id="3212964766-5">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="3212964766-7">(</span><span class="p" data-group-id="3212964766-7">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The <code class="inline">receive</code> expression can be augmented with a timeout:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="7541452570-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="7541452570-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="5051437265-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5051437265-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="7541452570-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="7541452570-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="5051437265-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="5051437265-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">receive...after</code> works exactly as <code class="inline">receive</code>, except that if no matching message
│ │ │  has arrived within <code class="inline">ExprT</code> milliseconds, then <code class="inline">BodyT</code> is evaluated instead. The
│ │ │  return value of <code class="inline">BodyT</code> then becomes the return value of the <code class="inline">receive...after</code>
│ │ │  expression. <code class="inline">ExprT</code> is to evaluate to an integer, or the atom <code class="inline">infinity</code>. The
│ │ │  allowed integer range is from 0 to 4294967295, that is, the longest possible
│ │ │  timeout is almost 50 days. With a zero value the timeout occurs immediately if
│ │ │  there is no matching message in the message queue.</p><p>The atom <code class="inline">infinity</code> will make the process wait indefinitely for a matching
│ │ │  message. This is the same as not using a timeout. It can be useful for timeout
│ │ │ -values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0517969577-1">(</span><span class="p" data-group-id="0517969577-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +values that are calculated at runtime.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">wait_for_onhook</span><span class="p" data-group-id="8587604922-1">(</span><span class="p" data-group-id="8587604922-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">onhook</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="0517969577-2">(</span><span class="p" data-group-id="0517969577-2">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">idle</span><span class="p" data-group-id="0517969577-3">(</span><span class="p" data-group-id="0517969577-3">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0517969577-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="0517969577-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0517969577-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0517969577-6">(</span><span class="p" data-group-id="0517969577-6">)</span><span class="p" data-group-id="0517969577-5">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="0517969577-7">(</span><span class="p" data-group-id="0517969577-7">)</span><span class="w">
│ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="8587604922-2">(</span><span class="p" data-group-id="8587604922-2">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">idle</span><span class="p" data-group-id="8587604922-3">(</span><span class="p" data-group-id="8587604922-3">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="8587604922-4">{</span><span class="ss">connect</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="8587604922-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">B</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="8587604922-5">{</span><span class="ss">busy</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8587604922-6">(</span><span class="p" data-group-id="8587604922-6">)</span><span class="p" data-group-id="8587604922-5">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">wait_for_onhook</span><span class="p" data-group-id="8587604922-7">(</span><span class="p" data-group-id="8587604922-7">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w">
│ │ │          </span><span class="mi">60000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">disconnect</span><span class="p" data-group-id="0517969577-8">(</span><span class="p" data-group-id="0517969577-8">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">error</span><span class="p" data-group-id="0517969577-9">(</span><span class="p" data-group-id="0517969577-9">)</span><span class="w">
│ │ │ +            </span><span class="nf">disconnect</span><span class="p" data-group-id="8587604922-8">(</span><span class="p" data-group-id="8587604922-8">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">error</span><span class="p" data-group-id="8587604922-9">(</span><span class="p" data-group-id="8587604922-9">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is legal to use a <code class="inline">receive...after</code> expression with no branches:</p><pre><code class="makeup erlang" translate="no"><span class="k">receive</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">ExprT</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyT</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>This construction does not consume any messages, only suspends execution in the
│ │ │ -process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="4303336186-1">(</span><span class="p" data-group-id="4303336186-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="4303336186-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4303336186-3">[</span><span class="nf">self</span><span class="p" data-group-id="4303336186-4">(</span><span class="p" data-group-id="4303336186-4">)</span><span class="p" data-group-id="4303336186-3">]</span><span class="p" data-group-id="4303336186-2">)</span><span class="p">.</span><span class="w">
│ │ │ +process for <code class="inline">ExprT</code> milliseconds. This can be used to implement simple timers.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">timer</span><span class="p" data-group-id="7899883252-1">(</span><span class="p" data-group-id="7899883252-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="7899883252-2">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7899883252-3">[</span><span class="nf">self</span><span class="p" data-group-id="7899883252-4">(</span><span class="p" data-group-id="7899883252-4">)</span><span class="p" data-group-id="7899883252-3">]</span><span class="p" data-group-id="7899883252-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">timer</span><span class="p" data-group-id="4303336186-5">(</span><span class="n">Pid</span><span class="p" data-group-id="4303336186-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">timer</span><span class="p" data-group-id="7899883252-5">(</span><span class="n">Pid</span><span class="p" data-group-id="7899883252-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w">
│ │ │          </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">timeout</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>For more information on timers in Erlang in general, see the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/time_correction.html#timers"><em>Timers</em></a> section of the
│ │ │  <a href="../../erts-15.2.7.2/doc/html/time_correction.html"><em>Time and Time Correction in Erlang</em></a>
│ │ │ @@ -591,21 +591,21 @@
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │  4&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">-</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │  5&gt; </span><span class="mf">0.0</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">+</span><span class="mf">0.0</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │  6&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="p" data-group-id="3863487323-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3863487323-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="3863487323-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3863487323-2">}</span><span class="p">.</span><span class="w">
│ │ │ +7&gt; </span><span class="p" data-group-id="0820891083-1">#{</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0820891083-1">}</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="0820891083-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0820891083-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -8&gt; </span><span class="p" data-group-id="3863487323-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3863487323-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="3863487323-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="3863487323-4">}</span><span class="p">.</span><span class="w">
│ │ │ +8&gt; </span><span class="p" data-group-id="0820891083-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0820891083-3">}</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p" data-group-id="0820891083-4">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">2.0</span><span class="p" data-group-id="0820891083-4">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -9&gt; </span><span class="p" data-group-id="3863487323-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="3863487323-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="3863487323-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="3863487323-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +9&gt; </span><span class="p" data-group-id="0820891083-5">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="0820891083-5">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="0820891083-6">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="0820891083-6">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -10&gt; </span><span class="p" data-group-id="3863487323-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="3863487323-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="3863487323-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="3863487323-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +10&gt; </span><span class="p" data-group-id="0820891083-7">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">2</span><span class="p" data-group-id="0820891083-7">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="p" data-group-id="0820891083-8">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="0820891083-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Prior to OTP 27, the term equivalence operators considered <code class="inline">0.0</code>
│ │ │  and <code class="inline">-0.0</code> to be the same term.</p><p>This was changed in OTP 27 but legacy code may have expected them to be
│ │ │  considered the same. To help users catch errors that may arise from an
│ │ │  upgrade, the compiler raises a warning when <code class="inline">0.0</code> is pattern-matched or used
│ │ │  in a term equivalence test.</p><p>If you need to match <code class="inline">0.0</code> specifically, the warning can be silenced by
│ │ │  writing <code class="inline">+0.0</code> instead, which produces the same term but makes the compiler
│ │ │  interpret the match as being done on purpose.</p></section><h2 id="arithmetic-expressions" class="section-heading">
│ │ │ @@ -631,15 +631,15 @@
│ │ │  </span><span class="mi">0</span><span class="gp unselectable">
│ │ │  8&gt; </span><span class="mi">2#10</span><span class="w"> </span><span class="ow">bor</span><span class="w"> </span><span class="mi">2#01</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │  9&gt; </span><span class="ss">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">10</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │       in operator  +/2
│ │ │          called as a + 10</span><span class="gp unselectable">
│ │ │ -10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="7556241170-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="7556241170-1">)</span><span class="p">.</span><span class="w">
│ │ │ +10&gt; </span><span class="mi">1</span><span class="w"> </span><span class="nf">bsl</span><span class="w"> </span><span class="p" data-group-id="2665363070-1">(</span><span class="mi">1</span><span class="w"> </span><span class="ow">bsl</span><span class="w"> </span><span class="mi">64</span><span class="p" data-group-id="2665363070-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: a system limit has been reached
│ │ │       in operator  bsl/2
│ │ │          called as 1 bsl 18446744073709551616</span></code></pre><h2 id="boolean-expressions" class="section-heading">
│ │ │    <a href="#boolean-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Boolean Expressions</span>
│ │ │ @@ -658,136 +658,136 @@
│ │ │    <a href="#short-circuit-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Short-Circuit Expressions</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="ow">orelse</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p><code class="inline">Expr2</code> is evaluated only if necessary. That is, <code class="inline">Expr2</code> is evaluated only if:</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">false</code> in an <code class="inline">orelse</code> expression.</li></ul><p>or</p><ul><li><code class="inline">Expr1</code> evaluates to <code class="inline">true</code> in an <code class="inline">andalso</code> expression.</li></ul><p>Returns either the value of <code class="inline">Expr1</code> (that is, <code class="inline">true</code> or <code class="inline">false</code>) or the value of
│ │ │ -<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="5515129544-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5515129544-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../lib/stdlib-6.2.2.2/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ -never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="3671457933-1">(</span><span class="n">L</span><span class="p" data-group-id="3671457933-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="3671457933-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="3671457933-3">(</span><span class="n">L</span><span class="p" data-group-id="3671457933-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3671457933-4">(</span><span class="n">L</span><span class="p" data-group-id="3671457933-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3671457933-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ -<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="6089965020-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6089965020-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="6089965020-2">]</span><span class="p" data-group-id="6089965020-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pred</span><span class="p" data-group-id="6089965020-3">(</span><span class="n">Hd</span><span class="p" data-group-id="6089965020-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="6089965020-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="6089965020-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="6089965020-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6089965020-6">[</span><span class="p" data-group-id="6089965020-6">]</span><span class="p" data-group-id="6089965020-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<code class="inline">Expr2</code> (if <code class="inline">Expr2</code> is evaluated).</p><p><em>Example 1:</em></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="o">-</span><span class="mf">1.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nc">math</span><span class="p">:</span><span class="nf">sqrt</span><span class="p" data-group-id="4933199236-1">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="4933199236-1">)</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">of</span></code></pre><p>This works even if <code class="inline">A</code> is less than <code class="inline">-1.0</code>, since in that case, <a href="../../lib/stdlib-6.2.2.2/doc/html/math.html#sqrt/1"><code class="inline">math:sqrt/1</code></a> is
│ │ │ +never evaluated.</p><p><em>Example 2:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">OnlyOne</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">is_atom</span><span class="p" data-group-id="5767554477-1">(</span><span class="n">L</span><span class="p" data-group-id="5767554477-1">)</span><span class="w"> </span><span class="nf">orelse</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="5767554477-2">(</span><span class="nf">is_list</span><span class="p" data-group-id="5767554477-3">(</span><span class="n">L</span><span class="p" data-group-id="5767554477-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5767554477-4">(</span><span class="n">L</span><span class="p" data-group-id="5767554477-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5767554477-2">)</span><span class="p">,</span></code></pre><p><code class="inline">Expr2</code> is not required to evaluate to a Boolean value. Because of that,
│ │ │ +<code class="inline">andalso</code> and <code class="inline">orelse</code> are tail-recursive.</p><p><em>Example 3 (tail-recursive function):</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="8334970063-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8334970063-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="8334970063-2">]</span><span class="p" data-group-id="8334970063-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pred</span><span class="p" data-group-id="8334970063-3">(</span><span class="n">Hd</span><span class="p" data-group-id="8334970063-3">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">all</span><span class="p" data-group-id="8334970063-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8334970063-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="8334970063-5">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8334970063-6">[</span><span class="p" data-group-id="8334970063-6">]</span><span class="p" data-group-id="8334970063-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R13A, <code class="inline">Expr2</code> was required to evaluate to a Boolean value,
│ │ │  and as consequence, <code class="inline">andalso</code> and <code class="inline">orelse</code> were <strong>not</strong> tail-recursive.</p></section><h2 id="list-operations" class="section-heading">
│ │ │    <a href="#list-operations" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">List Operations</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="n">Expr1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">Expr2</span><span class="w">
│ │ │  </span><span class="n">Expr1</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="n">Expr2</span></code></pre><p>The list concatenation operator <code class="inline">++</code> appends its second argument to its first
│ │ │  and returns the resulting list.</p><p>The list subtraction operator <code class="inline">--</code> produces a list that is a copy of the first
│ │ │  argument. The procedure is as follows: for each element in the second argument,
│ │ │ -the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0246072868-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0246072868-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="0246072868-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0246072868-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0246072868-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0246072868-3">]</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="0246072868-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0246072868-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="0246072868-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0246072868-5">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0246072868-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0246072868-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │ +the first occurrence of this element (if any) is removed.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2936606134-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2936606134-1">]</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2936606134-2">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2936606134-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2936606134-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2936606134-3">]</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="2936606134-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2936606134-4">]</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="p" data-group-id="2936606134-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2936606134-5">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2936606134-6">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2936606134-6">]</span></code></pre><h2 id="map-expressions" class="section-heading">
│ │ │    <a href="#map-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Map Expressions</span>
│ │ │  </h2>
│ │ │  <h3 id="creating-maps" class="section-heading">
│ │ │    <a href="#creating-maps" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating Maps</span>
│ │ │  </h3>
│ │ │  <p>Constructing a new map is done by letting an expression <code class="inline">K</code> be associated with
│ │ │ -another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2952294948-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="2952294948-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ -association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1515039813-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="1515039813-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2698673622-1">#{</span><span class="p" data-group-id="2698673622-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │ +another expression <code class="inline">V</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5277778349-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="5277778349-1">}</span></code></pre><p>New maps can include multiple associations at construction by listing every
│ │ │ +association:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3330644280-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="3330644280-1">}</span></code></pre><p>An empty map is constructed by not associating any terms with each other:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5578054484-1">#{</span><span class="p" data-group-id="5578054484-1">}</span></code></pre><p>All keys and values in the map are terms. Any expression is first evaluated and
│ │ │  then the resulting terms are used as <em>key</em> and <em>value</em> respectively.</p><p>Keys and values are separated by the <code class="inline">=&gt;</code> arrow and associations are separated
│ │ │ -by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1066476374-1">#{</span><span class="p" data-group-id="1066476374-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1066476374-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1066476374-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1066476374-3">&gt;&gt;</span><span class="p" data-group-id="1066476374-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1066476374-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1066476374-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1066476374-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1066476374-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="1066476374-6">}</span><span class="p" data-group-id="1066476374-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1066476374-7">#{</span><span class="p" data-group-id="1066476374-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1066476374-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="1066476374-9">(</span><span class="p" data-group-id="1066476374-9">)</span><span class="p" data-group-id="1066476374-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ -map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5905653646-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5905653646-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5905653646-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="5905653646-2">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="5905653646-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="5905653646-3">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5905653646-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="5905653646-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │ +by a comma (<code class="inline">,</code>).</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2572417807-1">#{</span><span class="p" data-group-id="2572417807-1">}</span><span class="p">,</span><span class="w">                 </span><span class="c1">% empty map</span><span class="w">
│ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2572417807-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2572417807-3">&lt;&lt;</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="2572417807-3">&gt;&gt;</span><span class="p" data-group-id="2572417807-2">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% single association with literals</span><span class="w">
│ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2572417807-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="2572417807-4">}</span><span class="p">,</span><span class="w">   </span><span class="c1">% multiple associations with literals</span><span class="w">
│ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2572417807-5">#{</span><span class="ss">k</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2572417807-6">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="2572417807-6">}</span><span class="p" data-group-id="2572417807-5">}</span><span class="p">,</span><span class="w">       </span><span class="c1">% single association with variables</span><span class="w">
│ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2572417807-7">#{</span><span class="p" data-group-id="2572417807-8">{</span><span class="s">&quot;w&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2572417807-8">}</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="2572417807-9">(</span><span class="p" data-group-id="2572417807-9">)</span><span class="p" data-group-id="2572417807-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% compound key associated with an evaluated expression</span></code></pre><p>Here, <code class="inline">A</code> and <code class="inline">B</code> are any expressions and <code class="inline">M0</code> through <code class="inline">M4</code> are the resulting
│ │ │ +map terms.</p><p>If two matching keys are declared, the latter key takes precedence.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1777692200-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1777692200-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1777692200-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p" data-group-id="1777692200-2">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="1777692200-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="1777692200-3">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1777692200-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="1777692200-4">}</span></code></pre><p>The order in which the expressions constructing the keys (and their associated
│ │ │  values) are evaluated is not defined. The syntactic order of the key-value pairs
│ │ │  in the construction is of no relevance, except in the recently mentioned case of
│ │ │  two matching keys.</p><h3 id="updating-maps" class="section-heading">
│ │ │    <a href="#updating-maps" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating Maps</span>
│ │ │  </h3>
│ │ │  <p>Updating a map has a similar syntax as constructing it.</p><p>An expression defining the map to be updated is put in front of the expression
│ │ │ -defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="2870104314-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="2870104314-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map and <code class="inline">K</code> and <code class="inline">V</code> are any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │ +defining the keys to be updated and their respective values:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="9870364272-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="9870364272-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map and <code class="inline">K</code> and <code class="inline">V</code> are any expression.</p><p>If key <code class="inline">K</code> does not match any existing key in the map, a new association is
│ │ │  created from key <code class="inline">K</code> to value <code class="inline">V</code>.</p><p>If key <code class="inline">K</code> matches an existing key in map <code class="inline">M</code>, its associated value is replaced
│ │ │  by the new value <code class="inline">V</code>. In both cases, the evaluated map expression returns a new
│ │ │ -map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="0588333118-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="0588333118-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression and <code class="inline">K</code> is an expression
│ │ │ +map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p>To only update an existing value, the following syntax is used:</p><pre><code class="makeup erlang" translate="no"><span class="n">M</span><span class="p" data-group-id="5642791567-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="5642791567-1">}</span></code></pre><p>Here <code class="inline">M</code> is a term of type map, <code class="inline">V</code> is an expression and <code class="inline">K</code> is an expression
│ │ │  that evaluates to an existing key in <code class="inline">M</code>.</p><p>If key <code class="inline">K</code> does not match any existing keys in map <code class="inline">M</code>, an exception of type
│ │ │  <code class="inline">badkey</code> is raised at runtime. If a matching key <code class="inline">K</code> is present in map <code class="inline">M</code>,
│ │ │  its associated value is replaced by the new value <code class="inline">V</code>, and the evaluated map
│ │ │ -expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0908737579-1">#{</span><span class="p" data-group-id="0908737579-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="0908737579-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0908737579-2">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="0908737579-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0908737579-3">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="0908737579-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0908737579-5">(</span><span class="p" data-group-id="0908737579-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="0908737579-6">(</span><span class="p" data-group-id="0908737579-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="0908737579-4">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="0908737579-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="0908737579-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; was added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3864331186-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="3864331186-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3864331186-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="3864331186-2">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">M</span><span class="p" data-group-id="3864331186-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="3864331186-3">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3864331186-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="3864331186-4">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="n">M</span><span class="p" data-group-id="3864331186-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="3864331186-5">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3864331186-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="3864331186-6">}</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="n">M</span><span class="p" data-group-id="3864331186-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="3864331186-7">}</span><span class="p">.</span><span class="w">
│ │ │ +expression returns a new map.</p><p>If <code class="inline">M</code> is not of type map, an exception of type <code class="inline">badmap</code> is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="n">M0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4032443455-1">#{</span><span class="p" data-group-id="4032443455-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M0</span><span class="p" data-group-id="4032443455-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4032443455-2">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M1</span><span class="p" data-group-id="4032443455-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4032443455-3">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M2</span><span class="p" data-group-id="4032443455-4">#{</span><span class="s">&quot;function&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4032443455-5">(</span><span class="p" data-group-id="4032443455-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="4032443455-6">(</span><span class="p" data-group-id="4032443455-6">)</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="4032443455-4">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">M4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M3</span><span class="p" data-group-id="4032443455-7">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4032443455-7">}</span><span class="p">.</span><span class="w">  </span><span class="c1">% &#39;a&#39; and &#39;b&#39; was added in `M1` and `M2`.</span></code></pre><p>Here <code class="inline">M0</code> is any map. It follows that <code class="inline">M1</code> through <code class="inline">M4</code> are maps as well.</p><p><em>More examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0527873183-1">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p" data-group-id="0527873183-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0527873183-2">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="p" data-group-id="0527873183-2">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="n">M</span><span class="p" data-group-id="0527873183-3">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0527873183-3">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0527873183-4">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0527873183-4">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="n">M</span><span class="p" data-group-id="0527873183-5">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0527873183-5">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0527873183-6">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0527873183-6">}</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="n">M</span><span class="p" data-group-id="0527873183-7">#{</span><span class="mf">1.0</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="0527873183-7">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument</span></code></pre><p>As in construction, the order in which the key and value expressions are
│ │ │  evaluated is not defined. The syntactic order of the key-value pairs in the
│ │ │  update is of no relevance, except in the case where two keys match. In that
│ │ │  case, the latter value is used.</p><h3 id="maps-in-patterns" class="section-heading">
│ │ │    <a href="#maps-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Maps in Patterns</span>
│ │ │  </h3>
│ │ │ -<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8712922307-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="8712922307-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │ +<p>Matching of key-value associations from maps is done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8378333796-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="8378333796-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here <code class="inline">M</code> is any map. The key <code class="inline">K</code> must be a
│ │ │  <a href="expressions.html#guard-expressions">guard expression</a>, with all variables already
│ │ │  bound. <code class="inline">V</code> can be any pattern with either bound or unbound variables.</p><p>If the variable <code class="inline">V</code> is unbound, it becomes bound to the value associated with
│ │ │  the key <code class="inline">K</code>, which must exist in the map <code class="inline">M</code>. If the variable <code class="inline">V</code> is bound, it
│ │ │  must match the value associated with <code class="inline">K</code> in <code class="inline">M</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, the expression defining the key <code class="inline">K</code> was restricted to be
│ │ │ -either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5815959668-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5815959668-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5815959668-2">}</span><span class="p" data-group-id="5815959668-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5815959668-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5815959668-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5815959668-4">}</span><span class="p" data-group-id="5815959668-3">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="5815959668-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="5815959668-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="5815959668-6">}</span><span class="p" data-group-id="5815959668-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5815959668-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5815959668-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5815959668-8">}</span><span class="p" data-group-id="5815959668-7">}</span><span class="gp unselectable">
│ │ │ +either a single variable or a literal.</p></section><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9369955487-1">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9369955487-2">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9369955487-2">}</span><span class="p" data-group-id="9369955487-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9369955487-3">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9369955487-4">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9369955487-4">}</span><span class="p" data-group-id="9369955487-3">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="9369955487-5">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9369955487-6">{</span><span class="mi">1</span><span class="p">,</span><span class="n">B</span><span class="p" data-group-id="9369955487-6">}</span><span class="p" data-group-id="9369955487-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9369955487-7">#{</span><span class="s">&quot;tuple&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9369955487-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9369955487-8">}</span><span class="p" data-group-id="9369955487-7">}</span><span class="gp unselectable">
│ │ │  3&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9455717814-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="9455717814-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │ +</span><span class="mi">2</span><span class="p">.</span></code></pre><p>This binds variable <code class="inline">B</code> to integer <code class="inline">2</code>.</p><p>Similarly, multiple values from the map can be matched:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5590420036-1">#{</span><span class="n">K1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Kn</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Vn</span><span class="p" data-group-id="5590420036-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>Here keys <code class="inline">K1</code> through <code class="inline">Kn</code> are any expressions with literals or bound
│ │ │  variables. If all key expressions evaluate successfully and all keys
│ │ │  exist in map <code class="inline">M</code>, all variables in <code class="inline">V1 .. Vn</code> is matched to the
│ │ │  associated values of their respective keys.</p><p>If the matching conditions are not met the match fails.</p><p>Note that when matching a map, only the <code class="inline">:=</code> operator (not the <code class="inline">=&gt;</code>) is allowed
│ │ │  as a delimiter for the associations.</p><p>The order in which keys are declared in matching has no relevance.</p><p>Duplicate keys are allowed in matching and match each pattern associated to the
│ │ │ -keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6637739944-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="6637739944-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5067111023-1">#{</span><span class="p" data-group-id="5067111023-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map, otherwise it
│ │ │ -fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7650313601-1">#{</span><span class="p" data-group-id="7650313601-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7650313601-3">(</span><span class="n">List</span><span class="p" data-group-id="7650313601-3">)</span><span class="p" data-group-id="7650313601-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="7650313601-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys are allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2259093331-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2259093331-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="2259093331-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2259093331-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +keys:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5322117185-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V2</span><span class="p" data-group-id="5322117185-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span></code></pre><p>The empty map literal (<code class="inline">#{}</code>) matches any map when used as a pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8124822990-1">#{</span><span class="p" data-group-id="8124822990-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>This expression matches if the expression <code class="inline">Expr</code> is of type map, otherwise it
│ │ │ +fails with an exception <code class="inline">badmatch</code>.</p><p>Here the key to be retrieved is constructed from an expression:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5115875609-1">#{</span><span class="p" data-group-id="5115875609-2">{</span><span class="ss">tag</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="5115875609-3">(</span><span class="n">List</span><span class="p" data-group-id="5115875609-3">)</span><span class="p" data-group-id="5115875609-2">}</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="p" data-group-id="5115875609-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map</span></code></pre><p><code class="inline">List</code> must be an already bound variable.</p><h4>Matching Syntax</h4><p>Matching of literals as keys are allowed in function heads:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% only start if not_started</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="7676813913-1">(</span><span class="ss">start</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7676813913-2">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">not_started</span><span class="p" data-group-id="7676813913-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7676813913-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2259093331-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2259093331-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="2259093331-4">}</span><span class="p" data-group-id="2259093331-3">}</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7676813913-3">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7676813913-4">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="7676813913-4">}</span><span class="p" data-group-id="7676813913-3">}</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% only change if started</span><span class="w">
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="2259093331-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2259093331-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="2259093331-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2259093331-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="7676813913-5">(</span><span class="ss">change</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7676813913-6">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">start</span><span class="p" data-group-id="7676813913-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7676813913-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2259093331-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="2259093331-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="2259093331-8">}</span><span class="p" data-group-id="2259093331-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │ +    </span><span class="p" data-group-id="7676813913-7">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">S</span><span class="p" data-group-id="7676813913-8">#{</span><span class="ss">state</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">changed</span><span class="p" data-group-id="7676813913-8">}</span><span class="p" data-group-id="7676813913-7">}</span><span class="p">;</span></code></pre><h3 id="maps-in-guards" class="section-heading">
│ │ │    <a href="#maps-in-guards" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Maps in Guards</span>
│ │ │  </h3>
│ │ │  <p>Maps are allowed in guards as long as all subexpressions are valid guard
│ │ │  expressions.</p><p>The following guard BIFs handle maps:</p><ul><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#is_map/1">is_map/1</a> in the <code class="inline">erlang</code> module</li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#is_map_key/2">is_map_key/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#map_get/2">map_get/2</a> in the <code class="inline">erlang</code> module</li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#map_size/1">map_size/1</a> in the <code class="inline">erlang</code> module</li></ul><h2 id="bit-syntax-expressions" class="section-heading">
│ │ │    <a href="#bit-syntax-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Bit Syntax Expressions</span>
│ │ │  </h2>
│ │ │  <p>The bit syntax operates on <em>bit strings</em>. A bit string is a sequence of bits
│ │ │ -ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8945112040-1">&lt;&lt;</span><span class="p" data-group-id="8945112040-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8945112040-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="8945112040-2">&gt;&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8945112040-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="8945112040-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │ +ordered from the most significant bit to the least significant bit.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4659815579-1">&lt;&lt;</span><span class="p" data-group-id="4659815579-1">&gt;&gt;</span><span class="w">  </span><span class="c1">% The empty bit string, zero length</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4659815579-2">&lt;&lt;</span><span class="n">E1</span><span class="p" data-group-id="4659815579-2">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4659815579-3">&lt;&lt;</span><span class="n">E1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">En</span><span class="p" data-group-id="4659815579-3">&gt;&gt;</span></code></pre><p>Each element <code class="inline">Ei</code> specifies a <em>segment</em> of the bit string. The segments are
│ │ │  ordered left to right from the most significant bit to the least significant bit
│ │ │  of the bit string.</p><p>Each segment specification <code class="inline">Ei</code> is a value, whose default type is <code class="inline">integer</code>,
│ │ │  followed by an optional <em>size expression</em> and an optional <em>type specifier list</em>.</p><pre><code class="makeup erlang" translate="no"><span class="n">Ei</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Value</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │       </span><span class="n">Value</span><span class="o">/</span><span class="n">TypeSpecifierList</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │       </span><span class="n">Value</span><span class="p">:</span><span class="n">Size</span><span class="o">/</span><span class="n">TypeSpecifierList</span></code></pre><p>When used in a bit string construction, <code class="inline">Value</code> is an expression that is to
│ │ │  evaluate to an integer, float, or bit string. If the expression is not a single
│ │ │ @@ -798,34 +798,34 @@
│ │ │  <a href="expressions.html#guard-expressions">guard expression</a> that evaluates to an
│ │ │  integer. All variables in the guard expression must be already bound.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 23, <code class="inline">Size</code> was restricted to be an integer or a variable
│ │ │  bound to an integer.</p></section><p>The value of <code class="inline">Size</code> specifies the size of the segment in units (see below). The
│ │ │  default value depends on the type (see below):</p><ul><li>For <code class="inline">integer</code> it is 8.</li><li>For <code class="inline">float</code> it is 64.</li><li>For <code class="inline">binary</code> and <code class="inline">bitstring</code> it is the whole binary or bit string.</li></ul><p>In matching, the default value for a binary or bit string segment is only valid
│ │ │  for the last element. All other bit string or binary elements in the matching
│ │ │  must have a size specification.</p><p><a href="" id="binaries"></a></p><p><strong>Binaries</strong></p><p>A bit string with a length that is a multiple of 8 bits is known as a <em>binary</em>,
│ │ │  which is the most common and useful type of bit string.</p><p>A binary has a canonical representation in memory. Here follows a sequence of
│ │ │ -bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5690155540-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="5690155540-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ -information about binaries apply just as well for bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3854537496-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3854537496-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3854537496-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3854537496-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +bytes where each byte's value is its sequence number:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7042534893-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p" data-group-id="7042534893-1">&gt;&gt;</span></code></pre><p>Bit strings are a later generalization of binaries, so many texts and much
│ │ │ +information about binaries apply just as well for bit strings.</p><p><strong>Example:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4202614887-1">&lt;&lt;</span><span class="n">A</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4202614887-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4202614887-2">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4202614887-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:3: a binary field without size is only allowed at the end of a binary pattern</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="3854537496-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="3854537496-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3854537496-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3854537496-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3854537496-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="3854537496-5">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="4202614887-3">&lt;&lt;</span><span class="n">A</span><span class="p">:</span><span class="mi">3</span><span class="o">/</span><span class="ss">binary</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="4202614887-3">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4202614887-4">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4202614887-4">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4202614887-5">&lt;&lt;</span><span class="s">&quot;abcde&quot;</span><span class="p" data-group-id="4202614887-5">&gt;&gt;</span><span class="gp unselectable">
│ │ │  3&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3854537496-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="3854537496-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +</span><span class="p" data-group-id="4202614887-6">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4202614887-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │  4&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3854537496-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="3854537496-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │ +</span><span class="p" data-group-id="4202614887-7">&lt;&lt;</span><span class="s">&quot;de&quot;</span><span class="p" data-group-id="4202614887-7">&gt;&gt;</span></code></pre><p>For the <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code> types, <code class="inline">Size</code> must not be given. The size
│ │ │  of the segment is implicitly determined by the type and value itself.</p><p><code class="inline">TypeSpecifierList</code> is a list of type specifiers, in any order, separated by
│ │ │  hyphens (-). Default values are used for any omitted type specifiers.</p><ul><li><p><strong><code class="inline">Type</code>= <code class="inline">integer</code> | <code class="inline">float</code> | <code class="inline">binary</code> | <code class="inline">bytes</code> | <code class="inline">bitstring</code> | <code class="inline">bits</code> |
│ │ │  <code class="inline">utf8</code> | <code class="inline">utf16</code> | <code class="inline">utf32</code></strong> - The default is <code class="inline">integer</code>. <code class="inline">bytes</code> is a
│ │ │  shorthand for <code class="inline">binary</code> and <code class="inline">bits</code> is a shorthand for <code class="inline">bitstring</code>. See below
│ │ │  for more information about the <code class="inline">utf</code> types.</p></li><li><p><strong><code class="inline">Signedness</code>= <code class="inline">signed</code> | <code class="inline">unsigned</code></strong> - Only matters for matching and when
│ │ │  the type is <code class="inline">integer</code>. The default is <code class="inline">unsigned</code>.</p></li><li><p><strong><code class="inline">Endianness</code>= <code class="inline">big</code> | <code class="inline">little</code> | <code class="inline">native</code></strong> - Specifies byte level (octet
│ │ │  level) endianness (byte order). Native-endian means that the endianness is
│ │ │  resolved at load time to be either big-endian or little-endian, depending on
│ │ │  what is native for the CPU that the Erlang machine is run on. Endianness only
│ │ │  matters when the <strong>Type</strong> is either <code class="inline">integer</code>, <code class="inline">utf16</code>, <code class="inline">utf32</code>, or <code class="inline">float</code>. The
│ │ │ -default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9278220503-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="9278220503-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9278220503-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="9278220503-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9278220503-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9278220503-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │ +default is <code class="inline">big</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1730699202-1">&lt;&lt;</span><span class="mi">16#1234</span><span class="p">:</span><span class="mi">16</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="1730699202-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1730699202-2">&lt;&lt;</span><span class="mi">16#3412</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1730699202-2">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1730699202-3">&lt;&lt;</span><span class="mi">16#34</span><span class="p">:</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">16#12</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1730699202-3">&gt;&gt;</span></code></pre></li><li><p><strong><code class="inline">Unit</code>= <code class="inline">unit:IntegerLiteral</code></strong> - The allowed range is 1 through 256.
│ │ │  Defaults to 1 for <code class="inline">integer</code>, <code class="inline">float</code>, and <code class="inline">bitstring</code>, and to 8 for <code class="inline">binary</code>.
│ │ │  For types <code class="inline">bitstring</code>, <code class="inline">bits</code>, and <code class="inline">bytes</code>, it is not allowed to specify a
│ │ │  unit value different from the default value. No unit specifier must be given
│ │ │  for the types <code class="inline">utf8</code>, <code class="inline">utf16</code>, and <code class="inline">utf32</code>.</p></li></ul><h3 id="integer-segments" class="section-heading">
│ │ │    <a href="#integer-segments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -850,41 +850,41 @@
│ │ │    </a>
│ │ │    <span class="text">Binary segments</span>
│ │ │  </h3>
│ │ │  <p>In this section, the phrase &quot;binary segment&quot; refers to any one of the segment
│ │ │  types <code class="inline">binary</code>, <code class="inline">bitstring</code>, <code class="inline">bytes</code>, and <code class="inline">bits</code>.</p><p>See also the paragraphs about <a href="expressions.html#binaries">Binaries</a>.</p><p>When constructing binaries and no size is specified for a binary segment, the
│ │ │  entire binary value is interpolated into the binary being constructed. However,
│ │ │  the size in bits of the binary being interpolated must be evenly divisible by
│ │ │ -the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1833526552-1">&lt;&lt;</span><span class="p" data-group-id="1833526552-2">(</span><span class="p" data-group-id="1833526552-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1833526552-3">&gt;&gt;</span><span class="p" data-group-id="1833526552-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1833526552-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1833526552-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1833526552-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="1833526552-5">&lt;&lt;</span><span class="p" data-group-id="1833526552-6">(</span><span class="p" data-group-id="1833526552-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1833526552-7">&gt;&gt;</span><span class="p" data-group-id="1833526552-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1833526552-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1833526552-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1833526552-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="p" data-group-id="1833526552-9">&lt;&lt;</span><span class="p" data-group-id="1833526552-10">(</span><span class="p" data-group-id="1833526552-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1833526552-11">&gt;&gt;</span><span class="p" data-group-id="1833526552-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1833526552-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1833526552-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1833526552-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │ +the unit value for the segment; otherwise an exception is raised.</p><p>For example, the following examples all succeed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2297258028-1">&lt;&lt;</span><span class="p" data-group-id="2297258028-2">(</span><span class="p" data-group-id="2297258028-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2297258028-3">&gt;&gt;</span><span class="p" data-group-id="2297258028-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="2297258028-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2297258028-4">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2297258028-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="2297258028-5">&lt;&lt;</span><span class="p" data-group-id="2297258028-6">(</span><span class="p" data-group-id="2297258028-7">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2297258028-7">&gt;&gt;</span><span class="p" data-group-id="2297258028-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="2297258028-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2297258028-8">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2297258028-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="p" data-group-id="2297258028-9">&lt;&lt;</span><span class="p" data-group-id="2297258028-10">(</span><span class="p" data-group-id="2297258028-11">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2297258028-11">&gt;&gt;</span><span class="p" data-group-id="2297258028-10">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="2297258028-9">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2297258028-12">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2297258028-12">&gt;&gt;</span></code></pre><p>The first two examples have a unit value of 1 for the segment, while the third
│ │ │  segment has a unit value of 8.</p><p>Attempting to interpolate a bit string of size 1 into a binary segment with unit
│ │ │ -8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="7412056497-1">&lt;&lt;</span><span class="p" data-group-id="7412056497-2">(</span><span class="p" data-group-id="7412056497-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="7412056497-3">&gt;&gt;</span><span class="p" data-group-id="7412056497-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7412056497-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="4770769054-1">&lt;&lt;</span><span class="p" data-group-id="4770769054-2">(</span><span class="p" data-group-id="4770769054-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4770769054-3">&gt;&gt;</span><span class="p" data-group-id="4770769054-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="4770769054-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4770769054-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4770769054-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="p" data-group-id="4770769054-5">&lt;&lt;</span><span class="p" data-group-id="4770769054-6">(</span><span class="p" data-group-id="4770769054-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4770769054-7">&gt;&gt;</span><span class="p" data-group-id="4770769054-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4770769054-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4770769054-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="4770769054-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │ +8 (the default unit for <code class="inline">binary</code>) fails as shown in this example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9622962703-1">&lt;&lt;</span><span class="p" data-group-id="9622962703-2">(</span><span class="p" data-group-id="9622962703-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="9622962703-3">&gt;&gt;</span><span class="p" data-group-id="9622962703-2">)</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="9622962703-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="gt">** exception error: bad argument</span></code></pre><p>For the construction to succeed, the unit value of the segment must be 1:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1803307016-1">&lt;&lt;</span><span class="p" data-group-id="1803307016-2">(</span><span class="p" data-group-id="1803307016-3">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1803307016-3">&gt;&gt;</span><span class="p" data-group-id="1803307016-2">)</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1803307016-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1803307016-4">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1803307016-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="p" data-group-id="1803307016-5">&lt;&lt;</span><span class="p" data-group-id="1803307016-6">(</span><span class="p" data-group-id="1803307016-7">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1803307016-7">&gt;&gt;</span><span class="p" data-group-id="1803307016-6">)</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1803307016-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1803307016-8">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1803307016-8">&gt;&gt;</span></code></pre><p>Similarly, when matching a binary segment with no size specified, the match
│ │ │  succeeds if and only if the size in bits of the rest of the binary is evenly
│ │ │ -divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5132878724-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5132878724-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5132878724-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="5132878724-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5132878724-3">&lt;&lt;</span><span class="p" data-group-id="5132878724-3">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="5132878724-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5132878724-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5132878724-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="5132878724-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +divisible by the unit value:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4967840922-1">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4967840922-1">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4967840922-2">&lt;&lt;</span><span class="s">&quot;&quot;</span><span class="p" data-group-id="4967840922-2">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4967840922-3">&lt;&lt;</span><span class="p" data-group-id="4967840922-3">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="4967840922-4">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4967840922-4">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4967840922-5">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="4967840922-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;a&quot;&gt;&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="p" data-group-id="5132878724-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5132878724-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5132878724-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="5132878724-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5132878724-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="5132878724-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="p" data-group-id="5132878724-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5132878724-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5132878724-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5132878724-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="p" data-group-id="4967840922-6">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4967840922-6">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4967840922-7">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="4967840922-7">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4967840922-8">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="4967840922-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="p" data-group-id="4967840922-9">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4967840922-9">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4967840922-10">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="4967840922-10">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value &lt;&lt;&quot;abc&quot;&gt;&gt;</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="p" data-group-id="5132878724-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="5132878724-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5132878724-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="5132878724-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5132878724-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="5132878724-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │ +5&gt; </span><span class="p" data-group-id="4967840922-11">&lt;&lt;</span><span class="p">_</span><span class="o">/</span><span class="ss">binary</span><span class="o">-</span><span class="nc">unit</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="4967840922-11">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4967840922-12">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="4967840922-12">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4967840922-13">&lt;&lt;</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="4967840922-13">&gt;&gt;</span></code></pre><p>When a size is explicitly specified for a binary segment, the segment size in
│ │ │  bits is the value of <code class="inline">Size</code> multiplied by the default or explicit unit value.</p><p>When constructing binaries, the size of the binary being interpolated into the
│ │ │ -constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5035177816-1">&lt;&lt;</span><span class="p" data-group-id="5035177816-2">(</span><span class="p" data-group-id="5035177816-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="5035177816-3">&gt;&gt;</span><span class="p" data-group-id="5035177816-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5035177816-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5035177816-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="5035177816-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="5035177816-5">&lt;&lt;</span><span class="p" data-group-id="5035177816-6">(</span><span class="p" data-group-id="5035177816-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="5035177816-7">&gt;&gt;</span><span class="p" data-group-id="5035177816-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="5035177816-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +constructed binary must be at least as large as the size of the binary segment.</p><p><strong>Examples:</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8625079143-1">&lt;&lt;</span><span class="p" data-group-id="8625079143-2">(</span><span class="p" data-group-id="8625079143-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8625079143-3">&gt;&gt;</span><span class="p" data-group-id="8625079143-2">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8625079143-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8625079143-4">&lt;&lt;</span><span class="s">&quot;ab&quot;</span><span class="p" data-group-id="8625079143-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="8625079143-5">&lt;&lt;</span><span class="p" data-group-id="8625079143-6">(</span><span class="p" data-group-id="8625079143-7">&lt;&lt;</span><span class="s">&quot;a&quot;</span><span class="p" data-group-id="8625079143-7">&gt;&gt;</span><span class="p" data-group-id="8625079143-6">)</span><span class="p">:</span><span class="mi">2</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="8625079143-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: construction of binary failed
│ │ │          *** segment 1 of type &#39;binary&#39;: the value &lt;&lt;&quot;a&quot;&gt;&gt; is shorter than the size of the segment</span></code></pre><h3 id="unicode-segments" class="section-heading">
│ │ │    <a href="#unicode-segments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Unicode segments</span>
│ │ │  </h3>
│ │ │ @@ -900,78 +900,78 @@
│ │ │  range <code class="inline">0</code> through <code class="inline">16#D7FF</code> or <code class="inline">16#E000</code> through <code class="inline">16#10FFFF</code>. The match fails if the
│ │ │  returned value falls outside those ranges.</p><p>A segment of type <code class="inline">utf8</code> matches 1-4 bytes in the bit string, if the bit string
│ │ │  at the match position contains a valid UTF-8 sequence. (See RFC-3629 or the
│ │ │  Unicode standard.)</p><p>A segment of type <code class="inline">utf16</code> can match 2 or 4 bytes in the bit string. The match
│ │ │  fails if the bit string at the match position does not contain a legal UTF-16
│ │ │  encoding of a Unicode code point. (See RFC-2781 or the Unicode standard.)</p><p>A segment of type <code class="inline">utf32</code> can match 4 bytes in the bit string in the same way as
│ │ │  an <code class="inline">integer</code> segment matches 32 bits. The match fails if the resulting integer
│ │ │ -is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="1384942499-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="1384942499-4">&gt;&gt;</span><span class="w">
│ │ │ +is outside the legal ranges previously mentioned.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-3">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="7627446583-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-4">&lt;&lt;</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="7627446583-4">&gt;&gt;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1384942499-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="p" data-group-id="1384942499-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1384942499-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1384942499-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-9">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +</span><span class="mi">3</span><span class="o">&gt;</span><span class="w"> </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="7627446583-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-6">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="p" data-group-id="7627446583-7">&lt;&lt;</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="7627446583-7">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-8">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="7627446583-8">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-9">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-9">&gt;&gt;</span><span class="gp unselectable">
│ │ │  5&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="p" data-group-id="1384942499-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="1384942499-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1384942499-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-12">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +6&gt; </span><span class="p" data-group-id="7627446583-10">&lt;&lt;</span><span class="n">D</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="n">E</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="7627446583-10">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="7627446583-11">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-12">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-12">&gt;&gt;</span><span class="gp unselectable">
│ │ │  7&gt; </span><span class="n">D</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">273</span><span class="gp unselectable">
│ │ │  8&gt; </span><span class="n">F</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │ -9&gt; </span><span class="p" data-group-id="1384942499-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="1384942499-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1384942499-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-15">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +9&gt; </span><span class="p" data-group-id="7627446583-13">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">H</span><span class="o">/</span><span class="ss">binary</span><span class="p" data-group-id="7627446583-13">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-14">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="7627446583-14">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-15">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-15">&gt;&gt;</span><span class="gp unselectable">
│ │ │  10&gt; </span><span class="n">H</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="1384942499-16">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -11&gt; </span><span class="p" data-group-id="1384942499-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="1384942499-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="1384942499-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1384942499-19">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +</span><span class="p" data-group-id="7627446583-16">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">42</span><span class="p" data-group-id="7627446583-16">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +11&gt; </span><span class="p" data-group-id="7627446583-17">&lt;&lt;</span><span class="n">G</span><span class="p">,</span><span class="n">J</span><span class="o">/</span><span class="ss">bitstring</span><span class="p" data-group-id="7627446583-17">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">42</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="7627446583-18">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-19">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7627446583-19">&gt;&gt;</span><span class="gp unselectable">
│ │ │  12&gt; </span><span class="n">J</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1384942499-20">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-20">&lt;&lt;</span><span class="mi">17</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">10</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7627446583-20">&gt;&gt;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="1384942499-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="1384942499-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="1384942499-22">&gt;&gt;</span><span class="w">
│ │ │ +</span><span class="mi">13</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="7627446583-21">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="7627446583-21">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-22">&lt;&lt;</span><span class="mi">208</span><span class="p">,</span><span class="mi">128</span><span class="p" data-group-id="7627446583-22">&gt;&gt;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="1384942499-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="1384942499-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="1384942499-24">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -15&gt; </span><span class="p" data-group-id="1384942499-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="1384942499-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="1384942499-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1384942499-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1384942499-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1384942499-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="1384942499-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │ +</span><span class="mi">14</span><span class="o">&gt;</span><span class="w"> </span><span class="p" data-group-id="7627446583-23">&lt;&lt;</span><span class="mi">1</span><span class="p">:</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">:</span><span class="mi">7</span><span class="p" data-group-id="7627446583-23">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-24">&lt;&lt;</span><span class="mi">128</span><span class="p" data-group-id="7627446583-24">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +15&gt; </span><span class="p" data-group-id="7627446583-25">&lt;&lt;</span><span class="mi">16#123</span><span class="p">:</span><span class="mi">12</span><span class="o">/</span><span class="ss">little</span><span class="p" data-group-id="7627446583-25">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-26">&lt;&lt;</span><span class="mi">16#231</span><span class="p">:</span><span class="mi">12</span><span class="p" data-group-id="7627446583-26">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7627446583-27">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">:</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7627446583-27">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7627446583-28">&lt;&lt;</span><span class="mi">35</span><span class="p">,</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7627446583-28">&gt;&gt;</span></code></pre><p>Notice that bit string patterns cannot be nested.</p><p>Notice also that &quot;<code class="inline">B=&lt;&lt;1&gt;&gt;</code>&quot; is interpreted as &quot;<code class="inline">B =&lt; &lt;1&gt;&gt;</code>&quot; which is a syntax
│ │ │  error. The correct way is to write a space after <code class="inline">=</code>: &quot;<code class="inline">B = &lt;&lt;1&gt;&gt;</code>.</p><p>More examples are provided in <a href="../../doc/system/bit_syntax.html">Programming Examples</a>.</p><h2 id="fun-expressions" class="section-heading">
│ │ │    <a href="#fun-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Fun Expressions</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4375890369-1">[</span><span class="n">Name</span><span class="p" data-group-id="4375890369-1">]</span><span class="p" data-group-id="4375890369-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="4375890369-2">)</span><span class="w"> </span><span class="p" data-group-id="4375890369-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4375890369-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8070921938-1">[</span><span class="n">Name</span><span class="p" data-group-id="8070921938-1">]</span><span class="p" data-group-id="8070921938-2">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="8070921938-2">)</span><span class="w"> </span><span class="p" data-group-id="8070921938-3">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="8070921938-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4375890369-4">[</span><span class="n">Name</span><span class="p" data-group-id="4375890369-4">]</span><span class="p" data-group-id="4375890369-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="4375890369-5">)</span><span class="w"> </span><span class="p" data-group-id="4375890369-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="4375890369-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8070921938-4">[</span><span class="n">Name</span><span class="p" data-group-id="8070921938-4">]</span><span class="p" data-group-id="8070921938-5">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="8070921938-5">)</span><span class="w"> </span><span class="p" data-group-id="8070921938-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="8070921938-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                </span><span class="n">BodyK</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>A fun expression begins with the keyword <code class="inline">fun</code> and ends with the keyword <code class="inline">end</code>.
│ │ │  Between them is to be a function declaration, similar to a
│ │ │  <a href="ref_man_functions.html#function-declaration-syntax">regular function declaration</a>,
│ │ │  except that the function name is optional and is to be a variable, if any.</p><p>Variables in a fun head shadow the function name and both shadow variables in
│ │ │  the function clause surrounding the fun expression. Variables bound in a fun
│ │ │ -body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5161327434-1">(</span><span class="n">X</span><span class="p" data-group-id="5161327434-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +body are local to the fun body.</p><p>The return value of the expression is the resulting fun.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Fun1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8332626534-1">(</span><span class="n">X</span><span class="p" data-group-id="8332626534-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">+</span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="5161327434-2">(</span><span class="mi">2</span><span class="p" data-group-id="5161327434-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="n">Fun1</span><span class="p" data-group-id="8332626534-2">(</span><span class="mi">2</span><span class="p" data-group-id="8332626534-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5161327434-3">(</span><span class="n">X</span><span class="p" data-group-id="5161327434-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="5161327434-4">(</span><span class="n">X</span><span class="p" data-group-id="5161327434-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="n">Fun2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8332626534-3">(</span><span class="n">X</span><span class="p" data-group-id="8332626534-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="o">&gt;=</span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">gt</span><span class="p">;</span><span class="w"> </span><span class="p" data-group-id="8332626534-4">(</span><span class="n">X</span><span class="p" data-group-id="8332626534-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">lt</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="5161327434-5">(</span><span class="mi">7</span><span class="p" data-group-id="5161327434-5">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="n">Fun2</span><span class="p" data-group-id="8332626534-5">(</span><span class="mi">7</span><span class="p" data-group-id="8332626534-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">gt</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="5161327434-6">(</span><span class="mi">1</span><span class="p" data-group-id="5161327434-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="5161327434-7">(</span><span class="n">X</span><span class="p" data-group-id="5161327434-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="5161327434-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5161327434-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="n">Fun3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="8332626534-6">(</span><span class="mi">1</span><span class="p" data-group-id="8332626534-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="8332626534-7">(</span><span class="n">X</span><span class="p" data-group-id="8332626534-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Fact</span><span class="p" data-group-id="8332626534-8">(</span><span class="n">X</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8332626534-8">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.39074546</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="5161327434-9">(</span><span class="mi">4</span><span class="p" data-group-id="5161327434-9">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="n">Fun3</span><span class="p" data-group-id="8332626534-9">(</span><span class="mi">4</span><span class="p" data-group-id="8332626534-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">24</span></code></pre><p>The following fun expressions are also allowed:</p><pre><code class="makeup erlang" translate="no"><span class="k">fun</span><span class="w"> </span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span><span class="w">
│ │ │  </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">Name</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In <code class="inline">Name/Arity</code>, <code class="inline">Name</code> is an atom and <code class="inline">Arity</code> is an integer. <code class="inline">Name/Arity</code> must
│ │ │ -specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5667675194-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="5667675194-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5667675194-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="5667675194-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code>, and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │ +specify an existing local function. The expression is syntactic sugar for:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5067333760-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="5067333760-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5067333760-2">(</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="5067333760-2">)</span><span class="w"> </span><span class="k">end</span></code></pre><p>In <code class="inline">Module:Name/Arity</code>, <code class="inline">Module</code>, and <code class="inline">Name</code> are atoms and <code class="inline">Arity</code> is an
│ │ │  integer. <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> can also be variables. A fun defined in
│ │ │  this way refers to the function <code class="inline">Name</code> with arity <code class="inline">Arity</code> in the <em>latest</em>
│ │ │  version of module <code class="inline">Module</code>. A fun defined in this way is not dependent on the
│ │ │  code for the module in which it is defined.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R15, <code class="inline">Module</code>, <code class="inline">Name</code>, and <code class="inline">Arity</code> were not allowed to be
│ │ │  variables.</p></section><p>More examples are provided in <a href="../../doc/system/funs.html">Programming Examples</a>.</p><h2 id="catch-and-throw" class="section-heading">
│ │ │    <a href="#catch-and-throw" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -981,35 +981,35 @@
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">catch</span><span class="w"> </span><span class="n">Expr</span></code></pre><p>Returns the value of <code class="inline">Expr</code> unless an exception is raised during the evaluation. In
│ │ │  that case, the exception is caught. The return value depends on the class of the
│ │ │  exception:</p><ul><li><p><strong><code class="inline">error</code></strong> (a run-time error or the code called <a href="../../erts-15.2.7.2/doc/html/erlang.html#error/1"><code class="inline">error(Term)</code></a>) -
│ │ │  <code class="inline">{'EXIT',{Reason,Stack}}</code> is returned.</p></li><li><p><strong><code class="inline">exit</code></strong> (the code called <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit(Term)</code></a>) - <code class="inline">{'EXIT',Term}</code> is returned.</p></li><li><p><strong><code class="inline">throw</code></strong> (the code called <a href="../../erts-15.2.7.2/doc/html/erlang.html#throw/1"><code class="inline">throw(Term)</code></a>): <code class="inline">Term</code> is returned.</p></li></ul><p><code class="inline">Reason</code> depends on the type of error that occurred, and <code class="inline">Stack</code> is the stack of
│ │ │  recent function calls, see <a href="errors.html#exit_reasons">Exit Reasons</a>.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="k">catch</span><span class="w"> </span><span class="mi">1</span><span class="o">+</span><span class="ss">a</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7067477375-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="7067477375-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="7067477375-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7067477375-3">]</span><span class="p" data-group-id="7067477375-2">}</span><span class="p" data-group-id="7067477375-1">}</span></code></pre><p>The BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ -function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="7980636115-1">(</span><span class="ss">hello</span><span class="p" data-group-id="7980636115-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6325079675-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6325079675-2">{</span><span class="ss">badarith</span><span class="p">,</span><span class="p" data-group-id="6325079675-3">[</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6325079675-3">]</span><span class="p" data-group-id="6325079675-2">}</span><span class="p" data-group-id="6325079675-1">}</span></code></pre><p>The BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#throw/1"><code class="inline">throw(Any)</code></a> can be used for non-local return from a
│ │ │ +function. It must be evaluated within a <code class="inline">catch</code>, which returns the value <code class="inline">Any</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="3973594893-1">(</span><span class="ss">hello</span><span class="p" data-group-id="3973594893-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre><p>If <a href="../../erts-15.2.7.2/doc/html/erlang.html#throw/1"><code class="inline">throw/1</code></a> is not evaluated within a catch, a <code class="inline">nocatch</code> run-time
│ │ │  error occurs.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 24, the <code class="inline">catch</code> operator had the lowest precedence, making
│ │ │ -it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8372274053-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="8372274053-1">)</span><span class="p">.</span><span class="w">
│ │ │ +it necessary to add parentheses when combining it with the <code class="inline">match</code> operator:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4473470301-1">(</span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="4473470301-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span></code></pre><p>Starting from Erlang/OTP 24, the parentheses can be omitted:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="mi">42</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">42</span></code></pre></section><h2 id="try" class="section-heading">
│ │ │    <a href="#try" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Try</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="4903624690-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4903624690-1">]</span><span class="w"> </span><span class="p" data-group-id="4903624690-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="4903624690-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="2048976785-1">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2048976785-1">]</span><span class="w"> </span><span class="p" data-group-id="2048976785-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="2048976785-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="4903624690-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4903624690-3">]</span><span class="w"> </span><span class="p" data-group-id="4903624690-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="4903624690-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="2048976785-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2048976785-3">]</span><span class="w"> </span><span class="p" data-group-id="2048976785-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="2048976785-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>This is an enhancement of <a href="expressions.html#catch-and-throw">catch</a>. It gives the
│ │ │  possibility to:</p><ul><li>Distinguish between different exception classes.</li><li>Choose to handle only the desired ones.</li><li>Passing the others on to an enclosing <code class="inline">try</code> or <code class="inline">catch</code>, or to default error
│ │ │  handling.</li></ul><p>Notice that although the keyword <code class="inline">catch</code> is used in the <code class="inline">try</code> expression, there
│ │ │  is not a <code class="inline">catch</code> expression within the <code class="inline">try</code> expression.</p><p>It returns the value of <code class="inline">Exprs</code> (a sequence of expressions <code class="inline">Expr1, ..., ExprN</code>)
│ │ │  unless an exception occurs during the evaluation. In that case the exception is
│ │ │  caught and the patterns <code class="inline">ExceptionPattern</code> with the right exception class
│ │ │ @@ -1019,47 +1019,47 @@
│ │ │  stack trace is bound to the variable when the corresponding <code class="inline">ExceptionPattern</code>
│ │ │  matches.</p><p>If an exception occurs during evaluation of <code class="inline">Exprs</code> but there is no matching
│ │ │  <code class="inline">ExceptionPattern</code> of the right <code class="inline">Class</code> with a true guard sequence, the
│ │ │  exception is passed on as if <code class="inline">Exprs</code> had not been enclosed in a <code class="inline">try</code>
│ │ │  expression.</p><p>If an exception occurs during evaluation of <code class="inline">ExceptionBody</code>, it is not caught.</p><p>It is allowed to omit <code class="inline">Class</code> and <code class="inline">Stacktrace</code>. An omitted <code class="inline">Class</code> is shorthand
│ │ │  for <code class="inline">throw</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="1954222377-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="1954222377-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ExceptionPattern1</span><span class="w"> </span><span class="p" data-group-id="0240708120-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="0240708120-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="1954222377-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="1954222377-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ExceptionPatternN</span><span class="w"> </span><span class="p" data-group-id="0240708120-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="0240708120-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The <code class="inline">try</code> expression can have an <code class="inline">of</code> section:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="4013231975-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="4013231975-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="6421937425-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="6421937425-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="4013231975-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="4013231975-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="6421937425-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="6421937425-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="4013231975-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4013231975-3">]</span><span class="w"> </span><span class="p" data-group-id="4013231975-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="4013231975-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="6421937425-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="6421937425-3">]</span><span class="w"> </span><span class="p" data-group-id="6421937425-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="6421937425-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="4013231975-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="4013231975-5">]</span><span class="w"> </span><span class="p" data-group-id="4013231975-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="4013231975-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="6421937425-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="6421937425-5">]</span><span class="w"> </span><span class="p" data-group-id="6421937425-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="6421937425-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>If the evaluation of <code class="inline">Exprs</code> succeeds without an exception, the patterns
│ │ │  <code class="inline">Pattern</code> are sequentially matched against the result in the same way as for a
│ │ │  <a href="expressions.html#case">case</a> expression, except that if the matching fails, a
│ │ │  <code class="inline">try_clause</code> run-time error occurs instead of a <code class="inline">case_clause</code>.</p><p>Only exceptions occurring during the evaluation of <code class="inline">Exprs</code> can be caught by the
│ │ │  <code class="inline">catch</code> section. Exceptions occurring in a <code class="inline">Body</code> or due to a failed match are
│ │ │  not caught.</p><p>The <code class="inline">try</code> expression can also be augmented with an <code class="inline">after</code> section, intended to
│ │ │  be used for cleanup with side effects:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="2560465490-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="2560465490-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pattern1</span><span class="w"> </span><span class="p" data-group-id="9237862989-1">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9237862989-1">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="2560465490-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="2560465490-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PatternN</span><span class="w"> </span><span class="p" data-group-id="9237862989-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqN</span><span class="p" data-group-id="9237862989-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">BodyN</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="2560465490-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2560465490-3">]</span><span class="w"> </span><span class="p" data-group-id="2560465490-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="2560465490-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Class1</span><span class="p">:</span><span class="n">ExceptionPattern1</span><span class="p" data-group-id="9237862989-3">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9237862989-3">]</span><span class="w"> </span><span class="p" data-group-id="9237862989-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeq1</span><span class="p" data-group-id="9237862989-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBody1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="2560465490-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="2560465490-5">]</span><span class="w"> </span><span class="p" data-group-id="2560465490-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="2560465490-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ClassN</span><span class="p">:</span><span class="n">ExceptionPatternN</span><span class="p" data-group-id="9237862989-5">[</span><span class="p">:</span><span class="n">Stacktrace</span><span class="p" data-group-id="9237862989-5">]</span><span class="w"> </span><span class="p" data-group-id="9237862989-6">[</span><span class="k">when</span><span class="w"> </span><span class="n">ExceptionGuardSeqN</span><span class="p" data-group-id="9237862989-6">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="n">ExceptionBodyN</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p><code class="inline">AfterBody</code> is evaluated after either <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>, no matter which
│ │ │  one. The evaluated value of <code class="inline">AfterBody</code> is lost; the return value of the <code class="inline">try</code>
│ │ │  expression is the same with an <code class="inline">after</code> section as without.</p><p>Even if an exception occurs during evaluation of <code class="inline">Body</code> or <code class="inline">ExceptionBody</code>,
│ │ │  <code class="inline">AfterBody</code> is evaluated. In this case the exception is passed on after
│ │ │ @@ -1082,40 +1082,40 @@
│ │ │          </span><span class="n">ExpressionBody</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w">
│ │ │      </span><span class="n">AfterBody</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="w">
│ │ │  
│ │ │  </span><span class="k">try</span><span class="w"> </span><span class="n">Exprs</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">AfterBody</span><span class="w"> </span><span class="k">end</span></code></pre><p>Next is an example of using <code class="inline">after</code>. This closes the file, even in the event of
│ │ │  exceptions in <a href="../../lib/kernel-10.2.7.2/doc/html/file.html#read/2"><code class="inline">file:read/2</code></a> or in <a href="../../erts-15.2.7.2/doc/html/erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. The
│ │ │ -exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="6767783204-1">(</span><span class="n">Name</span><span class="p" data-group-id="6767783204-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6767783204-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="6767783204-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="6767783204-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6767783204-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="6767783204-4">]</span><span class="p" data-group-id="6767783204-3">)</span><span class="p">,</span><span class="w">
│ │ │ +exceptions are the same as without the <code class="inline">try</code>...<code class="inline">after</code>...<code class="inline">end</code> expression:</p><pre><code class="makeup erlang" translate="no"><span class="nf">termize_file</span><span class="p" data-group-id="9354471392-1">(</span><span class="n">Name</span><span class="p" data-group-id="9354471392-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9354471392-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">F</span><span class="p" data-group-id="9354471392-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="9354471392-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9354471392-4">[</span><span class="ss">read</span><span class="p">,</span><span class="ss">binary</span><span class="p" data-group-id="9354471392-4">]</span><span class="p" data-group-id="9354471392-3">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">try</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6767783204-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="6767783204-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="6767783204-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="6767783204-6">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="6767783204-7">(</span><span class="n">Bin</span><span class="p" data-group-id="6767783204-7">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9354471392-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="n">Bin</span><span class="p" data-group-id="9354471392-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9354471392-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="mi">1024</span><span class="o">*</span><span class="mi">1024</span><span class="p" data-group-id="9354471392-6">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9354471392-7">(</span><span class="n">Bin</span><span class="p" data-group-id="9354471392-7">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w">
│ │ │ -        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="6767783204-8">(</span><span class="n">F</span><span class="p" data-group-id="6767783204-8">)</span><span class="w">
│ │ │ +        </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="9354471392-8">(</span><span class="n">F</span><span class="p" data-group-id="9354471392-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Next is an example of using <code class="inline">try</code> to emulate <code class="inline">catch Expr</code>:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w"> </span><span class="n">Expr</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │      </span><span class="nc">throw</span><span class="p">:</span><span class="n">Term</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Term</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4627630796-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="4627630796-1">}</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4627630796-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="4627630796-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="4627630796-3">}</span><span class="p" data-group-id="4627630796-2">}</span><span class="w">
│ │ │ +    </span><span class="nc">exit</span><span class="p">:</span><span class="n">Reason</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6410571238-1">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="n">Reason</span><span class="p" data-group-id="6410571238-1">}</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nc">error</span><span class="p">:</span><span class="n">Reason</span><span class="p">:</span><span class="n">Stk</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6410571238-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="6410571238-3">{</span><span class="n">Reason</span><span class="p">,</span><span class="n">Stk</span><span class="p" data-group-id="6410571238-3">}</span><span class="p" data-group-id="6410571238-2">}</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Variables bound in the various parts of these expressions have different scopes.
│ │ │  Variables bound just after the <code class="inline">try</code> keyword are:</p><ul><li>bound in the <code class="inline">of</code> section</li><li>unsafe in both the <code class="inline">catch</code> and <code class="inline">after</code> sections, as well as after the whole
│ │ │  construct</li></ul><p>Variables bound in <code class="inline">of</code> section are:</p><ul><li>unbound in the <code class="inline">catch</code> section</li><li>unsafe in both the <code class="inline">after</code> section, as well as after the whole construct</li></ul><p>Variables bound in the <code class="inline">catch</code> section are unsafe in the <code class="inline">after</code> section, as
│ │ │  well as after the whole construct.</p><p>Variables bound in the <code class="inline">after</code> section are unsafe after the whole construct.</p><h2 id="parenthesized-expressions" class="section-heading">
│ │ │    <a href="#parenthesized-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Parenthesized Expressions</span>
│ │ │  </h2>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0697793174-1">(</span><span class="n">Expr</span><span class="p" data-group-id="0697793174-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3937114475-1">(</span><span class="n">Expr</span><span class="p" data-group-id="3937114475-1">)</span></code></pre><p>Parenthesized expressions are useful to override
│ │ │  <a href="expressions.html#prec">operator precedences</a>, for example, in arithmetic
│ │ │  expressions:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">7</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="1813296657-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1813296657-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="p" data-group-id="2259767932-1">(</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2259767932-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">9</span></code></pre><h2 id="block-expressions" class="section-heading">
│ │ │    <a href="#block-expressions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Block Expressions</span>
│ │ │  </h2>
│ │ │  <pre><code class="makeup erlang" translate="no"><span class="k">begin</span><span class="w">
│ │ │ @@ -1127,71 +1127,71 @@
│ │ │    <a href="#comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Comprehensions</span>
│ │ │  </h2>
│ │ │  <p>Comprehensions provide a succinct notation for iterating over one or more terms
│ │ │  and constructing a new term. Comprehensions come in three different flavors,
│ │ │ -depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1224985875-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="1224985875-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │ +depending on the type of term they build.</p><p>List comprehensions construct lists. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3428516979-1">[</span><span class="n">Expr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="3428516979-1">]</span></code></pre><p>Here, <code class="inline">Expr</code> is an arbitrary expression, and each <code class="inline">Qualifier</code> is either a
│ │ │  <strong>generator</strong> or a <strong>filter</strong>.</p><p>Bit string comprehensions construct bit strings or binaries. They have the
│ │ │ -following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8142834453-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="8142834453-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │ +following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8264114272-1">&lt;&lt;</span><span class="w"> </span><span class="n">BitStringExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="w"> </span><span class="p" data-group-id="8264114272-1">&gt;&gt;</span></code></pre><p><code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string. If
│ │ │  <code class="inline">BitStringExpr</code> is a function call, it must be enclosed in parentheses. Each
│ │ │ -<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7032550877-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="7032550877-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │ +<code class="inline">Qualifier</code> is either a <strong>generator</strong> or a <strong>filter</strong>.</p><p>Map comprehensions construct maps. They have the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3930403452-1">#{</span><span class="n">KeyExpr</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueExpr</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Qualifier1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">QualifierN</span><span class="p" data-group-id="3930403452-1">}</span></code></pre><p>Here, <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> are arbitrary expressions, and each <code class="inline">Qualifier</code>
│ │ │  is either a <strong>generator</strong> or a <strong>filter</strong>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Map comprehensions and map generators were introduced in Erlang/OTP 26.</p></section><p>There are three kinds of generators.</p><p>A <em>list generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">Pattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">ListExpr</span></code></pre><p>where <code class="inline">ListExpr</code> is an expression that evaluates to a list of terms.</p><p>A <em>bit string generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">BitstringPattern</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">BitStringExpr</span></code></pre><p>where <code class="inline">BitStringExpr</code> is an expression that evaluates to a bit string.</p><p>A <em>map generator</em> has the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">KeyPattern</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">ValuePattern</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">MapExpression</span></code></pre><p>where <code class="inline">MapExpr</code> is an expression that evaluates to a map, or a map iterator
│ │ │  obtained by calling <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#iterator/1"><code class="inline">maps:iterator/1</code></a> or <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#iterator/2"><code class="inline">maps:iterator/2</code></a>.</p><p>A <em>filter</em> is an expression that evaluates to <code class="inline">true</code> or <code class="inline">false</code>.</p><p>The variables in the generator patterns shadow previously bound variables,
│ │ │  including variables bound in a previous generator pattern.</p><p>Variables bound in a generator expression are not visible outside the
│ │ │ -expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2619803887-1">[</span><span class="p" data-group-id="2619803887-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="2619803887-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="2619803887-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2619803887-3">]</span><span class="p" data-group-id="2619803887-1">]</span><span class="p">.</span><span class="w">
│ │ │ +expression:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0441768065-1">[</span><span class="p" data-group-id="0441768065-2">{</span><span class="n">E</span><span class="p">,</span><span class="n">L</span><span class="p" data-group-id="0441768065-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="o">=</span><span class="p" data-group-id="0441768065-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0441768065-3">]</span><span class="p" data-group-id="0441768065-1">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">* 1:5: variable &#39;L&#39; is unbound</span></code></pre><p>A <strong>list comprehension</strong> returns a list, where the list elements are the result
│ │ │  of evaluating <code class="inline">Expr</code> for each combination of generator elements for which all
│ │ │  filters are true.</p><p>A <strong>bit string comprehension</strong> returns a bit string, which is created by
│ │ │  concatenating the results of evaluating <code class="inline">BitStringExpr</code> for each combination of
│ │ │  bit string generator elements for which all filters are true.</p><p>A <strong>map comprehension</strong> returns a map, where the map elements are the result of
│ │ │  evaluating <code class="inline">KeyExpr</code> and <code class="inline">ValueExpr</code> for each combination of generator elements
│ │ │  for which all filters are true. If the key expressions are not unique, the last
│ │ │ -occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0174599276-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0174599276-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0174599276-2">]</span><span class="p" data-group-id="0174599276-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0174599276-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0174599276-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6161481747-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6161481747-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="6161481747-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="6161481747-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6161481747-3">&gt;&gt;</span><span class="p" data-group-id="6161481747-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6161481747-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6161481747-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3424245161-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="3424245161-2">&lt;&lt;</span><span class="p" data-group-id="3424245161-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="3424245161-3">)</span><span class="p" data-group-id="3424245161-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="3424245161-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="3424245161-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="3424245161-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3424245161-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="3424245161-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3424245161-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3424245161-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9060154017-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="9060154017-2">&lt;&lt;</span><span class="p" data-group-id="9060154017-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="9060154017-3">)</span><span class="p" data-group-id="9060154017-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9060154017-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9060154017-4">]</span><span class="w"> </span><span class="p" data-group-id="9060154017-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9060154017-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9060154017-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="1570732826-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1570732826-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1570732826-2">]</span><span class="p" data-group-id="1570732826-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1570732826-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1570732826-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2002384257-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="2002384257-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2002384257-2">}</span><span class="p" data-group-id="2002384257-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2002384257-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="2002384257-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9349125890-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9349125890-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9349125890-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9349125890-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9349125890-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9349125890-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9005544911-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9005544911-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9005544911-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9005544911-3">[</span><span class="p" data-group-id="9005544911-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9005544911-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9005544911-5">[</span><span class="ss">a</span><span class="p" data-group-id="9005544911-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9005544911-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9005544911-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9005544911-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9005544911-7">}</span><span class="p" data-group-id="9005544911-3">]</span><span class="p" data-group-id="9005544911-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9005544911-8">[</span><span class="p" data-group-id="9005544911-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9005544911-9">}</span><span class="p">,</span><span class="p" data-group-id="9005544911-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9005544911-10">}</span><span class="p" data-group-id="9005544911-8">]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5917955089-1">[</span><span class="p" data-group-id="5917955089-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="5917955089-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5917955089-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5917955089-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5917955089-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5917955089-4">]</span><span class="p" data-group-id="5917955089-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5917955089-5">[</span><span class="p" data-group-id="5917955089-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5917955089-6">}</span><span class="p">,</span><span class="p" data-group-id="5917955089-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5917955089-7">}</span><span class="p">,</span><span class="p" data-group-id="5917955089-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5917955089-8">}</span><span class="p">,</span><span class="p" data-group-id="5917955089-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5917955089-9">}</span><span class="p">,</span><span class="p" data-group-id="5917955089-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5917955089-10">}</span><span class="p">,</span><span class="p" data-group-id="5917955089-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5917955089-11">}</span><span class="p" data-group-id="5917955089-5">]</span></code></pre><p>More examples are provided in
│ │ │ +occurrence is stored in the map.</p><p><strong>Examples:</strong></p><p>Multiplying each element in a list by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="2351388961-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="2351388961-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2351388961-2">]</span><span class="p" data-group-id="2351388961-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2351388961-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2351388961-3">]</span></code></pre><p>Multiplying each byte in a binary by two, returning a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="6928845606-1">[</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="6928845606-2">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="6928845606-2">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="6928845606-3">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6928845606-3">&gt;&gt;</span><span class="p" data-group-id="6928845606-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6928845606-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="6928845606-4">]</span></code></pre><p>Multiplying each byte in a binary by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8116362027-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="8116362027-2">&lt;&lt;</span><span class="p" data-group-id="8116362027-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="8116362027-3">)</span><span class="p" data-group-id="8116362027-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="8116362027-4">&lt;&lt;</span><span class="n">X</span><span class="p" data-group-id="8116362027-4">&gt;&gt;</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="p" data-group-id="8116362027-5">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8116362027-5">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="8116362027-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8116362027-6">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8116362027-6">&gt;&gt;</span></code></pre><p>Multiplying each element in a list by two, returning a binary:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9434021296-1">&lt;&lt;</span><span class="w"> </span><span class="p" data-group-id="9434021296-2">&lt;&lt;</span><span class="p" data-group-id="9434021296-3">(</span><span class="n">X</span><span class="o">*</span><span class="mi">2</span><span class="p" data-group-id="9434021296-3">)</span><span class="p" data-group-id="9434021296-2">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9434021296-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9434021296-4">]</span><span class="w"> </span><span class="p" data-group-id="9434021296-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9434021296-5">&lt;&lt;</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9434021296-5">&gt;&gt;</span></code></pre><p>Creating a mapping from an integer to its square:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8572449829-1">#{</span><span class="n">X</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="8572449829-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8572449829-2">]</span><span class="p" data-group-id="8572449829-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8572449829-3">#{</span><span class="mi">1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8572449829-3">}</span></code></pre><p>Multiplying the value of each element in a map by two:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="3124366868-1">#{</span><span class="n">K</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">V</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">K</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="3124366868-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3124366868-2">}</span><span class="p" data-group-id="3124366868-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3124366868-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="3124366868-3">}</span></code></pre><p>Filtering a list, keeping odd numbers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9987121540-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9987121540-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9987121540-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9987121540-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9987121540-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9987121540-3">]</span></code></pre><p>Filtering a list, keeping only elements that match:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9188067690-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="9188067690-2">{</span><span class="p">_</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9188067690-2">}</span><span class="o">=</span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9188067690-3">[</span><span class="p" data-group-id="9188067690-4">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9188067690-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9188067690-5">[</span><span class="ss">a</span><span class="p" data-group-id="9188067690-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9188067690-6">{</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="9188067690-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9188067690-7">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9188067690-7">}</span><span class="p" data-group-id="9188067690-3">]</span><span class="p" data-group-id="9188067690-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9188067690-8">[</span><span class="p" data-group-id="9188067690-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9188067690-9">}</span><span class="p">,</span><span class="p" data-group-id="9188067690-10">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9188067690-10">}</span><span class="p" data-group-id="9188067690-8">]</span></code></pre><p>Combining elements from two list generators:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="0003273138-1">[</span><span class="p" data-group-id="0003273138-2">{</span><span class="n">P</span><span class="p">,</span><span class="n">Q</span><span class="p" data-group-id="0003273138-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">P</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0003273138-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0003273138-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Q</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="0003273138-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0003273138-4">]</span><span class="p" data-group-id="0003273138-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0003273138-5">[</span><span class="p" data-group-id="0003273138-6">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0003273138-6">}</span><span class="p">,</span><span class="p" data-group-id="0003273138-7">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0003273138-7">}</span><span class="p">,</span><span class="p" data-group-id="0003273138-8">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0003273138-8">}</span><span class="p">,</span><span class="p" data-group-id="0003273138-9">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0003273138-9">}</span><span class="p">,</span><span class="p" data-group-id="0003273138-10">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0003273138-10">}</span><span class="p">,</span><span class="p" data-group-id="0003273138-11">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0003273138-11">}</span><span class="p" data-group-id="0003273138-5">]</span></code></pre><p>More examples are provided in
│ │ │  <a href="../../doc/system/list_comprehensions.html">Programming Examples.</a></p><p>When there are no generators, a comprehension returns either a term constructed
│ │ │  from a single element (the result of evaluating <code class="inline">Expr</code>) if all filters are true,
│ │ │  or a term constructed from no elements (that is, <code class="inline">[]</code> for list comprehension,
│ │ │ -<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="8120163044-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8120163044-2">(</span><span class="mi">2</span><span class="p" data-group-id="8120163044-2">)</span><span class="p" data-group-id="8120163044-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8120163044-3">[</span><span class="mi">2</span><span class="p" data-group-id="8120163044-3">]</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="8120163044-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="8120163044-5">(</span><span class="ss">x</span><span class="p" data-group-id="8120163044-5">)</span><span class="p" data-group-id="8120163044-4">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8120163044-6">[</span><span class="p" data-group-id="8120163044-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │ +<code class="inline">&lt;&lt;&gt;&gt;</code> for a bit string comprehension, and <code class="inline">#{}</code> for a map comprehension).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="4404233327-1">[</span><span class="mi">2</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4404233327-2">(</span><span class="mi">2</span><span class="p" data-group-id="4404233327-2">)</span><span class="p" data-group-id="4404233327-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4404233327-3">[</span><span class="mi">2</span><span class="p" data-group-id="4404233327-3">]</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="4404233327-4">[</span><span class="ss">x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4404233327-5">(</span><span class="ss">x</span><span class="p" data-group-id="4404233327-5">)</span><span class="p" data-group-id="4404233327-4">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4404233327-6">[</span><span class="p" data-group-id="4404233327-6">]</span></code></pre><p>What happens when the filter expression does not evaluate to a boolean value
│ │ │  depends on the expression:</p><ul><li>If the expression is a <a href="expressions.html#guard-expressions">guard expression</a>,
│ │ │  failure to evaluate or evaluating to a non-boolean value is equivalent to
│ │ │  evaluating to <code class="inline">false</code>.</li><li>If the expression is not a guard expression and evaluates to a non-Boolean
│ │ │  value <code class="inline">Val</code>, an exception <code class="inline">{bad_filter, Val}</code> is triggered at runtime. If the
│ │ │  evaluation of the expression raises an exception, it is not caught by the
│ │ │ -comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0526129533-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0526129533-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0526129533-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0526129533-2">]</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="0526129533-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="0526129533-3">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0526129533-4">[</span><span class="p" data-group-id="0526129533-4">]</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="p" data-group-id="0526129533-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0526129533-5">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0526129533-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0526129533-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9694875748-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9694875748-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9694875748-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9694875748-2">]</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9694875748-3">(</span><span class="n">E</span><span class="p" data-group-id="9694875748-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +comprehension.</li></ul><p><strong>Examples</strong> (using a guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3462103284-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3462103284-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3462103284-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3462103284-2">]</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="3462103284-3">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3462103284-3">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3462103284-4">[</span><span class="p" data-group-id="3462103284-4">]</span><span class="gp unselectable">
│ │ │ +3&gt; </span><span class="p" data-group-id="3462103284-5">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3462103284-5">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3462103284-6">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3462103284-6">]</span></code></pre><p><strong>Examples</strong> (using a non-guard expression as filter):</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3392975674-1">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3392975674-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3392975674-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3392975674-2">]</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="n">FaultyIsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3392975674-3">(</span><span class="n">E</span><span class="p" data-group-id="3392975674-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="p" data-group-id="9694875748-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="9694875748-5">(</span><span class="n">E</span><span class="p" data-group-id="9694875748-5">)</span><span class="p" data-group-id="9694875748-4">]</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="p" data-group-id="3392975674-4">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">FaultyIsEven</span><span class="p" data-group-id="3392975674-5">(</span><span class="n">E</span><span class="p" data-group-id="3392975674-5">)</span><span class="p" data-group-id="3392975674-4">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad filter 1</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9694875748-6">(</span><span class="n">E</span><span class="p" data-group-id="9694875748-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="n">IsEven</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3392975674-6">(</span><span class="n">E</span><span class="p" data-group-id="3392975674-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">42.17316486</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="p" data-group-id="9694875748-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="9694875748-8">(</span><span class="n">E</span><span class="p" data-group-id="9694875748-8">)</span><span class="p" data-group-id="9694875748-7">]</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="p" data-group-id="3392975674-7">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="3392975674-8">(</span><span class="n">E</span><span class="p" data-group-id="3392975674-8">)</span><span class="p" data-group-id="3392975674-7">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: an error occurred when evaluating an arithmetic expression
│ │ │       in operator  rem/2
│ │ │          called as a rem 2</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="p" data-group-id="9694875748-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="9694875748-10">(</span><span class="n">E</span><span class="p" data-group-id="9694875748-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="9694875748-11">(</span><span class="n">E</span><span class="p" data-group-id="9694875748-11">)</span><span class="p" data-group-id="9694875748-9">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9694875748-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9694875748-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │ +6&gt; </span><span class="p" data-group-id="3392975674-9">[</span><span class="n">E</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="3392975674-10">(</span><span class="n">E</span><span class="p" data-group-id="3392975674-10">)</span><span class="p">,</span><span class="w"> </span><span class="n">IsEven</span><span class="p" data-group-id="3392975674-11">(</span><span class="n">E</span><span class="p" data-group-id="3392975674-11">)</span><span class="p" data-group-id="3392975674-9">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3392975674-12">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3392975674-12">]</span></code></pre><p><a href="" id="guards"></a></p><h2 id="guard-sequences" class="section-heading">
│ │ │    <a href="#guard-sequences" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Guard Sequences</span>
│ │ │  </h2>
│ │ │  <p>A <em>guard sequence</em> is a sequence of guards, separated by semicolon (<code class="inline">;</code>). The
│ │ │  guard sequence is true if at least one of the guards is true. (The remaining
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/funs.html
│ │ │ @@ -117,402 +117,402 @@
│ │ │  
│ │ │  <h2 id="map" class="section-heading">
│ │ │    <a href="#map" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">map</span>
│ │ │  </h2>
│ │ │ -<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="4785925196-1">(</span><span class="p" data-group-id="4785925196-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4785925196-2">]</span><span class="p" data-group-id="4785925196-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4785925196-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="4785925196-4">(</span><span class="n">T</span><span class="p" data-group-id="4785925196-4">)</span><span class="p" data-group-id="4785925196-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="4785925196-5">(</span><span class="p" data-group-id="4785925196-6">[</span><span class="p" data-group-id="4785925196-6">]</span><span class="p" data-group-id="4785925196-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4785925196-7">[</span><span class="p" data-group-id="4785925196-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="6198262353-1">(</span><span class="p" data-group-id="6198262353-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6198262353-2">]</span><span class="p" data-group-id="6198262353-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6198262353-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="6198262353-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="5881439997-1">(</span><span class="p" data-group-id="5881439997-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5881439997-2">]</span><span class="p" data-group-id="5881439997-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5881439997-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="5881439997-4">(</span><span class="n">T</span><span class="p" data-group-id="5881439997-4">)</span><span class="p" data-group-id="5881439997-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="5881439997-5">(</span><span class="p" data-group-id="5881439997-6">[</span><span class="p" data-group-id="5881439997-6">]</span><span class="p" data-group-id="5881439997-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5881439997-7">[</span><span class="p" data-group-id="5881439997-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ -by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="3852448690-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3852448690-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3852448690-2">]</span><span class="p" data-group-id="3852448690-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3852448690-3">[</span><span class="n">F</span><span class="p" data-group-id="3852448690-4">(</span><span class="n">H</span><span class="p" data-group-id="3852448690-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="3852448690-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3852448690-5">)</span><span class="p" data-group-id="3852448690-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="3852448690-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3852448690-7">[</span><span class="p" data-group-id="3852448690-7">]</span><span class="p" data-group-id="3852448690-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3852448690-8">[</span><span class="p" data-group-id="3852448690-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ -follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="0458211843-1">(</span><span class="n">L</span><span class="p" data-group-id="0458211843-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="0458211843-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0458211843-3">(</span><span class="n">X</span><span class="p" data-group-id="0458211843-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0458211843-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add_one</span><span class="p" data-group-id="0458211843-4">(</span><span class="n">L</span><span class="p" data-group-id="0458211843-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="0458211843-5">(</span><span class="nf">fun</span><span class="p" data-group-id="0458211843-6">(</span><span class="n">X</span><span class="p" data-group-id="0458211843-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0458211843-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │ +<p>The following function, <code class="inline">double</code>, doubles every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="8207556925-1">(</span><span class="p" data-group-id="8207556925-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8207556925-2">]</span><span class="p" data-group-id="8207556925-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8207556925-3">[</span><span class="mi">2</span><span class="o">*</span><span class="n">H</span><span class="p">|</span><span class="nf">double</span><span class="p" data-group-id="8207556925-4">(</span><span class="n">T</span><span class="p" data-group-id="8207556925-4">)</span><span class="p" data-group-id="8207556925-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="8207556925-5">(</span><span class="p" data-group-id="8207556925-6">[</span><span class="p" data-group-id="8207556925-6">]</span><span class="p" data-group-id="8207556925-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8207556925-7">[</span><span class="p" data-group-id="8207556925-7">]</span><span class="p">.</span></code></pre><p>Hence, the argument entered as input is doubled as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">double</span><span class="p" data-group-id="2737012316-1">(</span><span class="p" data-group-id="2737012316-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2737012316-2">]</span><span class="p" data-group-id="2737012316-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2737012316-3">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p" data-group-id="2737012316-3">]</span></code></pre><p>The following function, <code class="inline">add_one</code>, adds one to every element in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">add_one</span><span class="p" data-group-id="4107195914-1">(</span><span class="p" data-group-id="4107195914-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4107195914-2">]</span><span class="p" data-group-id="4107195914-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4107195914-3">[</span><span class="n">H</span><span class="o">+</span><span class="mi">1</span><span class="p">|</span><span class="nf">add_one</span><span class="p" data-group-id="4107195914-4">(</span><span class="n">T</span><span class="p" data-group-id="4107195914-4">)</span><span class="p" data-group-id="4107195914-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="4107195914-5">(</span><span class="p" data-group-id="4107195914-6">[</span><span class="p" data-group-id="4107195914-6">]</span><span class="p" data-group-id="4107195914-5">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4107195914-7">[</span><span class="p" data-group-id="4107195914-7">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> have a similar structure. This can be used
│ │ │ +by writing a function <code class="inline">map</code> that expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="2213309270-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2213309270-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2213309270-2">]</span><span class="p" data-group-id="2213309270-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2213309270-3">[</span><span class="n">F</span><span class="p" data-group-id="2213309270-4">(</span><span class="n">H</span><span class="p" data-group-id="2213309270-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="2213309270-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2213309270-5">)</span><span class="p" data-group-id="2213309270-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="2213309270-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2213309270-7">[</span><span class="p" data-group-id="2213309270-7">]</span><span class="p" data-group-id="2213309270-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2213309270-8">[</span><span class="p" data-group-id="2213309270-8">]</span><span class="p">.</span></code></pre><p>The functions <code class="inline">double</code> and <code class="inline">add_one</code> can now be expressed in terms of <code class="inline">map</code> as
│ │ │ +follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">double</span><span class="p" data-group-id="6591560372-1">(</span><span class="n">L</span><span class="p" data-group-id="6591560372-1">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="6591560372-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6591560372-3">(</span><span class="n">X</span><span class="p" data-group-id="6591560372-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="o">*</span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6591560372-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add_one</span><span class="p" data-group-id="6591560372-4">(</span><span class="n">L</span><span class="p" data-group-id="6591560372-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="6591560372-5">(</span><span class="nf">fun</span><span class="p" data-group-id="6591560372-6">(</span><span class="n">X</span><span class="p" data-group-id="6591560372-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="6591560372-5">)</span><span class="p">.</span></code></pre><p><code class="inline">map(F, List)</code> is a function that takes a function <code class="inline">F</code> and a list <code class="inline">L</code> as
│ │ │  arguments and returns a new list, obtained by applying <code class="inline">F</code> to each of the
│ │ │  elements in <code class="inline">L</code>.</p><p>The process of abstracting out the common features of a number of different
│ │ │  programs is called <em>procedural abstraction</em>. Procedural abstraction can be used
│ │ │  to write several different functions that have a similar structure, but differ
│ │ │  in some minor detail. This is done as follows:</p><ol><li><em>Step 1.</em> Write one function that represents the common features of these
│ │ │  functions.</li><li><em>Step 2.</em> Parameterize the difference in terms of functions that are passed
│ │ │  as arguments to the common function.</li></ol><h2 id="foreach" class="section-heading">
│ │ │    <a href="#foreach" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">foreach</span>
│ │ │  </h2>
│ │ │  <p>This section illustrates procedural abstraction. Initially, the following two
│ │ │ -examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="8195218762-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8195218762-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8195218762-2">]</span><span class="p" data-group-id="8195218762-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8195218762-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8195218762-4">[</span><span class="n">H</span><span class="p" data-group-id="8195218762-4">]</span><span class="p" data-group-id="8195218762-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_list</span><span class="p" data-group-id="8195218762-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="8195218762-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">print_list</span><span class="p" data-group-id="8195218762-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8195218762-7">[</span><span class="p" data-group-id="8195218762-7">]</span><span class="p" data-group-id="8195218762-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="2532874704-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2532874704-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="2532874704-2">]</span><span class="p" data-group-id="2532874704-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +examples are written as conventional functions.</p><p>This function prints all elements of a list onto a stream:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="8929298332-1">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8929298332-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8929298332-2">]</span><span class="p" data-group-id="8929298332-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8929298332-3">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8929298332-4">[</span><span class="n">H</span><span class="p" data-group-id="8929298332-4">]</span><span class="p" data-group-id="8929298332-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_list</span><span class="p" data-group-id="8929298332-5">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="8929298332-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">print_list</span><span class="p" data-group-id="8929298332-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8929298332-7">[</span><span class="p" data-group-id="8929298332-7">]</span><span class="p" data-group-id="8929298332-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>This function broadcasts a message to a list of processes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">broadcast</span><span class="p" data-group-id="0615748705-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0615748705-2">[</span><span class="n">Pid</span><span class="p">|</span><span class="n">Pids</span><span class="p" data-group-id="0615748705-2">]</span><span class="p" data-group-id="0615748705-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">Msg</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">broadcast</span><span class="p" data-group-id="2532874704-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="2532874704-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">broadcast</span><span class="p" data-group-id="2532874704-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2532874704-5">[</span><span class="p" data-group-id="2532874704-5">]</span><span class="p" data-group-id="2532874704-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">broadcast</span><span class="p" data-group-id="0615748705-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">Pids</span><span class="p" data-group-id="0615748705-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">broadcast</span><span class="p" data-group-id="0615748705-4">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0615748705-5">[</span><span class="p" data-group-id="0615748705-5">]</span><span class="p" data-group-id="0615748705-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="p">.</span></code></pre><p>These two functions have a similar structure. They both iterate over a list and
│ │ │  do something to each element in the list. The &quot;something&quot; is passed on as an
│ │ │ -extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="3650574844-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3650574844-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3650574844-2">]</span><span class="p" data-group-id="3650574844-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="3650574844-3">(</span><span class="n">H</span><span class="p" data-group-id="3650574844-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="3650574844-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3650574844-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="3650574844-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3650574844-6">[</span><span class="p" data-group-id="3650574844-6">]</span><span class="p" data-group-id="3650574844-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="7878768222-1">(</span><span class="nf">fun</span><span class="p" data-group-id="7878768222-2">(</span><span class="n">H</span><span class="p" data-group-id="7878768222-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7878768222-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7878768222-4">[</span><span class="n">H</span><span class="p" data-group-id="7878768222-4">]</span><span class="p" data-group-id="7878768222-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7878768222-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="5542735152-1">(</span><span class="nf">fun</span><span class="p" data-group-id="5542735152-2">(</span><span class="n">Pid</span><span class="p" data-group-id="5542735152-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5542735152-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun ,L)</code>
│ │ │ +extra argument to the function that does this.</p><p>The function <code class="inline">foreach</code> expresses this similarity:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="4084414092-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4084414092-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4084414092-2">]</span><span class="p" data-group-id="4084414092-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="4084414092-3">(</span><span class="n">H</span><span class="p" data-group-id="4084414092-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="4084414092-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4084414092-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="4084414092-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4084414092-6">[</span><span class="p" data-group-id="4084414092-6">]</span><span class="p" data-group-id="4084414092-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">print_list</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="7311895896-1">(</span><span class="nf">fun</span><span class="p" data-group-id="7311895896-2">(</span><span class="n">H</span><span class="p" data-group-id="7311895896-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7311895896-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="7311895896-4">[</span><span class="n">H</span><span class="p" data-group-id="7311895896-4">]</span><span class="p" data-group-id="7311895896-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7311895896-1">)</span></code></pre><p>Using the function <code class="inline">foreach</code>, the function <code class="inline">broadcast</code> becomes:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="3039724312-1">(</span><span class="nf">fun</span><span class="p" data-group-id="3039724312-2">(</span><span class="n">Pid</span><span class="p" data-group-id="3039724312-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3039724312-1">)</span></code></pre><p><code class="inline">foreach</code> is evaluated for its side-effect and not its value. <code class="inline">foreach(Fun ,L)</code>
│ │ │  calls <code class="inline">Fun(X)</code> for each element <code class="inline">X</code> in <code class="inline">L</code> and the processing occurs in the
│ │ │  order that the elements were defined in <code class="inline">L</code>. <code class="inline">map</code> does not define the order in
│ │ │  which its elements are processed.</p><h2 id="syntax-of-funs" class="section-heading">
│ │ │    <a href="#syntax-of-funs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Syntax of Funs</span>
│ │ │  </h2>
│ │ │  <p>Funs are written with the following syntax (see
│ │ │ -<a href="../../doc/system/expressions.html#fun-expressions">Fun Expressions </a>for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1113368276-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="1113368276-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<a href="../../doc/system/expressions.html#fun-expressions">Fun Expressions </a>for full description):</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3655468532-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="n">ArgN</span><span class="p" data-group-id="3655468532-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">end</span></code></pre><p>This creates an anonymous function of <code class="inline">N</code> arguments and binds it to the variable
│ │ │  <code class="inline">F</code>.</p><p>Another function, <code class="inline">FunctionName</code>, written in the same module, can be passed as
│ │ │  an argument, using the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>With this form of function reference, the function that is referred to does not
│ │ │  need to be exported from the module.</p><p>It is also possible to refer to a function defined in a different module, with
│ │ │ -the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7350403229-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="7350403229-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7350403229-2">(</span><span class="p" data-group-id="7350403229-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7350403229-3">]</span><span class="p" data-group-id="7350403229-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="7350403229-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7350403229-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7350403229-5">]</span><span class="p" data-group-id="7350403229-4">)</span><span class="p">.</span><span class="w">
│ │ │ +the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">Module</span><span class="p">:</span><span class="n">FunctionName</span><span class="o">/</span><span class="n">Arity</span></code></pre><p>In this case, the function must be exported from the module in question.</p><p>The following program illustrates the different ways of creating funs:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1524581118-1">(</span><span class="ss">fun_test</span><span class="p" data-group-id="1524581118-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1524581118-2">(</span><span class="p" data-group-id="1524581118-3">[</span><span class="ss">t1</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">t2</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1524581118-3">]</span><span class="p" data-group-id="1524581118-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">import</span><span class="p" data-group-id="1524581118-4">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1524581118-5">[</span><span class="ss">map</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1524581118-5">]</span><span class="p" data-group-id="1524581118-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">t1</span><span class="p" data-group-id="7350403229-6">(</span><span class="p" data-group-id="7350403229-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="7350403229-7">(</span><span class="nf">fun</span><span class="p" data-group-id="7350403229-8">(</span><span class="n">X</span><span class="p" data-group-id="7350403229-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7350403229-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7350403229-9">]</span><span class="p" data-group-id="7350403229-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">t1</span><span class="p" data-group-id="1524581118-6">(</span><span class="p" data-group-id="1524581118-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="1524581118-7">(</span><span class="nf">fun</span><span class="p" data-group-id="1524581118-8">(</span><span class="n">X</span><span class="p" data-group-id="1524581118-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1524581118-9">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1524581118-9">]</span><span class="p" data-group-id="1524581118-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">t2</span><span class="p" data-group-id="7350403229-10">(</span><span class="p" data-group-id="7350403229-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="7350403229-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7350403229-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7350403229-12">]</span><span class="p" data-group-id="7350403229-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">t2</span><span class="p" data-group-id="1524581118-10">(</span><span class="p" data-group-id="1524581118-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">map</span><span class="p" data-group-id="1524581118-11">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1524581118-12">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1524581118-12">]</span><span class="p" data-group-id="1524581118-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="7350403229-13">(</span><span class="n">X</span><span class="p" data-group-id="7350403229-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="8735045932-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="8735045932-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ -<a href="../../erts-15.2.7.2/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3877110149-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="3877110149-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="3877110149-2">(</span><span class="n">F</span><span class="p" data-group-id="3877110149-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="nf">apply</span><span class="p" data-group-id="3877110149-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="3877110149-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="3877110149-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3877110149-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="3877110149-5">(</span><span class="n">N</span><span class="p" data-group-id="3877110149-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="1524581118-13">(</span><span class="n">X</span><span class="p" data-group-id="1524581118-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span></code></pre><p>The fun <code class="inline">F</code> can be evaluated with the following syntax:</p><pre><code class="makeup erlang" translate="no"><span class="n">F</span><span class="p" data-group-id="3918232489-1">(</span><span class="n">Arg1</span><span class="p">,</span><span class="w"> </span><span class="n">Arg2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Argn</span><span class="p" data-group-id="3918232489-1">)</span></code></pre><p>To check whether a term is a fun, use the test
│ │ │ +<a href="../../erts-15.2.7.2/doc/html/erlang.html#is_function/1"><code class="inline">is_function/1</code></a> in a guard.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4310705720-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4310705720-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_function</span><span class="p" data-group-id="4310705720-2">(</span><span class="n">F</span><span class="p" data-group-id="4310705720-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="nf">apply</span><span class="p" data-group-id="4310705720-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4310705720-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="4310705720-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="4310705720-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="4310705720-5">(</span><span class="n">N</span><span class="p" data-group-id="4310705720-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │     </span><span class="n">N</span><span class="p">.</span></code></pre><p>Funs are a distinct type. The BIFs <code class="inline">erlang:fun_info/1,2</code> can be used to retrieve
│ │ │  information about a fun, and the BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#fun_to_list/1"><code class="inline">erlang:fun_to_list/1</code></a> returns a textual
│ │ │  representation of a fun. The <a href="../../erts-15.2.7.2/doc/html/erlang.html#check_process_code/2"><code class="inline">check_process_code/2</code></a>
│ │ │  BIF returns <code class="inline">true</code> if the process contains funs that depend on the old version
│ │ │  of a module.</p><h2 id="variable-bindings-within-a-fun" class="section-heading">
│ │ │    <a href="#variable-bindings-within-a-fun" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Variable Bindings Within a Fun</span>
│ │ │  </h2>
│ │ │  <p>The scope rules for variables that occur in funs are as follows:</p><ul><li>All variables that occur in the head of a fun are assumed to be &quot;fresh&quot;
│ │ │  variables.</li><li>Variables that are defined before the fun, and that occur in function calls or
│ │ │ -guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="8739296543-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8739296543-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8739296543-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="8739296543-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="8739296543-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="8739296543-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="8739296543-4">(</span><span class="nf">fun</span><span class="p" data-group-id="8739296543-5">(</span><span class="n">X</span><span class="p" data-group-id="8739296543-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8739296543-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="8739296543-7">[</span><span class="n">X</span><span class="p" data-group-id="8739296543-7">]</span><span class="p" data-group-id="8739296543-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8739296543-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="8739296543-8">(</span><span class="n">Stream</span><span class="p" data-group-id="8739296543-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │ +guard tests within the fun, have the values they had outside the fun.</li><li>Variables cannot be exported from a fun.</li></ul><p>The following examples illustrate these rules:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="8133902108-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8133902108-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8133902108-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="8133902108-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="8133902108-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="8133902108-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="8133902108-4">(</span><span class="nf">fun</span><span class="p" data-group-id="8133902108-5">(</span><span class="n">X</span><span class="p" data-group-id="8133902108-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8133902108-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="8133902108-7">[</span><span class="n">X</span><span class="p" data-group-id="8133902108-7">]</span><span class="p" data-group-id="8133902108-6">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8133902108-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="8133902108-8">(</span><span class="n">Stream</span><span class="p" data-group-id="8133902108-8">)</span><span class="p">.</span></code></pre><p>Here, the variable <code class="inline">X</code>, defined in the head of the fun, is a new variable. The
│ │ │  variable <code class="inline">Stream</code>, which is used within the fun, gets its value from the
│ │ │  <code class="inline">file:open</code> line.</p><p>As any variable that occurs in the head of a fun is considered a new variable,
│ │ │ -it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="1639327033-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1639327033-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1639327033-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="1639327033-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="1639327033-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="1639327033-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="1639327033-4">(</span><span class="nf">fun</span><span class="p" data-group-id="1639327033-5">(</span><span class="n">File</span><span class="p" data-group-id="1639327033-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1639327033-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="1639327033-7">[</span><span class="n">File</span><span class="p" data-group-id="1639327033-7">]</span><span class="p" data-group-id="1639327033-6">)</span><span class="w">
│ │ │ -            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="1639327033-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="1639327033-8">(</span><span class="n">Stream</span><span class="p" data-group-id="1639327033-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │ +it is equally valid to write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">print_list</span><span class="p" data-group-id="5969869278-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5969869278-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5969869278-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Stream</span><span class="p" data-group-id="5969869278-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5969869278-3">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="ss">write</span><span class="p" data-group-id="5969869278-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="5969869278-4">(</span><span class="nf">fun</span><span class="p" data-group-id="5969869278-5">(</span><span class="n">File</span><span class="p" data-group-id="5969869278-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5969869278-6">(</span><span class="n">Stream</span><span class="p">,</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="5969869278-7">[</span><span class="n">File</span><span class="p" data-group-id="5969869278-7">]</span><span class="p" data-group-id="5969869278-6">)</span><span class="w">
│ │ │ +            </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5969869278-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">file</span><span class="p">:</span><span class="nf">close</span><span class="p" data-group-id="5969869278-8">(</span><span class="n">Stream</span><span class="p" data-group-id="5969869278-8">)</span><span class="p">.</span></code></pre><p>Here, <code class="inline">File</code> is used as the new variable instead of <code class="inline">X</code>. This is not so wise
│ │ │  because code in the fun body cannot refer to the variable <code class="inline">File</code>, which is
│ │ │  defined outside of the fun. Compiling this example gives the following
│ │ │  diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'File'
│ │ │        shadowed in 'fun'</code></pre><p>This indicates that the variable <code class="inline">File</code>, which is defined inside the fun,
│ │ │  collides with the variable <code class="inline">File</code>, which is defined outside the fun.</p><p>The rules for importing variables into a fun has the consequence that certain
│ │ │  pattern matching operations must be moved into guard expressions and cannot be
│ │ │  written in the head of the fun. For example, you might write the following code
│ │ │  if you intend the first clause of <code class="inline">F</code> to be evaluated when the value of its
│ │ │ -argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4619581524-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4619581524-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +argument is <code class="inline">Y</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="8718095690-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8718095690-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="4619581524-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4619581524-3">(</span><span class="n">X</span><span class="p" data-group-id="4619581524-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="8718095690-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8718095690-3">(</span><span class="n">X</span><span class="p" data-group-id="8718095690-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">;</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="4619581524-4">(</span><span class="p">_</span><span class="p" data-group-id="4619581524-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="8718095690-4">(</span><span class="p">_</span><span class="p" data-group-id="8718095690-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4619581524-2">)</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="0651879171-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0651879171-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8718095690-2">)</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>instead of writing the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="3608895572-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3608895572-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nf">map</span><span class="p" data-group-id="0651879171-2">(</span><span class="nf">fun</span><span class="p" data-group-id="0651879171-3">(</span><span class="n">Y</span><span class="p" data-group-id="0651879171-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">map</span><span class="p" data-group-id="3608895572-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3608895572-3">(</span><span class="n">Y</span><span class="p" data-group-id="3608895572-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">;</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="0651879171-4">(</span><span class="p">_</span><span class="p" data-group-id="0651879171-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="3608895572-4">(</span><span class="p">_</span><span class="p" data-group-id="3608895572-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │               </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0651879171-2">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3608895572-2">)</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="funs-and-module-lists" class="section-heading">
│ │ │    <a href="#funs-and-module-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Funs and Module Lists</span>
│ │ │  </h2>
│ │ │  <p>The following examples show a dialogue with the Erlang shell. All the higher
│ │ │  order functions discussed are exported from the module <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html"><code class="inline">lists</code></a>.</p><h3 id="map-1" class="section-heading">
│ │ │    <a href="#map-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">map</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="4729838062-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4729838062-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4729838062-2">]</span><span class="p" data-group-id="4729838062-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4729838062-3">[</span><span class="n">F</span><span class="p" data-group-id="4729838062-4">(</span><span class="n">H</span><span class="p" data-group-id="4729838062-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="4729838062-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4729838062-5">)</span><span class="p" data-group-id="4729838062-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="4729838062-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4729838062-7">[</span><span class="p" data-group-id="4729838062-7">]</span><span class="p" data-group-id="4729838062-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4729838062-8">[</span><span class="p" data-group-id="4729838062-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">map</span><span class="p" data-group-id="6495273298-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6495273298-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6495273298-2">]</span><span class="p" data-group-id="6495273298-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6495273298-3">[</span><span class="n">F</span><span class="p" data-group-id="6495273298-4">(</span><span class="n">H</span><span class="p" data-group-id="6495273298-4">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="6495273298-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6495273298-5">)</span><span class="p" data-group-id="6495273298-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="6495273298-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6495273298-7">[</span><span class="p" data-group-id="6495273298-7">]</span><span class="p" data-group-id="6495273298-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6495273298-8">[</span><span class="p" data-group-id="6495273298-8">]</span><span class="p">.</span></code></pre><p>It returns the list obtained by applying the function to every argument in the
│ │ │  list.</p><p>When a new fun is defined in the shell, the value of the fun is printed as
│ │ │ -<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2073560447-1">(</span><span class="n">X</span><span class="p" data-group-id="2073560447-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">Fun#&lt;erl_eval&gt;</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Double</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9245684504-1">(</span><span class="n">X</span><span class="p" data-group-id="9245684504-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2073560447-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2073560447-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2073560447-3">]</span><span class="p" data-group-id="2073560447-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2073560447-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="2073560447-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9245684504-2">(</span><span class="n">Double</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9245684504-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9245684504-3">]</span><span class="p" data-group-id="9245684504-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9245684504-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="9245684504-4">]</span></code></pre><h3 id="any" class="section-heading">
│ │ │    <a href="#any" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">any</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="2775897226-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2775897226-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2775897226-2">]</span><span class="p" data-group-id="2775897226-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="2775897226-3">(</span><span class="n">H</span><span class="p" data-group-id="2775897226-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#any/2"><code class="inline">lists:any/2</code></a> takes a predicate <code class="inline">P</code> of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">any</span><span class="p" data-group-id="7999315298-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7999315298-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7999315298-2">]</span><span class="p" data-group-id="7999315298-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="7999315298-3">(</span><span class="n">H</span><span class="p" data-group-id="7999315298-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="2775897226-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2775897226-4">)</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">any</span><span class="p" data-group-id="7999315298-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7999315298-4">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">any</span><span class="p" data-group-id="2775897226-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2775897226-6">[</span><span class="p" data-group-id="2775897226-6">]</span><span class="p" data-group-id="2775897226-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">any</span><span class="p" data-group-id="7999315298-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7999315298-6">[</span><span class="p" data-group-id="7999315298-6">]</span><span class="p" data-group-id="7999315298-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><p>A predicate is a function that returns <code class="inline">true</code> or <code class="inline">false</code>. <code class="inline">any</code> is <code class="inline">true</code> if
│ │ │  there is a term <code class="inline">X</code> in the list such that <code class="inline">P(X)</code> is <code class="inline">true</code>.</p><p>A predicate <code class="inline">Big(X)</code> is defined, which is <code class="inline">true</code> if its argument is greater that
│ │ │ -10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="7132061183-1">(</span><span class="n">X</span><span class="p" data-group-id="7132061183-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +10:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Big</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="6030996435-1">(</span><span class="n">X</span><span class="p" data-group-id="6030996435-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">10</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="p">;</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="7132061183-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7132061183-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="7132061183-3">]</span><span class="p" data-group-id="7132061183-2">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="6030996435-2">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6030996435-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6030996435-3">]</span><span class="p" data-group-id="6030996435-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="7132061183-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7132061183-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7132061183-5">]</span><span class="p" data-group-id="7132061183-4">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">any</span><span class="p" data-group-id="6030996435-4">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6030996435-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6030996435-5">]</span><span class="p" data-group-id="6030996435-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h3 id="all" class="section-heading">
│ │ │    <a href="#all" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">all</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="3088293425-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3088293425-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3088293425-2">]</span><span class="p" data-group-id="3088293425-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3088293425-3">(</span><span class="n">H</span><span class="p" data-group-id="3088293425-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="3088293425-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3088293425-4">)</span><span class="p">;</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#all/2"><code class="inline">lists:all/2</code></a> has the same arguments as <code class="inline">any</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">all</span><span class="p" data-group-id="3172800401-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3172800401-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="3172800401-2">]</span><span class="p" data-group-id="3172800401-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="3172800401-3">(</span><span class="n">H</span><span class="p" data-group-id="3172800401-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">  </span><span class="nf">all</span><span class="p" data-group-id="3172800401-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="3172800401-4">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="ss">false</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all</span><span class="p" data-group-id="3088293425-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3088293425-6">[</span><span class="p" data-group-id="3088293425-6">]</span><span class="p" data-group-id="3088293425-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="2199610507-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2199610507-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2199610507-2">]</span><span class="p" data-group-id="2199610507-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">all</span><span class="p" data-group-id="3172800401-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3172800401-6">[</span><span class="p" data-group-id="3172800401-6">]</span><span class="p" data-group-id="3172800401-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">true</span><span class="p">.</span></code></pre><p>It is <code class="inline">true</code> if the predicate applied to all elements in the list is <code class="inline">true</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="1001110138-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1001110138-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1001110138-2">]</span><span class="p" data-group-id="1001110138-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="2199610507-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2199610507-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="2199610507-4">]</span><span class="p" data-group-id="2199610507-3">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">all</span><span class="p" data-group-id="1001110138-3">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1001110138-4">[</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="1001110138-4">]</span><span class="p" data-group-id="1001110138-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><h3 id="foreach-1" class="section-heading">
│ │ │    <a href="#foreach-1" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">foreach</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="0687447434-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0687447434-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0687447434-2">]</span><span class="p" data-group-id="0687447434-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">F</span><span class="p" data-group-id="0687447434-3">(</span><span class="n">H</span><span class="p" data-group-id="0687447434-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="0687447434-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="0687447434-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="0687447434-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0687447434-6">[</span><span class="p" data-group-id="0687447434-6">]</span><span class="p" data-group-id="0687447434-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#foreach/2"><code class="inline">lists:foreach/2</code></a> takes a function of one argument and a list of terms:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="4902936301-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4902936301-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4902936301-2">]</span><span class="p" data-group-id="4902936301-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">F</span><span class="p" data-group-id="4902936301-3">(</span><span class="n">H</span><span class="p" data-group-id="4902936301-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="4902936301-4">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="4902936301-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="4902936301-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4902936301-6">[</span><span class="p" data-group-id="4902936301-6">]</span><span class="p" data-group-id="4902936301-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The function is applied to each argument in the list. <code class="inline">foreach</code> returns <code class="inline">ok</code>. It
│ │ │ -is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="9926542827-1">(</span><span class="nf">fun</span><span class="p" data-group-id="9926542827-2">(</span><span class="n">X</span><span class="p" data-group-id="9926542827-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9926542827-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="9926542827-4">[</span><span class="n">X</span><span class="p" data-group-id="9926542827-4">]</span><span class="p" data-group-id="9926542827-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9926542827-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9926542827-5">]</span><span class="p" data-group-id="9926542827-1">)</span><span class="p">.</span><span class="w">
│ │ │ +is only used for its side-effect:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="6851783501-1">(</span><span class="nf">fun</span><span class="p" data-group-id="6851783501-2">(</span><span class="n">X</span><span class="p" data-group-id="6851783501-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6851783501-3">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="6851783501-4">[</span><span class="n">X</span><span class="p" data-group-id="6851783501-4">]</span><span class="p" data-group-id="6851783501-3">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6851783501-5">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6851783501-5">]</span><span class="p" data-group-id="6851783501-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><h3 id="foldl" class="section-heading">
│ │ │    <a href="#foldl" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">foldl</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="4734685966-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4734685966-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="4734685966-2">]</span><span class="p" data-group-id="4734685966-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">foldl</span><span class="p" data-group-id="4734685966-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="4734685966-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="4734685966-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="4734685966-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foldl</span><span class="p" data-group-id="4734685966-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4734685966-6">[</span><span class="p" data-group-id="4734685966-6">]</span><span class="p" data-group-id="4734685966-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> takes a function of two arguments, an accumulator and a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foldl</span><span class="p" data-group-id="9934432650-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9934432650-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="9934432650-2">]</span><span class="p" data-group-id="9934432650-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">foldl</span><span class="p" data-group-id="9934432650-3">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="9934432650-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="9934432650-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="9934432650-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foldl</span><span class="p" data-group-id="9934432650-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9934432650-6">[</span><span class="p" data-group-id="9934432650-6">]</span><span class="p" data-group-id="9934432650-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Accu</span><span class="p">.</span></code></pre><p>The function is called with two arguments. The first argument is the successive
│ │ │  elements in the list. The second argument is the accumulator. The function must
│ │ │  return a new accumulator, which is used the next time the function is called.</p><p>If you have a list of lists <code class="inline">L = [&quot;I&quot;,&quot;like&quot;,&quot;Erlang&quot;]</code>, then you can sum the
│ │ │ -lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3771721478-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="3771721478-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3771721478-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="3771721478-2">]</span><span class="gp unselectable">
│ │ │ -10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="3771721478-3">(</span><span class="nf">fun</span><span class="p" data-group-id="3771721478-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="3771721478-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3771721478-5">(</span><span class="n">X</span><span class="p" data-group-id="3771721478-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3771721478-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">11</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="8361052715-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="8361052715-1">]</span><span class="p">,</span><span class="w">
│ │ │ +lengths of all the strings in <code class="inline">L</code> as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8123264309-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="8123264309-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8123264309-2">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="8123264309-2">]</span><span class="gp unselectable">
│ │ │ +10&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="8123264309-3">(</span><span class="nf">fun</span><span class="p" data-group-id="8123264309-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="8123264309-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8123264309-5">(</span><span class="n">X</span><span class="p" data-group-id="8123264309-5">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8123264309-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">11</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#foldl/3"><code class="inline">lists:foldl/3</code></a> works like a <code class="inline">while</code> loop in an imperative language:</p><pre><code class="makeup erlang" translate="no"><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="p" data-group-id="0505301012-1">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;like&quot;</span><span class="p">,</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="0505301012-1">]</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Sum</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">while</span><span class="p" data-group-id="8361052715-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8361052715-3">[</span><span class="p" data-group-id="8361052715-3">]</span><span class="p" data-group-id="8361052715-2">)</span><span class="p" data-group-id="8361052715-4">{</span><span class="w">
│ │ │ -    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8361052715-5">(</span><span class="nf">head</span><span class="p" data-group-id="8361052715-6">(</span><span class="n">L</span><span class="p" data-group-id="8361052715-6">)</span><span class="p" data-group-id="8361052715-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="8361052715-7">(</span><span class="n">L</span><span class="p" data-group-id="8361052715-7">)</span><span class="w">
│ │ │ +</span><span class="nf">while</span><span class="p" data-group-id="0505301012-2">(</span><span class="w"> </span><span class="n">L</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0505301012-3">[</span><span class="p" data-group-id="0505301012-3">]</span><span class="p" data-group-id="0505301012-2">)</span><span class="p" data-group-id="0505301012-4">{</span><span class="w">
│ │ │ +    </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="0505301012-5">(</span><span class="nf">head</span><span class="p" data-group-id="0505301012-6">(</span><span class="n">L</span><span class="p" data-group-id="0505301012-6">)</span><span class="p" data-group-id="0505301012-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">L</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tail</span><span class="p" data-group-id="0505301012-7">(</span><span class="n">L</span><span class="p" data-group-id="0505301012-7">)</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><h3 id="mapfoldl" class="section-heading">
│ │ │    <a href="#mapfoldl" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">mapfoldl</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="3464827624-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3464827624-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="3464827624-2">]</span><span class="p" data-group-id="3464827624-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3464827624-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="3464827624-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="3464827624-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="3464827624-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3464827624-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="3464827624-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="3464827624-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="3464827624-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3464827624-7">{</span><span class="p" data-group-id="3464827624-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="3464827624-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="3464827624-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">mapfoldl</span><span class="p" data-group-id="3464827624-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3464827624-10">[</span><span class="p" data-group-id="3464827624-10">]</span><span class="p" data-group-id="3464827624-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3464827624-11">{</span><span class="p" data-group-id="3464827624-12">[</span><span class="p" data-group-id="3464827624-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="3464827624-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ -then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="1677185370-1">(</span><span class="n">X</span><span class="p" data-group-id="1677185370-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1677185370-2">(</span><span class="n">X</span><span class="p" data-group-id="1677185370-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#mapfoldl/3"><code class="inline">lists:mapfoldl/3</code></a> simultaneously maps and folds over a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mapfoldl</span><span class="p" data-group-id="8592811203-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8592811203-2">[</span><span class="n">Hd</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="8592811203-2">]</span><span class="p" data-group-id="8592811203-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8592811203-3">{</span><span class="n">R</span><span class="p">,</span><span class="n">Accu1</span><span class="p" data-group-id="8592811203-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="8592811203-4">(</span><span class="n">Hd</span><span class="p">,</span><span class="w"> </span><span class="n">Accu0</span><span class="p" data-group-id="8592811203-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8592811203-5">{</span><span class="n">Rs</span><span class="p">,</span><span class="n">Accu2</span><span class="p" data-group-id="8592811203-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">mapfoldl</span><span class="p" data-group-id="8592811203-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu1</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="8592811203-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8592811203-7">{</span><span class="p" data-group-id="8592811203-8">[</span><span class="n">R</span><span class="p">|</span><span class="n">Rs</span><span class="p" data-group-id="8592811203-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu2</span><span class="p" data-group-id="8592811203-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">mapfoldl</span><span class="p" data-group-id="8592811203-9">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8592811203-10">[</span><span class="p" data-group-id="8592811203-10">]</span><span class="p" data-group-id="8592811203-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8592811203-11">{</span><span class="p" data-group-id="8592811203-12">[</span><span class="p" data-group-id="8592811203-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Accu</span><span class="p" data-group-id="8592811203-11">}</span><span class="p">.</span></code></pre><p>The following example shows how to change all letters in <code class="inline">L</code> to upper case and
│ │ │ +then count them.</p><p>First the change to upper case:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Upcase</span><span class="w"> </span><span class="o">=</span><span class="w">  </span><span class="nf">fun</span><span class="p" data-group-id="8482787617-1">(</span><span class="n">X</span><span class="p" data-group-id="8482787617-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="sc">$a</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w">  </span><span class="n">X</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="sc">$z</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$A</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="sc">$a</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8482787617-2">(</span><span class="n">X</span><span class="p" data-group-id="8482787617-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │  &gt; </span><span class="n">Upcase_word</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -</span><span class="nf">fun</span><span class="p" data-group-id="1677185370-3">(</span><span class="n">X</span><span class="p" data-group-id="1677185370-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1677185370-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="1677185370-4">)</span><span class="w">
│ │ │ +</span><span class="nf">fun</span><span class="p" data-group-id="8482787617-3">(</span><span class="n">X</span><span class="p" data-group-id="8482787617-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="8482787617-4">(</span><span class="n">Upcase</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8482787617-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="1677185370-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="1677185370-5">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">Upcase_word</span><span class="p" data-group-id="8482787617-5">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="8482787617-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;ERLANG&quot;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1677185370-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1677185370-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1677185370-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="1677185370-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="8815886753-1">(</span><span class="nf">fun</span><span class="p" data-group-id="8815886753-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="8815886753-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8815886753-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="8815886753-4">(</span><span class="n">Word</span><span class="p" data-group-id="8815886753-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8815886753-5">(</span><span class="n">Word</span><span class="p" data-group-id="8815886753-5">)</span><span class="p" data-group-id="8815886753-3">}</span><span class="w">
│ │ │ -</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8815886753-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8815886753-6">{</span><span class="p" data-group-id="8815886753-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="8815886753-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="8815886753-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="8482787617-6">(</span><span class="n">Upcase_word</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8482787617-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8482787617-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="8482787617-7">]</span></code></pre><p>Now, the fold and the map can be done at the same time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">mapfoldl</span><span class="p" data-group-id="1747494553-1">(</span><span class="nf">fun</span><span class="p" data-group-id="1747494553-2">(</span><span class="n">Word</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="1747494553-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1747494553-3">{</span><span class="n">Upcase_word</span><span class="p" data-group-id="1747494553-4">(</span><span class="n">Word</span><span class="p" data-group-id="1747494553-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1747494553-5">(</span><span class="n">Word</span><span class="p" data-group-id="1747494553-5">)</span><span class="p" data-group-id="1747494553-3">}</span><span class="w">
│ │ │ +</span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1747494553-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1747494553-6">{</span><span class="p" data-group-id="1747494553-7">[</span><span class="s">&quot;I&quot;</span><span class="p">,</span><span class="s">&quot;LIKE&quot;</span><span class="p">,</span><span class="s">&quot;ERLANG&quot;</span><span class="p" data-group-id="1747494553-7">]</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="1747494553-6">}</span></code></pre><h3 id="filter" class="section-heading">
│ │ │    <a href="#filter" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">filter</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#filter/2"><code class="inline">lists:filter/2</code></a> takes a predicate of one argument and a list and returns all elements
│ │ │ -in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="7903518603-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7903518603-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7903518603-2">]</span><span class="p" data-group-id="7903518603-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="7903518603-3">(</span><span class="n">H</span><span class="p" data-group-id="7903518603-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7903518603-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="7903518603-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7903518603-5">)</span><span class="p" data-group-id="7903518603-4">]</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="7903518603-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7903518603-6">)</span><span class="w">
│ │ │ +in the list that satisfy the predicate:</p><pre><code class="makeup erlang" translate="no"><span class="nf">filter</span><span class="p" data-group-id="1981125128-1">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1981125128-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1981125128-2">]</span><span class="p" data-group-id="1981125128-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1981125128-3">(</span><span class="n">H</span><span class="p" data-group-id="1981125128-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1981125128-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">filter</span><span class="p" data-group-id="1981125128-5">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1981125128-5">)</span><span class="p" data-group-id="1981125128-4">]</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="1981125128-6">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1981125128-6">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="7903518603-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7903518603-8">[</span><span class="p" data-group-id="7903518603-8">]</span><span class="p" data-group-id="7903518603-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7903518603-9">[</span><span class="p" data-group-id="7903518603-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="1340609569-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1340609569-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1340609569-2">]</span><span class="p" data-group-id="1340609569-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1340609569-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="1340609569-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="1981125128-7">(</span><span class="n">F</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1981125128-8">[</span><span class="p" data-group-id="1981125128-8">]</span><span class="p" data-group-id="1981125128-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1981125128-9">[</span><span class="p" data-group-id="1981125128-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9053167103-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9053167103-2">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9053167103-2">]</span><span class="p" data-group-id="9053167103-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9053167103-3">[</span><span class="mi">500</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="9053167103-3">]</span></code></pre><p>Combining maps and filters enables writing of very succinct code. For example,
│ │ │  to define a set difference function <code class="inline">diff(L1, L2)</code> to be the difference between
│ │ │ -the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="1542579794-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="1542579794-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">filter</span><span class="p" data-group-id="1542579794-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1542579794-3">(</span><span class="n">X</span><span class="p" data-group-id="1542579794-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="1542579794-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="1542579794-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="1542579794-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the list <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="1661131627-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="1661131627-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="1661131627-2">(</span><span class="nf">fun</span><span class="p" data-group-id="1661131627-3">(</span><span class="n">X</span><span class="p" data-group-id="1661131627-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="1661131627-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="1661131627-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="1661131627-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │ +the lists <code class="inline">L1</code> and <code class="inline">L2</code>, the code can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">diff</span><span class="p" data-group-id="3159294913-1">(</span><span class="n">L1</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="3159294913-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">filter</span><span class="p" data-group-id="3159294913-2">(</span><span class="nf">fun</span><span class="p" data-group-id="3159294913-3">(</span><span class="n">X</span><span class="p" data-group-id="3159294913-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ow">not</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="3159294913-4">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="3159294913-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="3159294913-2">)</span><span class="p">.</span></code></pre><p>This gives the list of all elements in L1 that are not contained in L2.</p><p>The AND intersection of the list <code class="inline">L1</code> and <code class="inline">L2</code> is also easily defined:</p><pre><code class="makeup erlang" translate="no"><span class="nf">intersection</span><span class="p" data-group-id="2186295813-1">(</span><span class="n">L1</span><span class="p">,</span><span class="n">L2</span><span class="p" data-group-id="2186295813-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">filter</span><span class="p" data-group-id="2186295813-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2186295813-3">(</span><span class="n">X</span><span class="p" data-group-id="2186295813-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">member</span><span class="p" data-group-id="2186295813-4">(</span><span class="n">X</span><span class="p">,</span><span class="n">L1</span><span class="p" data-group-id="2186295813-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">L2</span><span class="p" data-group-id="2186295813-2">)</span><span class="p">.</span></code></pre><h3 id="takewhile" class="section-heading">
│ │ │    <a href="#takewhile" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">takewhile</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#takewhile/2"><code class="inline">lists:takewhile/2</code></a> takes elements <code class="inline">X</code> from a list <code class="inline">L</code> as long as the predicate
│ │ │ -<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="2693415636-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2693415636-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2693415636-2">]</span><span class="p" data-group-id="2693415636-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="2693415636-3">(</span><span class="n">H</span><span class="p" data-group-id="2693415636-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2693415636-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="2693415636-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2693415636-5">)</span><span class="p" data-group-id="2693415636-4">]</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2693415636-6">[</span><span class="p" data-group-id="2693415636-6">]</span><span class="w">
│ │ │ +<code class="inline">P(X)</code> is true:</p><pre><code class="makeup erlang" translate="no"><span class="nf">takewhile</span><span class="p" data-group-id="7755215930-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7755215930-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7755215930-2">]</span><span class="p" data-group-id="7755215930-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="7755215930-3">(</span><span class="n">H</span><span class="p" data-group-id="7755215930-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7755215930-4">[</span><span class="n">H</span><span class="p">|</span><span class="nf">takewhile</span><span class="p" data-group-id="7755215930-5">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7755215930-5">)</span><span class="p" data-group-id="7755215930-4">]</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7755215930-6">[</span><span class="p" data-group-id="7755215930-6">]</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">takewhile</span><span class="p" data-group-id="2693415636-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2693415636-8">[</span><span class="p" data-group-id="2693415636-8">]</span><span class="p" data-group-id="2693415636-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2693415636-9">[</span><span class="p" data-group-id="2693415636-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="0837265441-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0837265441-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0837265441-2">]</span><span class="p" data-group-id="0837265441-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0837265441-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="0837265441-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │ +</span><span class="nf">takewhile</span><span class="p" data-group-id="7755215930-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7755215930-8">[</span><span class="p" data-group-id="7755215930-8">]</span><span class="p" data-group-id="7755215930-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7755215930-9">[</span><span class="p" data-group-id="7755215930-9">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">takewhile</span><span class="p" data-group-id="8513287787-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8513287787-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8513287787-2">]</span><span class="p" data-group-id="8513287787-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8513287787-3">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="8513287787-3">]</span></code></pre><h3 id="dropwhile" class="section-heading">
│ │ │    <a href="#dropwhile" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">dropwhile</span>
│ │ │  </h3>
│ │ │ -<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="6175258997-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175258997-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6175258997-2">]</span><span class="p" data-group-id="6175258997-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="6175258997-3">(</span><span class="n">H</span><span class="p" data-group-id="6175258997-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="6175258997-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="6175258997-4">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6175258997-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6175258997-5">]</span><span class="w">
│ │ │ +<p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#dropwhile/2"><code class="inline">lists:dropwhile/2</code></a> is the complement of <code class="inline">takewhile</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">dropwhile</span><span class="p" data-group-id="1711954734-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1711954734-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1711954734-2">]</span><span class="p" data-group-id="1711954734-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="1711954734-3">(</span><span class="n">H</span><span class="p" data-group-id="1711954734-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">dropwhile</span><span class="p" data-group-id="1711954734-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="1711954734-4">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1711954734-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="1711954734-5">]</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">dropwhile</span><span class="p" data-group-id="6175258997-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6175258997-7">[</span><span class="p" data-group-id="6175258997-7">]</span><span class="p" data-group-id="6175258997-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6175258997-8">[</span><span class="p" data-group-id="6175258997-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="4110880708-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4110880708-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4110880708-2">]</span><span class="p" data-group-id="4110880708-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4110880708-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="4110880708-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │ +</span><span class="nf">dropwhile</span><span class="p" data-group-id="1711954734-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1711954734-7">[</span><span class="p" data-group-id="1711954734-7">]</span><span class="p" data-group-id="1711954734-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1711954734-8">[</span><span class="p" data-group-id="1711954734-8">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">dropwhile</span><span class="p" data-group-id="1942799849-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1942799849-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1942799849-2">]</span><span class="p" data-group-id="1942799849-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1942799849-3">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1942799849-3">]</span></code></pre><h3 id="splitwith" class="section-heading">
│ │ │    <a href="#splitwith" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">splitwith</span>
│ │ │  </h3>
│ │ │  <p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#splitwith/2"><code class="inline">lists:splitwith/2</code></a> splits the list <code class="inline">L</code> into the two sublists <code class="inline">{L1, L2}</code>, where
│ │ │ -<code class="inline">L = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="4302123254-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4302123254-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">splitwith</span><span class="p" data-group-id="4302123254-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4302123254-3">[</span><span class="p" data-group-id="4302123254-3">]</span><span class="p" data-group-id="4302123254-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">L = takewhile(P, L)</code> and <code class="inline">L2 = dropwhile(P, L)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">splitwith</span><span class="p" data-group-id="0616122408-1">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0616122408-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">splitwith</span><span class="p" data-group-id="0616122408-2">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0616122408-3">[</span><span class="p" data-group-id="0616122408-3">]</span><span class="p" data-group-id="0616122408-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="4302123254-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4302123254-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4302123254-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4302123254-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="4302123254-6">(</span><span class="n">H</span><span class="p" data-group-id="4302123254-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="4302123254-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4302123254-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="4302123254-8">]</span><span class="p" data-group-id="4302123254-7">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4302123254-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="4302123254-10">(</span><span class="n">L</span><span class="p" data-group-id="4302123254-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4302123254-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="4302123254-11">]</span><span class="p" data-group-id="4302123254-9">}</span><span class="w">
│ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="0616122408-4">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0616122408-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0616122408-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0616122408-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="0616122408-6">(</span><span class="n">H</span><span class="p" data-group-id="0616122408-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">true</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">splitwith</span><span class="p" data-group-id="0616122408-7">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0616122408-8">[</span><span class="n">H</span><span class="p">|</span><span class="n">L</span><span class="p" data-group-id="0616122408-8">]</span><span class="p" data-group-id="0616122408-7">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0616122408-9">{</span><span class="nf">reverse</span><span class="p" data-group-id="0616122408-10">(</span><span class="n">L</span><span class="p" data-group-id="0616122408-10">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0616122408-11">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0616122408-11">]</span><span class="p" data-group-id="0616122408-9">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">splitwith</span><span class="p" data-group-id="4302123254-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4302123254-13">[</span><span class="p" data-group-id="4302123254-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4302123254-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4302123254-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="4302123254-15">(</span><span class="n">L</span><span class="p" data-group-id="4302123254-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4302123254-16">[</span><span class="p" data-group-id="4302123254-16">]</span><span class="p" data-group-id="4302123254-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="2870049819-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2870049819-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2870049819-2">]</span><span class="p" data-group-id="2870049819-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2870049819-3">{</span><span class="p" data-group-id="2870049819-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="2870049819-4">]</span><span class="p">,</span><span class="p" data-group-id="2870049819-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2870049819-5">]</span><span class="p" data-group-id="2870049819-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │ +</span><span class="nf">splitwith</span><span class="p" data-group-id="0616122408-12">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0616122408-13">[</span><span class="p" data-group-id="0616122408-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="0616122408-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0616122408-14">{</span><span class="nf">reverse</span><span class="p" data-group-id="0616122408-15">(</span><span class="n">L</span><span class="p" data-group-id="0616122408-15">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0616122408-16">[</span><span class="p" data-group-id="0616122408-16">]</span><span class="p" data-group-id="0616122408-14">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">splitwith</span><span class="p" data-group-id="1252709194-1">(</span><span class="n">Big</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1252709194-2">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1252709194-2">]</span><span class="p" data-group-id="1252709194-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1252709194-3">{</span><span class="p" data-group-id="1252709194-4">[</span><span class="mi">200</span><span class="p">,</span><span class="mi">500</span><span class="p">,</span><span class="mi">45</span><span class="p" data-group-id="1252709194-4">]</span><span class="p">,</span><span class="p" data-group-id="1252709194-5">[</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1252709194-5">]</span><span class="p" data-group-id="1252709194-3">}</span></code></pre><h2 id="funs-returning-funs" class="section-heading">
│ │ │    <a href="#funs-returning-funs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Funs Returning Funs</span>
│ │ │  </h2>
│ │ │  <p>So far, only functions that take funs as arguments have been described. More
│ │ │  powerful functions, that themselves return funs, can also be written. The
│ │ │  following examples illustrate these type of functions.</p><h3 id="simple-higher-order-functions" class="section-heading">
│ │ │    <a href="#simple-higher-order-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simple Higher Order Functions</span>
│ │ │  </h3>
│ │ │  <p><code class="inline">Adder(X)</code> is a function that given <code class="inline">X</code>, returns a new function <code class="inline">G</code> such that
│ │ │ -<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0099949222-1">(</span><span class="n">X</span><span class="p" data-group-id="0099949222-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="0099949222-2">(</span><span class="n">Y</span><span class="p" data-group-id="0099949222-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">G(K)</code> returns <code class="inline">K + X</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Adder</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3952171678-1">(</span><span class="n">X</span><span class="p" data-group-id="3952171678-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3952171678-2">(</span><span class="n">Y</span><span class="p" data-group-id="3952171678-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="0099949222-3">(</span><span class="mi">6</span><span class="p" data-group-id="0099949222-3">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">Add6</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Adder</span><span class="p" data-group-id="3952171678-3">(</span><span class="mi">6</span><span class="p" data-group-id="3952171678-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">6.72228031</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Add6</span><span class="p" data-group-id="0099949222-4">(</span><span class="mi">10</span><span class="p" data-group-id="0099949222-4">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">Add6</span><span class="p" data-group-id="3952171678-4">(</span><span class="mi">10</span><span class="p" data-group-id="3952171678-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">16</span></code></pre><h3 id="infinite-lists" class="section-heading">
│ │ │    <a href="#infinite-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Infinite Lists</span>
│ │ │  </h3>
│ │ │ -<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8128667743-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="8128667743-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8128667743-2">(</span><span class="p" data-group-id="8128667743-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8128667743-3">]</span><span class="p" data-group-id="8128667743-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">ints_from</span><span class="p" data-group-id="8128667743-4">(</span><span class="n">N</span><span class="p" data-group-id="8128667743-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="p" data-group-id="8128667743-5">(</span><span class="p" data-group-id="8128667743-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="8128667743-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="8128667743-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="8128667743-7">)</span><span class="p" data-group-id="8128667743-6">]</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="2591469499-1">(</span><span class="mi">1</span><span class="p" data-group-id="2591469499-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>The idea is to write something like:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6024975658-1">(</span><span class="ss">lazy</span><span class="p" data-group-id="6024975658-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6024975658-2">(</span><span class="p" data-group-id="6024975658-3">[</span><span class="ss">ints_from</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6024975658-3">]</span><span class="p" data-group-id="6024975658-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">ints_from</span><span class="p" data-group-id="6024975658-4">(</span><span class="n">N</span><span class="p" data-group-id="6024975658-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="p" data-group-id="6024975658-5">(</span><span class="p" data-group-id="6024975658-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6024975658-6">[</span><span class="n">N</span><span class="p">|</span><span class="nf">ints_from</span><span class="p" data-group-id="6024975658-7">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="6024975658-7">)</span><span class="p" data-group-id="6024975658-6">]</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Then proceed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">XX</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lazy</span><span class="p">:</span><span class="nf">ints_from</span><span class="p" data-group-id="1960134040-1">(</span><span class="mi">1</span><span class="p" data-group-id="1960134040-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">XX</span><span class="p" data-group-id="2591469499-2">(</span><span class="p" data-group-id="2591469499-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2591469499-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="2591469499-3">]</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">hd</span><span class="p" data-group-id="2591469499-4">(</span><span class="n">XX</span><span class="p" data-group-id="2591469499-5">(</span><span class="p" data-group-id="2591469499-5">)</span><span class="p" data-group-id="2591469499-4">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">XX</span><span class="p" data-group-id="1960134040-2">(</span><span class="p" data-group-id="1960134040-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1960134040-3">[</span><span class="mi">1</span><span class="p">|</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="p" data-group-id="1960134040-3">]</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">hd</span><span class="p" data-group-id="1960134040-4">(</span><span class="n">XX</span><span class="p" data-group-id="1960134040-5">(</span><span class="p" data-group-id="1960134040-5">)</span><span class="p" data-group-id="1960134040-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="2591469499-6">(</span><span class="n">XX</span><span class="p" data-group-id="2591469499-7">(</span><span class="p" data-group-id="2591469499-7">)</span><span class="p" data-group-id="2591469499-6">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">tl</span><span class="p" data-group-id="1960134040-6">(</span><span class="n">XX</span><span class="p" data-group-id="1960134040-7">(</span><span class="p" data-group-id="1960134040-7">)</span><span class="p" data-group-id="1960134040-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">lazy</span><span class="p">.</span><span class="mf">0.29874839</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">hd</span><span class="p" data-group-id="2591469499-8">(</span><span class="n">Y</span><span class="p" data-group-id="2591469499-9">(</span><span class="p" data-group-id="2591469499-9">)</span><span class="p" data-group-id="2591469499-8">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">hd</span><span class="p" data-group-id="1960134040-8">(</span><span class="n">Y</span><span class="p" data-group-id="1960134040-9">(</span><span class="p" data-group-id="1960134040-9">)</span><span class="p" data-group-id="1960134040-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span></code></pre><p>And so on. This is an example of &quot;lazy embedding&quot;.</p><h3 id="parsing" class="section-heading">
│ │ │    <a href="#parsing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Parsing</span>
│ │ │  </h3>
│ │ │ -<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="2832314484-1">(</span><span class="n">Toks</span><span class="p" data-group-id="2832314484-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2832314484-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="2832314484-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │ +<p>The following examples show parsers of the following type:</p><pre><code class="makeup erlang" translate="no"><span class="n">Parser</span><span class="p" data-group-id="5582905497-1">(</span><span class="n">Toks</span><span class="p" data-group-id="5582905497-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5582905497-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Tree</span><span class="p">,</span><span class="w"> </span><span class="n">Toks1</span><span class="p" data-group-id="5582905497-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">fail</span></code></pre><p><code class="inline">Toks</code> is the list of tokens to be parsed. A successful parse returns
│ │ │  <code class="inline">{ok, Tree, Toks1}</code>.</p><ul><li><code class="inline">Tree</code> is a parse tree.</li><li><code class="inline">Toks1</code> is a tail of <code class="inline">Tree</code> that contains symbols encountered after the
│ │ │  structure that was correctly parsed.</li></ul><p>An unsuccessful parse returns <code class="inline">fail</code>.</p><p>The following example illustrates a simple, functional parser that parses the
│ │ │  grammar:</p><pre><code class="text">(a | b) &amp; (c | d)</code></pre><p>The following code defines a function <code class="inline">pconst(X)</code> in the module <code class="inline">funparse</code>,
│ │ │ -which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="6442566497-1">(</span><span class="n">X</span><span class="p" data-group-id="6442566497-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6442566497-2">(</span><span class="n">T</span><span class="p" data-group-id="6442566497-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +which returns a fun that parses a list of tokens:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pconst</span><span class="p" data-group-id="2909087772-1">(</span><span class="n">X</span><span class="p" data-group-id="2909087772-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2909087772-2">(</span><span class="n">T</span><span class="p" data-group-id="2909087772-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │         </span><span class="k">case</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -           </span><span class="p" data-group-id="6442566497-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="6442566497-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6442566497-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6442566497-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6442566497-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6442566497-4">}</span><span class="p">;</span><span class="w">
│ │ │ +           </span><span class="p" data-group-id="2909087772-3">[</span><span class="n">X</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="2909087772-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2909087772-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2909087772-5">{</span><span class="ss">const</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="2909087772-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="2909087772-4">}</span><span class="p">;</span><span class="w">
│ │ │             </span><span class="p">_</span><span class="w">      </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">fail</span><span class="w">
│ │ │         </span><span class="k">end</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="6041262572-1">(</span><span class="ss">a</span><span class="p" data-group-id="6041262572-1">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>This function can be used as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">pconst</span><span class="p" data-group-id="0473272461-1">(</span><span class="ss">a</span><span class="p" data-group-id="0473272461-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">funparse</span><span class="p">.</span><span class="mf">0.22674075</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">P1</span><span class="p" data-group-id="6041262572-2">(</span><span class="p" data-group-id="6041262572-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6041262572-3">]</span><span class="p" data-group-id="6041262572-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6041262572-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="6041262572-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6041262572-5">}</span><span class="p">,</span><span class="p" data-group-id="6041262572-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6041262572-6">]</span><span class="p" data-group-id="6041262572-4">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">P1</span><span class="p" data-group-id="6041262572-7">(</span><span class="p" data-group-id="6041262572-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="6041262572-8">]</span><span class="p" data-group-id="6041262572-7">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">P1</span><span class="p" data-group-id="0473272461-2">(</span><span class="p" data-group-id="0473272461-3">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0473272461-3">]</span><span class="p" data-group-id="0473272461-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0473272461-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0473272461-5">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0473272461-5">}</span><span class="p">,</span><span class="p" data-group-id="0473272461-6">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="0473272461-6">]</span><span class="p" data-group-id="0473272461-4">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">P1</span><span class="p" data-group-id="0473272461-7">(</span><span class="p" data-group-id="0473272461-8">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="0473272461-8">]</span><span class="p" data-group-id="0473272461-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">fail</span></code></pre><p>Next, the two higher order functions <code class="inline">pand</code> and <code class="inline">por</code> are defined. They combine
│ │ │ -primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="5123828878-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="5123828878-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5123828878-2">(</span><span class="n">T</span><span class="p" data-group-id="5123828878-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="5123828878-3">(</span><span class="n">T</span><span class="p" data-group-id="5123828878-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5123828878-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="5123828878-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="5123828878-5">(</span><span class="n">T1</span><span class="p" data-group-id="5123828878-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="5123828878-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="5123828878-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="p" data-group-id="5123828878-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5123828878-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="5123828878-8">}</span><span class="p" data-group-id="5123828878-7">}</span><span class="p">;</span><span class="w">
│ │ │ +primitive parsers to produce more complex parsers.</p><p>First <code class="inline">pand</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pand</span><span class="p" data-group-id="8691959789-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="8691959789-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8691959789-2">(</span><span class="n">T</span><span class="p" data-group-id="8691959789-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="8691959789-3">(</span><span class="n">T</span><span class="p" data-group-id="8691959789-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8691959789-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8691959789-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="8691959789-5">(</span><span class="n">T1</span><span class="p" data-group-id="8691959789-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="8691959789-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="8691959789-6">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                        </span><span class="p" data-group-id="8691959789-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8691959789-8">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="8691959789-8">}</span><span class="p" data-group-id="8691959789-7">}</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │                  </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="ss">fail</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Given a parser <code class="inline">P1</code> for grammar <code class="inline">G1</code>, and a parser <code class="inline">P2</code> for grammar <code class="inline">G2</code>,
│ │ │  <code class="inline">pand(P1, P2)</code> returns a parser for the grammar, which consists of sequences of
│ │ │  tokens that satisfy <code class="inline">G1</code>, followed by sequences of tokens that satisfy <code class="inline">G2</code>.</p><p><code class="inline">por(P1, P2)</code> returns a parser for the language described by the grammar <code class="inline">G1</code> or
│ │ │ -<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="6409059936-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="6409059936-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6409059936-2">(</span><span class="n">T</span><span class="p" data-group-id="6409059936-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="6409059936-3">(</span><span class="n">T</span><span class="p" data-group-id="6409059936-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6409059936-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6409059936-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="6409059936-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6409059936-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="6409059936-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6409059936-5">}</span><span class="p">;</span><span class="w">
│ │ │ +<code class="inline">G2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">por</span><span class="p" data-group-id="0342862083-1">(</span><span class="n">P1</span><span class="p">,</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="0342862083-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0342862083-2">(</span><span class="n">T</span><span class="p" data-group-id="0342862083-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="k">case</span><span class="w"> </span><span class="n">P1</span><span class="p" data-group-id="0342862083-3">(</span><span class="n">T</span><span class="p" data-group-id="0342862083-3">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0342862083-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="0342862083-4">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="0342862083-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0342862083-6">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">R</span><span class="p" data-group-id="0342862083-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="0342862083-5">}</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="6409059936-7">(</span><span class="n">T</span><span class="p" data-group-id="6409059936-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="6409059936-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6409059936-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="p" data-group-id="6409059936-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6409059936-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="6409059936-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="6409059936-9">}</span><span class="p">;</span><span class="w">
│ │ │ +                </span><span class="k">case</span><span class="w"> </span><span class="n">P2</span><span class="p" data-group-id="0342862083-7">(</span><span class="n">T</span><span class="p" data-group-id="0342862083-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0342862083-8">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="0342862083-8">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                        </span><span class="p" data-group-id="0342862083-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0342862083-10">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">R1</span><span class="p" data-group-id="0342862083-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="0342862083-9">}</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">fail</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="ss">fail</span><span class="w">
│ │ │                  </span><span class="k">end</span><span class="w">
│ │ │          </span><span class="k">end</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The original problem was to parse the grammar <code class="inline">(a | b) &amp; (c | d)</code>. The following
│ │ │ -code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="9078148520-1">(</span><span class="p" data-group-id="9078148520-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">pand</span><span class="p" data-group-id="9078148520-2">(</span><span class="w">
│ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="9078148520-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="9078148520-4">(</span><span class="ss">a</span><span class="p" data-group-id="9078148520-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="9078148520-5">(</span><span class="ss">b</span><span class="p" data-group-id="9078148520-5">)</span><span class="p" data-group-id="9078148520-3">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="nf">por</span><span class="p" data-group-id="9078148520-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="9078148520-7">(</span><span class="ss">c</span><span class="p" data-group-id="9078148520-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="9078148520-8">(</span><span class="ss">d</span><span class="p" data-group-id="9078148520-8">)</span><span class="p" data-group-id="9078148520-6">)</span><span class="p" data-group-id="9078148520-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="0778855450-1">(</span><span class="n">List</span><span class="p" data-group-id="0778855450-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0778855450-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="0778855450-3">(</span><span class="p" data-group-id="0778855450-3">)</span><span class="p" data-group-id="0778855450-2">)</span><span class="p" data-group-id="0778855450-4">(</span><span class="n">List</span><span class="p" data-group-id="0778855450-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1767474790-1">(</span><span class="p" data-group-id="1767474790-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1767474790-2">]</span><span class="p" data-group-id="1767474790-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1767474790-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1767474790-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1767474790-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1767474790-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1767474790-6">}</span><span class="p" data-group-id="1767474790-5">}</span><span class="p">,</span><span class="p" data-group-id="1767474790-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1767474790-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1767474790-8">}</span><span class="p" data-group-id="1767474790-7">}</span><span class="p" data-group-id="1767474790-4">}</span><span class="p" data-group-id="1767474790-3">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1767474790-9">(</span><span class="p" data-group-id="1767474790-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1767474790-10">]</span><span class="p" data-group-id="1767474790-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1767474790-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1767474790-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1767474790-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1767474790-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1767474790-14">}</span><span class="p" data-group-id="1767474790-13">}</span><span class="p">,</span><span class="p" data-group-id="1767474790-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1767474790-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1767474790-16">}</span><span class="p" data-group-id="1767474790-15">}</span><span class="p" data-group-id="1767474790-12">}</span><span class="p" data-group-id="1767474790-11">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1767474790-17">(</span><span class="p" data-group-id="1767474790-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1767474790-18">]</span><span class="p" data-group-id="1767474790-17">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1767474790-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1767474790-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1767474790-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1767474790-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1767474790-22">}</span><span class="p" data-group-id="1767474790-21">}</span><span class="p">,</span><span class="p" data-group-id="1767474790-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1767474790-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1767474790-24">}</span><span class="p" data-group-id="1767474790-23">}</span><span class="p" data-group-id="1767474790-20">}</span><span class="p" data-group-id="1767474790-19">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1767474790-25">(</span><span class="p" data-group-id="1767474790-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1767474790-26">]</span><span class="p" data-group-id="1767474790-25">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1767474790-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1767474790-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1767474790-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1767474790-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1767474790-30">}</span><span class="p" data-group-id="1767474790-29">}</span><span class="p">,</span><span class="p" data-group-id="1767474790-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1767474790-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1767474790-32">}</span><span class="p" data-group-id="1767474790-31">}</span><span class="p" data-group-id="1767474790-28">}</span><span class="p" data-group-id="1767474790-27">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1767474790-33">(</span><span class="p" data-group-id="1767474790-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1767474790-34">]</span><span class="p" data-group-id="1767474790-33">)</span><span class="p">.</span><span class="w">
│ │ │ +code addresses this problem:</p><pre><code class="makeup erlang" translate="no"><span class="nf">grammar</span><span class="p" data-group-id="1136016012-1">(</span><span class="p" data-group-id="1136016012-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">pand</span><span class="p" data-group-id="1136016012-2">(</span><span class="w">
│ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="1136016012-3">(</span><span class="nf">pconst</span><span class="p" data-group-id="1136016012-4">(</span><span class="ss">a</span><span class="p" data-group-id="1136016012-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="1136016012-5">(</span><span class="ss">b</span><span class="p" data-group-id="1136016012-5">)</span><span class="p" data-group-id="1136016012-3">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="nf">por</span><span class="p" data-group-id="1136016012-6">(</span><span class="nf">pconst</span><span class="p" data-group-id="1136016012-7">(</span><span class="ss">c</span><span class="p" data-group-id="1136016012-7">)</span><span class="p">,</span><span class="w"> </span><span class="nf">pconst</span><span class="p" data-group-id="1136016012-8">(</span><span class="ss">d</span><span class="p" data-group-id="1136016012-8">)</span><span class="p" data-group-id="1136016012-6">)</span><span class="p" data-group-id="1136016012-2">)</span><span class="p">.</span></code></pre><p>The following code adds a parser interface to the grammar:</p><pre><code class="makeup erlang" translate="no"><span class="nf">parse</span><span class="p" data-group-id="2928856803-1">(</span><span class="n">List</span><span class="p" data-group-id="2928856803-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2928856803-2">(</span><span class="nf">grammar</span><span class="p" data-group-id="2928856803-3">(</span><span class="p" data-group-id="2928856803-3">)</span><span class="p" data-group-id="2928856803-2">)</span><span class="p" data-group-id="2928856803-4">(</span><span class="n">List</span><span class="p" data-group-id="2928856803-4">)</span><span class="p">.</span></code></pre><p>The parser can be tested as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1449518744-1">(</span><span class="p" data-group-id="1449518744-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1449518744-2">]</span><span class="p" data-group-id="1449518744-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1449518744-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1449518744-4">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1449518744-5">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1449518744-6">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1449518744-6">}</span><span class="p" data-group-id="1449518744-5">}</span><span class="p">,</span><span class="p" data-group-id="1449518744-7">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1449518744-8">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1449518744-8">}</span><span class="p" data-group-id="1449518744-7">}</span><span class="p" data-group-id="1449518744-4">}</span><span class="p" data-group-id="1449518744-3">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1449518744-9">(</span><span class="p" data-group-id="1449518744-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1449518744-10">]</span><span class="p" data-group-id="1449518744-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1449518744-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1449518744-12">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1449518744-13">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1449518744-14">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1449518744-14">}</span><span class="p" data-group-id="1449518744-13">}</span><span class="p">,</span><span class="p" data-group-id="1449518744-15">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1449518744-16">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1449518744-16">}</span><span class="p" data-group-id="1449518744-15">}</span><span class="p" data-group-id="1449518744-12">}</span><span class="p" data-group-id="1449518744-11">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1449518744-17">(</span><span class="p" data-group-id="1449518744-18">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1449518744-18">]</span><span class="p" data-group-id="1449518744-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1449518744-19">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1449518744-20">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1449518744-21">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1449518744-22">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1449518744-22">}</span><span class="p" data-group-id="1449518744-21">}</span><span class="p">,</span><span class="p" data-group-id="1449518744-23">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="1449518744-24">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1449518744-24">}</span><span class="p" data-group-id="1449518744-23">}</span><span class="p" data-group-id="1449518744-20">}</span><span class="p" data-group-id="1449518744-19">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1449518744-25">(</span><span class="p" data-group-id="1449518744-26">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1449518744-26">]</span><span class="p" data-group-id="1449518744-25">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1449518744-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1449518744-28">{</span><span class="ss">&#39;and&#39;</span><span class="p">,</span><span class="p" data-group-id="1449518744-29">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1449518744-30">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1449518744-30">}</span><span class="p" data-group-id="1449518744-29">}</span><span class="p">,</span><span class="p" data-group-id="1449518744-31">{</span><span class="ss">&#39;or&#39;</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="p" data-group-id="1449518744-32">{</span><span class="ss">const</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1449518744-32">}</span><span class="p" data-group-id="1449518744-31">}</span><span class="p" data-group-id="1449518744-28">}</span><span class="p" data-group-id="1449518744-27">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">funparse</span><span class="p">:</span><span class="nf">parse</span><span class="p" data-group-id="1449518744-33">(</span><span class="p" data-group-id="1449518744-34">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1449518744-34">]</span><span class="p" data-group-id="1449518744-33">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">fail</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="prog_ex_records.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/gen_server_concepts.html
│ │ │ @@ -157,63 +157,63 @@
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │  <p>An example of a simple server written in plain Erlang is provided in
│ │ │  <a href="design_principles.html#ch1">Overview</a>. The server can be reimplemented using
│ │ │ -<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9408581421-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="9408581421-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9408581421-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="9408581421-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">gen_server</code>, resulting in this callback module:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4412421643-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="4412421643-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4412421643-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="4412421643-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9408581421-3">(</span><span class="p" data-group-id="9408581421-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9408581421-4">]</span><span class="p" data-group-id="9408581421-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9408581421-5">(</span><span class="p" data-group-id="9408581421-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9408581421-6">]</span><span class="p" data-group-id="9408581421-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9408581421-7">(</span><span class="p" data-group-id="9408581421-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9408581421-8">]</span><span class="p" data-group-id="9408581421-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4412421643-3">(</span><span class="p" data-group-id="4412421643-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4412421643-4">]</span><span class="p" data-group-id="4412421643-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4412421643-5">(</span><span class="p" data-group-id="4412421643-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4412421643-6">]</span><span class="p" data-group-id="4412421643-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4412421643-7">(</span><span class="p" data-group-id="4412421643-8">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4412421643-8">]</span><span class="p" data-group-id="4412421643-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="9408581421-9">(</span><span class="p" data-group-id="9408581421-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9408581421-10">(</span><span class="p" data-group-id="9408581421-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="9408581421-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9408581421-12">[</span><span class="p" data-group-id="9408581421-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9408581421-13">[</span><span class="p" data-group-id="9408581421-13">]</span><span class="p" data-group-id="9408581421-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="4412421643-9">(</span><span class="p" data-group-id="4412421643-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4412421643-10">(</span><span class="p" data-group-id="4412421643-11">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4412421643-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4412421643-12">[</span><span class="p" data-group-id="4412421643-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4412421643-13">[</span><span class="p" data-group-id="4412421643-13">]</span><span class="p" data-group-id="4412421643-10">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="9408581421-14">(</span><span class="p" data-group-id="9408581421-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9408581421-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="9408581421-15">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="4412421643-14">(</span><span class="p" data-group-id="4412421643-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4412421643-15">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="4412421643-15">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="9408581421-16">(</span><span class="n">Ch</span><span class="p" data-group-id="9408581421-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9408581421-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9408581421-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9408581421-18">}</span><span class="p" data-group-id="9408581421-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="4412421643-16">(</span><span class="n">Ch</span><span class="p" data-group-id="4412421643-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4412421643-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4412421643-18">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4412421643-18">}</span><span class="p" data-group-id="4412421643-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="9408581421-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9408581421-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9408581421-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9408581421-21">(</span><span class="p" data-group-id="9408581421-21">)</span><span class="p" data-group-id="9408581421-20">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="4412421643-19">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4412421643-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4412421643-20">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="4412421643-21">(</span><span class="p" data-group-id="4412421643-21">)</span><span class="p" data-group-id="4412421643-20">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="9408581421-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9408581421-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9408581421-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9408581421-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="9408581421-24">(</span><span class="n">Chs</span><span class="p" data-group-id="9408581421-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9408581421-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9408581421-25">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="4412421643-22">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4412421643-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4412421643-23">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4412421643-23">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="4412421643-24">(</span><span class="n">Chs</span><span class="p" data-group-id="4412421643-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4412421643-25">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4412421643-25">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="9408581421-26">(</span><span class="p" data-group-id="9408581421-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9408581421-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9408581421-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9408581421-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9408581421-28">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9408581421-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9408581421-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="4412421643-26">(</span><span class="p" data-group-id="4412421643-27">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4412421643-27">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4412421643-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="4412421643-28">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4412421643-28">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4412421643-29">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4412421643-29">}</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-a-gen_server" class="section-heading">
│ │ │    <a href="#starting-a-gen_server" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting a Gen_Server</span>
│ │ │  </h2>
│ │ │  <p>In the example in the previous section, <code class="inline">gen_server</code> is started by calling
│ │ │ -<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="4186002150-1">(</span><span class="p" data-group-id="4186002150-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4186002150-2">(</span><span class="p" data-group-id="4186002150-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="4186002150-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4186002150-4">[</span><span class="p" data-group-id="4186002150-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4186002150-5">[</span><span class="p" data-group-id="4186002150-5">]</span><span class="p" data-group-id="4186002150-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4186002150-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="4186002150-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │ +<code class="inline">ch3:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="3079622090-1">(</span><span class="p" data-group-id="3079622090-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3079622090-2">(</span><span class="p" data-group-id="3079622090-3">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3079622090-3">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3079622090-4">[</span><span class="p" data-group-id="3079622090-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3079622090-5">[</span><span class="p" data-group-id="3079622090-5">]</span><span class="p" data-group-id="3079622090-2">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3079622090-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="3079622090-6">}</span></code></pre><p><code class="inline">start_link/0</code> calls function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a>.  This function
│ │ │  spawns and links to a new process, a <code class="inline">gen_server</code>.</p><ul><li><p>The first argument, <code class="inline">{local, ch3}</code>, specifies the name.
│ │ │  The gen_server is then locally registered as <code class="inline">ch3</code>.</p><p>If the name is omitted, the <code class="inline">gen_server</code> is not registered. Instead its pid
│ │ │  must be used. The name can also be given as <code class="inline">{global, Name}</code>, in which case
│ │ │  the <code class="inline">gen_server</code> is registered using <a href="../../lib/kernel-10.2.7.2/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a>.</p></li><li><p>The second argument, <code class="inline">ch3</code>, is the name of the callback module, which is
│ │ │  the module where the callback functions are located.</p><p>The interface functions (<code class="inline">start_link/0</code>, <code class="inline">alloc/0</code>, and <code class="inline">free/1</code>) are located
│ │ │  in the same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">handle_call/3</code>, and
│ │ │  <code class="inline">handle_cast/2</code>). It is usually good programming practice to have the code
│ │ │  corresponding to one process contained in a single module.</p></li><li><p>The third argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any indata and ignores the
│ │ │  argument.</p></li><li><p>The fourth argument, <code class="inline">[]</code>, is a list of options. See <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html"><code class="inline">gen_server</code></a>
│ │ │  for the available options.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_server</code> process calls the callback
│ │ │  function <code class="inline">ch3:init([])</code>. <code class="inline">init</code> is expected to return <code class="inline">{ok, State}</code>, where
│ │ │  <code class="inline">State</code> is the internal state of the <code class="inline">gen_server</code>. In this case, the state is
│ │ │ -the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7002544052-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7002544052-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7002544052-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="7002544052-3">(</span><span class="p" data-group-id="7002544052-3">)</span><span class="p" data-group-id="7002544052-2">}</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │ +the available channels.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9257998410-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9257998410-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9257998410-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="9257998410-3">(</span><span class="p" data-group-id="9257998410-3">)</span><span class="p" data-group-id="9257998410-2">}</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> is synchronous. It does not return until the
│ │ │  <code class="inline">gen_server</code> has been initialized and is ready to receive requests.</p><p><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/4</code></a> must be used if the <code class="inline">gen_server</code> is part of
│ │ │  a supervision tree, meaning that it was started by a supervisor. There
│ │ │  is another function, <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start/4"><code class="inline">gen_server:start/4</code></a>, to start a standalone
│ │ │  <code class="inline">gen_server</code> that is not part of a supervision tree.</p><h2 id="synchronous-requests-call" class="section-heading">
│ │ │    <a href="#synchronous-requests-call" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -221,32 +221,32 @@
│ │ │  </h2>
│ │ │  <p>The synchronous request <code class="inline">alloc()</code> is implemented using <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#call/2"><code class="inline">gen_server:call/2</code></a>:</p><pre><code class="text">alloc() -&gt;
│ │ │      gen_server:call(ch3, alloc).</code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code> and must agree with the name
│ │ │  used to start it. <code class="inline">alloc</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │  When the request is received, the <code class="inline">gen_server</code> calls
│ │ │  <code class="inline">handle_call(Request, From, State)</code>, which is expected to return
│ │ │  a tuple <code class="inline">{reply,Reply,State1}</code>. <code class="inline">Reply</code> is the reply that is to be sent back
│ │ │ -to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="4066070621-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4066070621-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4066070621-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4066070621-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="4066070621-3">(</span><span class="n">Chs</span><span class="p" data-group-id="4066070621-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4066070621-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4066070621-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │ +to the client, and <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_call</span><span class="p" data-group-id="0918784509-1">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="0918784509-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0918784509-2">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0918784509-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="0918784509-3">(</span><span class="n">Chs</span><span class="p" data-group-id="0918784509-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0918784509-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="0918784509-4">}</span><span class="p">.</span></code></pre><p>In this case, the reply is the allocated channel <code class="inline">Ch</code> and the new state is the
│ │ │  set of remaining available channels <code class="inline">Chs2</code>.</p><p>Thus, the call <code class="inline">ch3:alloc()</code> returns the allocated channel <code class="inline">Ch</code> and the
│ │ │  <code class="inline">gen_server</code> then waits for new requests, now with an updated list of
│ │ │  available channels.</p><h2 id="asynchronous-requests-cast" class="section-heading">
│ │ │    <a href="#asynchronous-requests-cast" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Asynchronous Requests - Cast</span>
│ │ │  </h2>
│ │ │ -<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="6443857282-1">(</span><span class="n">Ch</span><span class="p" data-group-id="6443857282-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6443857282-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6443857282-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="6443857282-3">}</span><span class="p" data-group-id="6443857282-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │ +<p>The asynchronous request <code class="inline">free(Ch)</code> is implemented using <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#cast/2"><code class="inline">gen_server:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">free</span><span class="p" data-group-id="4912056861-1">(</span><span class="n">Ch</span><span class="p" data-group-id="4912056861-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4912056861-2">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4912056861-3">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4912056861-3">}</span><span class="p" data-group-id="4912056861-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch3</code> is the name of the <code class="inline">gen_server</code>. <code class="inline">{free, Ch}</code> is the actual request.</p><p>The request is made into a message and sent to the <code class="inline">gen_server</code>.
│ │ │  <code class="inline">cast</code>, and thus <code class="inline">free</code>, then returns <code class="inline">ok</code>.</p><p>When the request is received, the <code class="inline">gen_server</code> calls
│ │ │  <code class="inline">handle_cast(Request, State)</code>, which is expected to return a tuple
│ │ │ -<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="9427269063-1">(</span><span class="p" data-group-id="9427269063-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="9427269063-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9427269063-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="9427269063-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="9427269063-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9427269063-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="9427269063-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │ +<code class="inline">{noreply,State1}</code>. <code class="inline">State1</code> is a new value for the state of the <code class="inline">gen_server</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_cast</span><span class="p" data-group-id="4375704134-1">(</span><span class="p" data-group-id="4375704134-2">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="4375704134-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4375704134-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="4375704134-3">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="4375704134-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4375704134-4">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="4375704134-4">}</span><span class="p">.</span></code></pre><p>In this case, the new state is the updated list of available channels <code class="inline">Chs2</code>.
│ │ │  The <code class="inline">gen_server</code> is now ready for new requests.</p><h2 id="stopping" class="section-heading">
│ │ │    <a href="#stopping" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stopping</span>
│ │ │  </h2>
│ │ │  <h3 id="in-a-supervision-tree" class="section-heading">
│ │ │ @@ -257,69 +257,69 @@
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_server</code> is part of a supervision tree, no stop function is needed.
│ │ │  The <code class="inline">gen_server</code> is automatically terminated by its supervisor.  Exactly how
│ │ │  this is done is defined by a <a href="sup_princ.html#shutdown">shutdown strategy</a>
│ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │  must be a time-out value and the <code class="inline">gen_server</code> must be set to trap exit signals
│ │ │  in function <code class="inline">init</code>. When ordered to shutdown, the <code class="inline">gen_server</code> then calls
│ │ │ -the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0883938106-1">(</span><span class="n">Args</span><span class="p" data-group-id="0883938106-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the callback function <code class="inline">terminate(shutdown, State)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5627682219-1">(</span><span class="n">Args</span><span class="p" data-group-id="5627682219-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="0883938106-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0883938106-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="5627682219-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5627682219-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0883938106-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0883938106-3">}</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5627682219-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5627682219-3">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="0883938106-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="0883938106-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="5627682219-4">(</span><span class="ss">shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="5627682219-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code for cleaning up here</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_servers" class="section-heading">
│ │ │    <a href="#standalone-gen_servers" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standalone Gen_Servers</span>
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_server</code> is not part of a supervision tree, a stop function
│ │ │  can be useful, for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">export</span><span class="p" data-group-id="7606893207-1">(</span><span class="p" data-group-id="7606893207-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7606893207-2">]</span><span class="p" data-group-id="7606893207-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">export</span><span class="p" data-group-id="1377285202-1">(</span><span class="p" data-group-id="1377285202-2">[</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1377285202-2">]</span><span class="p" data-group-id="1377285202-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="7606893207-3">(</span><span class="p" data-group-id="7606893207-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7606893207-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="7606893207-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="1377285202-3">(</span><span class="p" data-group-id="1377285202-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1377285202-4">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p" data-group-id="1377285202-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="7606893207-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7606893207-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7606893207-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7606893207-6">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="7606893207-7">(</span><span class="p" data-group-id="7606893207-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7606893207-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7606893207-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="1377285202-5">(</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1377285202-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1377285202-6">{</span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1377285202-6">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="1377285202-7">(</span><span class="p" data-group-id="1377285202-8">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="1377285202-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1377285202-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="7606893207-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7606893207-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="1377285202-9">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="1377285202-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The callback function handling the <code class="inline">stop</code> request returns a tuple
│ │ │  <code class="inline">{stop,normal,State1}</code>, where <code class="inline">normal</code> specifies that it is
│ │ │  a normal termination and <code class="inline">State1</code> is a new value for the state
│ │ │  of the <code class="inline">gen_server</code>.  This causes the <code class="inline">gen_server</code> to call
│ │ │  <code class="inline">terminate(normal, State1)</code> and then it terminates gracefully.</p><h2 id="handling-other-messages" class="section-heading">
│ │ │    <a href="#handling-other-messages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling Other Messages</span>
│ │ │  </h2>
│ │ │  <p>If the <code class="inline">gen_server</code> is to be able to receive other messages than requests,
│ │ │  the callback function <code class="inline">handle_info(Info, State)</code> must be implemented
│ │ │  to handle them.  Examples of other messages are exit messages,
│ │ │  if the <code class="inline">gen_server</code> is linked to other processes than the supervisor
│ │ │ -and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="7728651877-1">(</span><span class="p" data-group-id="7728651877-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="7728651877-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="7728651877-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +and it is trapping exit signals.</p><pre><code class="makeup erlang" translate="no"><span class="nf">handle_info</span><span class="p" data-group-id="4086196724-1">(</span><span class="p" data-group-id="4086196724-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="4086196724-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4086196724-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to handle exits here.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7728651877-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="7728651877-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="8734629616-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="8734629616-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4086196724-3">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">State1</span><span class="p" data-group-id="4086196724-3">}</span><span class="p">.</span></code></pre><p>The final function to implement is <code class="inline">code_change/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">code_change</span><span class="p" data-group-id="2689203387-1">(</span><span class="n">OldVsn</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="2689203387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Code to convert state (and more) during code change.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8734629616-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="8734629616-2">}</span><span class="p">.</span></code></pre>
│ │ │ +    </span><span class="p" data-group-id="2689203387-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NewState</span><span class="p" data-group-id="2689203387-2">}</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="design_principles.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/included_applications.html
│ │ │ @@ -161,75 +161,75 @@
│ │ │  belonging to the primary application.</p><h2 id="specifying-included-applications" class="section-heading">
│ │ │    <a href="#specifying-included-applications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Specifying Included Applications</span>
│ │ │  </h2>
│ │ │  <p>Which applications to include is defined by the <code class="inline">included_applications</code> key in
│ │ │ -the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5921291503-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5921291503-2">[</span><span class="p" data-group-id="5921291503-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="5921291503-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="5921291503-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5921291503-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="5921291503-6">]</span><span class="p" data-group-id="5921291503-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5921291503-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="5921291503-8">]</span><span class="p" data-group-id="5921291503-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5921291503-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="5921291503-10">]</span><span class="p" data-group-id="5921291503-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5921291503-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="5921291503-12">]</span><span class="p" data-group-id="5921291503-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5921291503-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="5921291503-15">[</span><span class="p" data-group-id="5921291503-15">]</span><span class="p" data-group-id="5921291503-14">}</span><span class="p" data-group-id="5921291503-13">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="5921291503-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5921291503-17">[</span><span class="p" data-group-id="5921291503-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="5921291503-18">}</span><span class="p" data-group-id="5921291503-17">]</span><span class="p" data-group-id="5921291503-16">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="5921291503-2">]</span><span class="p" data-group-id="5921291503-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │ +the <code class="inline">.app</code> file:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6464223373-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6464223373-2">[</span><span class="p" data-group-id="6464223373-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="6464223373-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6464223373-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6464223373-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="6464223373-6">]</span><span class="p" data-group-id="6464223373-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6464223373-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="6464223373-8">]</span><span class="p" data-group-id="6464223373-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6464223373-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="6464223373-10">]</span><span class="p" data-group-id="6464223373-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-11">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6464223373-12">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6464223373-12">]</span><span class="p" data-group-id="6464223373-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-13">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6464223373-14">{</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="6464223373-15">[</span><span class="p" data-group-id="6464223373-15">]</span><span class="p" data-group-id="6464223373-14">}</span><span class="p" data-group-id="6464223373-13">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6464223373-16">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6464223373-17">[</span><span class="p" data-group-id="6464223373-18">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6464223373-18">}</span><span class="p" data-group-id="6464223373-17">]</span><span class="p" data-group-id="6464223373-16">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6464223373-2">]</span><span class="p" data-group-id="6464223373-1">}</span><span class="p">.</span></code></pre><h2 id="synchronizing-processes-during-startup" class="section-heading">
│ │ │    <a href="#synchronizing-processes-during-startup" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Synchronizing Processes during Startup</span>
│ │ │  </h2>
│ │ │  <p>The supervisor tree of an included application is started as part of the
│ │ │  supervisor tree of the including application. If there is a need for
│ │ │  synchronization between processes in the including and included applications,
│ │ │  this can be achieved by using <em>start phases</em>.</p><p>Start phases are defined by the <code class="inline">start_phases</code> key in the <code class="inline">.app</code> file as a list
│ │ │  of tuples <code class="inline">{Phase,PhaseArgs}</code>, where <code class="inline">Phase</code> is an atom and <code class="inline">PhaseArgs</code> is a
│ │ │  term.</p><p>The value of the <code class="inline">mod</code> key of the including application must be set to
│ │ │  <code class="inline">{application_starter,[Module,StartArgs]}</code>, where <code class="inline">Module</code> as usual is the
│ │ │  application callback module. <code class="inline">StartArgs</code> is a term provided as argument to the
│ │ │ -callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3928829059-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3928829059-2">[</span><span class="p" data-group-id="3928829059-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="3928829059-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3928829059-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="3928829059-6">]</span><span class="p" data-group-id="3928829059-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="3928829059-8">]</span><span class="p" data-group-id="3928829059-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="3928829059-10">]</span><span class="p" data-group-id="3928829059-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-12">[</span><span class="p" data-group-id="3928829059-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="3928829059-14">[</span><span class="p" data-group-id="3928829059-14">]</span><span class="p" data-group-id="3928829059-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="3928829059-16">[</span><span class="p" data-group-id="3928829059-16">]</span><span class="p" data-group-id="3928829059-15">}</span><span class="p" data-group-id="3928829059-12">]</span><span class="p" data-group-id="3928829059-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3928829059-18">]</span><span class="p" data-group-id="3928829059-17">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="3928829059-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="3928829059-22">[</span><span class="p" data-group-id="3928829059-22">]</span><span class="p" data-group-id="3928829059-21">]</span><span class="p" data-group-id="3928829059-20">}</span><span class="p" data-group-id="3928829059-19">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-24">[</span><span class="p" data-group-id="3928829059-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="3928829059-25">}</span><span class="p" data-group-id="3928829059-24">]</span><span class="p" data-group-id="3928829059-23">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3928829059-2">]</span><span class="p" data-group-id="3928829059-1">}</span><span class="p">.</span><span class="w">
│ │ │ +callback function <code class="inline">Module:start/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6143048428-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6143048428-2">[</span><span class="p" data-group-id="6143048428-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Tree application&quot;</span><span class="p" data-group-id="6143048428-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6143048428-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-6">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">prim_app_server</span><span class="p" data-group-id="6143048428-6">]</span><span class="p" data-group-id="6143048428-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-8">[</span><span class="ss">prim_app_server</span><span class="p" data-group-id="6143048428-8">]</span><span class="p" data-group-id="6143048428-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-9">{</span><span class="ss">included_applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-10">[</span><span class="ss">incl_app</span><span class="p" data-group-id="6143048428-10">]</span><span class="p" data-group-id="6143048428-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-11">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-12">[</span><span class="p" data-group-id="6143048428-13">{</span><span class="ss">init</span><span class="p">,</span><span class="p" data-group-id="6143048428-14">[</span><span class="p" data-group-id="6143048428-14">]</span><span class="p" data-group-id="6143048428-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-15">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="6143048428-16">[</span><span class="p" data-group-id="6143048428-16">]</span><span class="p" data-group-id="6143048428-15">}</span><span class="p" data-group-id="6143048428-12">]</span><span class="p" data-group-id="6143048428-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-17">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-18">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6143048428-18">]</span><span class="p" data-group-id="6143048428-17">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-19">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-20">{</span><span class="ss">application_starter</span><span class="p">,</span><span class="p" data-group-id="6143048428-21">[</span><span class="ss">prim_app_cb</span><span class="p">,</span><span class="p" data-group-id="6143048428-22">[</span><span class="p" data-group-id="6143048428-22">]</span><span class="p" data-group-id="6143048428-21">]</span><span class="p" data-group-id="6143048428-20">}</span><span class="p" data-group-id="6143048428-19">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-23">{</span><span class="ss">env</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-24">[</span><span class="p" data-group-id="6143048428-25">{</span><span class="ss">file</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;/usr/local/log&quot;</span><span class="p" data-group-id="6143048428-25">}</span><span class="p" data-group-id="6143048428-24">]</span><span class="p" data-group-id="6143048428-23">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6143048428-2">]</span><span class="p" data-group-id="6143048428-1">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="3928829059-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3928829059-27">[</span><span class="p" data-group-id="3928829059-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="3928829059-28">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="3928829059-29">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="3928829059-31">]</span><span class="p" data-group-id="3928829059-30">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-33">[</span><span class="p" data-group-id="3928829059-33">]</span><span class="p" data-group-id="3928829059-32">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-35">[</span><span class="p" data-group-id="3928829059-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="3928829059-37">[</span><span class="p" data-group-id="3928829059-37">]</span><span class="p" data-group-id="3928829059-36">}</span><span class="p" data-group-id="3928829059-35">]</span><span class="p" data-group-id="3928829059-34">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="3928829059-39">]</span><span class="p" data-group-id="3928829059-38">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3928829059-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928829059-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="3928829059-42">[</span><span class="p" data-group-id="3928829059-42">]</span><span class="p" data-group-id="3928829059-41">}</span><span class="p" data-group-id="3928829059-40">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3928829059-27">]</span><span class="p" data-group-id="3928829059-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │ +</span><span class="p" data-group-id="6143048428-26">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6143048428-27">[</span><span class="p" data-group-id="6143048428-28">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Included application&quot;</span><span class="p" data-group-id="6143048428-28">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-29">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6143048428-29">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-30">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-31">[</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">incl_app_server</span><span class="p" data-group-id="6143048428-31">]</span><span class="p" data-group-id="6143048428-30">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-32">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-33">[</span><span class="p" data-group-id="6143048428-33">]</span><span class="p" data-group-id="6143048428-32">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-34">{</span><span class="ss">start_phases</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-35">[</span><span class="p" data-group-id="6143048428-36">{</span><span class="ss">go</span><span class="p">,</span><span class="p" data-group-id="6143048428-37">[</span><span class="p" data-group-id="6143048428-37">]</span><span class="p" data-group-id="6143048428-36">}</span><span class="p" data-group-id="6143048428-35">]</span><span class="p" data-group-id="6143048428-34">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-38">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-39">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6143048428-39">]</span><span class="p" data-group-id="6143048428-38">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6143048428-40">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6143048428-41">{</span><span class="ss">incl_app_cb</span><span class="p">,</span><span class="p" data-group-id="6143048428-42">[</span><span class="p" data-group-id="6143048428-42">]</span><span class="p" data-group-id="6143048428-41">}</span><span class="p" data-group-id="6143048428-40">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6143048428-27">]</span><span class="p" data-group-id="6143048428-26">}</span><span class="p">.</span></code></pre><p>When starting a primary application with included applications, the primary
│ │ │  application is started the normal way, that is:</p><ul><li>The application controller creates an application master for the application</li><li>The application master calls <code class="inline">Module:start(normal, StartArgs)</code> to start the
│ │ │  top supervisor.</li></ul><p>Then, for the primary application and each included application in top-down,
│ │ │  left-to-right order, the application master calls
│ │ │  <code class="inline">Module:start_phase(Phase, Type, PhaseArgs)</code> for each phase defined for the
│ │ │  primary application, in that order. If a phase is not defined for an included
│ │ │  application, the function is not called for this phase and application.</p><p>The following requirements apply to the <code class="inline">.app</code> file for an included application:</p><ul><li>The <code class="inline">{mod, {Module,StartArgs}}</code> option must be included. This option is used
│ │ │  to find the callback module <code class="inline">Module</code> of the application. <code class="inline">StartArgs</code> is
│ │ │  ignored, as <code class="inline">Module:start/2</code> is called only for the primary application.</li><li>If the included application itself contains included applications, instead the
│ │ │  <code class="inline">{mod, {application_starter, [Module,StartArgs]}}</code> option must be included.</li><li>The <code class="inline">{start_phases, [{Phase,PhaseArgs}]}</code> option must be included, and the set
│ │ │  of specified phases must be a subset of the set of phases specified for the
│ │ │  primary application.</li></ul><p>When starting <code class="inline">prim_app</code> as defined above, the application controller calls the
│ │ │  following callback functions before <code class="inline">application:start(prim_app)</code> returns a
│ │ │ -value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9749432421-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="9749432421-1">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="9749432421-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9749432421-3">[</span><span class="p" data-group-id="9749432421-3">]</span><span class="p" data-group-id="9749432421-2">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="9749432421-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9749432421-5">[</span><span class="p" data-group-id="9749432421-5">]</span><span class="p" data-group-id="9749432421-4">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="9749432421-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9749432421-7">[</span><span class="p" data-group-id="9749432421-7">]</span><span class="p" data-group-id="9749432421-6">)</span><span class="w">
│ │ │ - </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="9749432421-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9749432421-9">[</span><span class="p" data-group-id="9749432421-9">]</span><span class="p" data-group-id="9749432421-8">)</span><span class="w">
│ │ │ +value:</p><pre><code class="makeup erlang" translate="no"><span class="nc">application</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8604281891-1">(</span><span class="ss">prim_app</span><span class="p" data-group-id="8604281891-1">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start</span><span class="p" data-group-id="8604281891-2">(</span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604281891-3">[</span><span class="p" data-group-id="8604281891-3">]</span><span class="p" data-group-id="8604281891-2">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="8604281891-4">(</span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604281891-5">[</span><span class="p" data-group-id="8604281891-5">]</span><span class="p" data-group-id="8604281891-4">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">prim_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="8604281891-6">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604281891-7">[</span><span class="p" data-group-id="8604281891-7">]</span><span class="p" data-group-id="8604281891-6">)</span><span class="w">
│ │ │ + </span><span class="p">=&gt;</span><span class="w"> </span><span class="nc">incl_app_cb</span><span class="p">:</span><span class="nf">start_phase</span><span class="p" data-group-id="8604281891-8">(</span><span class="ss">go</span><span class="p">,</span><span class="w"> </span><span class="ss">normal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8604281891-9">[</span><span class="p" data-group-id="8604281891-9">]</span><span class="p" data-group-id="8604281891-8">)</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="applications.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/install-win32.html
│ │ │ @@ -295,15 +295,15 @@
│ │ │  </span><span class="gp unselectable">$ </span><span class="">cd erts/emulator
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │  </span><span class="gp unselectable">$ </span><span class="">cd ../etc
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make debug
│ │ │  </span></code></pre><p>and sometimes</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make local_setup
│ │ │  </span></code></pre><p>So now when you run <code class="inline">$ERL_TOP/erl.exe</code>, you should have a debug compiled
│ │ │ -emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="4897992233-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="4897992233-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │ +emulator, which you will see if you do a:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="2651248239-1">(</span><span class="ss">system_version</span><span class="p" data-group-id="2651248239-1">)</span><span class="p">.</span></code></pre><p>in the erlang shell. If the returned string contains <code class="inline">[debug]</code>, you
│ │ │  got a debug compiled emulator.</p><p>To hack the erlang libraries, you simply do a <code class="inline">make opt</code> in the
│ │ │  specific &quot;applications&quot; directory, like:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │  </span></code></pre><p>or even in the source directory...</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib/src
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make opt
│ │ │  </span></code></pre><p>Note that you're expected to have a fresh Erlang in your path when
│ │ │  doing this, preferably the plain 27 you have built in the previous
│ │ │ @@ -318,19 +318,19 @@
│ │ │  </span><span class="">:$ERL_TOP/erts/etc/win32/wsl_tools:$ERL_TOP/bootstrap/bin:$PATH
│ │ │  </span></code></pre><p>That should make it possible to rebuild any library without hassle...</p><p>If you want to copy a library (an application) newly built, to a
│ │ │  release area, you do like with the emulator:</p><pre><code class="makeup shell" translate="no"><span class="gp unselectable">$ </span><span class="">cd $ERL_TOP/lib/stdlib
│ │ │  </span><span class="gp unselectable">$ </span><span class="">make TESTROOT=/tmp/erlang_release release
│ │ │  </span></code></pre><p>Remember that:</p><ul><li><p>  Windows specific C-code goes in the <code class="inline">$ERL_TOP/erts/emulator/sys/win32</code>,
│ │ │  <code class="inline">$ERL_TOP/erts/emulator/drivers/win32</code> or <code class="inline">$ERL_TOP/erts/etc/win32</code>.</p></li><li><p>  Windows specific erlang code should be used conditionally and the
│ │ │  host OS tested in <em>runtime</em>, the exactly same beam files should be
│ │ │ -distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="5461350602-1">(</span><span class="p" data-group-id="5461350602-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5461350602-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5461350602-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="5461350602-3">(</span><span class="p" data-group-id="5461350602-3">)</span><span class="p">;</span><span class="w">
│ │ │ +distributed for every platform! So write code like:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">os</span><span class="p">:</span><span class="nf">type</span><span class="p" data-group-id="2030931076-1">(</span><span class="p" data-group-id="2030931076-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2030931076-2">{</span><span class="ss">win32</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2030931076-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">do_windows_specific</span><span class="p" data-group-id="2030931076-3">(</span><span class="p" data-group-id="2030931076-3">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Other</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="5461350602-4">(</span><span class="p" data-group-id="5461350602-4">)</span><span class="w">
│ │ │ +        </span><span class="nf">do_fallback_or_exit</span><span class="p" data-group-id="2030931076-4">(</span><span class="p" data-group-id="2030931076-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre></li></ul><p>That's basically all you need to get going.</p><h2 id="frequently-asked-questions" class="section-heading">
│ │ │    <a href="#frequently-asked-questions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Frequently Asked Questions</span>
│ │ │  </h2>
│ │ │  <ul><li><p>  Q: So, now I can build Erlang using GCC on Windows?</p><p>A: No, unfortunately not. You'll need Microsoft's Visual C++
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/list_comprehensions.html
│ │ │ @@ -117,33 +117,33 @@
│ │ │  
│ │ │  <h2 id="simple-examples" class="section-heading">
│ │ │    <a href="#simple-examples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simple Examples</span>
│ │ │  </h2>
│ │ │ -<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3187695832-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="3187695832-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3187695832-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3187695832-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3187695832-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3187695832-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │ +<p>This section starts with a simple example, showing a generator and a filter:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7895765839-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7895765839-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7895765839-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7895765839-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7895765839-3">[</span><span class="ss">a</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7895765839-3">]</span></code></pre><p>This is read as follows: The list of X such that X is taken from the list
│ │ │  <code class="inline">[1,2,a,...]</code> and X is greater than 3.</p><p>The notation <code class="inline">X &lt;- [1,2,a,...]</code> is a generator and the expression <code class="inline">X &gt; 3</code> is a
│ │ │  filter.</p><p>An additional filter, <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_integer/1"><code class="inline">is_integer(X)</code></a>, can be added to
│ │ │ -restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7336472319-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="7336472319-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7336472319-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="7336472319-3">(</span><span class="n">X</span><span class="p" data-group-id="7336472319-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7336472319-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7336472319-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7336472319-4">]</span></code></pre><p>Generators can be combined. For example, the Cartesian product of two lists can
│ │ │ -be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5786497462-1">[</span><span class="p" data-group-id="5786497462-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5786497462-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5786497462-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5786497462-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="5786497462-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5786497462-4">]</span><span class="p" data-group-id="5786497462-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5786497462-5">[</span><span class="p" data-group-id="5786497462-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5786497462-6">}</span><span class="p">,</span><span class="p" data-group-id="5786497462-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5786497462-7">}</span><span class="p">,</span><span class="p" data-group-id="5786497462-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5786497462-8">}</span><span class="p">,</span><span class="p" data-group-id="5786497462-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5786497462-9">}</span><span class="p">,</span><span class="p" data-group-id="5786497462-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="5786497462-10">}</span><span class="p">,</span><span class="p" data-group-id="5786497462-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="5786497462-11">}</span><span class="p" data-group-id="5786497462-5">]</span></code></pre><h2 id="quick-sort" class="section-heading">
│ │ │ +restrict the result to integers:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1039947993-1">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1039947993-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1039947993-2">]</span><span class="p">,</span><span class="w"> </span><span class="nf">is_integer</span><span class="p" data-group-id="1039947993-3">(</span><span class="n">X</span><span class="p" data-group-id="1039947993-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1039947993-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1039947993-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="1039947993-4">]</span></code></pre><p>Generators can be combined. For example, the Cartesian product of two lists can
│ │ │ +be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="9485358098-1">[</span><span class="p" data-group-id="9485358098-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9485358098-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9485358098-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9485358098-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="9485358098-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9485358098-4">]</span><span class="p" data-group-id="9485358098-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9485358098-5">[</span><span class="p" data-group-id="9485358098-6">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9485358098-6">}</span><span class="p">,</span><span class="p" data-group-id="9485358098-7">{</span><span class="mi">1</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9485358098-7">}</span><span class="p">,</span><span class="p" data-group-id="9485358098-8">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9485358098-8">}</span><span class="p">,</span><span class="p" data-group-id="9485358098-9">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9485358098-9">}</span><span class="p">,</span><span class="p" data-group-id="9485358098-10">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9485358098-10">}</span><span class="p">,</span><span class="p" data-group-id="9485358098-11">{</span><span class="mi">3</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9485358098-11">}</span><span class="p" data-group-id="9485358098-5">]</span></code></pre><h2 id="quick-sort" class="section-heading">
│ │ │    <a href="#quick-sort" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Quick Sort</span>
│ │ │  </h2>
│ │ │ -<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="8875077425-1">(</span><span class="p" data-group-id="8875077425-2">[</span><span class="p" data-group-id="8875077425-2">]</span><span class="p" data-group-id="8875077425-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8875077425-3">[</span><span class="p" data-group-id="8875077425-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="8875077425-4">(</span><span class="p" data-group-id="8875077425-5">[</span><span class="p">_</span><span class="p" data-group-id="8875077425-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="8875077425-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">sort</span><span class="p" data-group-id="8875077425-6">(</span><span class="p" data-group-id="8875077425-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8875077425-7">]</span><span class="p" data-group-id="8875077425-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="8875077425-8">(</span><span class="p" data-group-id="8875077425-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="8875077425-9">]</span><span class="p" data-group-id="8875077425-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8875077425-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="8875077425-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ -    </span><span class="nf">sort</span><span class="p" data-group-id="8875077425-11">(</span><span class="p" data-group-id="8875077425-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="8875077425-12">]</span><span class="p" data-group-id="8875077425-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │ +<p>The well-known quick sort routine can be written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sort</span><span class="p" data-group-id="2738239185-1">(</span><span class="p" data-group-id="2738239185-2">[</span><span class="p" data-group-id="2738239185-2">]</span><span class="p" data-group-id="2738239185-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2738239185-3">[</span><span class="p" data-group-id="2738239185-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="2738239185-4">(</span><span class="p" data-group-id="2738239185-5">[</span><span class="p">_</span><span class="p" data-group-id="2738239185-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="2738239185-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">L</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">sort</span><span class="p" data-group-id="2738239185-6">(</span><span class="p" data-group-id="2738239185-7">[</span><span class="n">Pivot</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2738239185-7">]</span><span class="p" data-group-id="2738239185-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="2738239185-8">(</span><span class="p" data-group-id="2738239185-9">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="2738239185-9">]</span><span class="p" data-group-id="2738239185-8">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2738239185-10">[</span><span class="n">Pivot</span><span class="p" data-group-id="2738239185-10">]</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ +    </span><span class="nf">sort</span><span class="p" data-group-id="2738239185-11">(</span><span class="p" data-group-id="2738239185-12">[</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">Pivot</span><span class="p" data-group-id="2738239185-12">]</span><span class="p" data-group-id="2738239185-11">)</span><span class="p">.</span></code></pre><p>The expression <code class="inline">[X || X &lt;- T, X &lt; Pivot]</code> is the list of all elements in <code class="inline">T</code>
│ │ │  that are less than <code class="inline">Pivot</code>.</p><p><code class="inline">[X || X &lt;- T, X &gt;= Pivot]</code> is the list of all elements in <code class="inline">T</code> that are greater
│ │ │  than or equal to <code class="inline">Pivot</code>.</p><p>With the algorithm above, a list is sorted as follows:</p><ul><li>A list with zero or one element is trivially sorted.</li><li>For lists with more than one element:<ol><li>The first element in the list is isolated as the pivot element.</li><li>The remaining list is partitioned into two sublists, such that:</li></ol><ul><li>The first sublist contains all elements that are smaller than the pivot
│ │ │  element.</li><li>The second sublist contains all elements that are greater than or equal to
│ │ │  the pivot element.</li></ul><ol><li>The sublists are recursively sorted by the same algorithm and the results
│ │ │  are combined, resulting in a list consisting of:</li></ol><ul><li>All elements from the first sublist, that is all elements smaller than the
│ │ │  pivot element, in sorted order.</li><li>The pivot element.</li><li>All elements from the second sublist, that is all elements greater than or
│ │ │  equal to the pivot element, in sorted order.</li></ul></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>While the sorting algorithm as shown above serves as a nice example to
│ │ │ @@ -151,93 +151,93 @@
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html"><code class="inline">lists</code></a> module contains sorting functions that are implemented in a more
│ │ │  efficient way.</p></section><h2 id="permutations" class="section-heading">
│ │ │    <a href="#permutations" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Permutations</span>
│ │ │  </h2>
│ │ │ -<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="7022367955-1">(</span><span class="p" data-group-id="7022367955-2">[</span><span class="p" data-group-id="7022367955-2">]</span><span class="p" data-group-id="7022367955-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7022367955-3">[</span><span class="p" data-group-id="7022367955-4">[</span><span class="p" data-group-id="7022367955-4">]</span><span class="p" data-group-id="7022367955-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">perms</span><span class="p" data-group-id="7022367955-5">(</span><span class="n">L</span><span class="p" data-group-id="7022367955-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7022367955-6">[</span><span class="p" data-group-id="7022367955-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7022367955-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="7022367955-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="7022367955-9">[</span><span class="n">H</span><span class="p" data-group-id="7022367955-9">]</span><span class="p" data-group-id="7022367955-8">)</span><span class="p" data-group-id="7022367955-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │ +<p>The following example generates all permutations of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="nf">perms</span><span class="p" data-group-id="9720613534-1">(</span><span class="p" data-group-id="9720613534-2">[</span><span class="p" data-group-id="9720613534-2">]</span><span class="p" data-group-id="9720613534-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9720613534-3">[</span><span class="p" data-group-id="9720613534-4">[</span><span class="p" data-group-id="9720613534-4">]</span><span class="p" data-group-id="9720613534-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">perms</span><span class="p" data-group-id="9720613534-5">(</span><span class="n">L</span><span class="p" data-group-id="9720613534-5">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9720613534-6">[</span><span class="p" data-group-id="9720613534-7">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9720613534-7">]</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">H</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nf">perms</span><span class="p" data-group-id="9720613534-8">(</span><span class="n">L</span><span class="o">--</span><span class="p" data-group-id="9720613534-9">[</span><span class="n">H</span><span class="p" data-group-id="9720613534-9">]</span><span class="p" data-group-id="9720613534-8">)</span><span class="p" data-group-id="9720613534-6">]</span><span class="p">.</span></code></pre><p>This takes <code class="inline">H</code> from <code class="inline">L</code> in all possible ways. The result is the set of all lists
│ │ │  <code class="inline">[H|T]</code>, where <code class="inline">T</code> is the set of all possible permutations of <code class="inline">L</code>, with <code class="inline">H</code>
│ │ │ -removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="3376783445-1">(</span><span class="p" data-group-id="3376783445-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3376783445-2">]</span><span class="p" data-group-id="3376783445-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3376783445-3">[</span><span class="p" data-group-id="3376783445-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3376783445-4">]</span><span class="p">,</span><span class="p" data-group-id="3376783445-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="3376783445-5">]</span><span class="p">,</span><span class="p" data-group-id="3376783445-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="3376783445-6">]</span><span class="p">,</span><span class="p" data-group-id="3376783445-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3376783445-7">]</span><span class="p">,</span><span class="p" data-group-id="3376783445-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="3376783445-8">]</span><span class="p">,</span><span class="p" data-group-id="3376783445-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3376783445-9">]</span><span class="p" data-group-id="3376783445-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │ +removed:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">perms</span><span class="p" data-group-id="9794757095-1">(</span><span class="p" data-group-id="9794757095-2">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="9794757095-2">]</span><span class="p" data-group-id="9794757095-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9794757095-3">[</span><span class="p" data-group-id="9794757095-4">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="9794757095-4">]</span><span class="p">,</span><span class="p" data-group-id="9794757095-5">[</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="9794757095-5">]</span><span class="p">,</span><span class="p" data-group-id="9794757095-6">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">g</span><span class="p" data-group-id="9794757095-6">]</span><span class="p">,</span><span class="p" data-group-id="9794757095-7">[</span><span class="ss">u</span><span class="p">,</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9794757095-7">]</span><span class="p">,</span><span class="p" data-group-id="9794757095-8">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">u</span><span class="p" data-group-id="9794757095-8">]</span><span class="p">,</span><span class="p" data-group-id="9794757095-9">[</span><span class="ss">g</span><span class="p">,</span><span class="ss">u</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9794757095-9">]</span><span class="p" data-group-id="9794757095-3">]</span></code></pre><h2 id="pythagorean-triplets" class="section-heading">
│ │ │    <a href="#pythagorean-triplets" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Pythagorean Triplets</span>
│ │ │  </h2>
│ │ │  <p>Pythagorean triplets are sets of integers <code class="inline">{A,B,C}</code> such that
│ │ │  <code class="inline">A**2 + B**2 = C**2</code>.</p><p>The function <code class="inline">pyth(N)</code> generates a list of all integers <code class="inline">{A,B,C}</code> such that
│ │ │  <code class="inline">A**2 + B**2 = C**2</code> and where the sum of the sides is equal to, or less than,
│ │ │ -<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="6910006188-1">(</span><span class="n">N</span><span class="p" data-group-id="6910006188-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6910006188-2">[</span><span class="w"> </span><span class="p" data-group-id="6910006188-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="6910006188-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ -        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6910006188-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="6910006188-4">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6910006188-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="6910006188-5">)</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="6910006188-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="6910006188-6">)</span><span class="p">,</span><span class="w">
│ │ │ +<code class="inline">N</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth</span><span class="p" data-group-id="7547663150-1">(</span><span class="n">N</span><span class="p" data-group-id="7547663150-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7547663150-2">[</span><span class="w"> </span><span class="p" data-group-id="7547663150-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="7547663150-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ +        </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7547663150-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="7547663150-4">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7547663150-5">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="7547663150-5">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="7547663150-6">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="7547663150-6">)</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6910006188-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8295491668-1">(</span><span class="mi">3</span><span class="p" data-group-id="8295491668-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8295491668-2">[</span><span class="p" data-group-id="8295491668-2">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8295491668-3">(</span><span class="mi">11</span><span class="p" data-group-id="8295491668-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8295491668-4">[</span><span class="p" data-group-id="8295491668-4">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8295491668-5">(</span><span class="mi">12</span><span class="p" data-group-id="8295491668-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8295491668-6">[</span><span class="p" data-group-id="8295491668-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8295491668-7">}</span><span class="p">,</span><span class="p" data-group-id="8295491668-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8295491668-8">}</span><span class="p" data-group-id="8295491668-6">]</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="8295491668-9">(</span><span class="mi">50</span><span class="p" data-group-id="8295491668-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8295491668-10">[</span><span class="p" data-group-id="8295491668-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8295491668-11">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8295491668-12">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="8295491668-13">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="8295491668-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="8295491668-15">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="8295491668-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="8295491668-17">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="8295491668-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="8295491668-19">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="8295491668-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="8295491668-21">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8295491668-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="8295491668-22">}</span><span class="p" data-group-id="8295491668-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="1106981632-1">(</span><span class="n">N</span><span class="p" data-group-id="1106981632-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="p" data-group-id="1106981632-2">[</span><span class="p" data-group-id="1106981632-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="1106981632-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ -       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1106981632-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="1106981632-4">)</span><span class="p">,</span><span class="w">
│ │ │ -       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1106981632-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="1106981632-5">)</span><span class="p">,</span><span class="w">
│ │ │ -       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="1106981632-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="1106981632-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7547663150-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7967186351-1">(</span><span class="mi">3</span><span class="p" data-group-id="7967186351-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7967186351-2">[</span><span class="p" data-group-id="7967186351-2">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7967186351-3">(</span><span class="mi">11</span><span class="p" data-group-id="7967186351-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7967186351-4">[</span><span class="p" data-group-id="7967186351-4">]</span><span class="p">.</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7967186351-5">(</span><span class="mi">12</span><span class="p" data-group-id="7967186351-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7967186351-6">[</span><span class="p" data-group-id="7967186351-7">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7967186351-7">}</span><span class="p">,</span><span class="p" data-group-id="7967186351-8">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7967186351-8">}</span><span class="p" data-group-id="7967186351-6">]</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">pyth</span><span class="p" data-group-id="7967186351-9">(</span><span class="mi">50</span><span class="p" data-group-id="7967186351-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7967186351-10">[</span><span class="p" data-group-id="7967186351-11">{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7967186351-11">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-12">{</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7967186351-12">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-13">{</span><span class="mi">5</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="7967186351-13">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-14">{</span><span class="mi">6</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="7967186351-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-15">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="7967186351-15">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-16">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="7967186351-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-17">{</span><span class="mi">9</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="7967186351-17">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-18">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="7967186351-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-19">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">15</span><span class="p" data-group-id="7967186351-19">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-20">{</span><span class="mi">12</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="7967186351-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-21">{</span><span class="mi">15</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">17</span><span class="p" data-group-id="7967186351-21">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7967186351-22">{</span><span class="mi">16</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">20</span><span class="p" data-group-id="7967186351-22">}</span><span class="p" data-group-id="7967186351-10">]</span></code></pre><p>The following code reduces the search space and is more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pyth1</span><span class="p" data-group-id="5830607907-1">(</span><span class="n">N</span><span class="p" data-group-id="5830607907-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="p" data-group-id="5830607907-2">[</span><span class="p" data-group-id="5830607907-3">{</span><span class="n">A</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">C</span><span class="p" data-group-id="5830607907-3">}</span><span class="w"> </span><span class="p">||</span><span class="w">
│ │ │ +       </span><span class="n">A</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="5830607907-4">(</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="5830607907-4">)</span><span class="p">,</span><span class="w">
│ │ │ +       </span><span class="n">B</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="5830607907-5">(</span><span class="n">A</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="5830607907-5">)</span><span class="p">,</span><span class="w">
│ │ │ +       </span><span class="n">C</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">seq</span><span class="p" data-group-id="5830607907-6">(</span><span class="n">B</span><span class="o">+</span><span class="mi">1</span><span class="p">,</span><span class="n">N</span><span class="p" data-group-id="5830607907-6">)</span><span class="p">,</span><span class="w">
│ │ │         </span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">+</span><span class="n">C</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w">
│ │ │ -       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="1106981632-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │ +       </span><span class="n">A</span><span class="o">*</span><span class="n">A</span><span class="o">+</span><span class="n">B</span><span class="o">*</span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">C</span><span class="o">*</span><span class="n">C</span><span class="w"> </span><span class="p" data-group-id="5830607907-2">]</span><span class="p">.</span></code></pre><h2 id="simplifications-with-list-comprehensions" class="section-heading">
│ │ │    <a href="#simplifications-with-list-comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simplifications With List Comprehensions</span>
│ │ │  </h2>
│ │ │  <p>As an example, list comprehensions can be used to simplify some of the functions
│ │ │ -in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="1214132135-1">(</span><span class="n">L</span><span class="p" data-group-id="1214132135-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="1214132135-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="1214132135-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="1214132135-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1214132135-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1214132135-4">[</span><span class="n">Fun</span><span class="p" data-group-id="1214132135-5">(</span><span class="n">X</span><span class="p" data-group-id="1214132135-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1214132135-4">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">filter</span><span class="p" data-group-id="1214132135-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="1214132135-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1214132135-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="1214132135-8">(</span><span class="n">X</span><span class="p" data-group-id="1214132135-8">)</span><span class="p" data-group-id="1214132135-7">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │ +in <code class="inline">lists.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="4642226727-1">(</span><span class="n">L</span><span class="p" data-group-id="4642226727-1">)</span><span class="w">   </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="4642226727-2">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">L1</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L1</span><span class="p" data-group-id="4642226727-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="4642226727-3">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4642226727-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4642226727-4">[</span><span class="n">Fun</span><span class="p" data-group-id="4642226727-5">(</span><span class="n">X</span><span class="p" data-group-id="4642226727-5">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4642226727-4">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">filter</span><span class="p" data-group-id="4642226727-6">(</span><span class="n">Pred</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="4642226727-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4642226727-7">[</span><span class="n">X</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Pred</span><span class="p" data-group-id="4642226727-8">(</span><span class="n">X</span><span class="p" data-group-id="4642226727-8">)</span><span class="p" data-group-id="4642226727-7">]</span><span class="p">.</span></code></pre><h2 id="variable-bindings-in-list-comprehensions" class="section-heading">
│ │ │    <a href="#variable-bindings-in-list-comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Variable Bindings in List Comprehensions</span>
│ │ │  </h2>
│ │ │  <p>The scope rules for variables that occur in list comprehensions are as follows:</p><ul><li>All variables that occur in a generator pattern are assumed to be &quot;fresh&quot;
│ │ │  variables.</li><li>Any variables that are defined before the list comprehension, and that are
│ │ │  used in filters, have the values they had before the list comprehension.</li><li>Variables cannot be exported from a list comprehension.</li></ul><p>As an example of these rules, suppose you want to write the function <code class="inline">select</code>,
│ │ │  which selects certain elements from a list of tuples. Suppose you write
│ │ │  <code class="inline">select(X, L) -&gt; [Y || {X, Y} &lt;- L].</code> with the intention of extracting all
│ │ │  tuples from <code class="inline">L</code>, where the first item is <code class="inline">X</code>.</p><p>Compiling this gives the following diagnostic:</p><pre><code class="text">./FileName.erl:Line: Warning: variable 'X' shadowed in generate</code></pre><p>This diagnostic warns that the variable <code class="inline">X</code> in the pattern is not the same as
│ │ │ -the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="3116825945-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="3116825945-2">[</span><span class="p" data-group-id="3116825945-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3116825945-3">}</span><span class="p">,</span><span class="p" data-group-id="3116825945-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3116825945-4">}</span><span class="p">,</span><span class="p" data-group-id="3116825945-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3116825945-5">}</span><span class="p">,</span><span class="p" data-group-id="3116825945-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3116825945-6">}</span><span class="p" data-group-id="3116825945-2">]</span><span class="p" data-group-id="3116825945-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3116825945-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3116825945-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ -written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="7820397734-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="7820397734-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="7820397734-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="7820397734-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7820397734-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="7820397734-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ -the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="6510649259-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="6510649259-2">[</span><span class="p" data-group-id="6510649259-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6510649259-3">}</span><span class="p">,</span><span class="p" data-group-id="6510649259-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6510649259-4">}</span><span class="p">,</span><span class="p" data-group-id="6510649259-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6510649259-5">}</span><span class="p">,</span><span class="p" data-group-id="6510649259-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="6510649259-6">}</span><span class="p" data-group-id="6510649259-2">]</span><span class="p" data-group-id="6510649259-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6510649259-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="6510649259-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ -same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="1705427782-1">[</span><span class="p" data-group-id="1705427782-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="1705427782-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1705427782-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1705427782-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="1705427782-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1705427782-4">]</span><span class="p" data-group-id="1705427782-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1705427782-5">[</span><span class="p" data-group-id="1705427782-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1705427782-6">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1705427782-7">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1705427782-8">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1705427782-9">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1705427782-10">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1705427782-11">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1705427782-12">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1705427782-13">}</span><span class="p">,</span><span class="p" data-group-id="1705427782-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="1705427782-14">}</span><span class="p" data-group-id="1705427782-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehensions is
│ │ │ +the variable <code class="inline">X</code> that occurs in the function head.</p><p>Evaluating <code class="inline">select</code> gives the following result:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="1191196525-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="1191196525-2">[</span><span class="p" data-group-id="1191196525-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1191196525-3">}</span><span class="p">,</span><span class="p" data-group-id="1191196525-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1191196525-4">}</span><span class="p">,</span><span class="p" data-group-id="1191196525-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1191196525-5">}</span><span class="p">,</span><span class="p" data-group-id="1191196525-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1191196525-6">}</span><span class="p" data-group-id="1191196525-2">]</span><span class="p" data-group-id="1191196525-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1191196525-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1191196525-7">]</span></code></pre><p>This is not the wanted result. To achieve the desired effect, <code class="inline">select</code> must be
│ │ │ +written as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="5920659486-1">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="5920659486-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="p" data-group-id="5920659486-2">[</span><span class="n">Y</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="p" data-group-id="5920659486-3">{</span><span class="n">X1</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="5920659486-3">}</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">X1</span><span class="p" data-group-id="5920659486-2">]</span><span class="p">.</span></code></pre><p>The generator now contains unbound variables and the test has been moved into
│ │ │ +the filter.</p><p>This now works as expected:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">select</span><span class="p" data-group-id="1980175429-1">(</span><span class="ss">b</span><span class="p">,</span><span class="p" data-group-id="1980175429-2">[</span><span class="p" data-group-id="1980175429-3">{</span><span class="ss">a</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1980175429-3">}</span><span class="p">,</span><span class="p" data-group-id="1980175429-4">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1980175429-4">}</span><span class="p">,</span><span class="p" data-group-id="1980175429-5">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1980175429-5">}</span><span class="p">,</span><span class="p" data-group-id="1980175429-6">{</span><span class="ss">b</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1980175429-6">}</span><span class="p" data-group-id="1980175429-2">]</span><span class="p" data-group-id="1980175429-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1980175429-7">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1980175429-7">]</span></code></pre><p>Also note that a variable in a generator pattern will shadow a variable with the
│ │ │ +same name bound in a previous generator pattern. For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="3631348911-1">[</span><span class="p" data-group-id="3631348911-2">{</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p" data-group-id="3631348911-2">}</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="3631348911-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3631348911-3">]</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="o">=</span><span class="n">Y</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="p" data-group-id="3631348911-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3631348911-4">]</span><span class="p" data-group-id="3631348911-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3631348911-5">[</span><span class="p" data-group-id="3631348911-6">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3631348911-6">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-7">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3631348911-7">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-8">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3631348911-8">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-9">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3631348911-9">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-10">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3631348911-10">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-11">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3631348911-11">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-12">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3631348911-12">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-13">{</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3631348911-13">}</span><span class="p">,</span><span class="p" data-group-id="3631348911-14">{</span><span class="ss">c</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3631348911-14">}</span><span class="p" data-group-id="3631348911-5">]</span></code></pre><p>A consequence of the rules for importing variables into a list comprehensions is
│ │ │  that certain pattern matching operations must be moved into the filters and
│ │ │ -cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1788095739-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1788095739-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +cannot be written directly in the generators.</p><p>To illustrate this, do <em>not</em> write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="6884082122-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6884082122-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1788095739-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1788095739-2">]</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4994938262-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4994938262-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6884082122-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6884082122-2">]</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Instead, write as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="1949963113-1">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1949963113-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4994938262-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4994938262-2">]</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1949963113-2">[</span><span class="w"> </span><span class="n">Expression</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">PatternInvolving</span><span class="w"> </span><span class="n">Y1</span><span class="w">  </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">Expr</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Y1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1949963113-2">]</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="funs.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/listhandling.html
│ │ │ @@ -120,105 +120,105 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating a List</span>
│ │ │  </h2>
│ │ │  <p>Lists can only be built starting from the end and attaching list elements at the
│ │ │  beginning. If you use the <code class="inline">++</code> operator as follows, a new list is created that
│ │ │  is a copy of the elements in <code class="inline">List1</code>, followed by <code class="inline">List2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">List1</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="n">List2</span></code></pre><p>Looking at how <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#append/2"><code class="inline">lists:append/2</code></a> or <code class="inline">++</code> would be implemented in plain Erlang,
│ │ │ -clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="7104519138-1">(</span><span class="p" data-group-id="7104519138-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7104519138-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="7104519138-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7104519138-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="7104519138-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="7104519138-4">)</span><span class="p" data-group-id="7104519138-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">append</span><span class="p" data-group-id="7104519138-5">(</span><span class="p" data-group-id="7104519138-6">[</span><span class="p" data-group-id="7104519138-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="7104519138-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +clearly the first list is copied:</p><pre><code class="makeup erlang" translate="no"><span class="nf">append</span><span class="p" data-group-id="5754496859-1">(</span><span class="p" data-group-id="5754496859-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="5754496859-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5754496859-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5754496859-3">[</span><span class="n">H</span><span class="p">|</span><span class="nf">append</span><span class="p" data-group-id="5754496859-4">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5754496859-4">)</span><span class="p" data-group-id="5754496859-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">append</span><span class="p" data-group-id="5754496859-5">(</span><span class="p" data-group-id="5754496859-6">[</span><span class="p" data-group-id="5754496859-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Tail</span><span class="p" data-group-id="5754496859-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Tail</span><span class="p">.</span></code></pre><p>When recursing and building a list, it is important to ensure that you attach
│ │ │  the new elements to the beginning of the list. In this way, you will build <em>one</em>
│ │ │ -list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="3930541776-1">(</span><span class="n">N</span><span class="p" data-group-id="3930541776-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="3930541776-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3930541776-3">[</span><span class="p" data-group-id="3930541776-3">]</span><span class="p" data-group-id="3930541776-2">)</span><span class="p">.</span><span class="w">
│ │ │ +list, not hundreds or thousands of copies of the growing result list.</p><p>Let us first see how it is not to be done:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">bad_fib</span><span class="p" data-group-id="9572240565-1">(</span><span class="n">N</span><span class="p" data-group-id="9572240565-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="9572240565-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9572240565-3">[</span><span class="p" data-group-id="9572240565-3">]</span><span class="p" data-group-id="9572240565-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="3930541776-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="3930541776-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="9572240565-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="9572240565-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Fibs</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">bad_fib</span><span class="p" data-group-id="3930541776-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="3930541776-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">bad_fib</span><span class="p" data-group-id="3930541776-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="3930541776-7">[</span><span class="n">Current</span><span class="p" data-group-id="3930541776-7">]</span><span class="p" data-group-id="3930541776-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │ +</span><span class="nf">bad_fib</span><span class="p" data-group-id="9572240565-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="9572240565-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">bad_fib</span><span class="p" data-group-id="9572240565-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9572240565-7">[</span><span class="n">Current</span><span class="p" data-group-id="9572240565-7">]</span><span class="p" data-group-id="9572240565-6">)</span><span class="p">.</span></code></pre><p>Here more than one list is built. In each iteration step a new list is created
│ │ │  that is one element longer than the new previous list.</p><p>To avoid copying the result in each iteration, build the list in reverse order
│ │ │ -and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="9345962221-1">(</span><span class="n">N</span><span class="p" data-group-id="9345962221-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="9345962221-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9345962221-3">[</span><span class="p" data-group-id="9345962221-3">]</span><span class="p" data-group-id="9345962221-2">)</span><span class="p">.</span><span class="w">
│ │ │ +and reverse the list when you are done:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5658144013-1">(</span><span class="n">N</span><span class="p" data-group-id="5658144013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5658144013-2">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5658144013-3">[</span><span class="p" data-group-id="5658144013-3">]</span><span class="p" data-group-id="5658144013-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="9345962221-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="9345962221-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="9345962221-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="9345962221-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="9345962221-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="9345962221-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="9345962221-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9345962221-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="9345962221-8">]</span><span class="p" data-group-id="9345962221-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5658144013-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="5658144013-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="5658144013-5">(</span><span class="n">Fibs</span><span class="p" data-group-id="5658144013-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5658144013-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Fibs</span><span class="p" data-group-id="5658144013-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">tail_recursive_fib</span><span class="p" data-group-id="5658144013-7">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Next</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5658144013-8">[</span><span class="n">Current</span><span class="p">|</span><span class="n">Fibs</span><span class="p" data-group-id="5658144013-8">]</span><span class="p" data-group-id="5658144013-7">)</span><span class="p">.</span></code></pre><h2 id="list-comprehensions" class="section-heading">
│ │ │    <a href="#list-comprehensions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">List Comprehensions</span>
│ │ │  </h2>
│ │ │ -<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3428371394-1">[</span><span class="n">Expr</span><span class="p" data-group-id="3428371394-2">(</span><span class="n">E</span><span class="p" data-group-id="3428371394-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="3428371394-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0145532870-1">(</span><span class="p" data-group-id="0145532870-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0145532870-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0145532870-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0145532870-3">[</span><span class="n">Expr</span><span class="p" data-group-id="0145532870-4">(</span><span class="n">E</span><span class="p" data-group-id="0145532870-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0145532870-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0145532870-5">)</span><span class="p" data-group-id="0145532870-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0145532870-6">(</span><span class="p" data-group-id="0145532870-7">[</span><span class="p" data-group-id="0145532870-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="0145532870-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0145532870-8">[</span><span class="p" data-group-id="0145532870-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ -will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5267369712-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="5267369712-2">(</span><span class="n">E</span><span class="p" data-group-id="5267369712-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5267369712-1">]</span><span class="p">,</span><span class="w">
│ │ │ +<p>A list comprehension:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6691091010-1">[</span><span class="n">Expr</span><span class="p" data-group-id="6691091010-2">(</span><span class="n">E</span><span class="p" data-group-id="6691091010-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6691091010-1">]</span></code></pre><p>is basically translated to a local function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5751269247-1">(</span><span class="p" data-group-id="5751269247-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="5751269247-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="5751269247-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5751269247-3">[</span><span class="n">Expr</span><span class="p" data-group-id="5751269247-4">(</span><span class="n">E</span><span class="p" data-group-id="5751269247-4">)</span><span class="p">|</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5751269247-5">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="5751269247-5">)</span><span class="p" data-group-id="5751269247-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="5751269247-6">(</span><span class="p" data-group-id="5751269247-7">[</span><span class="p" data-group-id="5751269247-7">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="5751269247-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5751269247-8">[</span><span class="p" data-group-id="5751269247-8">]</span><span class="p">.</span></code></pre><p>If the result of the list comprehension will <em>obviously</em> not be used, a list
│ │ │ +will not be constructed. For example, in this code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8654676671-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="8654676671-2">(</span><span class="n">E</span><span class="p" data-group-id="8654676671-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="8654676671-1">]</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>or in this code:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="n">Var</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4419704829-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="4419704829-2">(</span><span class="n">E</span><span class="p" data-group-id="4419704829-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="4419704829-1">]</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7880967867-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="7880967867-2">(</span><span class="n">E</span><span class="p" data-group-id="7880967867-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7880967867-1">]</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">some_function</span><span class="p" data-group-id="4419704829-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4419704829-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │ +</span><span class="nf">some_function</span><span class="p" data-group-id="7880967867-3">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7880967867-3">)</span><span class="p">,</span></code></pre><p>the value is not assigned to a variable, not passed to another function, and not
│ │ │  returned. This means that there is no need to construct a list and the compiler
│ │ │ -will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0633736573-1">(</span><span class="p" data-group-id="0633736573-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0633736573-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0633736573-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Expr</span><span class="p" data-group-id="0633736573-3">(</span><span class="n">E</span><span class="p" data-group-id="0633736573-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0633736573-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0633736573-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0633736573-5">(</span><span class="p" data-group-id="0633736573-6">[</span><span class="p" data-group-id="0633736573-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="0633736573-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0633736573-7">[</span><span class="p" data-group-id="0633736573-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ -not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7704070312-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="7704070312-2">(</span><span class="n">E</span><span class="p" data-group-id="7704070312-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7704070312-1">]</span><span class="p">,</span><span class="w">
│ │ │ +will simplify the code for the list comprehension to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0834649065-1">(</span><span class="p" data-group-id="0834649065-2">[</span><span class="n">E</span><span class="p">|</span><span class="n">Tail</span><span class="p" data-group-id="0834649065-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0834649065-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Expr</span><span class="p" data-group-id="0834649065-3">(</span><span class="n">E</span><span class="p" data-group-id="0834649065-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0834649065-4">(</span><span class="n">Tail</span><span class="p">,</span><span class="w"> </span><span class="n">Expr</span><span class="p" data-group-id="0834649065-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">&#39;lc^0&#39;</span><span class="p" data-group-id="0834649065-5">(</span><span class="p" data-group-id="0834649065-6">[</span><span class="p" data-group-id="0834649065-6">]</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Expr</span><span class="p" data-group-id="0834649065-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0834649065-7">[</span><span class="p" data-group-id="0834649065-7">]</span><span class="p">.</span></code></pre><p>The compiler also understands that assigning to <code class="inline">_</code> means that the value will
│ │ │ +not be used. Therefore, the code in the following example will also be optimized:</p><pre><code class="makeup erlang" translate="no"><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9729178629-1">[</span><span class="nc">io</span><span class="p">:</span><span class="nf">put_chars</span><span class="p" data-group-id="9729178629-2">(</span><span class="n">E</span><span class="p" data-group-id="9729178629-2">)</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">E</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9729178629-1">]</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="deep-and-flat-lists" class="section-heading">
│ │ │    <a href="#deep-and-flat-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deep and Flat Lists</span>
│ │ │  </h2>
│ │ │  <p><a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a> builds an entirely new list. It is therefore expensive, and
│ │ │  even <em>more</em> expensive than the <code class="inline">++</code> operator (which copies its left argument,
│ │ │  but not its right argument).</p><p>In the following situations it is unnecessary to call <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#flatten/1"><code class="inline">lists:flatten/1</code></a>:</p><ul><li>When sending data to a port. Ports understand deep lists so there is no reason
│ │ │  to flatten the list before sending it to the port.</li><li>When calling BIFs that accept deep lists, such as
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#list_to_binary/1"><code class="inline">list_to_binary/1</code></a> or
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#iolist_to_binary/1"><code class="inline">iolist_to_binary/1</code></a>.</li><li>When you know that your list is only one level deep. Use <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#append/1"><code class="inline">lists:append/1</code></a>
│ │ │ -instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="0845165237-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="0845165237-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="4907203905-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="4907203905-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="4907203905-2">)</span><span class="p" data-group-id="4907203905-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2759519093-1">[</span><span class="mi">0</span><span class="p" data-group-id="2759519093-1">]</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="2759519093-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="2759519093-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2106739125-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2106739125-1">]</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">port_command</span><span class="p" data-group-id="2106739125-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="2106739125-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="7606291181-1">(</span><span class="p" data-group-id="7606291181-2">[</span><span class="p" data-group-id="7606291181-3">[</span><span class="mi">1</span><span class="p" data-group-id="7606291181-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7606291181-4">[</span><span class="mi">2</span><span class="p" data-group-id="7606291181-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7606291181-5">[</span><span class="mi">3</span><span class="p" data-group-id="7606291181-5">]</span><span class="p" data-group-id="7606291181-2">]</span><span class="p" data-group-id="7606291181-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7606291181-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7606291181-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="6513131459-1">(</span><span class="p" data-group-id="6513131459-2">[</span><span class="p" data-group-id="6513131459-3">[</span><span class="mi">1</span><span class="p" data-group-id="6513131459-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6513131459-4">[</span><span class="mi">2</span><span class="p" data-group-id="6513131459-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6513131459-5">[</span><span class="mi">3</span><span class="p" data-group-id="6513131459-5">]</span><span class="p" data-group-id="6513131459-2">]</span><span class="p" data-group-id="6513131459-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6513131459-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6513131459-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │ +instead.</li></ul><p><em>Examples:</em></p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="0424609637-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">DeepList</span><span class="p" data-group-id="0424609637-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">port_command</span><span class="p" data-group-id="5877030779-1">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="5877030779-2">(</span><span class="n">DeepList</span><span class="p" data-group-id="5877030779-2">)</span><span class="p" data-group-id="5877030779-1">)</span></code></pre><p>A common way to send a zero-terminated string to a port is the following:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9191332604-1">[</span><span class="mi">0</span><span class="p" data-group-id="9191332604-1">]</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="9191332604-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="9191332604-2">)</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TerminatedStr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2123869758-1">[</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="2123869758-1">]</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">port_command</span><span class="p" data-group-id="2123869758-2">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">TerminatedStr</span><span class="p" data-group-id="2123869758-2">)</span></code></pre><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">append</span><span class="p" data-group-id="0097169795-1">(</span><span class="p" data-group-id="0097169795-2">[</span><span class="p" data-group-id="0097169795-3">[</span><span class="mi">1</span><span class="p" data-group-id="0097169795-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0097169795-4">[</span><span class="mi">2</span><span class="p" data-group-id="0097169795-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0097169795-5">[</span><span class="mi">3</span><span class="p" data-group-id="0097169795-5">]</span><span class="p" data-group-id="0097169795-2">]</span><span class="p" data-group-id="0097169795-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0097169795-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0097169795-6">]</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">flatten</span><span class="p" data-group-id="8149374161-1">(</span><span class="p" data-group-id="8149374161-2">[</span><span class="p" data-group-id="8149374161-3">[</span><span class="mi">1</span><span class="p" data-group-id="8149374161-3">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8149374161-4">[</span><span class="mi">2</span><span class="p" data-group-id="8149374161-4">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8149374161-5">[</span><span class="mi">3</span><span class="p" data-group-id="8149374161-5">]</span><span class="p" data-group-id="8149374161-2">]</span><span class="p" data-group-id="8149374161-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8149374161-6">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8149374161-6">]</span></code></pre><h2 id="recursive-list-functions" class="section-heading">
│ │ │    <a href="#recursive-list-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Recursive List Functions</span>
│ │ │  </h2>
│ │ │  <p>There are two basic ways to write a function that traverses a list and
│ │ │  produces a new list.</p><p>The first way is writing a <em>body-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="9464698210-1">(</span><span class="p" data-group-id="9464698210-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="9464698210-2">]</span><span class="p" data-group-id="9464698210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9464698210-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="9464698210-4">(</span><span class="n">T</span><span class="p" data-group-id="9464698210-4">)</span><span class="p" data-group-id="9464698210-3">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">add_42_body</span><span class="p" data-group-id="9464698210-5">(</span><span class="p" data-group-id="9464698210-6">[</span><span class="p" data-group-id="9464698210-6">]</span><span class="p" data-group-id="9464698210-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9464698210-7">[</span><span class="p" data-group-id="9464698210-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="2895452870-1">(</span><span class="n">List</span><span class="p" data-group-id="2895452870-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="2895452870-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2895452870-3">[</span><span class="p" data-group-id="2895452870-3">]</span><span class="p" data-group-id="2895452870-2">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="2895452870-4">(</span><span class="p" data-group-id="2895452870-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2895452870-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2895452870-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="2895452870-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2895452870-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2895452870-7">]</span><span class="p" data-group-id="2895452870-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">add_42_tail</span><span class="p" data-group-id="2895452870-8">(</span><span class="p" data-group-id="2895452870-9">[</span><span class="p" data-group-id="2895452870-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2895452870-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2895452870-10">(</span><span class="n">Acc</span><span class="p" data-group-id="2895452870-10">)</span><span class="p">.</span></code></pre><p>In early version of Erlang the tail-recursive function would typically
│ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="7293102649-1">(</span><span class="p" data-group-id="7293102649-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="7293102649-2">]</span><span class="p" data-group-id="7293102649-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7293102649-3">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">add_42_body</span><span class="p" data-group-id="7293102649-4">(</span><span class="n">T</span><span class="p" data-group-id="7293102649-4">)</span><span class="p" data-group-id="7293102649-3">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">add_42_body</span><span class="p" data-group-id="7293102649-5">(</span><span class="p" data-group-id="7293102649-6">[</span><span class="p" data-group-id="7293102649-6">]</span><span class="p" data-group-id="7293102649-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7293102649-7">[</span><span class="p" data-group-id="7293102649-7">]</span><span class="p">.</span></code></pre><p>The second way is writing a <em>tail-recursive</em> function:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% Add 42 to each integer in the list.</span><span class="w">
│ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="2716098394-1">(</span><span class="n">List</span><span class="p" data-group-id="2716098394-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="2716098394-2">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2716098394-3">[</span><span class="p" data-group-id="2716098394-3">]</span><span class="p" data-group-id="2716098394-2">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="2716098394-4">(</span><span class="p" data-group-id="2716098394-5">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="2716098394-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2716098394-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">add_42_tail</span><span class="p" data-group-id="2716098394-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2716098394-7">[</span><span class="n">H</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2716098394-7">]</span><span class="p" data-group-id="2716098394-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">add_42_tail</span><span class="p" data-group-id="2716098394-8">(</span><span class="p" data-group-id="2716098394-9">[</span><span class="p" data-group-id="2716098394-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2716098394-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2716098394-10">(</span><span class="n">Acc</span><span class="p" data-group-id="2716098394-10">)</span><span class="p">.</span></code></pre><p>In early version of Erlang the tail-recursive function would typically
│ │ │  be more efficient. In modern versions of Erlang, there is usually not
│ │ │  much difference in performance between a body-recursive list function and
│ │ │  tail-recursive function that reverses the list at the end. Therefore,
│ │ │  concentrate on writing beautiful code and forget about the performance
│ │ │  of your list functions. In the time-critical parts of your code,
│ │ │  <em>measure</em> before rewriting your code.</p><p>For a thorough discussion about tail and body recursion, see
│ │ │  <a href="http://ferd.ca/erlang-s-tail-recursion-is-not-a-silver-bullet.html">Erlang's Tail Recursion is Not a Silver Bullet</a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>This section is about list functions that <em>construct</em> lists. A tail-recursive
│ │ │  function that does not construct a list runs in constant space, while the
│ │ │  corresponding body-recursive function uses stack space proportional to the
│ │ │  length of the list.</p></section><p>For example, a function that sums a list of integers, is <em>not</em> to be written as
│ │ │ -follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="0155135496-1">(</span><span class="p" data-group-id="0155135496-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0155135496-2">]</span><span class="p" data-group-id="0155135496-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="0155135496-3">(</span><span class="n">T</span><span class="p" data-group-id="0155135496-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">recursive_sum</span><span class="p" data-group-id="0155135496-4">(</span><span class="p" data-group-id="0155135496-5">[</span><span class="p" data-group-id="0155135496-5">]</span><span class="p" data-group-id="0155135496-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="6591144947-1">(</span><span class="n">L</span><span class="p" data-group-id="6591144947-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="6591144947-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6591144947-2">)</span><span class="p">.</span><span class="w">
│ │ │ +follows:</p><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">recursive_sum</span><span class="p" data-group-id="0184866995-1">(</span><span class="p" data-group-id="0184866995-2">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="0184866995-2">]</span><span class="p" data-group-id="0184866995-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">H</span><span class="o">+</span><span class="nf">recursive_sum</span><span class="p" data-group-id="0184866995-3">(</span><span class="n">T</span><span class="p" data-group-id="0184866995-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">recursive_sum</span><span class="p" data-group-id="0184866995-4">(</span><span class="p" data-group-id="0184866995-5">[</span><span class="p" data-group-id="0184866995-5">]</span><span class="p" data-group-id="0184866995-4">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span></code></pre><p>Instead:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nf">sum</span><span class="p" data-group-id="8961089128-1">(</span><span class="n">L</span><span class="p" data-group-id="8961089128-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="8961089128-2">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8961089128-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="6591144947-3">(</span><span class="p" data-group-id="6591144947-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="6591144947-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="6591144947-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="6591144947-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="6591144947-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">sum</span><span class="p" data-group-id="6591144947-6">(</span><span class="p" data-group-id="6591144947-7">[</span><span class="p" data-group-id="6591144947-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="6591144947-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="8961089128-3">(</span><span class="p" data-group-id="8961089128-4">[</span><span class="n">H</span><span class="p">|</span><span class="n">T</span><span class="p" data-group-id="8961089128-4">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="8961089128-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">sum</span><span class="p" data-group-id="8961089128-5">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">H</span><span class="p" data-group-id="8961089128-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">sum</span><span class="p" data-group-id="8961089128-6">(</span><span class="p" data-group-id="8961089128-7">[</span><span class="p" data-group-id="8961089128-7">]</span><span class="p">,</span><span class="w"> </span><span class="n">Sum</span><span class="p" data-group-id="8961089128-6">)</span><span class="w">    </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Sum</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="maps.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/macros.html
│ │ │ @@ -117,56 +117,56 @@
│ │ │  
│ │ │  <h2 id="file-inclusion" class="section-heading">
│ │ │    <a href="#file-inclusion" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">File Inclusion</span>
│ │ │  </h2>
│ │ │ -<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5326191248-1">(</span><span class="n">File</span><span class="p" data-group-id="5326191248-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="5326191248-2">(</span><span class="n">File</span><span class="p" data-group-id="5326191248-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │ +<p>A file can be included as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6817589704-1">(</span><span class="n">File</span><span class="p" data-group-id="6817589704-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="6817589704-2">(</span><span class="n">File</span><span class="p" data-group-id="6817589704-2">)</span><span class="p">.</span></code></pre><p><code class="inline">File</code>, a string, is to point out a file. The contents of this file are included
│ │ │  as is, at the position of the directive.</p><p>Include files are typically used for record and macro definitions that are
│ │ │  shared by several modules. It is recommended to use the file name extension
│ │ │  <code class="inline">.hrl</code> for include files.</p><p><code class="inline">File</code> can start with a path component <code class="inline">$VAR</code>, for some string <code class="inline">VAR</code>. If that is
│ │ │  the case, the value of the environment variable <code class="inline">VAR</code> as returned by
│ │ │  <code class="inline">os:getenv(VAR)</code> is substituted for <code class="inline">$VAR</code>. If <code class="inline">os:getenv(VAR)</code> returns <code class="inline">false</code>,
│ │ │  <code class="inline">$VAR</code> is left as is.</p><p>If the filename <code class="inline">File</code> is absolute (possibly after variable substitution), the
│ │ │  include file with that name is included. Otherwise, the specified file is
│ │ │  searched for in the following directories, and in this order:</p><ol><li>The current working directory</li><li>The directory where the module is being compiled</li><li>The directories given by the <code class="inline">include</code> option</li></ol><p>For details, see <a href="../../erts-15.2.7.2/doc/html/erlc_cmd.html">erlc</a> in ERTS and
│ │ │ -<a href="../../lib/compiler-8.6.1.2/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7999250264-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="7999250264-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7999250264-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="7999250264-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7999250264-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="7999250264-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7999250264-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="7999250264-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │ +<a href="../../lib/compiler-8.6.1.2/doc/html/compile.html"><code class="inline">compile</code></a> in Compiler.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9948330433-1">(</span><span class="s">&quot;my_records.hrl&quot;</span><span class="p" data-group-id="9948330433-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9948330433-2">(</span><span class="s">&quot;incdir/my_records.hrl&quot;</span><span class="p" data-group-id="9948330433-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9948330433-3">(</span><span class="s">&quot;/home/user/proj/my_records.hrl&quot;</span><span class="p" data-group-id="9948330433-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9948330433-4">(</span><span class="s">&quot;$PROJ_ROOT/my_records.hrl&quot;</span><span class="p" data-group-id="9948330433-4">)</span><span class="p">.</span></code></pre><p><code class="inline">include_lib</code> is similar to <code class="inline">include</code>, but is not to point out an absolute file.
│ │ │  Instead, the first path component (possibly after variable substitution) is
│ │ │ -assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="0939367193-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="0939367193-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │ +assumed to be the name of an application.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="4109422194-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="4109422194-1">)</span><span class="p">.</span></code></pre><p>The code server uses <code class="inline">code:lib_dir(kernel)</code> to find the directory of the current
│ │ │  (latest) version of Kernel, and then the subdirectory <code class="inline">include</code> is searched for
│ │ │  the file <code class="inline">file.hrl</code>.</p><h2 id="defining-and-using-macros" class="section-heading">
│ │ │    <a href="#defining-and-using-macros" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Defining and Using Macros</span>
│ │ │  </h2>
│ │ │ -<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4835913475-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4835913475-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4835913475-2">(</span><span class="n">Func</span><span class="p" data-group-id="4835913475-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="4835913475-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4835913475-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │ +<p>A macro is defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4235723108-1">(</span><span class="n">Const</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4235723108-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4235723108-2">(</span><span class="n">Func</span><span class="p" data-group-id="4235723108-3">(</span><span class="n">Var1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">VarN</span><span class="p" data-group-id="4235723108-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="4235723108-2">)</span><span class="p">.</span></code></pre><p>A macro definition can be placed anywhere among the attributes and function
│ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │  macro.</p><p>If a macro is used in several modules, it is recommended that the macro
│ │ │  definition is placed in an include file.</p><p>A macro is used as follows:</p><pre><code class="text">?Const
│ │ │  ?Func(Arg1,...,ArgN)</code></pre><p>Macros are expanded during compilation. A simple macro <code class="inline">?Const</code> is replaced with
│ │ │ -<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3395942315-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="3395942315-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">Replacement</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4588038320-1">(</span><span class="n">TIMEOUT</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="4588038320-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">call</span><span class="p" data-group-id="3395942315-2">(</span><span class="n">Request</span><span class="p" data-group-id="3395942315-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="3395942315-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="3395942315-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="2778470402-1">(</span><span class="n">Request</span><span class="p" data-group-id="2778470402-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2778470402-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="2778470402-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │ +</span><span class="nf">call</span><span class="p" data-group-id="4588038320-2">(</span><span class="n">Request</span><span class="p" data-group-id="4588038320-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4588038320-3">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">TIMEOUT</span><span class="p" data-group-id="4588038320-3">)</span><span class="p">.</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">call</span><span class="p" data-group-id="5606374654-1">(</span><span class="n">Request</span><span class="p" data-group-id="5606374654-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="5606374654-2">(</span><span class="ss">refserver</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p" data-group-id="5606374654-2">)</span><span class="p">.</span></code></pre><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> is replaced with <code class="inline">Replacement</code>, where all
│ │ │  occurrences of a variable <code class="inline">Var</code> from the macro definition are replaced with the
│ │ │ -corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9750437298-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="9750437298-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9750437298-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9750437298-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9750437298-3">}</span><span class="p" data-group-id="9750437298-1">)</span><span class="p">.</span><span class="w">
│ │ │ +corresponding argument <code class="inline">Arg</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8642413727-1">(</span><span class="n">MACRO1</span><span class="p" data-group-id="8642413727-2">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8642413727-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8642413727-3">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8642413727-3">}</span><span class="p" data-group-id="8642413727-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="9750437298-4">(</span><span class="n">X</span><span class="p" data-group-id="9750437298-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="9750437298-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="9750437298-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="9750437298-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="9750437298-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="3848509306-1">(</span><span class="n">X</span><span class="p" data-group-id="3848509306-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3848509306-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3848509306-2">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3848509306-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="3848509306-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="8642413727-4">(</span><span class="n">X</span><span class="p" data-group-id="8642413727-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="8642413727-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p" data-group-id="8642413727-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">MACRO1</span><span class="p" data-group-id="8642413727-6">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="mi">123</span><span class="p" data-group-id="8642413727-6">)</span></code></pre><p>This is expanded to:</p><pre><code class="makeup erlang" translate="no"><span class="nf">bar</span><span class="p" data-group-id="9616637210-1">(</span><span class="n">X</span><span class="p" data-group-id="9616637210-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9616637210-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9616637210-2">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9616637210-3">{</span><span class="ss">a</span><span class="p">,</span><span class="n">X</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="mi">123</span><span class="p" data-group-id="9616637210-3">}</span><span class="p">.</span></code></pre><p>It is good programming practice, but not mandatory, to ensure that a macro
│ │ │  definition is a valid Erlang syntactic form.</p><p>To view the result of macro expansion, a module can be compiled with the <code class="inline">'P'</code>
│ │ │  option. <code class="inline">compile:file(File, ['P'])</code>. This produces a listing of the parsed code
│ │ │  after preprocessing and parse transforms, in the file <code class="inline">File.P</code>.</p><h2 id="predefined-macros" class="section-heading">
│ │ │    <a href="#predefined-macros" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Predefined Macros</span>
│ │ │ @@ -185,29 +185,29 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Macros Overloading</span>
│ │ │  </h2>
│ │ │  <p>It is possible to overload macros, except for predefined macros. An overloaded
│ │ │  macro has more than one definition, each with a different number of arguments.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Support for overloading of macros was added in Erlang 5.7.5/OTP R13B04.</p></section><p>A macro <code class="inline">?Func(Arg1,...,ArgN)</code> with a (possibly empty) list of arguments results
│ │ │  in an error message if there is at least one definition of <code class="inline">Func</code> with
│ │ │ -arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7013392833-1">(</span><span class="n">F0</span><span class="p" data-group-id="7013392833-2">(</span><span class="p" data-group-id="7013392833-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="7013392833-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7013392833-3">(</span><span class="n">F1</span><span class="p" data-group-id="7013392833-4">(</span><span class="n">A</span><span class="p" data-group-id="7013392833-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="7013392833-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7013392833-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="7013392833-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="8214737312-1">(</span><span class="p" data-group-id="8214737312-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +arguments, but none with N arguments.</p><p>Assuming these definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0955216882-1">(</span><span class="n">F0</span><span class="p" data-group-id="0955216882-2">(</span><span class="p" data-group-id="0955216882-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="0955216882-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0955216882-3">(</span><span class="n">F1</span><span class="p" data-group-id="0955216882-4">(</span><span class="n">A</span><span class="p" data-group-id="0955216882-4">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="0955216882-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0955216882-5">(</span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="nc">m</span><span class="p">:</span><span class="ss">f</span><span class="p" data-group-id="0955216882-5">)</span><span class="p">.</span></code></pre><p>the following does not work:</p><pre><code class="makeup erlang" translate="no"><span class="nf">f0</span><span class="p" data-group-id="6163906086-1">(</span><span class="p" data-group-id="6163906086-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="o">?</span><span class="n">F0</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, an empty list of arguments expected.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">f1</span><span class="p" data-group-id="8214737312-2">(</span><span class="n">A</span><span class="p" data-group-id="8214737312-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="8214737312-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="8214737312-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ -    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="7604570848-1">(</span><span class="p" data-group-id="7604570848-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="7604570848-2">(</span><span class="p" data-group-id="7604570848-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │ +</span><span class="nf">f1</span><span class="p" data-group-id="6163906086-2">(</span><span class="n">A</span><span class="p" data-group-id="6163906086-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">F1</span><span class="p" data-group-id="6163906086-3">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="6163906086-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% No, exactly one argument expected.</span></code></pre><p>On the other hand,</p><pre><code class="text">f() -&gt;
│ │ │ +    ?C().</code></pre><p>is expanded to</p><pre><code class="makeup erlang" translate="no"><span class="nf">f</span><span class="p" data-group-id="4146279694-1">(</span><span class="p" data-group-id="4146279694-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">m</span><span class="p">:</span><span class="nf">f</span><span class="p" data-group-id="4146279694-2">(</span><span class="p" data-group-id="4146279694-2">)</span><span class="p">.</span></code></pre><h2 id="removing-a-macro-definition" class="section-heading">
│ │ │    <a href="#removing-a-macro-definition" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Removing a macro definition</span>
│ │ │  </h2>
│ │ │ -<p>A definition of macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="8968129171-1">(</span><span class="n">Macro</span><span class="p" data-group-id="8968129171-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │ +<p>A definition of macro can be removed as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">undef</span><span class="p" data-group-id="8297319527-1">(</span><span class="n">Macro</span><span class="p" data-group-id="8297319527-1">)</span><span class="p">.</span></code></pre><h2 id="conditional-compilation" class="section-heading">
│ │ │    <a href="#conditional-compilation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Conditional Compilation</span>
│ │ │  </h2>
│ │ │  <p>The following macro directives support conditional compilation:</p><ul><li><p><strong><code class="inline">-ifdef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is
│ │ │  defined.</p></li><li><p><strong><code class="inline">-ifndef(Macro).</code></strong> - Evaluate the following lines only if <code class="inline">Macro</code> is not
│ │ │ @@ -219,43 +219,43 @@
│ │ │  true, and the <code class="inline">Condition</code> evaluates to true, the lines following the <code class="inline">elif</code>
│ │ │  are evaluated instead.</p></li><li><p><strong><code class="inline">-endif.</code></strong> - Specifies the end of a series of control flow directives.</p></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Macro directives cannot be used inside functions.</p></section><p>Syntactically, the <code class="inline">Condition</code> in <code class="inline">if</code> and <code class="inline">elif</code> must be a
│ │ │  <a href="expressions.html#guard-expressions">guard expression</a>. Other constructs (such as
│ │ │  a <code class="inline">case</code> expression) result in a compilation error.</p><p>As opposed to the standard guard expressions, an expression in an <code class="inline">if</code> and
│ │ │  <code class="inline">elif</code> also supports calling the psuedo-function <code class="inline">defined(Name)</code>, which tests
│ │ │  whether the <code class="inline">Name</code> argument is the name of a previously defined macro.
│ │ │  <code class="inline">defined(Name)</code> evaluates to <code class="inline">true</code> if the macro is defined and <code class="inline">false</code>
│ │ │ -otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4320573169-1">(</span><span class="ss">m</span><span class="p" data-group-id="4320573169-1">)</span><span class="p">.</span><span class="w">
│ │ │ +otherwise. An attempt to call other functions results in a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1180437302-1">(</span><span class="ss">m</span><span class="p" data-group-id="1180437302-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="4320573169-2">(</span><span class="ss">debug</span><span class="p" data-group-id="4320573169-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4320573169-3">(</span><span class="n">LOG</span><span class="p" data-group-id="4320573169-4">(</span><span class="n">X</span><span class="p" data-group-id="4320573169-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4320573169-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4320573169-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="4320573169-6">]</span><span class="p" data-group-id="4320573169-5">)</span><span class="p" data-group-id="4320573169-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="1180437302-2">(</span><span class="ss">debug</span><span class="p" data-group-id="1180437302-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1180437302-3">(</span><span class="n">LOG</span><span class="p" data-group-id="1180437302-4">(</span><span class="n">X</span><span class="p" data-group-id="1180437302-4">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1180437302-5">(</span><span class="s">&quot;{</span><span class="si">~p</span><span class="s">,</span><span class="si">~p</span><span class="s">}: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1180437302-6">[</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="o">?</span><span class="n">LINE</span><span class="p">,</span><span class="n">X</span><span class="p" data-group-id="1180437302-6">]</span><span class="p" data-group-id="1180437302-5">)</span><span class="p" data-group-id="1180437302-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4320573169-7">(</span><span class="n">LOG</span><span class="p" data-group-id="4320573169-8">(</span><span class="n">X</span><span class="p" data-group-id="4320573169-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4320573169-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1180437302-7">(</span><span class="n">LOG</span><span class="p" data-group-id="1180437302-8">(</span><span class="n">X</span><span class="p" data-group-id="1180437302-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1180437302-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When trace output is desired, <code class="inline">debug</code> is to be defined when the module <code class="inline">m</code> is
│ │ │  compiled:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erlc -Ddebug m.erl</span><span class="w">
│ │ │  
│ │ │  </span><span class="ow">or</span><span class="w">
│ │ │  
│ │ │ -</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="2306385199-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2306385199-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="2306385199-2">}</span><span class="p" data-group-id="2306385199-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2306385199-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="2306385199-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provide the user
│ │ │ -with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3778255681-1">(</span><span class="ss">m</span><span class="p" data-group-id="3778255681-1">)</span><span class="w">
│ │ │ +</span><span class="mi">1</span><span class="o">&gt;</span><span class="w"> </span><span class="nf">c</span><span class="p" data-group-id="0082816474-1">(</span><span class="ss">m</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0082816474-2">{</span><span class="ss">d</span><span class="p">,</span><span class="w"> </span><span class="ss">debug</span><span class="p" data-group-id="0082816474-2">}</span><span class="p" data-group-id="0082816474-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0082816474-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">m</span><span class="p" data-group-id="0082816474-3">}</span></code></pre><p><code class="inline">?LOG(Arg)</code> is then expanded to a call to <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> and provide the user
│ │ │ +with some simple trace output.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0735210373-1">(</span><span class="ss">m</span><span class="p" data-group-id="0735210373-1">)</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="3778255681-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="3778255681-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="0735210373-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">25</span><span class="p" data-group-id="0735210373-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Code that will work in OTP 25 or higher</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="3778255681-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="3778255681-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">elif</span><span class="p" data-group-id="0735210373-3">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="p" data-group-id="0735210373-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Code that will work in OTP 26 or higher</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Code that will work in OTP 24 or lower.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro to conditionally select code depending on
│ │ │ -release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0720102700-1">(</span><span class="ss">m</span><span class="p" data-group-id="0720102700-1">)</span><span class="w">
│ │ │ +release.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3285822768-1">(</span><span class="ss">m</span><span class="p" data-group-id="3285822768-1">)</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="0720102700-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="0720102700-3">(</span><span class="ss">debug</span><span class="p" data-group-id="0720102700-3">)</span><span class="p" data-group-id="0720102700-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">if</span><span class="p" data-group-id="3285822768-2">(</span><span class="o">?</span><span class="n">OTP_RELEASE</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">26</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">defined</span><span class="p" data-group-id="3285822768-3">(</span><span class="ss">debug</span><span class="p" data-group-id="3285822768-3">)</span><span class="p" data-group-id="3285822768-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Debugging code that requires OTP 26 or later.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Non-debug code that works in any release.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>This code uses the <code class="inline">OTP_RELEASE</code> macro and <code class="inline">defined(debug)</code> to compile debug
│ │ │  code only for OTP 26 or later.</p><h2 id="the-feature-directive" class="section-heading">
│ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │ @@ -270,44 +270,44 @@
│ │ │  used. In practice this means it should appear before any <code class="inline">-export(..)</code> or record
│ │ │  definitions.</p><h2 id="error-and-warning-directives" class="section-heading">
│ │ │    <a href="#error-and-warning-directives" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">-error() and -warning() directives</span>
│ │ │  </h2>
│ │ │ -<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0477344382-1">(</span><span class="ss">t</span><span class="p" data-group-id="0477344382-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0477344382-2">(</span><span class="p" data-group-id="0477344382-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0477344382-3">]</span><span class="p" data-group-id="0477344382-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>The directive <code class="inline">-error(Term)</code> causes a compilation error.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0260893952-1">(</span><span class="ss">t</span><span class="p" data-group-id="0260893952-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0260893952-2">(</span><span class="p" data-group-id="0260893952-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0260893952-3">]</span><span class="p" data-group-id="0260893952-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="0477344382-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="0477344382-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="0477344382-5">(</span><span class="p" data-group-id="0477344382-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">ifdef</span><span class="p" data-group-id="0260893952-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="0260893952-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="0260893952-5">(</span><span class="p" data-group-id="0260893952-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">else</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="0477344382-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="0477344382-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="0477344382-7">(</span><span class="p" data-group-id="0477344382-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">error</span><span class="p" data-group-id="0260893952-6">(</span><span class="s">&quot;Macro VERSION must be defined.&quot;</span><span class="p" data-group-id="0260893952-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="0260893952-7">(</span><span class="p" data-group-id="0260893952-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span></code></pre><p>The error message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ -t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3935009959-1">(</span><span class="ss">t</span><span class="p" data-group-id="3935009959-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3935009959-2">(</span><span class="p" data-group-id="3935009959-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3935009959-3">]</span><span class="p" data-group-id="3935009959-2">)</span><span class="p">.</span><span class="w">
│ │ │ +t.erl:7: -error(&quot;Macro VERSION must be defined.&quot;).</code></pre><p>The directive <code class="inline">-warning(Term)</code> causes a compilation warning.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7684168061-1">(</span><span class="ss">t</span><span class="p" data-group-id="7684168061-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7684168061-2">(</span><span class="p" data-group-id="7684168061-3">[</span><span class="ss">version</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7684168061-3">]</span><span class="p" data-group-id="7684168061-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="3935009959-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="3935009959-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="3935009959-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="3935009959-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3935009959-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="3935009959-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">ifndef</span><span class="p" data-group-id="7684168061-4">(</span><span class="n">VERSION</span><span class="p" data-group-id="7684168061-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">warning</span><span class="p" data-group-id="7684168061-5">(</span><span class="s">&quot;Macro VERSION not defined -- using default version.&quot;</span><span class="p" data-group-id="7684168061-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7684168061-6">(</span><span class="n">VERSION</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;0&quot;</span><span class="p" data-group-id="7684168061-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">endif</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">version</span><span class="p" data-group-id="3935009959-7">(</span><span class="p" data-group-id="3935009959-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │ +</span><span class="nf">version</span><span class="p" data-group-id="7684168061-7">(</span><span class="p" data-group-id="7684168061-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VERSION</span><span class="p">.</span></code></pre><p>The warning message will look like this:</p><pre><code class="text">% erlc t.erl
│ │ │  t.erl:5: Warning: -warning(&quot;Macro VERSION not defined -- using default version.&quot;).</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The <code class="inline">-error()</code> and <code class="inline">-warning()</code> directives were added in Erlang/OTP 19.</p></section><h2 id="stringifying-macro-arguments" class="section-heading">
│ │ │    <a href="#stringifying-macro-arguments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stringifying Macro Arguments</span>
│ │ │  </h2>
│ │ │  <p>The construction <code class="inline">??Arg</code>, where <code class="inline">Arg</code> is a macro argument, is expanded to a
│ │ │  string containing the tokens of the argument. This is similar to the <code class="inline">#arg</code>
│ │ │ -stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4326929851-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="4326929851-2">(</span><span class="n">Call</span><span class="p" data-group-id="4326929851-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4326929851-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4326929851-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="4326929851-4">]</span><span class="p" data-group-id="4326929851-3">)</span><span class="p" data-group-id="4326929851-1">)</span><span class="p">.</span><span class="w">
│ │ │ +stringifying construction in C.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8795031523-1">(</span><span class="n">TESTCALL</span><span class="p" data-group-id="8795031523-2">(</span><span class="n">Call</span><span class="p" data-group-id="8795031523-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8795031523-3">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8795031523-4">[</span><span class="o">?</span><span class="o">?</span><span class="n">Call</span><span class="p">,</span><span class="w"> </span><span class="n">Call</span><span class="p" data-group-id="8795031523-4">]</span><span class="p" data-group-id="8795031523-3">)</span><span class="p" data-group-id="8795031523-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="4326929851-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="4326929851-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4326929851-6">)</span><span class="p" data-group-id="4326929851-5">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="4326929851-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="4326929851-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4326929851-8">)</span><span class="p" data-group-id="4326929851-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3332768070-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="3332768070-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="3332768070-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3332768070-3">)</span><span class="p" data-group-id="3332768070-2">]</span><span class="p" data-group-id="3332768070-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3332768070-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="3332768070-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="3332768070-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3332768070-6">)</span><span class="p" data-group-id="3332768070-5">]</span><span class="p" data-group-id="3332768070-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="8795031523-5">(</span><span class="nf">myfunction</span><span class="p" data-group-id="8795031523-6">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8795031523-6">)</span><span class="p" data-group-id="8795031523-5">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="o">?</span><span class="n">TESTCALL</span><span class="p" data-group-id="8795031523-7">(</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="8795031523-8">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8795031523-8">)</span><span class="p" data-group-id="8795031523-7">)</span><span class="p">.</span></code></pre><p>results in</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4474204117-1">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4474204117-2">[</span><span class="s">&quot;myfunction ( 1 , 2 )&quot;</span><span class="p">,</span><span class="nf">myfunction</span><span class="p" data-group-id="4474204117-3">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4474204117-3">)</span><span class="p" data-group-id="4474204117-2">]</span><span class="p" data-group-id="4474204117-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4474204117-4">(</span><span class="s">&quot;Call </span><span class="si">~s</span><span class="s">: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="4474204117-5">[</span><span class="s">&quot;you : function ( 2 , 1 )&quot;</span><span class="p">,</span><span class="nc">you</span><span class="p">:</span><span class="nf">function</span><span class="p" data-group-id="4474204117-6">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4474204117-6">)</span><span class="p" data-group-id="4474204117-5">]</span><span class="p" data-group-id="4474204117-4">)</span><span class="p">.</span></code></pre><p>That is, a trace output, with both the function called and the resulting value.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="expressions.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/maps.html
│ │ │ @@ -148,16 +148,16 @@
│ │ │  single function that constructs the map using the map syntax and always use
│ │ │  it.</p></li><li><p>Always update the map using the <code class="inline">:=</code> operator (that is, requiring that an
│ │ │  element with that key already exists). The <code class="inline">:=</code> operator is slightly more
│ │ │  efficient, and it helps catching mispellings of keys.</p></li><li><p>Whenever possible, match multiple map elements at once.</p></li><li><p>Whenever possible, update multiple map elements at once.</p></li><li><p>Avoid default values and the <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> function. If there are default
│ │ │  values, sharing of keys between different instances of the map will be less
│ │ │  effective, and it is not possible to match multiple elements having default
│ │ │  values in one go.</p></li><li><p>To avoid having to deal with a map that may lack some keys, <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#merge/2"><code class="inline">maps:merge/2</code></a> can
│ │ │ -efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5078460577-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="5078460577-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="5078460577-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="5078460577-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │ +efficiently add multiple default values. For example:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4952132250-1">#{</span><span class="ss">shoe_size</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="ss">editor</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">emacs</span><span class="p" data-group-id="4952132250-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="4952132250-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="4952132250-2">)</span></code></pre></li></ul><h2 id="using-maps-as-dictionaries" class="section-heading">
│ │ │    <a href="#using-maps-as-dictionaries" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using Maps as Dictionaries</span>
│ │ │  </h2>
│ │ │  <p>Using a map as a dictionary implies the following usage pattern:</p><ul><li>Keys are usually variables not known at compile-time.</li><li>There can be any number of elements in the map.</li><li>Usually, no more than one element is looked up or updated at once.</li></ul><p>Given that usage pattern, the difference in performance between using the map
│ │ │  syntax and the maps module is usually small. Therefore, which one to use is
│ │ │ @@ -167,18 +167,18 @@
│ │ │  choice.</li></ul><h2 id="using-maps-as-sets" class="section-heading">
│ │ │    <a href="#using-maps-as-sets" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using Maps as Sets</span>
│ │ │  </h2>
│ │ │  <p>Starting in OTP 24, the <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html"><code class="inline">sets</code></a> module has an option to represent sets as maps.
│ │ │ -Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="8608899009-1">(</span><span class="p" data-group-id="8608899009-2">[</span><span class="p" data-group-id="8608899009-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8608899009-3">}</span><span class="p" data-group-id="8608899009-2">]</span><span class="p" data-group-id="8608899009-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8608899009-4">#{</span><span class="p" data-group-id="8608899009-4">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="8608899009-5">(</span><span class="p" data-group-id="8608899009-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="8608899009-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8608899009-7">[</span><span class="p" data-group-id="8608899009-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8608899009-8">}</span><span class="p" data-group-id="8608899009-7">]</span><span class="p" data-group-id="8608899009-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8608899009-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8608899009-10">[</span><span class="p" data-group-id="8608899009-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8608899009-11">[</span><span class="p" data-group-id="8608899009-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8608899009-12">[</span><span class="p" data-group-id="8608899009-12">]</span><span class="p" data-group-id="8608899009-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │ +Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="2504289015-1">(</span><span class="p" data-group-id="2504289015-2">[</span><span class="p" data-group-id="2504289015-3">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2504289015-3">}</span><span class="p" data-group-id="2504289015-2">]</span><span class="p" data-group-id="2504289015-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2504289015-4">#{</span><span class="p" data-group-id="2504289015-4">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">sets</span><span class="p">:</span><span class="nf">from_list</span><span class="p" data-group-id="2504289015-5">(</span><span class="p" data-group-id="2504289015-6">[</span><span class="ss">x</span><span class="p">,</span><span class="ss">y</span><span class="p">,</span><span class="ss">z</span><span class="p" data-group-id="2504289015-6">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2504289015-7">[</span><span class="p" data-group-id="2504289015-8">{</span><span class="ss">version</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2504289015-8">}</span><span class="p" data-group-id="2504289015-7">]</span><span class="p" data-group-id="2504289015-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2504289015-9">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2504289015-10">[</span><span class="p" data-group-id="2504289015-10">]</span><span class="p">,</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2504289015-11">[</span><span class="p" data-group-id="2504289015-11">]</span><span class="p">,</span><span class="ss">z</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2504289015-12">[</span><span class="p" data-group-id="2504289015-12">]</span><span class="p" data-group-id="2504289015-9">}</span></code></pre><p><code class="inline">sets</code> backed by maps is generally the most efficient set representation, with a
│ │ │  few possible exceptions:</p><ul><li><a href="../../lib/stdlib-6.2.2.2/doc/html/ordsets.html#intersection/2"><code class="inline">ordsets:intersection/2</code></a> can be more efficient than <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html#intersection/2"><code class="inline">sets:intersection/2</code></a>. If
│ │ │  the intersection operation is frequently used and operations that operate on a
│ │ │  single element in a set (such as <code class="inline">is_element/2</code>) are avoided, <a href="../../lib/stdlib-6.2.2.2/doc/html/ordsets.html"><code class="inline">ordsets</code></a> can
│ │ │  be a better choice than <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the intersection operation is frequently used and operations that operate
│ │ │  on a single element in a set (such as <code class="inline">is_element/2</code>) must also be efficient,
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gb_sets.html"><code class="inline">gb_sets</code></a> can potentially be a better choice than <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html"><code class="inline">sets</code></a>.</li><li>If the elements of the set are integers in a fairly compact range, the set can
│ │ │  be represented as an integer where each bit represents an element in the set.
│ │ │ @@ -203,18 +203,18 @@
│ │ │  for the runtime system).</p></li><li><p><strong>N</strong> - The number of elements in the map.</p></li><li><p><strong>Keys</strong> - A tuple with keys of the map: <code class="inline">{Key1,...,KeyN}</code>. The keys are
│ │ │  sorted.</p></li><li><p><strong>Value1</strong> - The value corresponding to the first key in the key tuple.</p></li><li><p><strong>ValueN</strong> - The value corresponding to the last key in the key tuple.</p></li></ul><p>As an example, let us look at how the map <code class="inline">#{a =&gt; foo, z =&gt; bar}</code> is
│ │ │  represented:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: left;">4</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;"><em>2</em></td><td style="text-align: center;"><code class="inline">{a,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: left;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, z =&gt; bar}</em></p><p>Let us update the map: <code class="inline">M#{q =&gt; baz}</code>. The map now looks like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;"><em>3</em></td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bar</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bar}</em></p><p>Finally, change the value of one element: <code class="inline">M#{z := bird}</code>. The map now looks
│ │ │  like this:</p><table><thead><tr><th style="text-align: center;">0</th><th style="text-align: left;">1</th><th style="text-align: center;">2</th><th style="text-align: center;">3</th><th style="text-align: center;">4</th><th style="text-align: center;">5</th></tr></thead><tbody><tr><td style="text-align: center;"><strong>FLATMAP</strong></td><td style="text-align: left;"><em>3</em></td><td style="text-align: center;"><code class="inline">{a,q,z}</code></td><td style="text-align: center;"><code class="inline">foo</code></td><td style="text-align: center;"><code class="inline">baz</code></td><td style="text-align: center;"><code class="inline">bird</code></td></tr></tbody></table><p><em>Table: #{a =&gt; foo, q =&gt; baz, z =&gt; bird}</em></p><p>When the value for an existing key is updated, the key tuple is not updated,
│ │ │  allowing the key tuple to be shared with other instances of the map that have
│ │ │  the same keys. In fact, the key tuple can be shared between all maps with the
│ │ │  same keys with some care. To arrange that, define a function that returns a map.
│ │ │ -For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="7540201445-1">(</span><span class="p" data-group-id="7540201445-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7540201445-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="7540201445-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │ +For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="8718605303-1">(</span><span class="p" data-group-id="8718605303-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8718605303-2">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">default</span><span class="p" data-group-id="8718605303-2">}</span><span class="p">.</span></code></pre><p>Defined like this, the key tuple <code class="inline">{a,b,c}</code> will be a global literal. To ensure
│ │ │  that the key tuple is shared when creating an instance of the map, always call
│ │ │ -<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="0678394791-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0678394791-2">(</span><span class="p" data-group-id="0678394791-2">)</span><span class="p" data-group-id="0678394791-1">)</span><span class="p" data-group-id="0678394791-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="0678394791-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │ +<code class="inline">new()</code> and modify the returned map:</p><pre><code class="makeup erlang" translate="no"><span class="w">    </span><span class="p" data-group-id="7324165150-1">(</span><span class="n">SOME_MODULE</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="7324165150-2">(</span><span class="p" data-group-id="7324165150-2">)</span><span class="p" data-group-id="7324165150-1">)</span><span class="p" data-group-id="7324165150-3">#{</span><span class="ss">a</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7324165150-3">}</span><span class="p">.</span></code></pre><p>Using the map syntax with small maps is particularly efficient. As long as the
│ │ │  keys are known at compile-time, the map is updated in one go, making the time to
│ │ │  update a map essentially constant regardless of the number of keys updated. The
│ │ │  same goes for matching. (When the keys are variables, one or more of the keys
│ │ │  could be identical, so the operations need to be performed sequentially from
│ │ │  left to right.)</p><p>The memory size for a small map is the size of all keys and values plus 5 words.
│ │ │  See <a href="memory.html">Memory</a> for more information about memory sizes.</p><h3 id="how-large-maps-are-implemented" class="section-heading">
│ │ │    <a href="#how-large-maps-are-implemented" class="hover-link">
│ │ │ @@ -241,21 +241,21 @@
│ │ │    <a href="#using-the-map-syntax" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using the Map Syntax</span>
│ │ │  </h2>
│ │ │  <p>Using the map syntax is usually slightly more efficient than using the
│ │ │  corresponding function in the <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html"><code class="inline">maps</code></a> module.</p><p>The gain in efficiency for the map syntax is more noticeable for the following
│ │ │ -operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="6849750957-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="6849750957-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="9884071358-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="9884071358-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="9884071358-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="9884071358-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="9884071358-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="9884071358-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ -right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="5720035155-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="5720035155-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ -left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8674071068-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="8674071068-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="8674071068-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="8674071068-2">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="8674071068-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="8674071068-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │ +operations that can only be achieved using the map syntax:</p><ul><li>Matching multiple literal keys</li><li>Updating multiple literal keys</li><li>Adding multiple literal keys to a map</li></ul><p>For example:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="8167803993-1">#{</span><span class="ss">x</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="ss">z</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="8167803993-1">}</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="3248823055-1">(</span><span class="ss">x</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="3248823055-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="3248823055-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="3248823055-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">update</span><span class="p" data-group-id="3248823055-3">(</span><span class="ss">z</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p">,</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="3248823055-3">)</span></code></pre><p>If the map is a small map, the first example runs roughly three times as fast.</p><p>Note that for variable keys, the elements are updated sequentially from left to
│ │ │ +right. For example, given the following update with variable keys:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="4261340636-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="4261340636-1">}</span></code></pre><p>the compiler rewrites it like this to ensure that the updates are applied from
│ │ │ +left to right:</p><pre><code class="makeup erlang" translate="no"><span class="n">Map2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map1</span><span class="p" data-group-id="9220511219-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9220511219-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map2</span><span class="p" data-group-id="9220511219-2">#{</span><span class="n">Key2</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9220511219-2">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Map3</span><span class="p" data-group-id="9220511219-3">#{</span><span class="n">Key3</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="9220511219-3">}</span></code></pre><p>If a key is known to exist in a map, using the <code class="inline">:=</code> operator is slightly more
│ │ │  efficient than using the <code class="inline">=&gt;</code> operator for a small map.</p><h2 id="using-the-functions-in-the-maps-module" class="section-heading">
│ │ │    <a href="#using-the-functions-in-the-maps-module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Using the Functions in the maps Module</span>
│ │ │  </h2>
│ │ │  <p>Here follows some notes about most of the functions in the <code class="inline">maps</code> module. For
│ │ │ @@ -306,23 +306,23 @@
│ │ │    <a href="#maps-get-3" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">maps:get/3</span>
│ │ │  </h3>
│ │ │  <p>As an optimization, the compiler will rewrite a call to <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> to Erlang
│ │ │  code similar to the following:</p><pre><code class="makeup erlang" translate="no"><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">Map</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="2757473865-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="2757473865-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="2757473865-2">#{</span><span class="p" data-group-id="2757473865-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="3171721347-1">#{</span><span class="n">Key</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Value</span><span class="p" data-group-id="3171721347-1">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Value</span><span class="p">;</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="3171721347-2">#{</span><span class="p" data-group-id="3171721347-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Default</span><span class="w">
│ │ │           </span><span class="k">end</span></code></pre><p>This is reasonably efficient, but if a small map is used as an alternative to
│ │ │  using a record it is often better not to rely on default values as it prevents
│ │ │  sharing of keys, which may in the end use more memory than what you save from
│ │ │  not storing default values in the map.</p><p>If default values are nevertheless required, instead of calling <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a>
│ │ │  multiple times, consider putting the default values in a map and merging that
│ │ │ -map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1504498935-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="1504498935-1">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="1504498935-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="1504498935-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │ +map with the other map:</p><pre><code class="makeup erlang" translate="no"><span class="n">DefaultMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8815147325-1">#{</span><span class="n">Key1</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Value2</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">KeyN</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">ValueN</span><span class="p" data-group-id="8815147325-1">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">MapWithDefaultsApplied</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">merge</span><span class="p" data-group-id="8815147325-2">(</span><span class="n">DefaultMap</span><span class="p">,</span><span class="w"> </span><span class="n">OtherMap</span><span class="p" data-group-id="8815147325-2">)</span></code></pre><p>This helps share keys between the default map and the one you applied defaults
│ │ │  to, as long as the default map contains <em>all</em> the keys that will ever be used
│ │ │  and not just the ones with default values. Whether this is faster than calling
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> multiple times depends on the size of the map and the number of
│ │ │  default values.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before OTP 26.0 <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html#get/3"><code class="inline">maps:get/3</code></a> was implemented by calling the function instead
│ │ │  of rewriting it as an Erlang expression. It is now slightly faster but can no
│ │ │  longer be traced.</p></section><h3 id="maps-intersect-2-maps-intersect_with-3" class="section-heading">
│ │ │    <a href="#maps-intersect-2-maps-intersect_with-3" class="hover-link">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/modules.html
│ │ │ @@ -118,20 +118,20 @@
│ │ │  <h2 id="module-syntax" class="section-heading">
│ │ │    <a href="#module-syntax" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Module Syntax</span>
│ │ │  </h2>
│ │ │  <p>Erlang code is divided into <em>modules</em>. A module consists of a sequence of
│ │ │ -attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4641111714-1">(</span><span class="ss">m</span><span class="p" data-group-id="4641111714-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4641111714-2">(</span><span class="p" data-group-id="4641111714-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4641111714-3">]</span><span class="p" data-group-id="4641111714-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │ +attributes and function declarations, each terminated by a period (<code class="inline">.</code>).</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4665534913-1">(</span><span class="ss">m</span><span class="p" data-group-id="4665534913-1">)</span><span class="p">.</span><span class="w">          </span><span class="c1">% module attribute</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4665534913-2">(</span><span class="p" data-group-id="4665534913-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4665534913-3">]</span><span class="p" data-group-id="4665534913-2">)</span><span class="p">.</span><span class="w">   </span><span class="c1">% module attribute</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="4641111714-4">(</span><span class="n">N</span><span class="p" data-group-id="4641111714-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="4641111714-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4641111714-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="4641111714-6">(</span><span class="mi">0</span><span class="p" data-group-id="4641111714-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="4665534913-4">(</span><span class="n">N</span><span class="p" data-group-id="4665534913-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="o">&gt;</span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% beginning of function declaration</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="4665534913-5">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4665534913-5">)</span><span class="p">;</span><span class="w">   </span><span class="c1">%  |</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="4665534913-6">(</span><span class="mi">0</span><span class="p" data-group-id="4665534913-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">           </span><span class="c1">%  |</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">               </span><span class="c1">% end of function declaration</span></code></pre><p>For a description of function declarations, see
│ │ │  <a href="ref_man_functions.html">Function Declaration Syntax</a>.</p><h2 id="module-attributes" class="section-heading">
│ │ │    <a href="#module-attributes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Module Attributes</span>
│ │ │  </h2>
│ │ │ @@ -176,71 +176,71 @@
│ │ │  meaning.</p></section></li></ul><h3 id="behaviour-module-attribute" class="section-heading">
│ │ │    <a href="#behaviour-module-attribute" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Behaviour Module Attribute</span>
│ │ │  </h3>
│ │ │  <p>It is possible to specify that the module is the callback module for a
│ │ │ -<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6556452559-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="6556452559-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │ +<em>behaviour</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8721289877-1">(</span><span class="n">Behaviour</span><span class="p" data-group-id="8721289877-1">)</span><span class="p">.</span></code></pre><p>The atom <code class="inline">Behaviour</code> gives the name of the behaviour, which can be a
│ │ │  user-defined behaviour or one of the following OTP standard behaviours:</p><ul><li><code class="inline">gen_server</code></li><li><code class="inline">gen_statem</code></li><li><code class="inline">gen_event</code></li><li><code class="inline">supervisor</code></li></ul><p>The spelling <code class="inline">behavior</code> is also accepted.</p><p>The callback functions of the module can be specified either directly by the
│ │ │ -exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="1547661310-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="1547661310-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3884361199-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="3884361199-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │ +exported function <code class="inline">behaviour_info/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="5768475914-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="5768475914-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Callbacks</span><span class="p">.</span></code></pre><p>or by a <code class="inline">-callback</code> attribute for each callback function:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5861097312-1">(</span><span class="n">Arguments</span><span class="p" data-group-id="5861097312-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="p">.</span></code></pre><p>Here, <code class="inline">Arguments</code> is a list of zero or more arguments. The <code class="inline">-callback</code> attribute
│ │ │  is to be preferred since the extra type information can be used by tools to
│ │ │  produce documentation or find discrepancies.</p><p>Read more about behaviours and callback modules in
│ │ │  <a href="../../doc/system/spec_proc.html#behaviours">OTP Design Principles</a>.</p><h3 id="record-definitions" class="section-heading">
│ │ │    <a href="#record-definitions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Record Definitions</span>
│ │ │  </h3>
│ │ │ -<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8098593027-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="8098593027-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │ +<p>The same syntax as for module attributes is used for record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5205273194-1">(</span><span class="n">Record</span><span class="p">,</span><span class="w"> </span><span class="n">Fields</span><span class="p" data-group-id="5205273194-1">)</span><span class="p">.</span></code></pre><p>Record definitions are allowed anywhere in a module, also among the function
│ │ │  declarations. Read more in <a href="ref_man_records.html">Records</a>.</p><h3 id="preprocessor" class="section-heading">
│ │ │    <a href="#preprocessor" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Preprocessor</span>
│ │ │  </h3>
│ │ │  <p>The same syntax as for module attributes is used by the preprocessor, which
│ │ │ -supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0201126614-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="0201126614-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0201126614-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="0201126614-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.html">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │ +supports file inclusion, macros, and conditional compilation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1671885019-1">(</span><span class="s">&quot;SomeFile.hrl&quot;</span><span class="p" data-group-id="1671885019-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1671885019-2">(</span><span class="n">Macro</span><span class="p">,</span><span class="w"> </span><span class="n">Replacement</span><span class="p" data-group-id="1671885019-2">)</span><span class="p">.</span></code></pre><p>Read more in <a href="macros.html">Preprocessor</a>.</p><h3 id="setting-file-and-line" class="section-heading">
│ │ │    <a href="#setting-file-and-line" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Setting File and Line</span>
│ │ │  </h3>
│ │ │  <p>The same syntax as for module attributes is used for changing the pre-defined
│ │ │ -macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="6017317470-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="6017317470-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │ +macros <code class="inline">?FILE</code> and <code class="inline">?LINE</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">file</span><span class="p" data-group-id="1927419878-1">(</span><span class="n">File</span><span class="p">,</span><span class="w"> </span><span class="n">Line</span><span class="p" data-group-id="1927419878-1">)</span><span class="p">.</span></code></pre><p>This attribute is used by tools, such as Yecc, to inform the compiler that the
│ │ │  source program is generated by another tool. It also indicates the
│ │ │  correspondence of source files to lines of the original user-written file, from
│ │ │  which the source program is produced.</p><h3 id="types-and-function-specifications" class="section-heading">
│ │ │    <a href="#types-and-function-specifications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Types and function specifications</span>
│ │ │  </h3>
│ │ │  <p>A similar syntax as for module attributes is used for specifying types and
│ │ │ -function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="3410725528-1">(</span><span class="p" data-group-id="3410725528-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="3410725528-2">(</span><span class="p" data-group-id="3410725528-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3410725528-3">(</span><span class="p" data-group-id="3410725528-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="3410725528-4">(</span><span class="nf">integer</span><span class="p" data-group-id="3410725528-5">(</span><span class="p" data-group-id="3410725528-5">)</span><span class="p" data-group-id="3410725528-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3410725528-6">(</span><span class="p" data-group-id="3410725528-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.html">Types and Function specifications</a>.</p><p>The description is based on
│ │ │ +function specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_type</span><span class="p" data-group-id="7325025846-1">(</span><span class="p" data-group-id="7325025846-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="7325025846-2">(</span><span class="p" data-group-id="7325025846-2">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7325025846-3">(</span><span class="p" data-group-id="7325025846-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">my_function</span><span class="p" data-group-id="7325025846-4">(</span><span class="nf">integer</span><span class="p" data-group-id="7325025846-5">(</span><span class="p" data-group-id="7325025846-5">)</span><span class="p" data-group-id="7325025846-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7325025846-6">(</span><span class="p" data-group-id="7325025846-6">)</span><span class="p">.</span></code></pre><p>Read more in <a href="typespec.html">Types and Function specifications</a>.</p><p>The description is based on
│ │ │  <a href="http://www.erlang.org/eeps/eep-0008.html">EEP8 - Types and function specifications</a>,
│ │ │  which is not to be further updated.</p><h3 id="documentation-attributes" class="section-heading">
│ │ │    <a href="#documentation-attributes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Documentation attributes</span>
│ │ │  </h3>
│ │ │  <p>The module attribute <code class="inline">-doc(Documentation)</code> is used to provide user documentation
│ │ │ -for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="9017914361-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="9017914361-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">example</span><span class="p" data-group-id="9017914361-2">(</span><span class="p" data-group-id="9017914361-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents.The
│ │ │ +for a function/type/callback:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="8277771140-1">(</span><span class="s">&quot;Example documentation&quot;</span><span class="p" data-group-id="8277771140-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">example</span><span class="p" data-group-id="8277771140-2">(</span><span class="p" data-group-id="8277771140-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The attribute should be placed just before the entity it documents.The
│ │ │  parenthesis are optional around <code class="inline">Documentation</code>. The allowed values for
│ │ │  <code class="inline">Documentation</code> are:</p><ul><li><p><strong><a href="data_types.html#string">literal string</a> or
│ │ │  <a href="expressions.html#unicode-segments">utf-8 encoded binary string</a></strong> - The string
│ │ │  documenting the entity. Any literal string is allowed, so both
│ │ │  <a href="data_types.html#tqstring">triple quoted strings</a> and
│ │ │  <a href="data_types.html#sigil">sigils</a> that translate to literal strings can be used.
│ │ │ -The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2418246973-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="2418246973-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2418246973-2">(</span><span class="p" data-group-id="2418246973-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="2418246973-3">&gt;&gt;</span><span class="p" data-group-id="2418246973-2">)</span><span class="p">.</span><span class="w">
│ │ │ +The following examples are equivalent:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2508175793-1">(</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="p" data-group-id="2508175793-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">doc</span><span class="p" data-group-id="2508175793-2">(</span><span class="p" data-group-id="2508175793-3">&lt;&lt;</span><span class="s">&quot;Example \&quot;docs\&quot;&quot;</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="2508175793-3">&gt;&gt;</span><span class="p" data-group-id="2508175793-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~S/Example &quot;docs&quot;/</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="s">&quot;
│ │ │     Example &quot;</span><span class="ss">docs</span><span class="s">&quot;
│ │ │     &quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="na">doc</span><span class="w"> </span><span class="s">~B|Example &quot;docs&quot;|</span><span class="p">.</span></code></pre><p>For clarity it is recommended to use either normal <code class="inline">&quot;strings&quot;</code> or triple
│ │ │  quoted strings for documentation attributes.</p></li><li><p><strong><code class="inline">{file,</code> <a href="../../lib/kernel-10.2.7.2/doc/html/file.html#t:name/0"><code class="inline">file:name/0</code></a> <code class="inline">}</code></strong> - Read the contents of filename and use
│ │ │  that as the documentation string.</p></li><li><p><strong><code class="inline">false</code></strong> - Set the current entity as hidden, that is, it should not be
│ │ │ @@ -253,15 +253,15 @@
│ │ │    <a href="#the-feature-directive" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The feature directive</span>
│ │ │  </h2>
│ │ │  <p>While not a module attribute, but rather a directive (since it might affect
│ │ │  syntax), there is the <code class="inline">-feature(..)</code> directive used for enabling and disabling
│ │ │ -<a href="../../doc/system/features.html#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="3749655090-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="3749655090-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.html#feature-directive">feature directive</a> can only appear
│ │ │ +<a href="../../doc/system/features.html#features">features</a>.</p><p>The syntax is similar to that of an attribute, but has two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">feature</span><span class="p" data-group-id="7125629251-1">(</span><span class="n">FeatureName</span><span class="p">,</span><span class="w"> </span><span class="ss">enable</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">disable</span><span class="p" data-group-id="7125629251-1">)</span><span class="p">.</span></code></pre><p>Note that the <a href="macros.html#feature-directive">feature directive</a> can only appear
│ │ │  in a prefix of the module.</p><h2 id="comments" class="section-heading">
│ │ │    <a href="#comments" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Comments</span>
│ │ │  </h2>
│ │ │  <p>Comments can be placed anywhere in a module except within strings and
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/nif.html
│ │ │ @@ -133,26 +133,26 @@
│ │ │    <span class="text">Erlang Program</span>
│ │ │  </h2>
│ │ │  <p>Even if all functions of a module are NIFs, an Erlang module is still needed for
│ │ │  two reasons:</p><ul><li>The NIF library must be explicitly loaded by Erlang code in the same module.</li><li>All NIFs of a module must have an Erlang implementation as well.</li></ul><p>Normally these are minimal stub implementations that throw an exception. But
│ │ │  they can also be used as fallback implementations for functions that do not have
│ │ │  native implementations on some architectures.</p><p>NIF libraries are loaded by calling <a href="../../erts-15.2.7.2/doc/html/erlang.html#load_nif/2"><code class="inline">erlang:load_nif/2</code></a>, with the name of the
│ │ │  shared library as argument. The second argument can be any term that will be
│ │ │ -passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3206733754-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="3206733754-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3206733754-2">(</span><span class="p" data-group-id="3206733754-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3206733754-3">]</span><span class="p" data-group-id="3206733754-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="3206733754-4">(</span><span class="p" data-group-id="3206733754-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3206733754-5">]</span><span class="p" data-group-id="3206733754-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="3206733754-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3206733754-6">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3206733754-7">(</span><span class="p" data-group-id="3206733754-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="3206733754-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3206733754-8">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="3206733754-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="3206733754-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="3206733754-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="3206733754-10">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">bar</span><span class="p" data-group-id="3206733754-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="3206733754-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="3206733754-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="3206733754-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │ +passed on to the library and used for initialization:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9692111967-1">(</span><span class="ss">complex6</span><span class="p" data-group-id="9692111967-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9692111967-2">(</span><span class="p" data-group-id="9692111967-3">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9692111967-3">]</span><span class="p" data-group-id="9692111967-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="9692111967-4">(</span><span class="p" data-group-id="9692111967-5">[</span><span class="ss">foo</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">bar</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9692111967-5">]</span><span class="p" data-group-id="9692111967-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="9692111967-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9692111967-6">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="9692111967-7">(</span><span class="p" data-group-id="9692111967-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="9692111967-8">(</span><span class="s">&quot;./complex6_nif&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9692111967-8">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="9692111967-9">(</span><span class="p">_</span><span class="n">X</span><span class="p" data-group-id="9692111967-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="9692111967-10">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="9692111967-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">bar</span><span class="p" data-group-id="9692111967-11">(</span><span class="p">_</span><span class="n">Y</span><span class="p" data-group-id="9692111967-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="9692111967-12">(</span><span class="ss">nif_library_not_loaded</span><span class="p" data-group-id="9692111967-12">)</span><span class="p">.</span></code></pre><p>Here, the directive <code class="inline">on_load</code> is used to get function <code class="inline">init</code> to be automatically
│ │ │  called when the module is loaded. If <code class="inline">init</code> returns anything other than <code class="inline">ok</code>,
│ │ │  such when the loading of the NIF library fails in this example, the module is
│ │ │  unloaded and calls to functions within it, fail.</p><p>Loading the NIF library overrides the stub implementations and cause calls to
│ │ │  <code class="inline">foo</code> and <code class="inline">bar</code> to be dispatched to the NIF implementations instead.</p><h2 id="nif-library-code" class="section-heading">
│ │ │    <a href="#nif-library-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -209,23 +209,23 @@
│ │ │    <a href="#running-the-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running the Example</span>
│ │ │  </h2>
│ │ │  <p><em>Step 1.</em> Compile the C code:</p><pre><code class="text">unix&gt; gcc -o complex6_nif.so -fpic -shared complex.c complex6_nif.c
│ │ │  windows&gt; cl -LD -MD -Fe complex6_nif.dll complex.c complex6_nif.c</code></pre><p><em>Step 2:</em> Start Erlang and compile the Erlang code:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="9541885246-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="9541885246-1">)</span><span class="w"> </span><span class="p" data-group-id="9541885246-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="9541885246-2">]</span><span class="w"> </span><span class="p" data-group-id="9541885246-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="9541885246-3">]</span><span class="w"> </span><span class="p" data-group-id="9541885246-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="9541885246-4">]</span><span class="w"> </span><span class="p" data-group-id="9541885246-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="9541885246-5">]</span><span class="w"> </span><span class="p" data-group-id="9541885246-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="9541885246-6">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="w"> </span><span class="n">R13B04</span><span class="w"> </span><span class="p" data-group-id="4648300535-1">(</span><span class="ss">erts</span><span class="o">-</span><span class="mf">5.7</span><span class="p">.</span><span class="mi">5</span><span class="p" data-group-id="4648300535-1">)</span><span class="w"> </span><span class="p" data-group-id="4648300535-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="4648300535-2">]</span><span class="w"> </span><span class="p" data-group-id="4648300535-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">4</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="4648300535-3">]</span><span class="w"> </span><span class="p" data-group-id="4648300535-4">[</span><span class="nc">rq</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="4648300535-4">]</span><span class="w"> </span><span class="p" data-group-id="4648300535-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">0</span><span class="p" data-group-id="4648300535-5">]</span><span class="w"> </span><span class="p" data-group-id="4648300535-6">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="4648300535-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="9541885246-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="9541885246-7">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="9541885246-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="9541885246-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9541885246-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="9541885246-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="3613627106-1">(</span><span class="mi">3</span><span class="p" data-group-id="3613627106-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V5</span><span class="p">.</span><span class="mf">7.5</span><span class="w">  </span><span class="p" data-group-id="4648300535-7">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="4648300535-7">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="4648300535-8">(</span><span class="ss">complex6</span><span class="p" data-group-id="4648300535-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4648300535-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">complex6</span><span class="p" data-group-id="4648300535-9">}</span></code></pre><p><em>Step 3:</em> Run the example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5948641373-1">(</span><span class="mi">3</span><span class="p" data-group-id="5948641373-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="3613627106-2">(</span><span class="mi">5</span><span class="p" data-group-id="3613627106-2">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">bar</span><span class="p" data-group-id="5948641373-2">(</span><span class="mi">5</span><span class="p" data-group-id="5948641373-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="3613627106-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="3613627106-3">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">complex6</span><span class="p">:</span><span class="nf">foo</span><span class="p" data-group-id="5948641373-3">(</span><span class="s">&quot;not an integer&quot;</span><span class="p" data-group-id="5948641373-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument
│ │ │       in function  complex6:foo/1
│ │ │          called as comlpex6:foo(&quot;not an integer&quot;)</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/opaques.html
│ │ │ @@ -122,24 +122,24 @@
│ │ │    <span class="text">Opaque Type Aliases</span>
│ │ │  </h2>
│ │ │  <p>The main use case for opacity in Erlang is to hide the implementation of a data
│ │ │  type, enabling evolving the API while minimizing the risk of breaking consumers.
│ │ │  The runtime does not check opacity. Dialyzer provides some opacity-checking, but
│ │ │  the rest is up to convention.</p><p>This document explains what Erlang opacity is (and the trade-offs involved) via
│ │ │  the example of the <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html#t:set/0"><code class="inline">sets:set()</code></a> data type. This type <em>was</em>
│ │ │ -defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="4656340223-1">(</span><span class="n">Element</span><span class="p" data-group-id="4656340223-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="4656340223-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="4656340223-3">(</span><span class="n">Element</span><span class="p" data-group-id="4656340223-3">)</span><span class="p" data-group-id="4656340223-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ -<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="6059261427-1">(</span><span class="n">Element</span><span class="p" data-group-id="6059261427-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="6059261427-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="6059261427-3">(</span><span class="n">Element</span><span class="p" data-group-id="6059261427-3">)</span><span class="p" data-group-id="6059261427-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="6059261427-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="6059261427-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │ +defined in the <code class="inline">sets</code> module like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="8060874792-1">(</span><span class="n">Element</span><span class="p" data-group-id="8060874792-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="8060874792-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="8060874792-3">(</span><span class="n">Element</span><span class="p" data-group-id="8060874792-3">)</span><span class="p" data-group-id="8060874792-2">}</span><span class="p">.</span></code></pre><p>OTP 24 changed the definition to the following in
│ │ │ +<a href="https://github.com/erlang/otp/commit/e66941e8d7c47b973dff94c0308ea85a6be1958e">this commit</a>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">set</span><span class="p" data-group-id="0954569155-1">(</span><span class="n">Element</span><span class="p" data-group-id="0954569155-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">set</span><span class="p" data-group-id="0954569155-2">{</span><span class="ss">segs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">segs</span><span class="p" data-group-id="0954569155-3">(</span><span class="n">Element</span><span class="p" data-group-id="0954569155-3">)</span><span class="p" data-group-id="0954569155-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0954569155-4">#{</span><span class="n">Element</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="o">?</span><span class="n">VALUE</span><span class="p" data-group-id="0954569155-4">}</span><span class="p">.</span></code></pre><p>And this change was safer and more backwards-compatible than if the type had
│ │ │  been defined with <code class="inline">-type</code> instead of <code class="inline">-opaque</code>. Here is why: when a module
│ │ │  defines an <code class="inline">-opaque</code>, the contract is that only the defining module should rely
│ │ │  on the definition of the type: no other modules should rely on the definition.</p><p>This means that code that pattern-matched on <code class="inline">set</code> as a record/tuple technically
│ │ │  broke the contract, and opted in to being potentially broken when the definition
│ │ │  of <code class="inline">set()</code> changed. Before OTP 24, this code printed <code class="inline">ok</code>. In OTP 24 it may
│ │ │ -error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="0513985117-1">(</span><span class="p" data-group-id="0513985117-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="0513985117-2">(</span><span class="n">Set</span><span class="p" data-group-id="0513985117-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0513985117-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="0513985117-3">)</span><span class="w">
│ │ │ +error:</p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">sets</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="4932317111-1">(</span><span class="p" data-group-id="4932317111-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="n">Set</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_tuple</span><span class="p" data-group-id="4932317111-2">(</span><span class="n">Set</span><span class="p" data-group-id="4932317111-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4932317111-3">(</span><span class="s">&quot;ok&quot;</span><span class="p" data-group-id="4932317111-3">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span></code></pre><p><strong>When working with an opaque defined in another module, here are some
│ │ │  recommendations:</strong></p><ul><li>Don't examine the underlying type using pattern-matching, guards, or functions
│ │ │  that reveal the type, such as <a href="../../erts-15.2.7.2/doc/html/erlang.html#tuple_size/1"><code class="inline">tuple_size/1</code></a> .</li><li>Instead, use functions provided by the module for working with the type. For
│ │ │  example, <code class="inline">sets</code> module provides <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html#new/0"><code class="inline">sets:new/0</code></a>, <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html#add_element/2"><code class="inline">sets:add_element/2</code></a>,
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html#is_element/2"><code class="inline">sets:is_element/2</code></a>, and so on.</li><li><p><a href="../../lib/stdlib-6.2.2.2/doc/html/sets.html#t:set/1"><code class="inline">sets:set(a)</code></a> is a subtype of <code class="inline">sets:set(a | b)</code> and not the
│ │ │  other way around. Generally, you can rely on the property that <code class="inline">the_opaque(T)</code>
│ │ │  is a subtype of <code class="inline">the_opaque(U)</code> when T is a subtype of U.</p></li></ul><p><strong>When defining your own opaques, here are some recommendations:</strong></p><ul><li>Since consumers are expected to not rely on the definition of the opaque type,
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/otp-patch-apply.html
│ │ │ @@ -201,15 +201,15 @@
│ │ │    </a>
│ │ │    <span class="text">Sanity check</span>
│ │ │  </h2>
│ │ │  <p>The application dependencies can be checked using the Erlang shell.
│ │ │  Application dependencies are verified among installed applications by
│ │ │  <code class="inline">otp_patch_apply</code>, but these are not necessarily those actually loaded.
│ │ │  By calling <code class="inline">system_information:sanity_check()</code> one can validate
│ │ │ -dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="6529571932-1">(</span><span class="p" data-group-id="6529571932-1">)</span><span class="p">.</span><span class="w">
│ │ │ +dependencies among applications actually loaded.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">system_information</span><span class="p">:</span><span class="nf">sanity_check</span><span class="p" data-group-id="0169595109-1">(</span><span class="p" data-group-id="0169595109-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Please take a look at the reference of <a href="../../lib/runtime_tools-2.1.1/doc/html/system_information.html#sanity_check/0" title="">sanity_check()</a> for more
│ │ │  information.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/patterns.html
│ │ │ @@ -128,18 +128,18 @@
│ │ │  succeeds, any unbound variables in the pattern become bound. If the matching
│ │ │  fails, an exception is raised.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** 1:1: variable &#39;X&#39; is unbound **</span><span class="gp unselectable">
│ │ │  2&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="gp unselectable">
│ │ │  3&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="p" data-group-id="1940185618-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1940185618-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1940185618-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1940185618-2">}</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="p" data-group-id="4444644438-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4444644438-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4444644438-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="4444644438-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value {1,2}</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="p" data-group-id="1940185618-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1940185618-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1940185618-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1940185618-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1940185618-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1940185618-5">}</span><span class="gp unselectable">
│ │ │ +5&gt; </span><span class="p" data-group-id="4444644438-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4444644438-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4444644438-4">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="4444644438-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4444644438-5">{</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4444644438-5">}</span><span class="gp unselectable">
│ │ │  6&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/prog_ex_records.html
│ │ │ @@ -122,105 +122,105 @@
│ │ │    <span class="text">Records and Tuples</span>
│ │ │  </h2>
│ │ │  <p>The main advantage of using records rather than tuples is that fields in a
│ │ │  record are accessed by name, whereas fields in a tuple are accessed by position.
│ │ │  To illustrate these differences, suppose that you want to represent a person
│ │ │  with the tuple <code class="inline">{Name, Address, Phone}</code>.</p><p>To write functions that manipulate this data, remember the following:</p><ul><li>The <code class="inline">Name</code> field is the first element of the tuple.</li><li>The <code class="inline">Address</code> field is the second element.</li><li>The <code class="inline">Phone</code> field is the third element.</li></ul><p>For example, to extract data from a variable <code class="inline">P</code> that contains such a tuple, you
│ │ │  can write the following code and then use pattern matching to extract the
│ │ │ -relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="4106360701-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="4106360701-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="4106360701-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="4106360701-2">)</span><span class="p">,</span><span class="w">
│ │ │ +relevant fields:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="9949579098-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="9949579098-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">element</span><span class="p" data-group-id="9949579098-2">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">P</span><span class="p" data-group-id="9949579098-2">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Such code is difficult to read and understand, and errors occur if the numbering
│ │ │  of the elements in the tuple is wrong. If the data representation of the fields
│ │ │  is changed, by re-ordering, adding, or removing fields, all references to the
│ │ │  person tuple must be checked and possibly modified.</p><p>Records allow references to the fields by name, instead of by position. In the
│ │ │ -following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287877262-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8287877262-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="8287877262-2">}</span><span class="p" data-group-id="8287877262-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │ +following example, a record instead of a tuple is used to store the data:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9432762668-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9432762668-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="9432762668-2">}</span><span class="p" data-group-id="9432762668-1">)</span><span class="p">.</span></code></pre><p>This enables references to the fields of the record by name. For example, if <code class="inline">P</code>
│ │ │  is a variable whose value is a <code class="inline">person</code> record, the following code access the
│ │ │  name and address fields of the records:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="n">Address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">address</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5988490921-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="5988490921-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Internally, records are represented using tagged tuples:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6814732163-1">{</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p" data-group-id="6814732163-1">}</span></code></pre><h2 id="defining-a-record" class="section-heading">
│ │ │    <a href="#defining-a-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Defining a Record</span>
│ │ │  </h2>
│ │ │  <p>This following definition of a <code class="inline">person</code> is used in several examples in this
│ │ │  section. Three fields are included, <code class="inline">name</code>, <code class="inline">phone</code>, and <code class="inline">address</code>. The default
│ │ │  values for <code class="inline">name</code> and <code class="inline">phone</code> is &quot;&quot; and [], respectively. The default value for
│ │ │  <code class="inline">address</code> is the atom <code class="inline">undefined</code>, since no default value is supplied for this
│ │ │ -field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1274937316-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1274937316-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1274937316-3">[</span><span class="p" data-group-id="1274937316-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="1274937316-2">}</span><span class="p" data-group-id="1274937316-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ -the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="7532251959-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7532251959-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7532251959-3">[</span><span class="p" data-group-id="7532251959-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="7532251959-2">}</span><span class="p" data-group-id="7532251959-1">)</span><span class="p">.</span><span class="w">
│ │ │ +field:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5531343874-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5531343874-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5531343874-3">[</span><span class="p" data-group-id="5531343874-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="5531343874-2">}</span><span class="p" data-group-id="5531343874-1">)</span><span class="p">.</span></code></pre><p>The record must be defined in the shell to enable use of the record syntax in
│ │ │ +the examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">rd</span><span class="p" data-group-id="3018971662-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3018971662-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3018971662-3">[</span><span class="p" data-group-id="3018971662-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="3018971662-2">}</span><span class="p" data-group-id="3018971662-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">person</span></code></pre><p>This is because record definitions are only available at compile time, not at
│ │ │  runtime. For details on records in the shell, see the <a href="../../lib/stdlib-6.2.2.2/doc/html/shell.html"><code class="inline">shell</code></a> manual page in
│ │ │  STDLIB.</p><h2 id="creating-a-record" class="section-heading">
│ │ │    <a href="#creating-a-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating a Record</span>
│ │ │  </h2>
│ │ │ -<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6763529735-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="6763529735-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6763529735-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="6763529735-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6763529735-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6763529735-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6763529735-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="6763529735-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ -special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9572183696-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9572183696-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9572183696-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9572183696-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │ +<p>A new <code class="inline">person</code> record is created as follows:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9832531872-1">{</span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="9832531872-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9832531872-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="9832531872-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9832531872-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9832531872-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9832531872-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="9832531872-3">}</span></code></pre><p>As the <code class="inline">address</code> field was omitted, its default value is used.</p><p>From Erlang 5.1/OTP R8B, a value to all fields in a record can be set with the
│ │ │ +special field <code class="inline">_</code>. <code class="inline">_</code> means &quot;all fields not explicitly specified&quot;.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3190770708-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="3190770708-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3190770708-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Jakob&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="3190770708-2">}</span></code></pre><p>It is primarily intended to be used in <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a> and
│ │ │  <a href="../../lib/mnesia-4.23.5/doc/html/mnesia.html#match_object/3"><code class="inline">mnesia:match_object/3</code></a>, to set record fields to the atom <code class="inline">'_'</code>. (This is a
│ │ │  wildcard in <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>.)</p><h2 id="accessing-a-record-field" class="section-heading">
│ │ │    <a href="#accessing-a-record-field" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Accessing a Record Field</span>
│ │ │  </h2>
│ │ │ -<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2778256618-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2778256618-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2778256618-2">]</span><span class="p" data-group-id="2778256618-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2778256618-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2778256618-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="2778256618-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="2778256618-3">}</span><span class="gp unselectable">
│ │ │ +<p>The following example shows how to access a record field:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5588601311-1">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5588601311-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5588601311-2">]</span><span class="p" data-group-id="5588601311-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5588601311-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5588601311-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5588601311-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">undefined</span><span class="p" data-group-id="5588601311-3">}</span><span class="gp unselectable">
│ │ │  &gt; </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><h2 id="updating-a-record" class="section-heading">
│ │ │    <a href="#updating-a-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating a Record</span>
│ │ │  </h2>
│ │ │ -<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8840742682-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="8840742682-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8840742682-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8840742682-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8840742682-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8840742682-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8840742682-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8840742682-3">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8840742682-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="8840742682-5">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8840742682-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8840742682-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8840742682-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8840742682-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │ +<p>The following example shows how to update a record:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3898020442-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="3898020442-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3898020442-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3898020442-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3898020442-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3898020442-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3898020442-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3898020442-3">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">P2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P1</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3898020442-5">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p" data-group-id="3898020442-5">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3898020442-6">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3898020442-7">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3898020442-7">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3898020442-6">}</span></code></pre><h2 id="type-testing" class="section-heading">
│ │ │    <a href="#type-testing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Testing</span>
│ │ │  </h2>
│ │ │  <p>The following example shows that the guard succeeds if <code class="inline">P</code> is record of type
│ │ │ -<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="1439309578-1">(</span><span class="n">P</span><span class="p" data-group-id="1439309578-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="1439309578-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="1439309578-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foo</span><span class="p" data-group-id="1439309578-3">(</span><span class="p">_</span><span class="p" data-group-id="1439309578-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │ +<code class="inline">person</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foo</span><span class="p" data-group-id="0650732680-1">(</span><span class="n">P</span><span class="p" data-group-id="0650732680-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="0650732680-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="0650732680-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">a_person</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foo</span><span class="p" data-group-id="0650732680-3">(</span><span class="p">_</span><span class="p" data-group-id="0650732680-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">not_a_person</span><span class="p">.</span></code></pre><h2 id="pattern-matching" class="section-heading">
│ │ │    <a href="#pattern-matching" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Pattern Matching</span>
│ │ │  </h2>
│ │ │  <p>Matching can be used in combination with records, as shown in the following
│ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3454995606-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="3454995606-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3454995606-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3454995606-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3454995606-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3454995606-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="3454995606-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="3454995606-3">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3454995606-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3454995606-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">P3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8008656760-1">{</span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="p" data-group-id="8008656760-2">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8008656760-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="o">=</span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8008656760-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8008656760-3">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8008656760-4">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="8008656760-4">]</span><span class="p">,</span><span class="ss">address</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;A street&quot;</span><span class="p" data-group-id="8008656760-3">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8008656760-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8008656760-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P3</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Joe&quot;</span></code></pre><p>The following function takes a list of <code class="inline">person</code> records and searches for the
│ │ │ -phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="2217596416-1">(</span><span class="p" data-group-id="2217596416-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2217596416-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="2217596416-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2217596416-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2217596416-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2217596416-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="2217596416-4">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="2217596416-5">(</span><span class="p" data-group-id="2217596416-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="2217596416-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2217596416-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">find_phone</span><span class="p" data-group-id="2217596416-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2217596416-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">find_phone</span><span class="p" data-group-id="2217596416-8">(</span><span class="p" data-group-id="2217596416-9">[</span><span class="p" data-group-id="2217596416-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="2217596416-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +phone number of a person with a particular name:</p><pre><code class="makeup erlang" translate="no"><span class="nf">find_phone</span><span class="p" data-group-id="9901611787-1">(</span><span class="p" data-group-id="9901611787-2">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9901611787-3">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="n">Phone</span><span class="p" data-group-id="9901611787-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9901611787-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9901611787-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9901611787-4">{</span><span class="ss">found</span><span class="p">,</span><span class="w">  </span><span class="n">Phone</span><span class="p" data-group-id="9901611787-4">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="9901611787-5">(</span><span class="p" data-group-id="9901611787-6">[</span><span class="p">_</span><span class="p">|</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="9901611787-6">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9901611787-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">find_phone</span><span class="p" data-group-id="9901611787-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9901611787-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">find_phone</span><span class="p" data-group-id="9901611787-8">(</span><span class="p" data-group-id="9901611787-9">[</span><span class="p" data-group-id="9901611787-9">]</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9901611787-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">not_found</span><span class="p">.</span></code></pre><p>The fields referred to in the pattern can be given in any order.</p><h2 id="nested-records" class="section-heading">
│ │ │    <a href="#nested-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Nested Records</span>
│ │ │  </h2>
│ │ │  <p>The value of a field in a record can be an instance of a record. Retrieval of
│ │ │  nested data can be done stepwise, or in a single step, as shown in the following
│ │ │ -example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9878483047-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9878483047-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="9878483047-2">}</span><span class="p" data-group-id="9878483047-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9878483047-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9878483047-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="9878483047-5">{</span><span class="p" data-group-id="9878483047-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="9878483047-4">}</span><span class="p" data-group-id="9878483047-3">)</span><span class="p">.</span><span class="w">
│ │ │ +example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9411859139-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9411859139-2">{</span><span class="ss">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Ericsson&quot;</span><span class="p" data-group-id="9411859139-2">}</span><span class="p" data-group-id="9411859139-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9411859139-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9411859139-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="9411859139-5">{</span><span class="p" data-group-id="9411859139-5">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p" data-group-id="9411859139-4">}</span><span class="p" data-group-id="9411859139-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">demo</span><span class="p" data-group-id="9878483047-6">(</span><span class="p" data-group-id="9878483047-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9878483047-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="9878483047-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="9878483047-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="9878483047-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9878483047-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="9878483047-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │ +</span><span class="nf">demo</span><span class="p" data-group-id="9411859139-6">(</span><span class="p" data-group-id="9411859139-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="n">P</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9411859139-7">{</span><span class="ss">name</span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">name</span><span class="p" data-group-id="9411859139-8">{</span><span class="ss">first</span><span class="o">=</span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="ss">last</span><span class="o">=</span><span class="s">&quot;Virding&quot;</span><span class="p" data-group-id="9411859139-8">}</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="o">=</span><span class="mi">123</span><span class="p" data-group-id="9411859139-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="n">First</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9411859139-9">(</span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="9411859139-9">)</span><span class="o">#</span><span class="ss">name</span><span class="p">.</span><span class="ss">first</span><span class="p">.</span></code></pre><p>Here, <code class="inline">demo()</code> evaluates to <code class="inline">&quot;Robert&quot;</code>.</p><h2 id="a-longer-example" class="section-heading">
│ │ │    <a href="#a-longer-example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">A Longer Example</span>
│ │ │  </h2>
│ │ │  <p>Comments are embedded in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% File: person.hrl</span><span class="w">
│ │ │  
│ │ │ @@ -230,48 +230,48 @@
│ │ │  </span><span class="c1">%%    name:  A string (default is undefined).</span><span class="w">
│ │ │  </span><span class="c1">%%    age:   An integer (default is undefined).</span><span class="w">
│ │ │  </span><span class="c1">%%    phone: A list of integers (default is []).</span><span class="w">
│ │ │  </span><span class="c1">%%    dict:  A dictionary containing various information</span><span class="w">
│ │ │  </span><span class="c1">%%           about the person.</span><span class="w">
│ │ │  </span><span class="c1">%%           A {Key, Value} list (default is the empty list).</span><span class="w">
│ │ │  </span><span class="c1">%%------------------------------------------------------------</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4460046616-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4460046616-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4460046616-3">[</span><span class="p" data-group-id="4460046616-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4460046616-4">[</span><span class="p" data-group-id="4460046616-4">]</span><span class="p" data-group-id="4460046616-2">}</span><span class="p" data-group-id="4460046616-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0859314344-1">(</span><span class="ss">person</span><span class="p" data-group-id="0859314344-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0859314344-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="0859314344-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="0859314344-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="0859314344-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8987279019-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8987279019-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8987279019-3">[</span><span class="p" data-group-id="8987279019-3">]</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8987279019-4">[</span><span class="p" data-group-id="8987279019-4">]</span><span class="p" data-group-id="8987279019-2">}</span><span class="p" data-group-id="8987279019-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6932924425-1">(</span><span class="ss">person</span><span class="p" data-group-id="6932924425-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6932924425-2">(</span><span class="s">&quot;person.hrl&quot;</span><span class="p" data-group-id="6932924425-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">compile</span><span class="p" data-group-id="6932924425-3">(</span><span class="ss">export_all</span><span class="p" data-group-id="6932924425-3">)</span><span class="p">.</span><span class="w"> </span><span class="c1">% For test purposes only.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% This creates an instance of a person.</span><span class="w">
│ │ │  </span><span class="c1">%%   Note: The phone number is not supplied so the</span><span class="w">
│ │ │  </span><span class="c1">%%         default value [] will be used.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="0859314344-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="0859314344-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0859314344-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0859314344-6">[</span><span class="p" data-group-id="0859314344-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="0859314344-7">}</span><span class="p">,</span><span class="w">
│ │ │ -                   </span><span class="p" data-group-id="0859314344-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="0859314344-8">}</span><span class="p" data-group-id="0859314344-6">]</span><span class="p" data-group-id="0859314344-5">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="6932924425-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="6932924425-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6932924425-5">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6932924425-6">[</span><span class="p" data-group-id="6932924425-7">{</span><span class="ss">computer_knowledge</span><span class="p">,</span><span class="w"> </span><span class="ss">excellent</span><span class="p" data-group-id="6932924425-7">}</span><span class="p">,</span><span class="w">
│ │ │ +                   </span><span class="p" data-group-id="6932924425-8">{</span><span class="ss">drinks</span><span class="p">,</span><span class="w"> </span><span class="ss">coke</span><span class="p" data-group-id="6932924425-8">}</span><span class="p" data-group-id="6932924425-6">]</span><span class="p" data-group-id="6932924425-5">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% This demonstrates matching in arguments</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print</span><span class="p" data-group-id="0859314344-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0859314344-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="0859314344-10">}</span><span class="p" data-group-id="0859314344-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0859314344-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ -            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0859314344-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="0859314344-12">]</span><span class="p" data-group-id="0859314344-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print</span><span class="p" data-group-id="6932924425-9">(</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6932924425-10">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="ss">dict</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="6932924425-10">}</span><span class="p" data-group-id="6932924425-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6932924425-11">(</span><span class="s">&quot;Name: </span><span class="si">~s</span><span class="s">, Age: </span><span class="si">~w</span><span class="s">, Phone: </span><span class="si">~w</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="w">
│ │ │ +            </span><span class="s">&quot;Dictionary: </span><span class="si">~w</span><span class="s">.</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6932924425-12">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Age</span><span class="p">,</span><span class="w"> </span><span class="n">Phone</span><span class="p">,</span><span class="w"> </span><span class="n">Dict</span><span class="p" data-group-id="6932924425-12">]</span><span class="p" data-group-id="6932924425-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Demonstrates type testing, selector, updating.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">birthday</span><span class="p" data-group-id="0859314344-13">(</span><span class="n">P</span><span class="p" data-group-id="0859314344-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="0859314344-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="0859314344-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0859314344-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0859314344-15">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">birthday</span><span class="p" data-group-id="6932924425-13">(</span><span class="n">P</span><span class="p" data-group-id="6932924425-13">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="6932924425-14">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="6932924425-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6932924425-15">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6932924425-15">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="0859314344-16">(</span><span class="p" data-group-id="0859314344-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="0859314344-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="0859314344-17">)</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="0859314344-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="0859314344-18">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">register_two_hackers</span><span class="p" data-group-id="6932924425-16">(</span><span class="p" data-group-id="6932924425-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="n">Hacker1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_hacker_without_phone</span><span class="p" data-group-id="6932924425-17">(</span><span class="s">&quot;Joe&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p" data-group-id="6932924425-17">)</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="n">OldHacker</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">birthday</span><span class="p" data-group-id="6932924425-18">(</span><span class="n">Hacker1</span><span class="p" data-group-id="6932924425-18">)</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="c1">% The central_register_server should have</span><span class="w">
│ │ │     </span><span class="c1">% an interface function for this.</span><span class="w">
│ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0859314344-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="0859314344-19">}</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0859314344-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0859314344-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ -                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0859314344-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0859314344-22">]</span><span class="p" data-group-id="0859314344-21">}</span><span class="p" data-group-id="0859314344-20">}</span><span class="p">.</span></code></pre>
│ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6932924425-19">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w"> </span><span class="n">Hacker1</span><span class="p" data-group-id="6932924425-19">}</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="ss">central_register_server</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="6932924425-20">{</span><span class="ss">register_person</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="n">OldHacker</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6932924425-21">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Robert&quot;</span><span class="p">,</span><span class="w">
│ │ │ +                              </span><span class="ss">phone</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6932924425-22">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6932924425-22">]</span><span class="p" data-group-id="6932924425-21">}</span><span class="p" data-group-id="6932924425-20">}</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="programming_examples.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/records_macros.html
│ │ │ @@ -124,40 +124,40 @@
│ │ │  </h2>
│ │ │  <p>To illustrate this, the messenger example from the previous section is divided
│ │ │  into the following five files:</p><ul><li><p><code class="inline">mess_config.hrl</code></p><p>Header file for configuration data</p></li><li><p><code class="inline">mess_interface.hrl</code></p><p>Interface definitions between the client and the messenger</p></li><li><p><code class="inline">user_interface.erl</code></p><p>Functions for the user interface</p></li><li><p><code class="inline">mess_client.erl</code></p><p>Functions for the client side of the messenger</p></li><li><p><code class="inline">mess_server.erl</code></p><p>Functions for the server side of the messenger</p></li></ul><p>While doing this, the message passing interface between the shell, the client,
│ │ │  and the server is cleaned up and is defined using <em>records</em>. Also, <em>macros</em> are
│ │ │  introduced:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_config.hrl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7921774891-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="7921774891-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2787234644-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="2787234644-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_interface.hrl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Message interface between client and server and client shell for</span><span class="w">
│ │ │  </span><span class="c1">%%% messenger program</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%Messages from Client to server received in server/1 function.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287013346-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="8287013346-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="8287013346-2">}</span><span class="p" data-group-id="8287013346-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287013346-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="8287013346-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8287013346-4">}</span><span class="p" data-group-id="8287013346-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5090008879-1">(</span><span class="ss">logon</span><span class="p">,</span><span class="p" data-group-id="5090008879-2">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="p" data-group-id="5090008879-2">}</span><span class="p" data-group-id="5090008879-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5090008879-3">(</span><span class="ss">message</span><span class="p">,</span><span class="p" data-group-id="5090008879-4">{</span><span class="ss">client_pid</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="5090008879-4">}</span><span class="p" data-group-id="5090008879-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% {&#39;EXIT&#39;, ClientPid, Reason}  (client terminated or unreachable.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Messages from Server to Client, received in await_result/0 function</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287013346-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="8287013346-6">{</span><span class="ss">message</span><span class="p" data-group-id="8287013346-6">}</span><span class="p" data-group-id="8287013346-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5090008879-5">(</span><span class="ss">abort_client</span><span class="p">,</span><span class="p" data-group-id="5090008879-6">{</span><span class="ss">message</span><span class="p" data-group-id="5090008879-6">}</span><span class="p" data-group-id="5090008879-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% Messages are: user_exists_at_other_node,</span><span class="w">
│ │ │  </span><span class="c1">%%%               you_are_not_logged_on</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287013346-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="8287013346-8">{</span><span class="ss">message</span><span class="p" data-group-id="8287013346-8">}</span><span class="p" data-group-id="8287013346-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5090008879-7">(</span><span class="ss">server_reply</span><span class="p">,</span><span class="p" data-group-id="5090008879-8">{</span><span class="ss">message</span><span class="p" data-group-id="5090008879-8">}</span><span class="p" data-group-id="5090008879-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% Messages are: logged_on</span><span class="w">
│ │ │  </span><span class="c1">%%%               receiver_not_found</span><span class="w">
│ │ │  </span><span class="c1">%%%               sent  (Message has been sent (no guarantee)</span><span class="w">
│ │ │  </span><span class="c1">%%% Messages from Server to Client received in client/1 function</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287013346-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="8287013346-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8287013346-10">}</span><span class="p" data-group-id="8287013346-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5090008879-9">(</span><span class="ss">message_from</span><span class="p">,</span><span class="p" data-group-id="5090008879-10">{</span><span class="ss">from_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="5090008879-10">}</span><span class="p" data-group-id="5090008879-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Messages from shell to Client received in client/1 function</span><span class="w">
│ │ │  </span><span class="c1">%%% spawn(mess_client, client, [server_node(), Name])</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8287013346-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="8287013346-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="8287013346-12">}</span><span class="p" data-group-id="8287013346-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5090008879-11">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="5090008879-12">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="5090008879-12">}</span><span class="p" data-group-id="5090008879-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% logoff</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE user_interface.erl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% User interface to the messenger program</span><span class="w">
│ │ │  </span><span class="c1">%%% login(Name)</span><span class="w">
│ │ │  </span><span class="c1">%%%     One user at a time can log in from each Erlang node in the</span><span class="w">
│ │ │ @@ -170,177 +170,177 @@
│ │ │  </span><span class="c1">%%%     Logs off anybody at that node</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% message(ToName, Message)</span><span class="w">
│ │ │  </span><span class="c1">%%%     sends Message to ToName. Error messages if the user of this</span><span class="w">
│ │ │  </span><span class="c1">%%%     function is not logged on or if ToName is not logged on at</span><span class="w">
│ │ │  </span><span class="c1">%%%     any node.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8870733020-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="8870733020-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8870733020-2">(</span><span class="p" data-group-id="8870733020-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="8870733020-3">]</span><span class="p" data-group-id="8870733020-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8870733020-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="8870733020-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="8870733020-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="8870733020-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0969497247-1">(</span><span class="ss">user_interface</span><span class="p" data-group-id="0969497247-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0969497247-2">(</span><span class="p" data-group-id="0969497247-3">[</span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0969497247-3">]</span><span class="p" data-group-id="0969497247-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0969497247-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="0969497247-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0969497247-5">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="0969497247-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="8870733020-6">(</span><span class="n">Name</span><span class="p" data-group-id="8870733020-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8870733020-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8870733020-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="0969497247-6">(</span><span class="n">Name</span><span class="p" data-group-id="0969497247-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="0969497247-7">(</span><span class="ss">mess_client</span><span class="p" data-group-id="0969497247-7">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="8870733020-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="8870733020-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8870733020-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="8870733020-10">]</span><span class="p" data-group-id="8870733020-9">)</span><span class="p" data-group-id="8870733020-8">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="0969497247-8">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="0969497247-9">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0969497247-10">[</span><span class="o">?</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0969497247-10">]</span><span class="p" data-group-id="0969497247-9">)</span><span class="p" data-group-id="0969497247-8">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="8870733020-11">(</span><span class="p" data-group-id="8870733020-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="0969497247-11">(</span><span class="p" data-group-id="0969497247-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="8870733020-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="8870733020-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="8870733020-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="8870733020-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="0969497247-12">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0969497247-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="0969497247-13">(</span><span class="ss">mess_client</span><span class="p" data-group-id="0969497247-13">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="8870733020-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="8870733020-14">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="0969497247-14">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0969497247-14">}</span><span class="p">,</span><span class="w">
│ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE----</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_client.erl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5133060131-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="5133060131-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5133060131-2">(</span><span class="p" data-group-id="5133060131-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5133060131-3">]</span><span class="p" data-group-id="5133060131-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5133060131-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="5133060131-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5133060131-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5133060131-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5133060131-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5133060131-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="5133060131-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5133060131-8">(</span><span class="p" data-group-id="5133060131-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="5133060131-7">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="5133060131-9">(</span><span class="p" data-group-id="5133060131-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5133060131-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5133060131-10">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6664379628-1">(</span><span class="ss">mess_client</span><span class="p" data-group-id="6664379628-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6664379628-2">(</span><span class="p" data-group-id="6664379628-3">[</span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6664379628-3">]</span><span class="p" data-group-id="6664379628-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6664379628-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="6664379628-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="6664379628-5">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="6664379628-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6664379628-6">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6664379628-6">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="6664379628-7">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="6664379628-8">(</span><span class="p" data-group-id="6664379628-8">)</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="6664379628-7">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="6664379628-9">(</span><span class="p" data-group-id="6664379628-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="6664379628-10">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6664379628-10">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5133060131-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5133060131-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="6664379628-11">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6664379628-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5133060131-12">(</span><span class="ss">normal</span><span class="p" data-group-id="5133060131-12">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5133060131-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5133060131-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5133060131-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="5133060131-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ -                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="5133060131-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="5133060131-16">(</span><span class="p" data-group-id="5133060131-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="5133060131-15">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="5133060131-17">(</span><span class="p" data-group-id="5133060131-17">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5133060131-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5133060131-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5133060131-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5133060131-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="5133060131-20">]</span><span class="p" data-group-id="5133060131-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6664379628-12">(</span><span class="ss">normal</span><span class="p" data-group-id="6664379628-12">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="6664379628-13">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6664379628-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6664379628-14">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="6664379628-14">}</span><span class="w"> </span><span class="o">!</span><span class="w">
│ │ │ +                </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="6664379628-15">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="nf">self</span><span class="p" data-group-id="6664379628-16">(</span><span class="p" data-group-id="6664379628-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="6664379628-15">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="6664379628-17">(</span><span class="p" data-group-id="6664379628-17">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6664379628-18">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6664379628-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6664379628-19">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6664379628-20">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6664379628-20">]</span><span class="p" data-group-id="6664379628-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="5133060131-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="5133060131-21">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="6664379628-21">(</span><span class="n">Server_Node</span><span class="p" data-group-id="6664379628-21">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="5133060131-22">(</span><span class="p" data-group-id="5133060131-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="6664379628-22">(</span><span class="p" data-group-id="6664379628-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="5133060131-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="5133060131-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5133060131-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5133060131-25">[</span><span class="n">Why</span><span class="p" data-group-id="5133060131-25">]</span><span class="p" data-group-id="5133060131-24">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5133060131-26">(</span><span class="ss">normal</span><span class="p" data-group-id="5133060131-26">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="5133060131-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="5133060131-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5133060131-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5133060131-29">[</span><span class="n">What</span><span class="p" data-group-id="5133060131-29">]</span><span class="p" data-group-id="5133060131-28">)</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="6664379628-23">{</span><span class="ss">message</span><span class="o">=</span><span class="n">Why</span><span class="p" data-group-id="6664379628-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6664379628-24">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6664379628-25">[</span><span class="n">Why</span><span class="p" data-group-id="6664379628-25">]</span><span class="p" data-group-id="6664379628-24">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6664379628-26">(</span><span class="ss">normal</span><span class="p" data-group-id="6664379628-26">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="6664379628-27">{</span><span class="ss">message</span><span class="o">=</span><span class="n">What</span><span class="p" data-group-id="6664379628-27">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6664379628-28">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6664379628-29">[</span><span class="n">What</span><span class="p" data-group-id="6664379628-29">]</span><span class="p" data-group-id="6664379628-28">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5133060131-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5133060131-31">[</span><span class="p" data-group-id="5133060131-31">]</span><span class="p" data-group-id="5133060131-30">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="5133060131-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="5133060131-32">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6664379628-30">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6664379628-31">[</span><span class="p" data-group-id="6664379628-31">]</span><span class="p" data-group-id="6664379628-30">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="6664379628-32">(</span><span class="ss">timeout</span><span class="p" data-group-id="6664379628-32">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE---</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%%----FILE mess_server.erl----</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% This is the server process of the messenger service</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0235487134-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="0235487134-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0235487134-2">(</span><span class="p" data-group-id="0235487134-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0235487134-3">]</span><span class="p" data-group-id="0235487134-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="0235487134-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="0235487134-4">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="0235487134-5">(</span><span class="p" data-group-id="0235487134-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="0235487134-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0235487134-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="0235487134-7">(</span><span class="p" data-group-id="0235487134-8">[</span><span class="p" data-group-id="0235487134-8">]</span><span class="p" data-group-id="0235487134-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7259533230-1">(</span><span class="ss">mess_server</span><span class="p" data-group-id="7259533230-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7259533230-2">(</span><span class="p" data-group-id="7259533230-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7259533230-3">]</span><span class="p" data-group-id="7259533230-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7259533230-4">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="7259533230-4">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="7259533230-5">(</span><span class="p" data-group-id="7259533230-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="7259533230-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7259533230-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="7259533230-7">(</span><span class="p" data-group-id="7259533230-8">[</span><span class="p" data-group-id="7259533230-8">]</span><span class="p" data-group-id="7259533230-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]</span><span class="w">
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="0235487134-9">(</span><span class="n">User_List</span><span class="p" data-group-id="0235487134-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0235487134-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235487134-11">[</span><span class="n">User_List</span><span class="p" data-group-id="0235487134-11">]</span><span class="p" data-group-id="0235487134-10">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="7259533230-9">(</span><span class="n">User_List</span><span class="p" data-group-id="7259533230-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7259533230-10">(</span><span class="s">&quot;User list = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7259533230-11">[</span><span class="n">User_List</span><span class="p" data-group-id="7259533230-11">]</span><span class="p" data-group-id="7259533230-10">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="0235487134-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="0235487134-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="0235487134-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-13">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="0235487134-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="0235487134-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0235487134-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="0235487134-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="0235487134-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-16">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="0235487134-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="0235487134-17">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="0235487134-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0235487134-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="0235487134-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-19">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="0235487134-20">(</span><span class="n">User_List</span><span class="p" data-group-id="0235487134-20">)</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">logon</span><span class="p" data-group-id="7259533230-12">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">username</span><span class="o">=</span><span class="n">Name</span><span class="p" data-group-id="7259533230-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="7259533230-13">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-13">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="7259533230-14">(</span><span class="n">New_User_List</span><span class="p" data-group-id="7259533230-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7259533230-15">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7259533230-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="7259533230-16">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-16">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="7259533230-17">(</span><span class="n">New_User_List</span><span class="p" data-group-id="7259533230-17">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="o">#</span><span class="ss">message</span><span class="p" data-group-id="7259533230-18">{</span><span class="ss">client_pid</span><span class="o">=</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="7259533230-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="7259533230-19">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-19">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="7259533230-20">(</span><span class="n">User_List</span><span class="p" data-group-id="7259533230-20">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="0235487134-21">(</span><span class="p" data-group-id="0235487134-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="0235487134-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0235487134-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235487134-24">[</span><span class="p" data-group-id="0235487134-24">]</span><span class="p" data-group-id="0235487134-23">)</span><span class="p" data-group-id="0235487134-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="7259533230-21">(</span><span class="p" data-group-id="7259533230-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7259533230-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7259533230-23">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7259533230-24">[</span><span class="p" data-group-id="7259533230-24">]</span><span class="p" data-group-id="7259533230-23">)</span><span class="p" data-group-id="7259533230-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="0235487134-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="7259533230-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="0235487134-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="7259533230-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="0235487134-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="0235487134-27">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="7259533230-27">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="7259533230-27">}</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="0235487134-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="0235487134-28">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="0235487134-29">(</span><span class="n">From</span><span class="p" data-group-id="0235487134-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0235487134-30">[</span><span class="p" data-group-id="0235487134-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0235487134-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="7259533230-28">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">logged_on</span><span class="p" data-group-id="7259533230-28">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="7259533230-29">(</span><span class="n">From</span><span class="p" data-group-id="7259533230-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7259533230-30">[</span><span class="p" data-group-id="7259533230-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7259533230-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="0235487134-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="0235487134-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-33">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="7259533230-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="7259533230-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-33">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server transfers a message between user</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="0235487134-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="7259533230-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="0235487134-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7259533230-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="0235487134-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="0235487134-36">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0235487134-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235487134-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="0235487134-38">}</span><span class="p" data-group-id="0235487134-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="0235487134-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-39">)</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">abort_client</span><span class="p" data-group-id="7259533230-36">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="7259533230-36">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7259533230-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7259533230-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7259533230-38">}</span><span class="p" data-group-id="7259533230-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="7259533230-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-39">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="0235487134-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="7259533230-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="0235487134-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="0235487134-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7259533230-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7259533230-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="0235487134-42">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="0235487134-42">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0235487134-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0235487134-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="0235487134-44">}</span><span class="p" data-group-id="0235487134-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="0235487134-45">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0235487134-45">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="0235487134-46">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="0235487134-46">}</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="7259533230-42">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">receiver_not_found</span><span class="p" data-group-id="7259533230-42">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7259533230-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7259533230-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7259533230-44">}</span><span class="p" data-group-id="7259533230-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="o">#</span><span class="ss">message_from</span><span class="p" data-group-id="7259533230-45">{</span><span class="ss">from_name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="7259533230-45">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w">  </span><span class="o">#</span><span class="ss">server_reply</span><span class="p" data-group-id="7259533230-46">{</span><span class="ss">message</span><span class="o">=</span><span class="ss">sent</span><span class="p" data-group-id="7259533230-46">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%%----END FILE---</span></code></pre><h2 id="header-files" class="section-heading">
│ │ │    <a href="#header-files" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Header Files</span>
│ │ │  </h2>
│ │ │  <p>As shown above, some files have extension <code class="inline">.hrl</code>. These are header files that
│ │ │ -are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="7989617675-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="7989617675-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="5996039530-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="5996039530-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │ +are included in the <code class="inline">.erl</code> files by:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="9794728127-1">(</span><span class="s">&quot;File_Name&quot;</span><span class="p" data-group-id="9794728127-1">)</span><span class="p">.</span></code></pre><p>for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="1527951561-1">(</span><span class="s">&quot;mess_interface.hrl&quot;</span><span class="p" data-group-id="1527951561-1">)</span><span class="p">.</span></code></pre><p>In the case above the file is fetched from the same directory as all the other
│ │ │  files in the messenger example. (<em>manual</em>).</p><p>.hrl files can contain any valid Erlang code but are most often used for record
│ │ │  and macro definitions.</p><h2 id="records" class="section-heading">
│ │ │    <a href="#records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Records</span>
│ │ │  </h2>
│ │ │ -<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4275893149-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="4275893149-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4275893149-2">}</span><span class="p" data-group-id="4275893149-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6806763588-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="6806763588-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="6806763588-2">}</span><span class="p" data-group-id="6806763588-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1475665409-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="1475665409-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="5801339811-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p">)</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9385737148-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="9385737148-1">}</span></code></pre><p>Notice that you do not have to worry about the order you assign values to the
│ │ │ +<p>A record is defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0452806971-1">(</span><span class="ss">name_of_record</span><span class="p">,</span><span class="p" data-group-id="0452806971-2">{</span><span class="ss">field_name1</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name2</span><span class="p">,</span><span class="w"> </span><span class="ss">field_name3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="0452806971-2">}</span><span class="p" data-group-id="0452806971-1">)</span><span class="p">.</span></code></pre><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1179690470-1">(</span><span class="ss">message_to</span><span class="p">,</span><span class="p" data-group-id="1179690470-2">{</span><span class="ss">to_name</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p" data-group-id="1179690470-2">}</span><span class="p" data-group-id="1179690470-1">)</span><span class="p">.</span></code></pre><p>This is equivalent to:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6468124301-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To_Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="6468124301-1">}</span></code></pre><p>Creating a record is best illustrated by an example:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="3351944953-1">{</span><span class="ss">message</span><span class="o">=</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">to_name</span><span class="o">=</span><span class="ss">fred</span><span class="p">)</span></code></pre><p>This creates:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7946871722-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="ss">fred</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="7946871722-1">}</span></code></pre><p>Notice that you do not have to worry about the order you assign values to the
│ │ │  various parts of the records when you create it. The advantage of using records
│ │ │  is that by placing their definitions in header files you can conveniently define
│ │ │  interfaces that are easy to change. For example, if you want to add a new field
│ │ │  to the record, you only have to change the code where the new field is used and
│ │ │  not at every place the record is referred to. If you leave out a field when
│ │ │  creating a record, it gets the value of the atom <code class="inline">undefined</code>. (<em>manual</em>)</p><p>Pattern matching with records is very similar to creating records. For example,
│ │ │ -inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="0275707918-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="0275707918-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4712423099-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="4712423099-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │ +inside a <code class="inline">case</code> or <code class="inline">receive</code>:</p><pre><code class="makeup erlang" translate="no"><span class="o">#</span><span class="ss">message_to</span><span class="p" data-group-id="9240128167-1">{</span><span class="ss">to_name</span><span class="o">=</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="o">=</span><span class="n">Message</span><span class="p" data-group-id="9240128167-1">}</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>This is the same as:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0388278376-1">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="0388278376-1">}</span></code></pre><h2 id="macros" class="section-heading">
│ │ │    <a href="#macros" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Macros</span>
│ │ │  </h2>
│ │ │  <p>Another thing that has been added to the messenger is a macro. The file
│ │ │  <code class="inline">mess_config.hrl</code> contains the definition:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Configure the location of the server node,</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0318870769-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="0318870769-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="6224072668-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="6224072668-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ -<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="1896640402-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1896640402-2">[</span><span class="p" data-group-id="1896640402-2">]</span><span class="p" data-group-id="1896640402-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9028200743-1">(</span><span class="ss">server_node</span><span class="p">,</span><span class="w"> </span><span class="ss">messenger@super</span><span class="p" data-group-id="9028200743-1">)</span><span class="p">.</span></code></pre><p>This file is included in <code class="inline">mess_server.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include</span><span class="p" data-group-id="4686882098-1">(</span><span class="s">&quot;mess_config.hrl&quot;</span><span class="p" data-group-id="4686882098-1">)</span><span class="p">.</span></code></pre><p>Every occurrence of <code class="inline">?server_node</code> in <code class="inline">mess_server.erl</code> is now replaced by
│ │ │ +<code class="inline">messenger@super</code>.</p><p>A macro is also used when spawning the server process:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="6691970482-1">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6691970482-2">[</span><span class="p" data-group-id="6691970482-2">]</span><span class="p" data-group-id="6691970482-1">)</span></code></pre><p>This is a standard macro (that is, defined by the system, not by the user).
│ │ │  <code class="inline">?MODULE</code> is always replaced by the name of the current module (that is, the
│ │ │  <code class="inline">-module</code> definition near the start of the file). There are more advanced ways
│ │ │  of using macros with, for example, <a href="macros.html#defining-and-using-macros">parameters</a>.</p><p>The three Erlang (<code class="inline">.erl</code>) files in the messenger example are individually
│ │ │  compiled into object code file (<code class="inline">.beam</code>). The Erlang system loads and links
│ │ │  these files into the system when they are referred to during execution of the
│ │ │  code. In this case, they are simply put in our current working directory (that
│ │ │  is, the place you have done &quot;cd&quot; to). There are ways of putting the <code class="inline">.beam</code>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/ref_man_functions.html
│ │ │ @@ -120,51 +120,51 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Function Declaration Syntax</span>
│ │ │  </h2>
│ │ │  <p>A <em>function declaration</em> is a sequence of function clauses separated by
│ │ │  semicolons, and terminated by a period (<code class="inline">.</code>).</p><p>A <em>function clause</em> consists of a <em>clause head</em> and a <em>clause body</em>, separated by
│ │ │  <code class="inline">-&gt;</code>.</p><p>A clause <em>head</em> consists of the function name, an argument list, and an optional
│ │ │ -guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="9648503035-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="9648503035-1">)</span><span class="w"> </span><span class="p" data-group-id="9648503035-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="9648503035-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +guard sequence beginning with the keyword <code class="inline">when</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">Name</span><span class="p" data-group-id="5776655705-1">(</span><span class="n">Pattern11</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">Pattern1N</span><span class="p" data-group-id="5776655705-1">)</span><span class="w"> </span><span class="p" data-group-id="5776655705-2">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeq1</span><span class="p" data-group-id="5776655705-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Body1</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">Name</span><span class="p" data-group-id="9648503035-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="9648503035-3">)</span><span class="w"> </span><span class="p" data-group-id="9648503035-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="9648503035-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="n">Name</span><span class="p" data-group-id="5776655705-3">(</span><span class="n">PatternK1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">PatternKN</span><span class="p" data-group-id="5776655705-3">)</span><span class="w"> </span><span class="p" data-group-id="5776655705-4">[</span><span class="k">when</span><span class="w"> </span><span class="n">GuardSeqK</span><span class="p" data-group-id="5776655705-4">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">BodyK</span><span class="p">.</span></code></pre><p>The function name is an atom. Each argument is a pattern.</p><p>The number of arguments <code class="inline">N</code> is the <em>arity</em> of the function. A function is
│ │ │  uniquely defined by the module name, function name, and arity. That is, two
│ │ │  functions with the same name and in the same module, but with different arities
│ │ │  are two different functions.</p><p>A function named <code class="inline">f</code> in module <code class="inline">mod</code> and with arity <code class="inline">N</code> is often denoted as
│ │ │  <code class="inline">mod:f/N</code>.</p><p>A clause <em>body</em> consists of a sequence of expressions separated by comma (<code class="inline">,</code>):</p><pre><code class="text">Expr1,
│ │ │  ...,
│ │ │  ExprN</code></pre><p>Valid Erlang expressions and guard sequences are described in
│ │ │ -<a href="expressions.html">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="9282893551-1">(</span><span class="n">N</span><span class="p" data-group-id="9282893551-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="9282893551-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9282893551-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │ +<a href="expressions.html">Expressions</a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">fact</span><span class="p" data-group-id="4079387688-1">(</span><span class="n">N</span><span class="p" data-group-id="4079387688-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% first clause head</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="4079387688-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4079387688-2">)</span><span class="p">;</span><span class="w">     </span><span class="c1">% first clause body</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="9282893551-3">(</span><span class="mi">0</span><span class="p" data-group-id="9282893551-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="4079387688-3">(</span><span class="mi">0</span><span class="p" data-group-id="4079387688-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">             </span><span class="c1">% second clause head</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">.</span><span class="w">                 </span><span class="c1">% second clause body</span></code></pre><p><a href="" id="eval"></a></p><h2 id="function-evaluation" class="section-heading">
│ │ │    <a href="#function-evaluation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Function Evaluation</span>
│ │ │  </h2>
│ │ │  <p>When a function <code class="inline">M:F/N</code> is called, first the code for the function is located.
│ │ │  If the function cannot be found, an <code class="inline">undef</code> runtime error occurs. Notice that
│ │ │  the function must be exported to be visible outside the module it is defined in.</p><p>If the function is found, the function clauses are scanned sequentially until a
│ │ │  clause is found that fulfills both of the following two conditions:</p><ol><li>The patterns in the clause head can be successfully matched against the given
│ │ │  arguments.</li><li>The guard sequence, if any, is true.</li></ol><p>If such a clause cannot be found, a <code class="inline">function_clause</code> runtime error occurs.</p><p>If such a clause is found, the corresponding clause body is evaluated. That is,
│ │ │  the expressions in the body are evaluated sequentially and the value of the last
│ │ │ -expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3766664142-1">(</span><span class="ss">mod</span><span class="p" data-group-id="3766664142-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3766664142-2">(</span><span class="p" data-group-id="3766664142-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3766664142-3">]</span><span class="p" data-group-id="3766664142-2">)</span><span class="p">.</span><span class="w">
│ │ │ +expression is returned.</p><p>Consider the function <code class="inline">fact</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8474368923-1">(</span><span class="ss">mod</span><span class="p" data-group-id="8474368923-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8474368923-2">(</span><span class="p" data-group-id="8474368923-3">[</span><span class="ss">fact</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8474368923-3">]</span><span class="p" data-group-id="8474368923-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="3766664142-4">(</span><span class="n">N</span><span class="p" data-group-id="3766664142-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="3766664142-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3766664142-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">fact</span><span class="p" data-group-id="3766664142-6">(</span><span class="mi">0</span><span class="p" data-group-id="3766664142-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="8474368923-4">(</span><span class="n">N</span><span class="p" data-group-id="8474368923-4">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="8474368923-5">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8474368923-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">fact</span><span class="p" data-group-id="8474368923-6">(</span><span class="mi">0</span><span class="p" data-group-id="8474368923-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">.</span></code></pre><p>Assume that you want to calculate the factorial for 1:</p><pre><code class="text">1&gt; mod:fact(1).</code></pre><p>Evaluation starts at the first clause. The pattern <code class="inline">N</code> is matched against
│ │ │  argument 1. The matching succeeds and the guard (<code class="inline">N &gt; 0</code>) is true, thus <code class="inline">N</code> is
│ │ │ -bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="4269323231-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="4269323231-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4269323231-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4269323231-2">)</span><span class="w">
│ │ │ -</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="4269323231-3">(</span><span class="mi">0</span><span class="p" data-group-id="4269323231-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │ +bound to 1, and the corresponding body is evaluated:</p><pre><code class="makeup erlang" translate="no"><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="0621900196-1">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="0621900196-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0621900196-2">(</span><span class="n">N</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">bound</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0621900196-2">)</span><span class="w">
│ │ │ +</span><span class="mi">1</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fact</span><span class="p" data-group-id="0621900196-3">(</span><span class="mi">0</span><span class="p" data-group-id="0621900196-3">)</span></code></pre><p>Now, <code class="inline">fact(0)</code> is called, and the function clauses are scanned
│ │ │  sequentially again. First, the pattern <code class="inline">N</code> is matched against 0. The
│ │ │  matching succeeds, but the guard (<code class="inline">N &gt; 0</code>) is false. Second, the
│ │ │  pattern <code class="inline">0</code> is matched against the argument <code class="inline">0</code>. The matching succeeds
│ │ │  and the body is evaluated:</p><pre><code class="text">1 * fact(0) =&gt;
│ │ │  1 * 1 =&gt;
│ │ │  1</code></pre><p>Evaluation has succeed and <code class="inline">mod:fact(1)</code> returns 1.</p><p>If <code class="inline">mod:fact/1</code> is called with a negative number as argument, no clause head
│ │ │  matches. A <code class="inline">function_clause</code> runtime error occurs.</p><h2 id="tail-recursion" class="section-heading">
│ │ │ @@ -173,17 +173,17 @@
│ │ │    </a>
│ │ │    <span class="text">Tail recursion</span>
│ │ │  </h2>
│ │ │  <p>If the last expression of a function body is a function call, a
│ │ │  <em>tail-recursive call</em> is done. This is to ensure that no system
│ │ │  resources, for example, call stack, are consumed. This means that an
│ │ │  infinite loop using tail-recursive calls will not exhaust the call
│ │ │ -stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2177705901-1">(</span><span class="n">N</span><span class="p" data-group-id="2177705901-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2177705901-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2177705901-3">[</span><span class="n">N</span><span class="p" data-group-id="2177705901-3">]</span><span class="p" data-group-id="2177705901-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="2177705901-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2177705901-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │ +stack and can (in principle) run forever.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="5072899408-1">(</span><span class="n">N</span><span class="p" data-group-id="5072899408-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5072899408-2">(</span><span class="s">&quot;</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072899408-3">[</span><span class="n">N</span><span class="p" data-group-id="5072899408-3">]</span><span class="p" data-group-id="5072899408-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="5072899408-4">(</span><span class="n">N</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5072899408-4">)</span><span class="p">.</span></code></pre><p>The earlier factorial example is a counter-example. It is not
│ │ │  tail-recursive, since a multiplication is done on the result of the recursive
│ │ │  call to <code class="inline">fact(N-1)</code>.</p><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │  </h2>
│ │ │ @@ -191,17 +191,17 @@
│ │ │  system. BIFs do things that are difficult or impossible to implement
│ │ │  in Erlang. Most of the BIFs belong to module <a href="../../erts-15.2.7.2/doc/html/erlang.html"><code class="inline">erlang</code></a>, but there
│ │ │  are also BIFs belonging to a few other modules, for example <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html"><code class="inline">lists</code></a>
│ │ │  and <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html"><code class="inline">ets</code></a>.</p><p>The most commonly used BIFs belonging to <a href="../../erts-15.2.7.2/doc/html/erlang.html"><code class="inline">erlang</code></a> are <em>auto-imported</em>. They do
│ │ │  not need to be prefixed with the module name. Which BIFs that are auto-imported
│ │ │  is specified in the <a href="../../erts-15.2.7.2/doc/html/erlang.html"><code class="inline">erlang</code></a> module in ERTS. For example, standard-type
│ │ │  conversion BIFs like <code class="inline">atom_to_list</code> and BIFs allowed in guards can be called
│ │ │ -without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="2776803326-1">(</span><span class="p" data-group-id="2776803326-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="2776803326-2">}</span><span class="p" data-group-id="2776803326-1">)</span><span class="p">.</span><span class="w">
│ │ │ +without specifying the module name.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="6741272640-1">(</span><span class="p" data-group-id="6741272640-2">{</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6741272640-2">}</span><span class="p" data-group-id="6741272640-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="2776803326-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="2776803326-3">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="6741272640-3">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="6741272640-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Erlang&quot;</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="documentation.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/ref_man_processes.html
│ │ │ @@ -125,18 +125,18 @@
│ │ │  (grow and shrink dynamically) with small memory footprint, fast to create and
│ │ │  terminate, and the scheduling overhead is low.</p><h2 id="process-creation" class="section-heading">
│ │ │    <a href="#process-creation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Process Creation</span>
│ │ │  </h2>
│ │ │ -<p>A process is created by calling <a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="8825111336-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="8825111336-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="8825111336-2">(</span><span class="p" data-group-id="8825111336-2">)</span><span class="w">
│ │ │ -  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="8825111336-3">(</span><span class="p" data-group-id="8825111336-3">)</span><span class="w">
│ │ │ -  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8825111336-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="8825111336-4">]</span><span class="w">
│ │ │ -    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8825111336-5">(</span><span class="p" data-group-id="8825111336-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │ +<p>A process is created by calling <a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn/3"><code class="inline">spawn()</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">spawn</span><span class="p" data-group-id="4812299287-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Args</span><span class="p" data-group-id="4812299287-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pid</span><span class="p" data-group-id="4812299287-2">(</span><span class="p" data-group-id="4812299287-2">)</span><span class="w">
│ │ │ +  </span><span class="n">Module</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="4812299287-3">(</span><span class="p" data-group-id="4812299287-3">)</span><span class="w">
│ │ │ +  </span><span class="n">Args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4812299287-4">[</span><span class="n">Arg1</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="n">ArgN</span><span class="p" data-group-id="4812299287-4">]</span><span class="w">
│ │ │ +    </span><span class="n">ArgI</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="4812299287-5">(</span><span class="p" data-group-id="4812299287-5">)</span></code></pre><p><code class="inline">spawn()</code> creates a new process and returns the pid.</p><p>The new process starts executing in <code class="inline">Module:Name(Arg1,...,ArgN)</code> where the
│ │ │  arguments are the elements of the (possible empty) <code class="inline">Args</code> argument list.</p><p>There exist a number of different <code class="inline">spawn</code> BIFs:</p><ul><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn/4"><code class="inline">spawn/1,2,3,4</code></a></li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn_link/4"><code class="inline">spawn_link/1,2,3,4</code></a></li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn_monitor/4"><code class="inline">spawn_monitor/1,2,3,4</code></a></li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn_opt/5"><code class="inline">spawn_opt/2,3,4,5</code></a></li><li><a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn_request/5"><code class="inline">spawn_request/1,2,3,4,5</code></a></li></ul><h2 id="registered-processes" class="section-heading">
│ │ │    <a href="#registered-processes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Registered Processes</span>
│ │ │  </h2>
│ │ │  <p>Besides addressing a process by using its pid, there are also BIFs for
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/ref_man_records.html
│ │ │ @@ -123,17 +123,17 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Defining Records</span>
│ │ │  </h2>
│ │ │  <p>A record definition consists of the name of the record, followed by the field
│ │ │  names of the record. Record and field names must be atoms. Each field can be
│ │ │  given an optional default value. If no default value is supplied, <code class="inline">undefined</code> is
│ │ │ -used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0255746647-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0255746647-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="0255746647-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="0255746647-3">]</span><span class="p">,</span><span class="w">
│ │ │ +used.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="4769945181-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4769945181-2">{</span><span class="n">Field1</span><span class="w"> </span><span class="p" data-group-id="4769945181-3">[</span><span class="o">=</span><span class="w"> </span><span class="n">Expr1</span><span class="p" data-group-id="4769945181-3">]</span><span class="p">,</span><span class="w">
│ │ │                 </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="0255746647-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="0255746647-4">]</span><span class="p" data-group-id="0255746647-2">}</span><span class="p" data-group-id="0255746647-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │ +               </span><span class="n">FieldN</span><span class="w"> </span><span class="p" data-group-id="4769945181-4">[</span><span class="o">=</span><span class="w"> </span><span class="n">ExprN</span><span class="p" data-group-id="4769945181-4">]</span><span class="p" data-group-id="4769945181-2">}</span><span class="p" data-group-id="4769945181-1">)</span><span class="p">.</span></code></pre><p>The default value for a field is an arbitrary expression, except that it must
│ │ │  not use any variables.</p><p>A record definition can be placed anywhere among the attributes and function
│ │ │  declarations of a module, but the definition must come before any usage of the
│ │ │  record.</p><p>If a record is used in several modules, it is recommended that the record
│ │ │  definition is placed in an include file.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, records can be defined in the Erlang shell
│ │ │  using the syntax described in this section. In earlier releases, it was
│ │ │  necessary to use the <a href="../../lib/stdlib-6.2.2.2/doc/html/shell.html"><code class="inline">shell</code></a> built-in function <code class="inline">rd/2</code>.</p></section><h2 id="creating-records" class="section-heading">
│ │ │    <a href="#creating-records" class="hover-link">
│ │ │ @@ -143,32 +143,32 @@
│ │ │  </h2>
│ │ │  <p>The following expression creates a new <code class="inline">Name</code> record where the value of each
│ │ │  field <code class="inline">FieldI</code> is the value of evaluating the corresponding expression <code class="inline">ExprI</code>:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>The fields can be in any order, not necessarily the same order as in the record
│ │ │  definition, and fields can be omitted. Omitted fields get their respective
│ │ │  default value instead.</p><p>If several fields are to be assigned the same value, the following construction
│ │ │  can be used:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK, _=ExprL}</code></pre><p>Omitted fields then get the value of evaluating <code class="inline">ExprL</code> instead of their default
│ │ │  values. This feature is primarily intended to be used to create patterns for ETS
│ │ │ -and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0993169983-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0993169983-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="0993169983-2">}</span><span class="p" data-group-id="0993169983-1">)</span><span class="p">.</span><span class="w">
│ │ │ +and Mnesia match functions.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2431855580-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2431855580-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="2431855580-2">}</span><span class="p" data-group-id="2431855580-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="0993169983-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="0993169983-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="0993169983-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0993169983-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="0993169983-5">}</span><span class="p" data-group-id="0993169983-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="2431855580-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="2431855580-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="2431855580-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2431855580-5">{</span><span class="ss">name</span><span class="o">=</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2431855580-5">}</span><span class="p" data-group-id="2431855580-4">)</span><span class="p">.</span></code></pre><h2 id="accessing-record-fields" class="section-heading">
│ │ │    <a href="#accessing-record-fields" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Accessing Record Fields</span>
│ │ │  </h2>
│ │ │  <pre><code class="text">Expr#Name.Field</code></pre><p>Returns the value of the specified field. <code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code>
│ │ │ -record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7871478151-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7871478151-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="7871478151-2">}</span><span class="p" data-group-id="7871478151-1">)</span><span class="p">.</span><span class="w">
│ │ │ +record.</p><p><em>Example</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8529022005-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8529022005-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="8529022005-2">}</span><span class="p" data-group-id="8529022005-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">get_person_name</span><span class="p" data-group-id="7871478151-3">(</span><span class="n">Person</span><span class="p" data-group-id="7871478151-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">get_person_name</span><span class="p" data-group-id="8529022005-3">(</span><span class="n">Person</span><span class="p" data-group-id="8529022005-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">.</span></code></pre><p>The following expression returns the position of the specified field in the
│ │ │ -tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="9645051532-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9645051532-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="9645051532-2">}</span><span class="p" data-group-id="9645051532-1">)</span><span class="p">.</span><span class="w">
│ │ │ +tuple representation of the record:</p><pre><code class="text">#Name.Field</code></pre><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7227220115-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7227220115-2">{</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">phone</span><span class="p">,</span><span class="w"> </span><span class="ss">address</span><span class="p" data-group-id="7227220115-2">}</span><span class="p" data-group-id="7227220115-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="9645051532-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9645051532-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="9645051532-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="9645051532-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="7227220115-3">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7227220115-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keyfind</span><span class="p" data-group-id="7227220115-4">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7227220115-4">)</span><span class="p">.</span></code></pre><h2 id="updating-records" class="section-heading">
│ │ │    <a href="#updating-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating Records</span>
│ │ │  </h2>
│ │ │  <pre><code class="text">Expr#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p><code class="inline">Expr</code> is to evaluate to a <code class="inline">Name</code> record. A copy of this record is returned,
│ │ │  with the value of each specified field <code class="inline">FieldI</code> changed to the value of
│ │ │ @@ -178,51 +178,51 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Records in Guards</span>
│ │ │  </h2>
│ │ │  <p>Since record expressions are expanded to tuple expressions, creating
│ │ │  records and accessing record fields are allowed in guards. However,
│ │ │  all subexpressions (for initializing fields), must be valid guard
│ │ │ -expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="2560491969-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2560491969-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="2560491969-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="2560491969-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +expressions as well.</p><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">handle</span><span class="p" data-group-id="2776534391-1">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2776534391-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Msg</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="o">#</span><span class="ss">msg</span><span class="p" data-group-id="2776534391-2">{</span><span class="ss">to</span><span class="o">=</span><span class="ss">void</span><span class="p">,</span><span class="w"> </span><span class="ss">no</span><span class="o">=</span><span class="mi">3</span><span class="p" data-group-id="2776534391-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle</span><span class="p" data-group-id="2560491969-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2560491969-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="4563739526-1">(</span><span class="n">P</span><span class="p" data-group-id="4563739526-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="4563739526-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="4563739526-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle</span><span class="p" data-group-id="2776534391-3">(</span><span class="n">Msg</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="2776534391-3">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">State</span><span class="o">#</span><span class="ss">state</span><span class="p">.</span><span class="ss">running</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>There is also a type test BIF <a href="../../erts-15.2.7.2/doc/html/erlang.html#is_record/2"><code class="inline">is_record(Term, RecordTag)</code></a>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="nf">is_person</span><span class="p" data-group-id="4444709921-1">(</span><span class="n">P</span><span class="p" data-group-id="4444709921-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_record</span><span class="p" data-group-id="4444709921-2">(</span><span class="n">P</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="4444709921-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">true</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">is_person</span><span class="p" data-group-id="4563739526-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="4563739526-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">is_person</span><span class="p" data-group-id="4444709921-3">(</span><span class="p">_</span><span class="n">P</span><span class="p" data-group-id="4444709921-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">false</span><span class="p">.</span></code></pre><h2 id="records-in-patterns" class="section-heading">
│ │ │    <a href="#records-in-patterns" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Records in Patterns</span>
│ │ │  </h2>
│ │ │  <p>A pattern that matches a certain record is created in the same way as a record
│ │ │  is created:</p><pre><code class="text">#Name{Field1=Expr1, ..., FieldK=ExprK}</code></pre><p>In this case, one or more of <code class="inline">Expr1</code> ... <code class="inline">ExprK</code> can be unbound variables.</p><h2 id="nested-records" class="section-heading">
│ │ │    <a href="#nested-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Nested Records</span>
│ │ │  </h2>
│ │ │ -<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1514948267-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1514948267-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="1514948267-2">}</span><span class="p" data-group-id="1514948267-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1514948267-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1514948267-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="1514948267-5">{</span><span class="p" data-group-id="1514948267-5">}</span><span class="p" data-group-id="1514948267-4">}</span><span class="p" data-group-id="1514948267-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1514948267-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1514948267-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="1514948267-8">{</span><span class="p" data-group-id="1514948267-8">}</span><span class="p" data-group-id="1514948267-7">}</span><span class="p" data-group-id="1514948267-6">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Assume the following record definitions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0116517148-1">(</span><span class="ss">nrec0</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0116517148-2">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested0&quot;</span><span class="p" data-group-id="0116517148-2">}</span><span class="p" data-group-id="0116517148-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0116517148-3">(</span><span class="ss">nrec1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0116517148-4">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested1&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec0</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec0</span><span class="p" data-group-id="0116517148-5">{</span><span class="p" data-group-id="0116517148-5">}</span><span class="p" data-group-id="0116517148-4">}</span><span class="p" data-group-id="0116517148-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0116517148-6">(</span><span class="ss">nrec2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0116517148-7">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;nested2&quot;</span><span class="p">,</span><span class="w"> </span><span class="ss">nrec1</span><span class="o">=</span><span class="o">#</span><span class="ss">nrec1</span><span class="p" data-group-id="0116517148-8">{</span><span class="p" data-group-id="0116517148-8">}</span><span class="p" data-group-id="0116517148-7">}</span><span class="p" data-group-id="0116517148-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="1514948267-9">{</span><span class="p" data-group-id="1514948267-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │ +</span><span class="n">N2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">#</span><span class="ss">nrec2</span><span class="p" data-group-id="0116517148-9">{</span><span class="p" data-group-id="0116517148-9">}</span><span class="p">,</span></code></pre><p>Accessing or updating nested records can be written without parentheses:</p><pre><code class="text">&quot;nested0&quot; = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
│ │ │      N0n = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = &quot;nested0a&quot;},</code></pre><p>which is equivalent to:</p><pre><code class="text">&quot;nested0&quot; = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0.name,
│ │ │  N0n = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0{name = &quot;nested0a&quot;},</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP R14, parentheses were necessary when accessing or updating
│ │ │  nested records.</p></section><h2 id="internal-representation-of-records" class="section-heading">
│ │ │    <a href="#internal-representation-of-records" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Internal Representation of Records</span>
│ │ │  </h2>
│ │ │  <p>Record expressions are translated to tuple expressions during compilation. A
│ │ │ -record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3374600018-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3374600018-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="3374600018-2">}</span><span class="p" data-group-id="3374600018-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ -obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="8824916733-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="8824916733-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8824916733-2">[</span><span class="n">Field</span><span class="p" data-group-id="8824916733-2">]</span><span class="w">
│ │ │ -</span><span class="nf">record_info</span><span class="p" data-group-id="8824916733-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="8824916733-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │ +record defined as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1101398854-1">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1101398854-2">{</span><span class="n">Field1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">FieldN</span><span class="p" data-group-id="1101398854-2">}</span><span class="p" data-group-id="1101398854-1">)</span><span class="p">.</span></code></pre><p>is internally represented by the tuple:</p><pre><code class="text">{Name, Value1, ..., ValueN}</code></pre><p>Here each <code class="inline">ValueI</code> is the default value for <code class="inline">FieldI</code>.</p><p>To each module using records, a pseudo function is added during compilation to
│ │ │ +obtain information about records:</p><pre><code class="makeup erlang" translate="no"><span class="nf">record_info</span><span class="p" data-group-id="6117965682-1">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="6117965682-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6117965682-2">[</span><span class="n">Field</span><span class="p" data-group-id="6117965682-2">]</span><span class="w">
│ │ │ +</span><span class="nf">record_info</span><span class="p" data-group-id="6117965682-3">(</span><span class="nb">size</span><span class="p">,</span><span class="w"> </span><span class="n">Record</span><span class="p" data-group-id="6117965682-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Size</span></code></pre><p><code class="inline">Size</code> is the size of the tuple representation, that is, one more than the
│ │ │  number of fields.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="macros.html" class="bottom-actions-button" rel="prev">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/release_handling.html
│ │ │ @@ -223,38 +223,38 @@
│ │ │    <span class="text">update</span>
│ │ │  </h3>
│ │ │  <p>If a more complex change has been made, for example, a change to the format of
│ │ │  the internal state of a <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html"><code class="inline">gen_server</code></a>, simple code replacement is not sufficient.
│ │ │  Instead, it is necessary to:</p><ul><li>Suspend the processes using the module (to avoid that they try to handle any
│ │ │  requests before the code replacement is completed).</li><li>Ask them to transform the internal state format and switch to the new version
│ │ │  of the module.</li><li>Remove the old version.</li><li>Resume the processes.</li></ul><p>This is called <em>synchronized code replacement</em> and for this the following
│ │ │ -instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2457860884-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2457860884-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="2457860884-2">}</span><span class="p" data-group-id="2457860884-1">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2457860884-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="2457860884-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │ +instructions are used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4358340702-1">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4358340702-2">{</span><span class="ss">advanced</span><span class="p">,</span><span class="w"> </span><span class="n">Extra</span><span class="p" data-group-id="4358340702-2">}</span><span class="p" data-group-id="4358340702-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4358340702-3">{</span><span class="ss">update</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="4358340702-3">}</span></code></pre><p><code class="inline">update</code> with argument <code class="inline">{advanced,Extra}</code> is used when changing the internal
│ │ │  state of a behaviour as described above. It causes behaviour processes to call
│ │ │  the callback function <code class="inline">code_change/3</code>, passing the term <code class="inline">Extra</code> and some other
│ │ │  information as arguments. See the manual pages for the respective behaviours and
│ │ │  <a href="appup_cookbook.html#int_state">Appup Cookbook</a>.</p><p><code class="inline">update</code> with argument <code class="inline">supervisor</code> is used when changing the start
│ │ │  specification of a supervisor. See <a href="appup_cookbook.html#sup">Appup Cookbook</a>.</p><p>When a module is to be updated, the release handler finds which processes that
│ │ │  are <em>using</em> the module by traversing the supervision tree of each running
│ │ │ -application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9048886047-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="9048886047-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │ +application and checking all the child specifications:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6197831651-1">{</span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="n">StartFunc</span><span class="p">,</span><span class="w"> </span><span class="n">Restart</span><span class="p">,</span><span class="w"> </span><span class="n">Shutdown</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Modules</span><span class="p" data-group-id="6197831651-1">}</span></code></pre><p>A process uses a module if the name is listed in <code class="inline">Modules</code> in the child
│ │ │  specification for the process.</p><p>If <code class="inline">Modules=dynamic</code>, which is the case for event managers, the event manager
│ │ │  process informs the release handler about the list of currently installed event
│ │ │  handlers (<code class="inline">gen_event</code>), and it is checked if the module name is in this list
│ │ │  instead.</p><p>The release handler suspends, asks for code change, and resumes processes by
│ │ │  calling the functions <code class="inline">sys:suspend/1,2</code>, <code class="inline">sys:change_code/4,5</code>, and
│ │ │  <code class="inline">sys:resume/1,2</code>, respectively.</p><h3 id="add_module-and-delete_module" class="section-heading">
│ │ │    <a href="#add_module-and-delete_module" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">add_module and delete_module</span>
│ │ │  </h3>
│ │ │ -<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7839284196-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="7839284196-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │ +<p>If a new module is introduced, the following instruction is used:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7270055494-1">{</span><span class="ss">add_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="7270055494-1">}</span></code></pre><p>This instruction loads module <code class="inline">Module</code>. When running Erlang in
│ │ │  embedded mode it is necessary to use this this instruction. It is not
│ │ │  strictly required when running Erlang in interactive mode, since the
│ │ │ -code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7693441704-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="7693441704-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │ +code server automatically searches for and loads unloaded modules.</p><p>The opposite of <code class="inline">add_module</code> is <code class="inline">delete_module</code>, which unloads a module:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1240699134-1">{</span><span class="nb">delete_module</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="1240699134-1">}</span></code></pre><p>Any process, in any application, with <code class="inline">Module</code> as residence module, is
│ │ │  killed when the instruction is evaluated. Therefore, the user must
│ │ │  ensure that all such processes are terminated before deleting module
│ │ │  <code class="inline">Module</code> to avoid a situation with failing supervisor restarts.</p><h3 id="application-instructions" class="section-heading">
│ │ │    <a href="#application-instructions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Application Instructions</span>
│ │ │ @@ -341,60 +341,60 @@
│ │ │  <code class="inline">.app</code> file.</li><li>Each <code class="inline">UpFromVsn</code> is a previous version of the application to upgrade from.</li><li>Each <code class="inline">DownToVsn</code> is a previous version of the application to downgrade to.</li><li>Each <code class="inline">Instructions</code> is a list of release handling instructions.</li></ul><p><code class="inline">UpFromVsn</code> and <code class="inline">DownToVsn</code> can also be specified as regular expressions. For
│ │ │  more information about the syntax and contents of the <code class="inline">.appup</code> file, see
│ │ │  <a href="../../lib/sasl-4.2.2/doc/html/appup.html"><code class="inline">appup</code></a> in SASL.</p><p><a href="appup_cookbook.html">Appup Cookbook</a> includes examples of <code class="inline">.appup</code> files for
│ │ │  typical upgrade/downgrade cases.</p><p><em>Example:</em> Consider the release <code class="inline">ch_rel-1</code> from
│ │ │  <a href="release_structure.html#ch_rel">Releases</a>. Assume you want to add a function
│ │ │  <code class="inline">available/0</code> to server <code class="inline">ch3</code>, which returns the number of available channels
│ │ │  (when trying out the example, make the change in a copy of the original
│ │ │ -directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7003014273-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="7003014273-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7003014273-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="7003014273-2">)</span><span class="p">.</span><span class="w">
│ │ │ +directory, to ensure that the first version is still available):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2303335749-1">(</span><span class="ss">ch3</span><span class="p" data-group-id="2303335749-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="2303335749-2">(</span><span class="ss">gen_server</span><span class="p" data-group-id="2303335749-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7003014273-3">(</span><span class="p" data-group-id="7003014273-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7003014273-4">]</span><span class="p" data-group-id="7003014273-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7003014273-5">(</span><span class="p" data-group-id="7003014273-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7003014273-6">]</span><span class="p" data-group-id="7003014273-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7003014273-7">(</span><span class="p" data-group-id="7003014273-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7003014273-8">]</span><span class="p" data-group-id="7003014273-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7003014273-9">(</span><span class="p" data-group-id="7003014273-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7003014273-10">]</span><span class="p" data-group-id="7003014273-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2303335749-3">(</span><span class="p" data-group-id="2303335749-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2303335749-4">]</span><span class="p" data-group-id="2303335749-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2303335749-5">(</span><span class="p" data-group-id="2303335749-6">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2303335749-6">]</span><span class="p" data-group-id="2303335749-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2303335749-7">(</span><span class="p" data-group-id="2303335749-8">[</span><span class="ss">available</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2303335749-8">]</span><span class="p" data-group-id="2303335749-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2303335749-9">(</span><span class="p" data-group-id="2303335749-10">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_call</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_cast</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2303335749-10">]</span><span class="p" data-group-id="2303335749-9">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="7003014273-11">(</span><span class="p" data-group-id="7003014273-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7003014273-12">(</span><span class="p" data-group-id="7003014273-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7003014273-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7003014273-14">[</span><span class="p" data-group-id="7003014273-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7003014273-15">[</span><span class="p" data-group-id="7003014273-15">]</span><span class="p" data-group-id="7003014273-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="2303335749-11">(</span><span class="p" data-group-id="2303335749-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="2303335749-12">(</span><span class="p" data-group-id="2303335749-13">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="2303335749-13">}</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2303335749-14">[</span><span class="p" data-group-id="2303335749-14">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2303335749-15">[</span><span class="p" data-group-id="2303335749-15">]</span><span class="p" data-group-id="2303335749-12">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="7003014273-16">(</span><span class="p" data-group-id="7003014273-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7003014273-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="7003014273-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="2303335749-16">(</span><span class="p" data-group-id="2303335749-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2303335749-17">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="2303335749-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="7003014273-18">(</span><span class="n">Ch</span><span class="p" data-group-id="7003014273-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7003014273-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7003014273-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7003014273-20">}</span><span class="p" data-group-id="7003014273-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="2303335749-18">(</span><span class="n">Ch</span><span class="p" data-group-id="2303335749-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="2303335749-19">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2303335749-20">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2303335749-20">}</span><span class="p" data-group-id="2303335749-19">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">available</span><span class="p" data-group-id="7003014273-21">(</span><span class="p" data-group-id="7003014273-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="7003014273-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="7003014273-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">available</span><span class="p" data-group-id="2303335749-21">(</span><span class="p" data-group-id="2303335749-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_server</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="2303335749-22">(</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">available</span><span class="p" data-group-id="2303335749-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="7003014273-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7003014273-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7003014273-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="7003014273-25">(</span><span class="p" data-group-id="7003014273-25">)</span><span class="p" data-group-id="7003014273-24">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="2303335749-23">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="2303335749-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2303335749-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="2303335749-25">(</span><span class="p" data-group-id="2303335749-25">)</span><span class="p" data-group-id="2303335749-24">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="7003014273-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7003014273-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7003014273-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7003014273-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="7003014273-28">(</span><span class="n">Chs</span><span class="p" data-group-id="7003014273-28">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7003014273-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7003014273-29">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_call</span><span class="p" data-group-id="7003014273-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7003014273-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="7003014273-31">(</span><span class="n">Chs</span><span class="p" data-group-id="7003014273-31">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7003014273-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7003014273-32">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="2303335749-26">(</span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2303335749-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2303335749-27">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2303335749-27">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="2303335749-28">(</span><span class="n">Chs</span><span class="p" data-group-id="2303335749-28">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2303335749-29">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2303335749-29">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_call</span><span class="p" data-group-id="2303335749-30">(</span><span class="ss">available</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2303335749-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">available</span><span class="p" data-group-id="2303335749-31">(</span><span class="n">Chs</span><span class="p" data-group-id="2303335749-31">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2303335749-32">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2303335749-32">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_cast</span><span class="p" data-group-id="7003014273-33">(</span><span class="p" data-group-id="7003014273-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7003014273-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7003014273-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="7003014273-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7003014273-35">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7003014273-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7003014273-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ -updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1430555462-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1430555462-2">[</span><span class="p" data-group-id="1430555462-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="1430555462-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1430555462-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="1430555462-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1430555462-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430555462-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1430555462-6">]</span><span class="p" data-group-id="1430555462-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1430555462-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430555462-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="1430555462-8">]</span><span class="p" data-group-id="1430555462-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1430555462-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430555462-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1430555462-10">]</span><span class="p" data-group-id="1430555462-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1430555462-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1430555462-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="1430555462-13">[</span><span class="p" data-group-id="1430555462-13">]</span><span class="p" data-group-id="1430555462-12">}</span><span class="p" data-group-id="1430555462-11">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1430555462-2">]</span><span class="p" data-group-id="1430555462-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │ +</span><span class="nf">handle_cast</span><span class="p" data-group-id="2303335749-33">(</span><span class="p" data-group-id="2303335749-34">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="2303335749-34">}</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2303335749-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="2303335749-35">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2303335749-35">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2303335749-36">{</span><span class="ss">noreply</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="2303335749-36">}</span><span class="p">.</span></code></pre><p>A new version of the <code class="inline">ch_app.app</code> file must now be created, where the version is
│ │ │ +updated:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7966237353-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7966237353-2">[</span><span class="p" data-group-id="7966237353-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="7966237353-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7966237353-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="7966237353-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7966237353-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7966237353-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="7966237353-6">]</span><span class="p" data-group-id="7966237353-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7966237353-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7966237353-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="7966237353-8">]</span><span class="p" data-group-id="7966237353-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7966237353-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7966237353-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="7966237353-10">]</span><span class="p" data-group-id="7966237353-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="7966237353-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7966237353-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="7966237353-13">[</span><span class="p" data-group-id="7966237353-13">]</span><span class="p" data-group-id="7966237353-12">}</span><span class="p" data-group-id="7966237353-11">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7966237353-2">]</span><span class="p" data-group-id="7966237353-1">}</span><span class="p">.</span></code></pre><p>To upgrade <code class="inline">ch_app</code> from <code class="inline">&quot;1&quot;</code> to <code class="inline">&quot;2&quot;</code> (and to downgrade from <code class="inline">&quot;2&quot;</code> to <code class="inline">&quot;1&quot;</code>),
│ │ │  you only need to load the new (old) version of the <code class="inline">ch3</code> callback module. Create
│ │ │ -the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3745924056-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3745924056-2">[</span><span class="p" data-group-id="3745924056-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745924056-4">[</span><span class="p" data-group-id="3745924056-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3745924056-5">}</span><span class="p" data-group-id="3745924056-4">]</span><span class="p" data-group-id="3745924056-3">}</span><span class="p" data-group-id="3745924056-2">]</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="3745924056-6">[</span><span class="p" data-group-id="3745924056-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3745924056-8">[</span><span class="p" data-group-id="3745924056-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="3745924056-9">}</span><span class="p" data-group-id="3745924056-8">]</span><span class="p" data-group-id="3745924056-7">}</span><span class="p" data-group-id="3745924056-6">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3745924056-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │ +the application upgrade file <code class="inline">ch_app.appup</code> in the <code class="inline">ebin</code> directory:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1918979754-1">{</span><span class="s">&quot;2&quot;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1918979754-2">[</span><span class="p" data-group-id="1918979754-3">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918979754-4">[</span><span class="p" data-group-id="1918979754-5">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1918979754-5">}</span><span class="p" data-group-id="1918979754-4">]</span><span class="p" data-group-id="1918979754-3">}</span><span class="p" data-group-id="1918979754-2">]</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="1918979754-6">[</span><span class="p" data-group-id="1918979754-7">{</span><span class="s">&quot;1&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1918979754-8">[</span><span class="p" data-group-id="1918979754-9">{</span><span class="nb">load_module</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1918979754-9">}</span><span class="p" data-group-id="1918979754-8">]</span><span class="p" data-group-id="1918979754-7">}</span><span class="p" data-group-id="1918979754-6">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1918979754-1">}</span><span class="p">.</span></code></pre><p><a href="" id="relup"></a></p><h2 id="release-upgrade-file" class="section-heading">
│ │ │    <a href="#release-upgrade-file" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Release Upgrade File</span>
│ │ │  </h2>
│ │ │  <p>To define how to upgrade/downgrade between the new version and previous versions
│ │ │  of a release, a <em>release upgrade file</em>, or in short <code class="inline">.relup</code> file, is to be
│ │ │ @@ -405,22 +405,22 @@
│ │ │  are to be added and deleted, and which applications that must be upgraded and/or
│ │ │  downgraded. The instructions for this are fetched from the <code class="inline">.appup</code> files and
│ │ │  transformed into a single list of low-level instructions in the right order.</p><p>If the <code class="inline">relup</code> file is relatively simple, it can be created manually. It is only
│ │ │  to contain low-level instructions.</p><p>For details about the syntax and contents of the release upgrade file, see
│ │ │  <a href="../../lib/sasl-4.2.2/doc/html/relup.html"><code class="inline">relup</code></a> in SASL.</p><p><em>Example, continued from the previous section:</em> You have a new version &quot;2&quot; of
│ │ │  <code class="inline">ch_app</code> and an <code class="inline">.appup</code> file. A new version of the <code class="inline">.rel</code> file is also needed.
│ │ │  This time the file is called <code class="inline">ch_rel-2.rel</code> and the release version string is
│ │ │ -changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9493780925-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9493780925-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="9493780925-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9493780925-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="9493780925-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9493780925-4">[</span><span class="p" data-group-id="9493780925-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="9493780925-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9493780925-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="9493780925-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9493780925-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="9493780925-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9493780925-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="9493780925-8">}</span><span class="p" data-group-id="9493780925-4">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9493780925-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │ +changed from &quot;A&quot; to &quot;B&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5991135990-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5991135990-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="5991135990-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5991135990-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="5991135990-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5991135990-4">[</span><span class="p" data-group-id="5991135990-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="5991135990-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5991135990-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="5991135990-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5991135990-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="5991135990-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5991135990-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;2&quot;</span><span class="p" data-group-id="5991135990-8">}</span><span class="p" data-group-id="5991135990-4">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5991135990-1">}</span><span class="p">.</span></code></pre><p>Now the <code class="inline">relup</code> file can be generated:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;]).
│ │ │  ok</code></pre><p>This generates a <code class="inline">relup</code> file with instructions for how to upgrade from version
│ │ │  &quot;A&quot; (&quot;ch_rel-1&quot;) to version &quot;B&quot; (&quot;ch_rel-2&quot;) and how to downgrade from version
│ │ │  &quot;B&quot; to version &quot;A&quot;.</p><p>Both the old and new versions of the <code class="inline">.app</code> and <code class="inline">.rel</code> files must be in the code
│ │ │  path, as well as the <code class="inline">.appup</code> and (new) <code class="inline">.beam</code> files. The code path can be
│ │ │  extended by using the option <code class="inline">path</code>:</p><pre><code class="text">1&gt; systools:make_relup(&quot;ch_rel-2&quot;, [&quot;ch_rel-1&quot;], [&quot;ch_rel-1&quot;],
│ │ │  [{path,[&quot;../ch_rel-1&quot;,
│ │ │  &quot;../ch_rel-1/lib/ch_app-1/ebin&quot;]}]).
│ │ │ @@ -433,25 +433,25 @@
│ │ │  <p>When you have made a new version of a release, a release package can be created
│ │ │  with this new version and transferred to the target environment.</p><p>To install the new version of the release in runtime, the <em>release
│ │ │  handler</em> is used. This is a process belonging to the SASL application,
│ │ │  which handles unpacking, installation, and removal of release
│ │ │  packages. The <a href="../../lib/sasl-4.2.2/doc/html/release_handler.html"><code class="inline">release_handler</code></a> module communicates with this process.</p><p>Assuming there is an operational target system with installation root directory
│ │ │  <code class="inline">$ROOT</code>, the release package with the new version of the release is to be copied
│ │ │  to <code class="inline">$ROOT/releases</code>.</p><p>First, <em>unpack</em> the release package. The files are then extracted from the
│ │ │ -package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="4834541155-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="4834541155-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4834541155-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="4834541155-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │ +package:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="3800723927-1">(</span><span class="n">ReleaseName</span><span class="p" data-group-id="3800723927-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3800723927-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p" data-group-id="3800723927-2">}</span></code></pre><ul><li><code class="inline">ReleaseName</code> is the name of the release package except the <code class="inline">.tar.gz</code>
│ │ │  extension.</li><li><code class="inline">Vsn</code> is the version of the unpacked release, as defined in its <code class="inline">.rel</code> file.</li></ul><p>A directory <code class="inline">$ROOT/lib/releases/Vsn</code> is created, where the <code class="inline">.rel</code> file, the boot
│ │ │  script <code class="inline">start.boot</code>, the system configuration file <code class="inline">sys.config</code>, and <code class="inline">relup</code> are
│ │ │  placed. For applications with new version numbers, the application directories
│ │ │  are placed under <code class="inline">$ROOT/lib</code>. Unchanged applications are not affected.</p><p>An unpacked release can be <em>installed</em>. The release handler then evaluates the
│ │ │ -instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="1467256487-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="1467256487-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1467256487-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1467256487-3">[</span><span class="p" data-group-id="1467256487-3">]</span><span class="p" data-group-id="1467256487-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │ +instructions in <code class="inline">relup</code>, step by step:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="6404146066-1">(</span><span class="n">Vsn</span><span class="p" data-group-id="6404146066-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6404146066-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">FromVsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6404146066-3">[</span><span class="p" data-group-id="6404146066-3">]</span><span class="p" data-group-id="6404146066-2">}</span></code></pre><p>If an error occurs during the installation, the system is rebooted using the old
│ │ │  version of the release. If installation succeeds, the system is afterwards using
│ │ │  the new version of the release, but if anything happens and the system is
│ │ │  rebooted, it starts using the previous version again.</p><p>To be made the default version, the newly installed release must be made
│ │ │  <em>permanent</em>, which means the previous version becomes <em>old</em>:</p><pre><code class="text">release_handler:make_permanent(Vsn) =&gt; ok</code></pre><p>The system keeps information about which versions are old and permanent in the
│ │ │ -files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="7831064487-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="7831064487-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7831064487-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7831064487-3">[</span><span class="p" data-group-id="7831064487-3">]</span><span class="p" data-group-id="7831064487-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │ +files <code class="inline">$ROOT/releases/RELEASES</code> and <code class="inline">$ROOT/releases/start_erl.data</code>.</p><p>To downgrade from <code class="inline">Vsn</code> to <code class="inline">FromVsn</code>, <code class="inline">install_release</code> must be called again:</p><pre><code class="makeup erlang" translate="no"><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="4617438030-1">(</span><span class="n">FromVsn</span><span class="p" data-group-id="4617438030-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4617438030-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Vsn</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4617438030-3">[</span><span class="p" data-group-id="4617438030-3">]</span><span class="p" data-group-id="4617438030-2">}</span></code></pre><p>An installed, but not permanent, release can be <em>removed</em>. Information about the
│ │ │  release is then deleted from <code class="inline">$ROOT/releases/RELEASES</code> and the release-specific
│ │ │  code, that is, the new application directories and the <code class="inline">$ROOT/releases/Vsn</code>
│ │ │  directory, are removed.</p><pre><code class="text">release_handler:remove_release(Vsn) =&gt; ok</code></pre><h3 id="example-continued-from-the-previous-sections" class="section-heading">
│ │ │    <a href="#example-continued-from-the-previous-sections" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example (continued from the previous sections)</span>
│ │ │ @@ -462,17 +462,17 @@
│ │ │  is needed, the file is to contain the empty list:</p><pre><code class="text">[].</code></pre><p><em>Step 2)</em> Start the system as a simple target system. In reality, it is to be
│ │ │  started as an embedded system. However, using <code class="inline">erl</code> with the correct boot script
│ │ │  and config file is enough for illustration purposes:</p><pre><code class="text">% cd $ROOT
│ │ │  % bin/erl -boot $ROOT/releases/A/start -config $ROOT/releases/A/sys
│ │ │  ...</code></pre><p><code class="inline">$ROOT</code> is the installation directory of the target system.</p><p><em>Step 3)</em> In another Erlang shell, generate start scripts and create a release
│ │ │  package for the new version <code class="inline">&quot;B&quot;</code>. Remember to include (a possible updated)
│ │ │  <code class="inline">sys.config</code> and the <code class="inline">relup</code> file. For more information, see
│ │ │ -<a href="release_handling.html#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="0501174905-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="0501174905-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="release_handling.html#relup">Release Upgrade File</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="1922581462-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="1922581462-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="0501174905-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="0501174905-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="1922581462-2">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="1922581462-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>The new release package now also contains version &quot;2&quot; of <code class="inline">ch_app</code> and the
│ │ │  <code class="inline">relup</code> file:</p><pre><code class="text">% tar tf ch_rel-2.tar
│ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │  ...
│ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ │ @@ -485,31 +485,31 @@
│ │ │  lib/ch_app-2/ebin/ch_sup.beam
│ │ │  lib/ch_app-2/ebin/ch3.beam
│ │ │  releases/B/start.boot
│ │ │  releases/B/relup
│ │ │  releases/B/sys.config
│ │ │  releases/B/ch_rel-2.rel
│ │ │  releases/ch_rel-2.rel</code></pre><p><em>Step 4)</em> Copy the release package <code class="inline">ch_rel-2.tar.gz</code> to the <code class="inline">$ROOT/releases</code>
│ │ │ -directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="1904334310-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="1904334310-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1904334310-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="1904334310-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │ +directory.</p><p><em>Step 5)</em> In the running target system, unpack the release package:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">unpack_release</span><span class="p" data-group-id="6342479687-1">(</span><span class="s">&quot;ch_rel-2&quot;</span><span class="p" data-group-id="6342479687-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6342479687-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="6342479687-2">}</span></code></pre><p>The new application version <code class="inline">ch_app-2</code> is installed under <code class="inline">$ROOT/lib</code> next to
│ │ │  <code class="inline">ch_app-1</code>. The <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code> directories are not affected, as
│ │ │  they have not changed.</p><p>Under <code class="inline">$ROOT/releases</code>, a new directory <code class="inline">B</code> is created, containing
│ │ │ -<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="4951486377-1">(</span><span class="p" data-group-id="4951486377-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">ch_rel-2.rel</code>, <code class="inline">start.boot</code>, <code class="inline">sys.config</code>, and <code class="inline">relup</code>.</p><p><em>Step 6)</em> Check if the function <code class="inline">ch3:available/0</code> is available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="4455398933-1">(</span><span class="p" data-group-id="4455398933-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: undefined function ch3:available/0</span></code></pre><p><em>Step 7)</em> Install the new release. The instructions in <code class="inline">$ROOT/releases/B/relup</code>
│ │ │  are executed one by one, resulting in the new version of <code class="inline">ch3</code> being loaded. The
│ │ │ -function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="3998279160-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="3998279160-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3998279160-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="3998279160-3">[</span><span class="p" data-group-id="3998279160-3">]</span><span class="p" data-group-id="3998279160-2">}</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="3998279160-4">(</span><span class="p" data-group-id="3998279160-4">)</span><span class="p">.</span><span class="w">
│ │ │ +function <code class="inline">ch3:available/0</code> is now available:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">install_release</span><span class="p" data-group-id="9409991278-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="9409991278-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9409991278-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="s">&quot;A&quot;</span><span class="p">,</span><span class="p" data-group-id="9409991278-3">[</span><span class="p" data-group-id="9409991278-3">]</span><span class="p" data-group-id="9409991278-2">}</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="nc">ch3</span><span class="p">:</span><span class="nf">available</span><span class="p" data-group-id="9409991278-4">(</span><span class="p" data-group-id="9409991278-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="3998279160-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="3998279160-5">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="9409991278-5">(</span><span class="ss">ch3</span><span class="p" data-group-id="9409991278-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;.../lib/ch_app-2/ebin/ch3.beam&quot;</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="3998279160-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="3998279160-6">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nc">code</span><span class="p">:</span><span class="nf">which</span><span class="p" data-group-id="9409991278-6">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="9409991278-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;.../lib/ch_app-1/ebin/ch_sup.beam&quot;</span></code></pre><p>Processes in <code class="inline">ch_app</code> for which code have not been updated, for example, the
│ │ │  supervisor, are still evaluating code from <code class="inline">ch_app-1</code>.</p><p><em>Step 8)</em> If the target system is now rebooted, it uses version &quot;A&quot; again. The
│ │ │ -&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="9643651112-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="9643651112-1">)</span><span class="p">.</span><span class="w">
│ │ │ +&quot;B&quot; version must be made permanent, to be used when the system is rebooted.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nc">release_handler</span><span class="p">:</span><span class="nf">make_permanent</span><span class="p" data-group-id="6468734012-1">(</span><span class="s">&quot;B&quot;</span><span class="p" data-group-id="6468734012-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p><a href="" id="sys"></a></p><h2 id="updating-application-specifications" class="section-heading">
│ │ │    <a href="#updating-application-specifications" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Updating Application Specifications</span>
│ │ │  </h2>
│ │ │  <p>When a new version of a release is installed, the application specifications are
│ │ │ @@ -518,15 +518,15 @@
│ │ │  boot script is generated from the same <code class="inline">.rel</code> file as is used to build the
│ │ │  release package itself.</p></section><p>Specifically, the application configuration parameters are automatically updated
│ │ │  according to (in increasing priority order):</p><ul><li>The data in the boot script, fetched from the new application resource file
│ │ │  <code class="inline">App.app</code></li><li>The new <code class="inline">sys.config</code></li><li>Command-line arguments <code class="inline">-App Par Val</code></li></ul><p>This means that parameter values set in the other system configuration files and
│ │ │  values set using <a href="../../lib/kernel-10.2.7.2/doc/html/application.html#set_env/3"><code class="inline">application:set_env/3</code></a> are disregarded.</p><p>When an installed release is made permanent, the system process <code class="inline">init</code> is set to
│ │ │  point out the new <code class="inline">sys.config</code>.</p><p>After the installation, the application controller compares the old and new
│ │ │  configuration parameters for all running applications and call the callback
│ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="5126032612-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="5126032612-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="n">Module</span><span class="p">:</span><span class="nf">config_change</span><span class="p" data-group-id="5201817107-1">(</span><span class="n">Changed</span><span class="p">,</span><span class="w"> </span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Removed</span><span class="p" data-group-id="5201817107-1">)</span></code></pre><ul><li><code class="inline">Module</code> is the application callback module as defined by the <code class="inline">mod</code> key in the
│ │ │  <code class="inline">.app</code> file.</li><li><code class="inline">Changed</code> and <code class="inline">New</code> are lists of <code class="inline">{Par,Val}</code> for all changed and added
│ │ │  configuration parameters, respectively.</li><li><code class="inline">Removed</code> is a list of all parameters <code class="inline">Par</code> that have been removed.</li></ul><p>The function is optional and can be omitted when implementing an application
│ │ │  callback module.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/release_structure.html
│ │ │ @@ -136,37 +136,37 @@
│ │ │    <a href="#release-resource-file" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Release Resource File</span>
│ │ │  </h2>
│ │ │  <p>To define a release, create a <em>release resource file</em>, or in short a <code class="inline">.rel</code>
│ │ │  file. In the file, specify the name and version of the release, which ERTS
│ │ │ -version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7600282394-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7600282394-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="7600282394-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7600282394-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="7600282394-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="7600282394-4">[</span><span class="p" data-group-id="7600282394-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="7600282394-5">}</span><span class="p">,</span><span class="w">
│ │ │ +version it is based on, and which applications it consists of:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8028320593-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8028320593-2">{</span><span class="n">Name</span><span class="p">,</span><span class="n">Vsn</span><span class="p" data-group-id="8028320593-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8028320593-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="n">EVsn</span><span class="p" data-group-id="8028320593-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8028320593-4">[</span><span class="p" data-group-id="8028320593-5">{</span><span class="n">Application1</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsn1</span><span class="p" data-group-id="8028320593-5">}</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7600282394-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="7600282394-6">}</span><span class="p" data-group-id="7600282394-4">]</span><span class="p" data-group-id="7600282394-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │ +  </span><span class="p" data-group-id="8028320593-6">{</span><span class="n">ApplicationN</span><span class="p">,</span><span class="w"> </span><span class="n">AppVsnN</span><span class="p" data-group-id="8028320593-6">}</span><span class="p" data-group-id="8028320593-4">]</span><span class="p" data-group-id="8028320593-1">}</span><span class="p">.</span></code></pre><p><code class="inline">Name</code>, <code class="inline">Vsn</code>, <code class="inline">EVsn</code>, and <code class="inline">AppVsn</code> are strings.</p><p>The file must be named <code class="inline">Rel.rel</code>, where <code class="inline">Rel</code> is a unique name.</p><p>Each <code class="inline">Application</code> (atom) and <code class="inline">AppVsn</code> is the name and version of an application
│ │ │  included in the release. The minimal release based on Erlang/OTP consists of the
│ │ │  Kernel and STDLIB applications, so these applications must be included in the
│ │ │  list.</p><p>If the release is to be upgraded, it must also include the SASL application.</p><p><a href="" id="ch_rel"></a></p><p>Here is an example showing the <code class="inline">.app</code> file for a release of <code class="inline">ch_app</code> from
│ │ │ -the <a href="applications.html#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1884582513-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1884582513-2">[</span><span class="p" data-group-id="1884582513-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="1884582513-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1884582513-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1884582513-4">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1884582513-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1884582513-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="1884582513-6">]</span><span class="p" data-group-id="1884582513-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1884582513-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1884582513-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="1884582513-8">]</span><span class="p" data-group-id="1884582513-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1884582513-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1884582513-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="1884582513-10">]</span><span class="p" data-group-id="1884582513-9">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1884582513-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1884582513-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="1884582513-13">[</span><span class="p" data-group-id="1884582513-13">]</span><span class="p" data-group-id="1884582513-12">}</span><span class="p" data-group-id="1884582513-11">}</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1884582513-2">]</span><span class="p" data-group-id="1884582513-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ -applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9090156170-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9090156170-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="9090156170-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9090156170-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="9090156170-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9090156170-4">[</span><span class="p" data-group-id="9090156170-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="9090156170-5">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9090156170-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="9090156170-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9090156170-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="9090156170-7">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9090156170-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="9090156170-8">}</span><span class="p" data-group-id="9090156170-4">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9090156170-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │ +the <a href="applications.html#ch_app">Applications</a> section:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6463729820-1">{</span><span class="ss">application</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_app</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6463729820-2">[</span><span class="p" data-group-id="6463729820-3">{</span><span class="ss">description</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Channel allocator&quot;</span><span class="p" data-group-id="6463729820-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6463729820-4">{</span><span class="ss">vsn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="6463729820-4">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6463729820-5">{</span><span class="ss">modules</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6463729820-6">[</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="ss">ch3</span><span class="p" data-group-id="6463729820-6">]</span><span class="p" data-group-id="6463729820-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6463729820-7">{</span><span class="ss">registered</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6463729820-8">[</span><span class="ss">ch3</span><span class="p" data-group-id="6463729820-8">]</span><span class="p" data-group-id="6463729820-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6463729820-9">{</span><span class="ss">applications</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6463729820-10">[</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="ss">sasl</span><span class="p" data-group-id="6463729820-10">]</span><span class="p" data-group-id="6463729820-9">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6463729820-11">{</span><span class="ss">mod</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6463729820-12">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="p" data-group-id="6463729820-13">[</span><span class="p" data-group-id="6463729820-13">]</span><span class="p" data-group-id="6463729820-12">}</span><span class="p" data-group-id="6463729820-11">}</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="6463729820-2">]</span><span class="p" data-group-id="6463729820-1">}</span><span class="p">.</span></code></pre><p>The <code class="inline">.rel</code> file must also contain <code class="inline">kernel</code>, <code class="inline">stdlib</code>, and <code class="inline">sasl</code>, as these
│ │ │ +applications are required by <code class="inline">ch_app</code>. The file is called <code class="inline">ch_rel-1.rel</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8882352117-1">{</span><span class="ss">release</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8882352117-2">{</span><span class="s">&quot;ch_rel&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;A&quot;</span><span class="p" data-group-id="8882352117-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8882352117-3">{</span><span class="ss">erts</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;14.2.5&quot;</span><span class="p" data-group-id="8882352117-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="8882352117-4">[</span><span class="p" data-group-id="8882352117-5">{</span><span class="ss">kernel</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;9.2.4&quot;</span><span class="p" data-group-id="8882352117-5">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8882352117-6">{</span><span class="ss">stdlib</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;5.2.3&quot;</span><span class="p" data-group-id="8882352117-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8882352117-7">{</span><span class="ss">sasl</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;4.2.1&quot;</span><span class="p" data-group-id="8882352117-7">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8882352117-8">{</span><span class="ss">ch_app</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8882352117-8">}</span><span class="p" data-group-id="8882352117-4">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8882352117-1">}</span><span class="p">.</span></code></pre><p><a href="" id="boot"></a></p><h2 id="generating-boot-scripts" class="section-heading">
│ │ │    <a href="#generating-boot-scripts" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Generating Boot Scripts</span>
│ │ │  </h2>
│ │ │  <p><a href="../../lib/sasl-4.2.2/doc/html/systools.html"><code class="inline">systools</code></a> in the SASL application includes tools to build and check
│ │ │  releases. The functions read the <code class="inline">.rel</code> and <code class="inline">.app</code> files and perform
│ │ │ @@ -190,17 +190,17 @@
│ │ │    <a href="#creating-a-release-package" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Creating a Release Package</span>
│ │ │  </h2>
│ │ │  <p>The <a href="../../lib/sasl-4.2.2/doc/html/systools.html#make_tar/2"><code class="inline">systools:make_tar/1,2</code></a> function takes a
│ │ │  <code class="inline">.rel</code> file as input and creates a zipped tar file with the code for
│ │ │ -the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="7546242651-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="7546242651-1">)</span><span class="p">.</span><span class="w">
│ │ │ +the specified applications, a <em>release package</em>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_script</span><span class="p" data-group-id="1286967539-1">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="1286967539-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="7546242651-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="7546242651-2">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="nc">systools</span><span class="p">:</span><span class="nf">make_tar</span><span class="p" data-group-id="1286967539-2">(</span><span class="s">&quot;ch_rel-1&quot;</span><span class="p" data-group-id="1286967539-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>The release package by default contains:</p><ul><li>The <code class="inline">.app</code> files</li><li>The <code class="inline">.rel</code> file</li><li>The object code for all applications, structured according to the
│ │ │  <a href="applications.html#app_dir">application directory structure</a></li><li>The binary boot script renamed to <code class="inline">start.boot</code></li></ul><pre><code class="text">% tar tf ch_rel-1.tar
│ │ │  lib/kernel-9.2.4/ebin/kernel.app
│ │ │  lib/kernel-9.2.4/ebin/application.beam
│ │ │  ...
│ │ │  lib/stdlib-5.2.3/ebin/stdlib.app
│ │ │  lib/stdlib-5.2.3/ebin/argparse.beam
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/robustness.html
│ │ │ @@ -128,68 +128,68 @@
│ │ │  </h2>
│ │ │  <p>Before improving the messenger program, let us look at some general principles,
│ │ │  using the ping pong program as an example. Recall that when &quot;ping&quot; finishes, it
│ │ │  tells &quot;pong&quot; that it has done so by sending the atom <code class="inline">finished</code> as a message to
│ │ │  &quot;pong&quot; so that &quot;pong&quot; can also finish. Another way to let &quot;pong&quot; finish is to
│ │ │  make &quot;pong&quot; exit if it does not receive a message from ping within a certain
│ │ │  time. This can be done by adding a <em>time-out</em> to <code class="inline">pong</code> as shown in the
│ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1739618949-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="1739618949-1">)</span><span class="p">.</span><span class="w">
│ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0026439005-1">(</span><span class="ss">tut19</span><span class="p" data-group-id="0026439005-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1739618949-2">(</span><span class="p" data-group-id="1739618949-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1739618949-3">]</span><span class="p" data-group-id="1739618949-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0026439005-2">(</span><span class="p" data-group-id="0026439005-3">[</span><span class="ss">start_ping</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">start_pong</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0026439005-3">]</span><span class="p" data-group-id="0026439005-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="1739618949-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739618949-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739618949-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739618949-6">[</span><span class="p" data-group-id="1739618949-6">]</span><span class="p" data-group-id="1739618949-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="0026439005-4">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0026439005-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0026439005-5">(</span><span class="s">&quot;ping finished</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0026439005-6">[</span><span class="p" data-group-id="0026439005-6">]</span><span class="p" data-group-id="0026439005-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="1739618949-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739618949-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1739618949-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739618949-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1739618949-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1739618949-10">(</span><span class="p" data-group-id="1739618949-10">)</span><span class="p" data-group-id="1739618949-9">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="0026439005-7">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0026439005-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0026439005-8">{</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0026439005-8">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0026439005-9">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0026439005-10">(</span><span class="p" data-group-id="0026439005-10">)</span><span class="p" data-group-id="0026439005-9">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739618949-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739618949-12">[</span><span class="p" data-group-id="1739618949-12">]</span><span class="p" data-group-id="1739618949-11">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0026439005-11">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0026439005-12">[</span><span class="p" data-group-id="0026439005-12">]</span><span class="p" data-group-id="0026439005-11">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping</span><span class="p" data-group-id="1739618949-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739618949-13">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping</span><span class="p" data-group-id="0026439005-13">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0026439005-13">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="1739618949-14">(</span><span class="p" data-group-id="1739618949-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="0026439005-14">(</span><span class="p" data-group-id="0026439005-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1739618949-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1739618949-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739618949-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739618949-17">[</span><span class="p" data-group-id="1739618949-17">]</span><span class="p" data-group-id="1739618949-16">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0026439005-15">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="0026439005-15">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0026439005-16">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0026439005-17">[</span><span class="p" data-group-id="0026439005-17">]</span><span class="p" data-group-id="0026439005-16">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="1739618949-18">(</span><span class="p" data-group-id="1739618949-18">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="0026439005-18">(</span><span class="p" data-group-id="0026439005-18">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1739618949-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739618949-20">[</span><span class="p" data-group-id="1739618949-20">]</span><span class="p" data-group-id="1739618949-19">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0026439005-19">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0026439005-20">[</span><span class="p" data-group-id="0026439005-20">]</span><span class="p" data-group-id="0026439005-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_pong</span><span class="p" data-group-id="1739618949-21">(</span><span class="p" data-group-id="1739618949-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="1739618949-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1739618949-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739618949-24">[</span><span class="p" data-group-id="1739618949-24">]</span><span class="p" data-group-id="1739618949-23">)</span><span class="p" data-group-id="1739618949-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_pong</span><span class="p" data-group-id="0026439005-21">(</span><span class="p" data-group-id="0026439005-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="0026439005-22">(</span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0026439005-23">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0026439005-24">[</span><span class="p" data-group-id="0026439005-24">]</span><span class="p" data-group-id="0026439005-23">)</span><span class="p" data-group-id="0026439005-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_ping</span><span class="p" data-group-id="1739618949-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="1739618949-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1739618949-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1739618949-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="1739618949-27">]</span><span class="p" data-group-id="1739618949-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │ +</span><span class="nf">start_ping</span><span class="p" data-group-id="0026439005-25">(</span><span class="n">Pong_Node</span><span class="p" data-group-id="0026439005-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="0026439005-26">(</span><span class="ss">tut19</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0026439005-27">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Node</span><span class="p" data-group-id="0026439005-27">]</span><span class="p" data-group-id="0026439005-26">)</span><span class="p">.</span></code></pre><p>After this is compiled and the file <code class="inline">tut19.beam</code> is copied to the necessary
│ │ │  directories, the following is seen on (pong@kosken):</p><pre><code class="text">(pong@kosken)1&gt; tut19:start_pong().
│ │ │  true
│ │ │  Pong received ping
│ │ │  Pong received ping
│ │ │  Pong received ping
│ │ │  Pong timed out</code></pre><p>And the following is seen on (ping@gollum):</p><pre><code class="text">(ping@gollum)1&gt; tut19:start_ping(pong@kosken).
│ │ │  &lt;0.36.0&gt;
│ │ │  Ping received pong
│ │ │  Ping received pong
│ │ │  Ping received pong
│ │ │ -ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="9263904405-1">(</span><span class="p" data-group-id="9263904405-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +ping finished</code></pre><p>The time-out is set in:</p><pre><code class="makeup erlang" translate="no"><span class="nf">pong</span><span class="p" data-group-id="6645099660-1">(</span><span class="p" data-group-id="6645099660-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9263904405-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9263904405-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9263904405-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9263904405-4">[</span><span class="p" data-group-id="9263904405-4">]</span><span class="p" data-group-id="9263904405-3">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6645099660-2">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="6645099660-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6645099660-3">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6645099660-4">[</span><span class="p" data-group-id="6645099660-4">]</span><span class="p" data-group-id="6645099660-3">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="9263904405-5">(</span><span class="p" data-group-id="9263904405-5">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="6645099660-5">(</span><span class="p" data-group-id="6645099660-5">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9263904405-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9263904405-7">[</span><span class="p" data-group-id="9263904405-7">]</span><span class="p" data-group-id="9263904405-6">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6645099660-6">(</span><span class="s">&quot;Pong timed out</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6645099660-7">[</span><span class="p" data-group-id="6645099660-7">]</span><span class="p" data-group-id="6645099660-6">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The time-out (<code class="inline">after 5000</code>) is started when <code class="inline">receive</code> is entered. The time-out
│ │ │  is canceled if <code class="inline">{ping,Ping_PID}</code> is received. If <code class="inline">{ping,Ping_PID}</code> is not
│ │ │  received, the actions following the time-out are done after 5000 milliseconds.
│ │ │  <code class="inline">after</code> must be last in the <code class="inline">receive</code>, that is, preceded by all other message
│ │ │  reception specifications in the <code class="inline">receive</code>. It is also possible to call a
│ │ │ -function that returned an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="2932179887-1">(</span><span class="p" data-group-id="2932179887-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │ +function that returned an integer for the time-out:</p><pre><code class="makeup erlang" translate="no"><span class="k">after</span><span class="w"> </span><span class="nf">pong_timeout</span><span class="p" data-group-id="6777562415-1">(</span><span class="p" data-group-id="6777562415-1">)</span><span class="w"> </span><span class="p">-&gt;</span></code></pre><p>In general, there are better ways than using time-outs to supervise parts of a
│ │ │  distributed Erlang system. Time-outs are usually appropriate to supervise
│ │ │  external events, for example, if you have expected a message from some external
│ │ │  system within a specified time. For example, a time-out can be used to log a
│ │ │  user out of the messenger system if they have not accessed it for, say, ten
│ │ │  minutes.</p><h2 id="error-handling" class="section-heading">
│ │ │    <a href="#error-handling" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -209,96 +209,96 @@
│ │ │  something called a <em>signal</em> to all the processes it has links to.</p><p>The signal carries information about the pid it was sent from and the exit
│ │ │  reason.</p><p>The default behaviour of a process that receives a normal exit is to ignore the
│ │ │  signal.</p><p>The default behaviour in the two other cases (that is, abnormal exit) above is
│ │ │  to:</p><ul><li>Bypass all messages to the receiving process.</li><li>Kill the receiving process.</li><li>Propagate the same error signal to the links of the killed process.</li></ul><p>In this way you can connect all processes in a transaction together using links.
│ │ │  If one of the processes exits abnormally, all the processes in the transaction
│ │ │  are killed. As it is often wanted to create a process and link to it at the same
│ │ │  time, there is a special BIF, <a href="../../erts-15.2.7.2/doc/html/erlang.html#spawn_link/1">spawn_link</a> that does the
│ │ │ -same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9679798075-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="9679798075-1">)</span><span class="p">.</span><span class="w">
│ │ │ +same as <code class="inline">spawn</code>, but also creates a link to the spawned process.</p><p>Now an example of the ping pong example using links to terminate &quot;pong&quot;:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9474704746-1">(</span><span class="ss">tut20</span><span class="p" data-group-id="9474704746-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9679798075-2">(</span><span class="p" data-group-id="9679798075-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9679798075-3">]</span><span class="p" data-group-id="9679798075-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9474704746-2">(</span><span class="p" data-group-id="9474704746-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9474704746-3">]</span><span class="p" data-group-id="9474704746-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="9679798075-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9679798075-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="9679798075-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="9679798075-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="9679798075-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9679798075-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="9474704746-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9474704746-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="9474704746-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="9474704746-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="9474704746-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9474704746-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="9679798075-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9679798075-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="9679798075-8">(</span><span class="ss">ping</span><span class="p" data-group-id="9679798075-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="9474704746-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9474704746-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="9474704746-8">(</span><span class="ss">ping</span><span class="p" data-group-id="9474704746-8">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="9679798075-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9679798075-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9679798075-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9679798075-11">(</span><span class="p" data-group-id="9679798075-11">)</span><span class="p" data-group-id="9679798075-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="9474704746-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9474704746-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9474704746-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="9474704746-11">(</span><span class="p" data-group-id="9474704746-11">)</span><span class="p" data-group-id="9474704746-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9679798075-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9679798075-13">[</span><span class="p" data-group-id="9679798075-13">]</span><span class="p" data-group-id="9679798075-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9474704746-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474704746-13">[</span><span class="p" data-group-id="9474704746-13">]</span><span class="p" data-group-id="9474704746-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="9679798075-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9679798075-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="9474704746-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="9474704746-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="9679798075-15">(</span><span class="p" data-group-id="9679798075-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="9474704746-15">(</span><span class="p" data-group-id="9474704746-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9679798075-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9679798075-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9679798075-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9679798075-18">[</span><span class="p" data-group-id="9679798075-18">]</span><span class="p" data-group-id="9679798075-17">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9474704746-16">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="9474704746-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9474704746-17">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474704746-18">[</span><span class="p" data-group-id="9474704746-18">]</span><span class="p" data-group-id="9474704746-17">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong</span><span class="p" data-group-id="9679798075-19">(</span><span class="p" data-group-id="9679798075-19">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong</span><span class="p" data-group-id="9474704746-19">(</span><span class="p" data-group-id="9474704746-19">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="9679798075-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="9679798075-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9679798075-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9679798075-22">[</span><span class="p" data-group-id="9679798075-22">]</span><span class="p" data-group-id="9679798075-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="9679798075-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9679798075-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="9679798075-24">]</span><span class="p" data-group-id="9679798075-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="9474704746-20">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="9474704746-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9474704746-21">(</span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474704746-22">[</span><span class="p" data-group-id="9474704746-22">]</span><span class="p" data-group-id="9474704746-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="9474704746-23">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut20</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9474704746-24">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="9474704746-24">]</span><span class="p" data-group-id="9474704746-23">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)3&gt; tut20:start(s2@kosken).
│ │ │  Pong received ping
│ │ │  &lt;3820.41.0&gt;
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong</code></pre><p>This is a slight modification of the ping pong program where both processes are
│ │ │  spawned from the same <code class="inline">start/1</code> function, and the &quot;ping&quot; process can be spawned
│ │ │  on a separate node. Notice the use of the <code class="inline">link</code> BIF. &quot;Ping&quot; calls
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#exit/1"><code class="inline">exit(ping)</code></a> when it finishes and this causes an exit signal to be
│ │ │  sent to &quot;pong&quot;, which also terminates.</p><p>It is possible to modify the default behaviour of a process so that it does not
│ │ │  get killed when it receives abnormal exit signals. Instead, all signals are
│ │ │  turned into normal messages on the format <code class="inline">{'EXIT',FromPID,Reason}</code> and added to
│ │ │ -the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="3082509033-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3082509033-1">)</span></code></pre><p>There are several other process flags, see <a href="../../erts-15.2.7.2/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │ +the end of the receiving process' message queue. This behaviour is set by:</p><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="7553552769-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7553552769-1">)</span></code></pre><p>There are several other process flags, see <a href="../../erts-15.2.7.2/doc/html/erlang.html#process_flag/2">erlang(3)</a>.
│ │ │  Changing the default behaviour of a process in this way is usually not done in
│ │ │  standard user programs, but is left to the supervisory programs in OTP. However,
│ │ │ -the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1610708460-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="1610708460-1">)</span><span class="p">.</span><span class="w">
│ │ │ +the ping pong program is modified to illustrate exit trapping.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5878526197-1">(</span><span class="ss">tut21</span><span class="p" data-group-id="5878526197-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1610708460-2">(</span><span class="p" data-group-id="1610708460-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1610708460-3">]</span><span class="p" data-group-id="1610708460-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5878526197-2">(</span><span class="p" data-group-id="5878526197-3">[</span><span class="ss">start</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w">  </span><span class="ss">ping</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5878526197-3">]</span><span class="p" data-group-id="5878526197-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping</span><span class="p" data-group-id="1610708460-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1610708460-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">link</span><span class="p" data-group-id="1610708460-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="1610708460-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="1610708460-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1610708460-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">ping</span><span class="p" data-group-id="5878526197-4">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5878526197-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">link</span><span class="p" data-group-id="5878526197-5">(</span><span class="n">Pong_Pid</span><span class="p" data-group-id="5878526197-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="5878526197-6">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5878526197-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="1610708460-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1610708460-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="1610708460-8">(</span><span class="ss">ping</span><span class="p" data-group-id="1610708460-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="5878526197-7">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5878526197-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="5878526197-8">(</span><span class="ss">ping</span><span class="p" data-group-id="5878526197-8">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">ping1</span><span class="p" data-group-id="1610708460-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1610708460-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1610708460-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1610708460-11">(</span><span class="p" data-group-id="1610708460-11">)</span><span class="p" data-group-id="1610708460-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">ping1</span><span class="p" data-group-id="5878526197-9">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5878526197-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Pong_Pid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5878526197-10">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5878526197-11">(</span><span class="p" data-group-id="5878526197-11">)</span><span class="p" data-group-id="5878526197-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">pong</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1610708460-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1610708460-13">[</span><span class="p" data-group-id="1610708460-13">]</span><span class="p" data-group-id="1610708460-12">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5878526197-12">(</span><span class="s">&quot;Ping received pong</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5878526197-13">[</span><span class="p" data-group-id="5878526197-13">]</span><span class="p" data-group-id="5878526197-12">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">ping1</span><span class="p" data-group-id="1610708460-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="1610708460-14">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">ping1</span><span class="p" data-group-id="5878526197-14">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">Pong_Pid</span><span class="p" data-group-id="5878526197-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong</span><span class="p" data-group-id="1610708460-15">(</span><span class="p" data-group-id="1610708460-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="1610708460-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1610708460-16">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">pong1</span><span class="p" data-group-id="1610708460-17">(</span><span class="p" data-group-id="1610708460-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">pong</span><span class="p" data-group-id="5878526197-15">(</span><span class="p" data-group-id="5878526197-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="5878526197-16">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5878526197-16">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">pong1</span><span class="p" data-group-id="5878526197-17">(</span><span class="p" data-group-id="5878526197-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">pong1</span><span class="p" data-group-id="1610708460-18">(</span><span class="p" data-group-id="1610708460-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">pong1</span><span class="p" data-group-id="5878526197-18">(</span><span class="p" data-group-id="5878526197-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1610708460-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="1610708460-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1610708460-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1610708460-21">[</span><span class="p" data-group-id="1610708460-21">]</span><span class="p" data-group-id="1610708460-20">)</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5878526197-19">{</span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="n">Ping_PID</span><span class="p" data-group-id="5878526197-19">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5878526197-20">(</span><span class="s">&quot;Pong received ping</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5878526197-21">[</span><span class="p" data-group-id="5878526197-21">]</span><span class="p" data-group-id="5878526197-20">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">Ping_PID</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">pong1</span><span class="p" data-group-id="1610708460-22">(</span><span class="p" data-group-id="1610708460-22">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1610708460-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1610708460-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1610708460-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1610708460-25">[</span><span class="p" data-group-id="1610708460-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="1610708460-26">}</span><span class="p" data-group-id="1610708460-25">]</span><span class="p" data-group-id="1610708460-24">)</span><span class="w">
│ │ │ +            </span><span class="nf">pong1</span><span class="p" data-group-id="5878526197-22">(</span><span class="p" data-group-id="5878526197-22">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="5878526197-23">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5878526197-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5878526197-24">(</span><span class="s">&quot;pong exiting, got </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5878526197-25">[</span><span class="p" data-group-id="5878526197-26">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="5878526197-26">}</span><span class="p" data-group-id="5878526197-25">]</span><span class="p" data-group-id="5878526197-24">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start</span><span class="p" data-group-id="1610708460-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="1610708460-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="1610708460-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1610708460-29">[</span><span class="p" data-group-id="1610708460-29">]</span><span class="p" data-group-id="1610708460-28">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="1610708460-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1610708460-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="1610708460-31">]</span><span class="p" data-group-id="1610708460-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │ +</span><span class="nf">start</span><span class="p" data-group-id="5878526197-27">(</span><span class="n">Ping_Node</span><span class="p" data-group-id="5878526197-27">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">PongPID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5878526197-28">(</span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">pong</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5878526197-29">[</span><span class="p" data-group-id="5878526197-29">]</span><span class="p" data-group-id="5878526197-28">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="5878526197-30">(</span><span class="n">Ping_Node</span><span class="p">,</span><span class="w"> </span><span class="ss">tut21</span><span class="p">,</span><span class="w"> </span><span class="ss">ping</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5878526197-31">[</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">PongPID</span><span class="p" data-group-id="5878526197-31">]</span><span class="p" data-group-id="5878526197-30">)</span><span class="p">.</span></code></pre><pre><code class="text">(s1@bill)1&gt; tut21:start(s2@gollum).
│ │ │  &lt;3820.39.0&gt;
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │  Pong received ping
│ │ │  Ping received pong
│ │ │ @@ -351,135 +351,135 @@
│ │ │  </span><span class="c1">%%% Started: messenger:client(Server_Node, Name)</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: logoff</span><span class="w">
│ │ │  </span><span class="c1">%%% To client: {message_to, ToName, Message}</span><span class="w">
│ │ │  </span><span class="c1">%%%</span><span class="w">
│ │ │  </span><span class="c1">%%% Configuration: change the server_node() function to return the</span><span class="w">
│ │ │  </span><span class="c1">%%% name of the node where the messenger server runs</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9607052694-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="9607052694-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9607052694-2">(</span><span class="p" data-group-id="9607052694-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9607052694-3">]</span><span class="p" data-group-id="9607052694-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7054614730-1">(</span><span class="ss">messenger</span><span class="p" data-group-id="7054614730-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7054614730-2">(</span><span class="p" data-group-id="7054614730-3">[</span><span class="ss">start_server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="ss">logon</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">logoff</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">message</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7054614730-3">]</span><span class="p" data-group-id="7054614730-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Change the function below to return the name of the node where the</span><span class="w">
│ │ │  </span><span class="c1">%%% messenger server runs</span><span class="w">
│ │ │ -</span><span class="nf">server_node</span><span class="p" data-group-id="9607052694-4">(</span><span class="p" data-group-id="9607052694-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_node</span><span class="p" data-group-id="7054614730-4">(</span><span class="p" data-group-id="7054614730-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">messenger@super</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% This is the server process for the &quot;messenger&quot;</span><span class="w">
│ │ │  </span><span class="c1">%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]</span><span class="w">
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="9607052694-5">(</span><span class="p" data-group-id="9607052694-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="9607052694-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9607052694-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="9607052694-7">(</span><span class="p" data-group-id="9607052694-8">[</span><span class="p" data-group-id="9607052694-8">]</span><span class="p" data-group-id="9607052694-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="7054614730-5">(</span><span class="p" data-group-id="7054614730-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="7054614730-6">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="7054614730-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="7054614730-7">(</span><span class="p" data-group-id="7054614730-8">[</span><span class="p" data-group-id="7054614730-8">]</span><span class="p" data-group-id="7054614730-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">server</span><span class="p" data-group-id="9607052694-9">(</span><span class="n">User_List</span><span class="p" data-group-id="9607052694-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server</span><span class="p" data-group-id="7054614730-9">(</span><span class="n">User_List</span><span class="p" data-group-id="7054614730-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9607052694-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="9607052694-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-11">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="9607052694-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9607052694-12">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9607052694-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="9607052694-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-14">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="9607052694-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="9607052694-15">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9607052694-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-17">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9607052694-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-19">[</span><span class="n">User_List</span><span class="p" data-group-id="9607052694-19">]</span><span class="p" data-group-id="9607052694-18">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">server</span><span class="p" data-group-id="9607052694-20">(</span><span class="n">User_List</span><span class="p" data-group-id="9607052694-20">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-10">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7054614730-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logon</span><span class="p" data-group-id="7054614730-11">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-11">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="7054614730-12">(</span><span class="n">New_User_List</span><span class="p" data-group-id="7054614730-12">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-13">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7054614730-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">New_User_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">server_logoff</span><span class="p" data-group-id="7054614730-14">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-14">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="7054614730-15">(</span><span class="n">New_User_List</span><span class="p" data-group-id="7054614730-15">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-16">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-16">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="7054614730-17">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-17">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7054614730-18">(</span><span class="s">&quot;list is now: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-19">[</span><span class="n">User_List</span><span class="p" data-group-id="7054614730-19">]</span><span class="p" data-group-id="7054614730-18">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">server</span><span class="p" data-group-id="7054614730-20">(</span><span class="n">User_List</span><span class="p" data-group-id="7054614730-20">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Start the server</span><span class="w">
│ │ │ -</span><span class="nf">start_server</span><span class="p" data-group-id="9607052694-21">(</span><span class="p" data-group-id="9607052694-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="9607052694-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="9607052694-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-24">[</span><span class="p" data-group-id="9607052694-24">]</span><span class="p" data-group-id="9607052694-23">)</span><span class="p" data-group-id="9607052694-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_server</span><span class="p" data-group-id="7054614730-21">(</span><span class="p" data-group-id="7054614730-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7054614730-22">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="7054614730-23">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">server</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-24">[</span><span class="p" data-group-id="7054614730-24">]</span><span class="p" data-group-id="7054614730-23">)</span><span class="p" data-group-id="7054614730-22">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server adds a new user to the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logon</span><span class="p" data-group-id="9607052694-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_logon</span><span class="p" data-group-id="7054614730-25">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check if logged on anywhere else</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="9607052694-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keymember</span><span class="p" data-group-id="7054614730-26">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-26">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="9607052694-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-27">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">user_exists_at_other_node</span><span class="p" data-group-id="7054614730-27">}</span><span class="p">,</span><span class="w">  </span><span class="c1">%reject logon</span><span class="w">
│ │ │              </span><span class="n">User_List</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="9607052694-28">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">link</span><span class="p" data-group-id="9607052694-29">(</span><span class="n">From</span><span class="p" data-group-id="9607052694-29">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9607052694-30">[</span><span class="p" data-group-id="9607052694-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9607052694-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-28">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">logged_on</span><span class="p" data-group-id="7054614730-28">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">link</span><span class="p" data-group-id="7054614730-29">(</span><span class="n">From</span><span class="p" data-group-id="7054614730-29">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7054614730-30">[</span><span class="p" data-group-id="7054614730-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7054614730-31">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-30">]</span><span class="w">        </span><span class="c1">%add user to the list</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Server deletes a user from the user list</span><span class="w">
│ │ │ -</span><span class="nf">server_logoff</span><span class="p" data-group-id="9607052694-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="9607052694-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-33">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">server_logoff</span><span class="p" data-group-id="7054614730-32">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keydelete</span><span class="p" data-group-id="7054614730-33">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-33">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  
│ │ │  </span><span class="c1">%%% Server transfers a message between user</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="9607052694-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="7054614730-34">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-34">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% check that the user is logged on and who he is</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9607052694-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7054614730-35">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-35">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="9607052694-36">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9607052694-38">}</span><span class="p" data-group-id="9607052694-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">server_transfer</span><span class="p" data-group-id="9607052694-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-39">)</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-36">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="ss">you_are_not_logged_on</span><span class="p" data-group-id="7054614730-36">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-37">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-38">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7054614730-38">}</span><span class="p" data-group-id="7054614730-37">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">server_transfer</span><span class="p" data-group-id="7054614730-39">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-39">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% If the user exists, send the message</span><span class="w">
│ │ │ -</span><span class="nf">server_transfer</span><span class="p" data-group-id="9607052694-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">server_transfer</span><span class="p" data-group-id="7054614730-40">(</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-40">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Find the receiver and send the message</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="9607052694-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="9607052694-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">keysearch</span><span class="p" data-group-id="7054614730-41">(</span><span class="n">To</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">User_List</span><span class="p" data-group-id="7054614730-41">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">false</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="9607052694-42">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="9607052694-44">}</span><span class="p" data-group-id="9607052694-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-45">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-45">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-46">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="9607052694-46">}</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-42">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">receiver_not_found</span><span class="p" data-group-id="7054614730-42">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-43">{</span><span class="ss">value</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-44">{</span><span class="n">ToPid</span><span class="p">,</span><span class="w"> </span><span class="n">To</span><span class="p" data-group-id="7054614730-44">}</span><span class="p" data-group-id="7054614730-43">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">ToPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-45">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-45">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-46">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">sent</span><span class="p" data-group-id="7054614730-46">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% User Commands</span><span class="w">
│ │ │ -</span><span class="nf">logon</span><span class="p" data-group-id="9607052694-47">(</span><span class="n">Name</span><span class="p" data-group-id="9607052694-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9607052694-48">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9607052694-48">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">logon</span><span class="p" data-group-id="7054614730-47">(</span><span class="n">Name</span><span class="p" data-group-id="7054614730-47">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="7054614730-48">(</span><span class="ss">mess_client</span><span class="p" data-group-id="7054614730-48">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="9607052694-49">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="nf">spawn</span><span class="p" data-group-id="9607052694-50">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-51">[</span><span class="nf">server_node</span><span class="p" data-group-id="9607052694-52">(</span><span class="p" data-group-id="9607052694-52">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9607052694-51">]</span><span class="p" data-group-id="9607052694-50">)</span><span class="p" data-group-id="9607052694-49">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="7054614730-49">(</span><span class="ss">mess_client</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="nf">spawn</span><span class="p" data-group-id="7054614730-50">(</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">client</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-51">[</span><span class="nf">server_node</span><span class="p" data-group-id="7054614730-52">(</span><span class="p" data-group-id="7054614730-52">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7054614730-51">]</span><span class="p" data-group-id="7054614730-50">)</span><span class="p" data-group-id="7054614730-49">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">already_logged_on</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">logoff</span><span class="p" data-group-id="9607052694-53">(</span><span class="p" data-group-id="9607052694-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">logoff</span><span class="p" data-group-id="7054614730-53">(</span><span class="p" data-group-id="7054614730-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="ss">logoff</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">message</span><span class="p" data-group-id="9607052694-54">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-54">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9607052694-55">(</span><span class="ss">mess_client</span><span class="p" data-group-id="9607052694-55">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │ +</span><span class="nf">message</span><span class="p" data-group-id="7054614730-54">(</span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-54">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="7054614730-55">(</span><span class="ss">mess_client</span><span class="p" data-group-id="7054614730-55">)</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="c1">% Test if the client is running</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_logged_on</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-56">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-56">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">mess_client</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-56">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-56">}</span><span class="p">,</span><span class="w">
│ │ │               </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% The client process which runs on each user node</span><span class="w">
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="9607052694-57">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9607052694-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9607052694-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9607052694-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-59">{</span><span class="nf">self</span><span class="p" data-group-id="9607052694-60">(</span><span class="p" data-group-id="9607052694-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="9607052694-59">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">await_result</span><span class="p" data-group-id="9607052694-61">(</span><span class="p" data-group-id="9607052694-61">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="9607052694-62">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9607052694-62">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="7054614730-57">(</span><span class="n">Server_Node</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7054614730-57">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7054614730-58">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="7054614730-58">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-59">{</span><span class="nf">self</span><span class="p" data-group-id="7054614730-60">(</span><span class="p" data-group-id="7054614730-60">)</span><span class="p">,</span><span class="w"> </span><span class="ss">logon</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7054614730-59">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">await_result</span><span class="p" data-group-id="7054614730-61">(</span><span class="p" data-group-id="7054614730-61">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="7054614730-62">(</span><span class="n">Server_Node</span><span class="p" data-group-id="7054614730-62">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="9607052694-63">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9607052694-63">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="7054614730-63">(</span><span class="n">Server_Node</span><span class="p" data-group-id="7054614730-63">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="ss">logoff</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="9607052694-64">(</span><span class="ss">normal</span><span class="p" data-group-id="9607052694-64">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-65">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-65">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9607052694-66">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="9607052694-66">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9607052694-67">{</span><span class="nf">self</span><span class="p" data-group-id="9607052694-68">(</span><span class="p" data-group-id="9607052694-68">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-67">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">await_result</span><span class="p" data-group-id="9607052694-69">(</span><span class="p" data-group-id="9607052694-69">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-70">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-70">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9607052694-71">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-72">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="9607052694-72">]</span><span class="p" data-group-id="9607052694-71">)</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="7054614730-64">(</span><span class="ss">normal</span><span class="p" data-group-id="7054614730-64">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-65">{</span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-65">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7054614730-66">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">Server_Node</span><span class="p" data-group-id="7054614730-66">}</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7054614730-67">{</span><span class="nf">self</span><span class="p" data-group-id="7054614730-68">(</span><span class="p" data-group-id="7054614730-68">)</span><span class="p">,</span><span class="w"> </span><span class="ss">message_to</span><span class="p">,</span><span class="w"> </span><span class="n">ToName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-67">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">await_result</span><span class="p" data-group-id="7054614730-69">(</span><span class="p" data-group-id="7054614730-69">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-70">{</span><span class="ss">message_from</span><span class="p">,</span><span class="w"> </span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-70">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7054614730-71">(</span><span class="s">&quot;Message from </span><span class="si">~p</span><span class="s">: </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-72">[</span><span class="n">FromName</span><span class="p">,</span><span class="w"> </span><span class="n">Message</span><span class="p" data-group-id="7054614730-72">]</span><span class="p" data-group-id="7054614730-71">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">client</span><span class="p" data-group-id="9607052694-73">(</span><span class="n">Server_Node</span><span class="p" data-group-id="9607052694-73">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">client</span><span class="p" data-group-id="7054614730-73">(</span><span class="n">Server_Node</span><span class="p" data-group-id="7054614730-73">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% wait for a response from the server</span><span class="w">
│ │ │ -</span><span class="nf">await_result</span><span class="p" data-group-id="9607052694-74">(</span><span class="p" data-group-id="9607052694-74">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">await_result</span><span class="p" data-group-id="7054614730-74">(</span><span class="p" data-group-id="7054614730-74">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-75">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="9607052694-75">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9607052694-76">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-77">[</span><span class="n">Why</span><span class="p" data-group-id="9607052694-77">]</span><span class="p" data-group-id="9607052694-76">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="9607052694-78">(</span><span class="ss">normal</span><span class="p" data-group-id="9607052694-78">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="9607052694-79">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="9607052694-79">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9607052694-80">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-81">[</span><span class="n">What</span><span class="p" data-group-id="9607052694-81">]</span><span class="p" data-group-id="9607052694-80">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-75">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="ss">stop</span><span class="p">,</span><span class="w"> </span><span class="n">Why</span><span class="p" data-group-id="7054614730-75">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Stop the client</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7054614730-76">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-77">[</span><span class="n">Why</span><span class="p" data-group-id="7054614730-77">]</span><span class="p" data-group-id="7054614730-76">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="7054614730-78">(</span><span class="ss">normal</span><span class="p" data-group-id="7054614730-78">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7054614730-79">{</span><span class="ss">messenger</span><span class="p">,</span><span class="w"> </span><span class="n">What</span><span class="p" data-group-id="7054614730-79">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Normal response</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7054614730-80">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-81">[</span><span class="n">What</span><span class="p" data-group-id="7054614730-81">]</span><span class="p" data-group-id="7054614730-80">)</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9607052694-82">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9607052694-83">[</span><span class="p" data-group-id="9607052694-83">]</span><span class="p" data-group-id="9607052694-82">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="9607052694-84">(</span><span class="ss">timeout</span><span class="p" data-group-id="9607052694-84">)</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7054614730-82">(</span><span class="s">&quot;No response from server</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7054614730-83">[</span><span class="p" data-group-id="7054614730-83">]</span><span class="p" data-group-id="7054614730-82">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="7054614730-84">(</span><span class="ss">timeout</span><span class="p" data-group-id="7054614730-84">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The following changes are added:</p><p>The messenger server traps exits. If it receives an exit signal,
│ │ │  <code class="inline">{'EXIT',From,Reason}</code>, this means that a client process has terminated or is
│ │ │  unreachable for one of the following reasons:</p><ul><li>The user has logged off (the &quot;logoff&quot; message is removed).</li><li>The network connection to the client is broken.</li><li>The node on which the client process resides has gone down.</li><li>The client processes has done some illegal operation.</li></ul><p>If an exit signal is received as above, the tuple <code class="inline">{From,Name}</code> is deleted from
│ │ │  the servers <code class="inline">User_List</code> using the <code class="inline">server_logoff</code> function. If the node on which
│ │ │  the server runs goes down, an exit signal (automatically generated by the
│ │ │  system) is sent to all of the client processes:
│ │ │  <code class="inline">{'EXIT',MessengerPID,noconnection}</code> causing all the client processes to
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/search.html
│ │ │ @@ -108,15 +108,15 @@
│ │ │  <div id="search">
│ │ │    <h1>
│ │ │      <span></span>
│ │ │    </h1>
│ │ │  
│ │ │    <div class="loading"><div></div><div></div><div></div><div></div></div>
│ │ │  </div>
│ │ │ -<script src="dist/search_data-3853893B.js"></script>
│ │ │ +<script src="dist/search_data-DBFDB6FD.js"></script>
│ │ │      <footer class="footer">
│ │ │        <p>
│ │ │  
│ │ │          <span class="line">
│ │ │            <button class="a-main footer-button display-quick-switch" title="Search HexDocs packages">
│ │ │              Search HexDocs
│ │ │            </button>
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/seq_prog.html
│ │ │ @@ -136,293 +136,293 @@
│ │ │  </span><span class="mi">7</span><span class="gp unselectable">
│ │ │  2&gt; </span></code></pre><p>As shown, the Erlang shell numbers the lines that can be entered, (as 1&gt; 2&gt;) and
│ │ │  that it correctly says that 2 + 5 is 7. If you make writing mistakes in the
│ │ │  shell, you can delete with the backspace key, as in most shells. There are many
│ │ │  more editing commands in the shell (see
│ │ │  <a href="../../erts-15.2.7.2/doc/html/tty.html">tty - A command line interface</a> in ERTS User's Guide).</p><p>(Notice that many line numbers given by the shell in the following examples are
│ │ │  out of sequence. This is because this tutorial was written and code-tested in
│ │ │ -separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="1144630429-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="1144630429-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │ +separate sessions).</p><p>Here is a bit more complex calculation:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">2&gt; </span><span class="p" data-group-id="0960499030-1">(</span><span class="mi">42</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">77</span><span class="p" data-group-id="0960499030-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">66</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">3</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">2618.0</span></code></pre><p>Notice the use of brackets, the multiplication operator <code class="inline">*</code>, and the division
│ │ │  operator <code class="inline">/</code>, as in normal arithmetic (see
│ │ │  <a href="../../doc/system/expressions.html">Expressions</a>).</p><p>Press Control-C to shut down the Erlang system and the Erlang shell.</p><p>The following output is shown:</p><pre><code class="text">BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
│ │ │         (v)ersion (k)ill (D)b-tables (d)istribution
│ │ │  a
│ │ │ -$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../erts-15.2.7.2/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="5703215658-1">(</span><span class="p" data-group-id="5703215658-1">)</span><span class="p">.</span><span class="w">
│ │ │ +$</code></pre><p>Type <code class="inline">a</code> to leave the Erlang system.</p><p>Another way to shut down the Erlang system is by entering <a href="../../erts-15.2.7.2/doc/html/erlang.html#halt/0"><code class="inline">halt/0</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">halt</span><span class="p" data-group-id="9948274193-1">(</span><span class="p" data-group-id="9948274193-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="err">$</span></code></pre><h2 id="modules-and-functions" class="section-heading">
│ │ │    <a href="#modules-and-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Modules and Functions</span>
│ │ │  </h2>
│ │ │  <p>A programming language is not much use if you only can run code from the shell.
│ │ │  So here is a small Erlang program. Enter it into a file named <code class="inline">tut.erl</code> using a
│ │ │  suitable text editor. The file name <code class="inline">tut.erl</code> is important, and also that it is
│ │ │  in the same directory as the one where you started <code class="inline">erl</code>). If you are lucky your
│ │ │  editor has an Erlang mode that makes it easier for you to enter and format your
│ │ │  code nicely (see <a href="../../lib/tools-4.1.1/doc/html/erlang_mode_chapter.html">The Erlang mode for Emacs</a>
│ │ │  in Tools User's Guide), but you can manage perfectly well without. Here is the
│ │ │ -code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4673601237-1">(</span><span class="ss">tut</span><span class="p" data-group-id="4673601237-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4673601237-2">(</span><span class="p" data-group-id="4673601237-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4673601237-3">]</span><span class="p" data-group-id="4673601237-2">)</span><span class="p">.</span><span class="w">
│ │ │ +code to enter:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8796671090-1">(</span><span class="ss">tut</span><span class="p" data-group-id="8796671090-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8796671090-2">(</span><span class="p" data-group-id="8796671090-3">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8796671090-3">]</span><span class="p" data-group-id="8796671090-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">double</span><span class="p" data-group-id="4673601237-4">(</span><span class="n">X</span><span class="p" data-group-id="4673601237-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">double</span><span class="p" data-group-id="8796671090-4">(</span><span class="n">X</span><span class="p" data-group-id="8796671090-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">2</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">X</span><span class="p">.</span></code></pre><p>It is not hard to guess that this program doubles the value of numbers. The
│ │ │  first two lines of the code are described later. Let us compile the program.
│ │ │ -This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="5480935102-1">(</span><span class="ss">tut</span><span class="p" data-group-id="5480935102-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5480935102-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="5480935102-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │ +This can be done in an Erlang shell as follows, where <code class="inline">c</code> means compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">3&gt; </span><span class="nf">c</span><span class="p" data-group-id="0948734825-1">(</span><span class="ss">tut</span><span class="p" data-group-id="0948734825-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0948734825-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut</span><span class="p" data-group-id="0948734825-2">}</span></code></pre><p>The <code class="inline">{ok,tut}</code> means that the compilation is OK. If it says <code class="inline">error</code> it means
│ │ │  that there is some mistake in the text that you entered. Additional error
│ │ │  messages gives an idea to what is wrong so you can modify the text and then try
│ │ │ -to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="9346297740-1">(</span><span class="mi">10</span><span class="p" data-group-id="9346297740-1">)</span><span class="p">.</span><span class="w">
│ │ │ +to compile the program again.</p><p>Now run the program:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="9924719309-1">(</span><span class="mi">10</span><span class="p" data-group-id="9924719309-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">20</span></code></pre><p>As expected, double of 10 is 20.</p><p>Now let us get back to the first two lines of the code. Erlang programs are
│ │ │  written in files. Each file contains an Erlang <em>module</em>. The first line of code
│ │ │ -in the module is the module name (see <a href="../../doc/system/modules.html">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1979572708-1">(</span><span class="ss">tut</span><span class="p" data-group-id="1979572708-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │ +in the module is the module name (see <a href="../../doc/system/modules.html">Modules</a>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0104637826-1">(</span><span class="ss">tut</span><span class="p" data-group-id="0104637826-1">)</span><span class="p">.</span></code></pre><p>Thus, the module is called <em>tut</em>. Notice the full stop <code class="inline">.</code> at the end of the
│ │ │  line. The files which are used to store the module must have the same name as
│ │ │  the module but with the extension <code class="inline">.erl</code>. In this case the file name is
│ │ │  <code class="inline">tut.erl</code>. When using a function in another module, the syntax
│ │ │  <code class="inline">module_name:function_name(arguments)</code> is used. So the following means call
│ │ │ -function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="3254985770-1">(</span><span class="mi">10</span><span class="p" data-group-id="3254985770-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ -which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1232626309-1">(</span><span class="p" data-group-id="1232626309-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1232626309-2">]</span><span class="p" data-group-id="1232626309-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │ +function <code class="inline">double</code> in module <code class="inline">tut</code> with argument <code class="inline">10</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">4&gt; </span><span class="nc">tut</span><span class="p">:</span><span class="nf">double</span><span class="p" data-group-id="6465894334-1">(</span><span class="mi">10</span><span class="p" data-group-id="6465894334-1">)</span><span class="p">.</span></code></pre><p>The second line says that the module <code class="inline">tut</code> contains a function called <code class="inline">double</code>,
│ │ │ +which takes one argument (<code class="inline">X</code> in our example):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0636470296-1">(</span><span class="p" data-group-id="0636470296-2">[</span><span class="ss">double</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0636470296-2">]</span><span class="p" data-group-id="0636470296-1">)</span><span class="p">.</span></code></pre><p>The second line also says that this function can be called from outside the
│ │ │  module <code class="inline">tut</code>. More about this later. Again, notice the <code class="inline">.</code> at the end of the
│ │ │  line.</p><p>Now for a more complicated example, the factorial of a number. For example, the
│ │ │ -factorial of 4 is 4 <em> 3 </em> 2 * 1, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8633553876-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="8633553876-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8633553876-2">(</span><span class="p" data-group-id="8633553876-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8633553876-3">]</span><span class="p" data-group-id="8633553876-2">)</span><span class="p">.</span><span class="w">
│ │ │ +factorial of 4 is 4 <em> 3 </em> 2 * 1, which equals 24.</p><p>Enter the following code in a file named <code class="inline">tut1.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4430800840-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="4430800840-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4430800840-2">(</span><span class="p" data-group-id="4430800840-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4430800840-3">]</span><span class="p" data-group-id="4430800840-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="8633553876-4">(</span><span class="mi">1</span><span class="p" data-group-id="8633553876-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="4430800840-4">(</span><span class="mi">1</span><span class="p" data-group-id="4430800840-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="8633553876-5">(</span><span class="n">N</span><span class="p" data-group-id="8633553876-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="8633553876-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8633553876-6">)</span><span class="p">.</span></code></pre><p>So this is a module, called <code class="inline">tut1</code> that contains a function called <code class="inline">fac&gt;</code>, which
│ │ │ -takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1.:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="0703686536-1">(</span><span class="mi">1</span><span class="p" data-group-id="0703686536-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="4430800840-5">(</span><span class="n">N</span><span class="p" data-group-id="4430800840-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="4430800840-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4430800840-6">)</span><span class="p">.</span></code></pre><p>So this is a module, called <code class="inline">tut1</code> that contains a function called <code class="inline">fac&gt;</code>, which
│ │ │ +takes one argument, <code class="inline">N</code>.</p><p>The first part says that the factorial of 1 is 1.:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="0511589787-1">(</span><span class="mi">1</span><span class="p" data-group-id="0511589787-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">;</span></code></pre><p>Notice that this part ends with a semicolon <code class="inline">;</code> that indicates that there is
│ │ │  more of the function <code class="inline">fac&gt;</code> to come.</p><p>The second part says that the factorial of N is N multiplied by the factorial of
│ │ │ -N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="8874135909-1">(</span><span class="n">N</span><span class="p" data-group-id="8874135909-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="8874135909-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="8874135909-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ -this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="4107864379-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="4107864379-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4107864379-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="4107864379-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="8397214275-1">(</span><span class="mi">4</span><span class="p" data-group-id="8397214275-1">)</span><span class="p">.</span><span class="w">
│ │ │ +N - 1:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fac</span><span class="p" data-group-id="9938017069-1">(</span><span class="n">N</span><span class="p" data-group-id="9938017069-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="9938017069-2">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9938017069-2">)</span><span class="p">.</span></code></pre><p>Notice that this part ends with a <code class="inline">.</code> saying that there are no more parts of
│ │ │ +this function.</p><p>Compile the file:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">5&gt; </span><span class="nf">c</span><span class="p" data-group-id="2029185930-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="2029185930-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2029185930-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="2029185930-2">}</span></code></pre><p>And now calculate the factorial of 4.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">fac</span><span class="p" data-group-id="9229551341-1">(</span><span class="mi">4</span><span class="p" data-group-id="9229551341-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">24</span></code></pre><p>Here the function <code class="inline">fac&gt;</code> in module <code class="inline">tut1</code> is called with argument <code class="inline">4</code>.</p><p>A function can have many arguments. Let us expand the module <code class="inline">tut1</code> with the
│ │ │ -function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1414473816-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1414473816-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1414473816-2">(</span><span class="p" data-group-id="1414473816-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1414473816-3">]</span><span class="p" data-group-id="1414473816-2">)</span><span class="p">.</span><span class="w">
│ │ │ +function to multiply two numbers:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0849487506-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="0849487506-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0849487506-2">(</span><span class="p" data-group-id="0849487506-3">[</span><span class="ss">fac</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">mult</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0849487506-3">]</span><span class="p" data-group-id="0849487506-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="1414473816-4">(</span><span class="mi">1</span><span class="p" data-group-id="1414473816-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="0849487506-4">(</span><span class="mi">1</span><span class="p" data-group-id="0849487506-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">fac</span><span class="p" data-group-id="1414473816-5">(</span><span class="n">N</span><span class="p" data-group-id="1414473816-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="1414473816-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1414473816-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">fac</span><span class="p" data-group-id="0849487506-5">(</span><span class="n">N</span><span class="p" data-group-id="0849487506-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="nf">fac</span><span class="p" data-group-id="0849487506-6">(</span><span class="n">N</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0849487506-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">mult</span><span class="p" data-group-id="1414473816-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="1414473816-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">mult</span><span class="p" data-group-id="0849487506-7">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0849487506-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">Y</span><span class="p">.</span></code></pre><p>Notice that it is also required to expand the <code class="inline">-export</code> line with the
│ │ │ -information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="1537928103-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="1537928103-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1537928103-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="1537928103-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="6638412620-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6638412620-1">)</span><span class="p">.</span><span class="w">
│ │ │ +information that there is another function <code class="inline">mult</code> with two arguments.</p><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">7&gt; </span><span class="nf">c</span><span class="p" data-group-id="7089564729-1">(</span><span class="ss">tut1</span><span class="p" data-group-id="7089564729-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7089564729-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut1</span><span class="p" data-group-id="7089564729-2">}</span></code></pre><p>Try out the new function <code class="inline">mult</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">8&gt; </span><span class="nc">tut1</span><span class="p">:</span><span class="nf">mult</span><span class="p" data-group-id="2010022548-1">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2010022548-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">12</span></code></pre><p>In this example the numbers are integers and the arguments in the functions in
│ │ │  the code <code class="inline">N</code>, <code class="inline">X</code>, and <code class="inline">Y</code> are called variables. Variables must start with a
│ │ │  capital letter (see <a href="../../doc/system/expressions.html">Variables</a>). Examples of
│ │ │  variables are <code class="inline">Number</code>, <code class="inline">ShoeSize</code>, and <code class="inline">Age</code>.</p><h2 id="atoms" class="section-heading">
│ │ │    <a href="#atoms" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Atoms</span>
│ │ │  </h2>
│ │ │  <p>Atom is another data type in Erlang. Atoms start with a small letter (see
│ │ │  <a href="../../doc/system/data_types.html">Atom</a>), for example, <code class="inline">charles</code>, <code class="inline">centimeter</code>, and
│ │ │  <code class="inline">inch</code>. Atoms are simply names, nothing else. They are not like variables, which
│ │ │  can have a value.</p><p>Enter the next program in a file named <code class="inline">tut2.erl</code>). It can be useful for
│ │ │ -converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1704386148-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="1704386148-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1704386148-2">(</span><span class="p" data-group-id="1704386148-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1704386148-3">]</span><span class="p" data-group-id="1704386148-2">)</span><span class="p">.</span><span class="w">
│ │ │ +converting from inches to centimeters and conversely:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1038253010-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="1038253010-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1038253010-2">(</span><span class="p" data-group-id="1038253010-3">[</span><span class="ss">convert</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1038253010-3">]</span><span class="p" data-group-id="1038253010-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="1704386148-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="1704386148-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="1038253010-4">(</span><span class="n">M</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="1038253010-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">M</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert</span><span class="p" data-group-id="1704386148-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="1704386148-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="9726308367-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="9726308367-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9726308367-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="9726308367-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="2592421684-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="2592421684-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">convert</span><span class="p" data-group-id="1038253010-5">(</span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="1038253010-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">N</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p">.</span></code></pre><p>Compile:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">9&gt; </span><span class="nf">c</span><span class="p" data-group-id="5409506520-1">(</span><span class="ss">tut2</span><span class="p" data-group-id="5409506520-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5409506520-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut2</span><span class="p" data-group-id="5409506520-2">}</span></code></pre><p>Test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">10&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="5598727428-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="5598727428-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">1.1811023622047243</span><span class="gp unselectable">
│ │ │ -11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="2592421684-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="2592421684-2">)</span><span class="p">.</span><span class="w">
│ │ │ +11&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="5598727428-2">(</span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="ss">centimeter</span><span class="p" data-group-id="5598727428-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">17.78</span></code></pre><p>Notice the introduction of decimals (floating point numbers) without any
│ │ │  explanation. Hopefully you can cope with that.</p><p>Let us see what happens if something other than <code class="inline">centimeter</code> or <code class="inline">inch</code> is
│ │ │ -entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="9140798265-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="9140798265-1">)</span><span class="p">.</span><span class="w">
│ │ │ +entered in the <code class="inline">convert</code> function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">12&gt; </span><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="5926659932-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">miles</span><span class="p" data-group-id="5926659932-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no function clause matching tut2:convert(3,miles) (tut2.erl, line 4)</span></code></pre><p>The two parts of the <code class="inline">convert</code> function are called its clauses. As shown,
│ │ │  <code class="inline">miles</code> is not part of either of the clauses. The Erlang system cannot <em>match</em>
│ │ │  either of the clauses so an error message <code class="inline">function_clause</code> is returned. The
│ │ │  shell formats the error message nicely, but the error tuple is saved in the
│ │ │ -shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="2996172640-1">(</span><span class="mi">12</span><span class="p" data-group-id="2996172640-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2996172640-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="2996172640-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="2996172640-4">[</span><span class="p" data-group-id="2996172640-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ -                                </span><span class="p" data-group-id="2996172640-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="2996172640-6">]</span><span class="p">,</span><span class="w">
│ │ │ -                                </span><span class="p" data-group-id="2996172640-7">[</span><span class="p" data-group-id="2996172640-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="2996172640-8">}</span><span class="p">,</span><span class="p" data-group-id="2996172640-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="2996172640-9">}</span><span class="p" data-group-id="2996172640-7">]</span><span class="p" data-group-id="2996172640-5">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="2996172640-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="2996172640-11">[</span><span class="p" data-group-id="2996172640-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="2996172640-12">}</span><span class="p">,</span><span class="p" data-group-id="2996172640-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="2996172640-13">}</span><span class="p" data-group-id="2996172640-11">]</span><span class="p" data-group-id="2996172640-10">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="2996172640-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="2996172640-15">[</span><span class="p" data-group-id="2996172640-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="2996172640-16">}</span><span class="p">,</span><span class="p" data-group-id="2996172640-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="2996172640-17">}</span><span class="p" data-group-id="2996172640-15">]</span><span class="p" data-group-id="2996172640-14">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="2996172640-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="2996172640-19">[</span><span class="p" data-group-id="2996172640-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="2996172640-20">}</span><span class="p">,</span><span class="p" data-group-id="2996172640-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="2996172640-21">}</span><span class="p" data-group-id="2996172640-19">]</span><span class="p" data-group-id="2996172640-18">}</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="2996172640-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                 </span><span class="p" data-group-id="2996172640-23">[</span><span class="p" data-group-id="2996172640-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="2996172640-24">}</span><span class="p">,</span><span class="p" data-group-id="2996172640-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="2996172640-25">}</span><span class="p" data-group-id="2996172640-23">]</span><span class="p" data-group-id="2996172640-22">}</span><span class="p" data-group-id="2996172640-4">]</span><span class="p" data-group-id="2996172640-3">}</span><span class="p" data-group-id="2996172640-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │ +shell's history list and can be output by the shell command <code class="inline">v/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">13&gt; </span><span class="nf">v</span><span class="p" data-group-id="3572987158-1">(</span><span class="mi">12</span><span class="p" data-group-id="3572987158-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3572987158-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="3572987158-3">{</span><span class="ss">function_clause</span><span class="p">,</span><span class="p" data-group-id="3572987158-4">[</span><span class="p" data-group-id="3572987158-5">{</span><span class="ss">tut2</span><span class="p">,</span><span class="ss">convert</span><span class="p">,</span><span class="w">
│ │ │ +                                </span><span class="p" data-group-id="3572987158-6">[</span><span class="mi">3</span><span class="p">,</span><span class="ss">miles</span><span class="p" data-group-id="3572987158-6">]</span><span class="p">,</span><span class="w">
│ │ │ +                                </span><span class="p" data-group-id="3572987158-7">[</span><span class="p" data-group-id="3572987158-8">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;tut2.erl&quot;</span><span class="p" data-group-id="3572987158-8">}</span><span class="p">,</span><span class="p" data-group-id="3572987158-9">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3572987158-9">}</span><span class="p" data-group-id="3572987158-7">]</span><span class="p" data-group-id="3572987158-5">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="3572987158-10">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="3572987158-11">[</span><span class="p" data-group-id="3572987158-12">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="3572987158-12">}</span><span class="p">,</span><span class="p" data-group-id="3572987158-13">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="3572987158-13">}</span><span class="p" data-group-id="3572987158-11">]</span><span class="p" data-group-id="3572987158-10">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="3572987158-14">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="3572987158-15">[</span><span class="p" data-group-id="3572987158-16">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="3572987158-16">}</span><span class="p">,</span><span class="p" data-group-id="3572987158-17">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="3572987158-17">}</span><span class="p" data-group-id="3572987158-15">]</span><span class="p" data-group-id="3572987158-14">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="3572987158-18">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="3572987158-19">[</span><span class="p" data-group-id="3572987158-20">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="3572987158-20">}</span><span class="p">,</span><span class="p" data-group-id="3572987158-21">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="3572987158-21">}</span><span class="p" data-group-id="3572987158-19">]</span><span class="p" data-group-id="3572987158-18">}</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="3572987158-22">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                 </span><span class="p" data-group-id="3572987158-23">[</span><span class="p" data-group-id="3572987158-24">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="3572987158-24">}</span><span class="p">,</span><span class="p" data-group-id="3572987158-25">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="3572987158-25">}</span><span class="p" data-group-id="3572987158-23">]</span><span class="p" data-group-id="3572987158-22">}</span><span class="p" data-group-id="3572987158-4">]</span><span class="p" data-group-id="3572987158-3">}</span><span class="p" data-group-id="3572987158-2">}</span></code></pre><h2 id="tuples" class="section-heading">
│ │ │    <a href="#tuples" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Tuples</span>
│ │ │  </h2>
│ │ │ -<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="6324052852-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="6324052852-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │ +<p>Now the <code class="inline">tut2</code> program is hardly good programming style. Consider:</p><pre><code class="makeup erlang" translate="no"><span class="nc">tut2</span><span class="p">:</span><span class="nf">convert</span><span class="p" data-group-id="4783970097-1">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">inch</span><span class="p" data-group-id="4783970097-1">)</span><span class="p">.</span></code></pre><p>Does this mean that 3 is in inches? Or does it mean that 3 is in centimeters and
│ │ │  is to be converted to inches? Erlang has a way to group things together to make
│ │ │  things more understandable. These are called <em>tuples</em> and are surrounded by
│ │ │  curly brackets, <code class="inline">{</code> and <code class="inline">}</code>.</p><p>So, <code class="inline">{inch,3}</code> denotes 3 inches and <code class="inline">{centimeter,5}</code> denotes 5 centimeters. Now
│ │ │  let us write a new program that converts centimeters to inches and conversely.
│ │ │ -Enter the following code in a file called <code class="inline">tut3.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4321763074-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="4321763074-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4321763074-2">(</span><span class="p" data-group-id="4321763074-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4321763074-3">]</span><span class="p" data-group-id="4321763074-2">)</span><span class="p">.</span><span class="w">
│ │ │ +Enter the following code in a file called <code class="inline">tut3.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7329774692-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="7329774692-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7329774692-2">(</span><span class="p" data-group-id="7329774692-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7329774692-3">]</span><span class="p" data-group-id="7329774692-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="4321763074-4">(</span><span class="p" data-group-id="4321763074-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4321763074-5">}</span><span class="p" data-group-id="4321763074-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4321763074-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="4321763074-6">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="4321763074-7">(</span><span class="p" data-group-id="4321763074-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4321763074-8">}</span><span class="p" data-group-id="4321763074-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4321763074-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="4321763074-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="2993383062-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="2993383062-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2993383062-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="2993383062-2">}</span><span class="gp unselectable">
│ │ │ -15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2993383062-3">(</span><span class="p" data-group-id="2993383062-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2993383062-4">}</span><span class="p" data-group-id="2993383062-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2993383062-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="2993383062-5">}</span><span class="gp unselectable">
│ │ │ -16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2993383062-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2993383062-7">(</span><span class="p" data-group-id="2993383062-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="2993383062-8">}</span><span class="p" data-group-id="2993383062-7">)</span><span class="p" data-group-id="2993383062-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2993383062-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="2993383062-9">}</span></code></pre><p>Notice on line 16 that 5 inches is converted to centimeters and back again and
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="7329774692-4">(</span><span class="p" data-group-id="7329774692-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7329774692-5">}</span><span class="p" data-group-id="7329774692-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7329774692-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7329774692-6">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="7329774692-7">(</span><span class="p" data-group-id="7329774692-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7329774692-8">}</span><span class="p" data-group-id="7329774692-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7329774692-9">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7329774692-9">}</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">14&gt; </span><span class="nf">c</span><span class="p" data-group-id="4772741747-1">(</span><span class="ss">tut3</span><span class="p" data-group-id="4772741747-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4772741747-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut3</span><span class="p" data-group-id="4772741747-2">}</span><span class="gp unselectable">
│ │ │ +15&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="4772741747-3">(</span><span class="p" data-group-id="4772741747-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="4772741747-4">}</span><span class="p" data-group-id="4772741747-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4772741747-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">12.7</span><span class="p" data-group-id="4772741747-5">}</span><span class="gp unselectable">
│ │ │ +16&gt; </span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="4772741747-6">(</span><span class="nc">tut3</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="4772741747-7">(</span><span class="p" data-group-id="4772741747-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="4772741747-8">}</span><span class="p" data-group-id="4772741747-7">)</span><span class="p" data-group-id="4772741747-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4772741747-9">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">5.0</span><span class="p" data-group-id="4772741747-9">}</span></code></pre><p>Notice on line 16 that 5 inches is converted to centimeters and back again and
│ │ │  reassuringly get back to the original value. That is, the argument to a function
│ │ │  can be the result of another function. Consider how line 16 (above) works. The
│ │ │  argument given to the function <code class="inline">{inch,5}</code> is first matched against the first
│ │ │  head clause of <code class="inline">convert_length</code>, that is, <code class="inline">convert_length({centimeter,X})</code>. It
│ │ │  can be seen that <code class="inline">{centimeter,X}</code> does not match <code class="inline">{inch,5}</code> (the head is the bit
│ │ │  before the <code class="inline">-&gt;</code>). This having failed, let us try the head of the next clause
│ │ │  that is, <code class="inline">convert_length({inch,Y})</code>. This matches, and <code class="inline">Y</code> gets the value 5.</p><p>Tuples can have more than two parts, in fact as many parts as you want, and
│ │ │  contain any valid Erlang <em>term</em>. For example, to represent the temperature of
│ │ │ -various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8539552197-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8539552197-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8539552197-2">}</span><span class="p" data-group-id="8539552197-1">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8539552197-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8539552197-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8539552197-4">}</span><span class="p" data-group-id="8539552197-3">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8539552197-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8539552197-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8539552197-6">}</span><span class="p" data-group-id="8539552197-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │ +various cities of the world:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0823952199-1">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0823952199-2">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0823952199-2">}</span><span class="p" data-group-id="0823952199-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0823952199-3">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0823952199-4">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0823952199-4">}</span><span class="p" data-group-id="0823952199-3">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0823952199-5">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0823952199-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0823952199-6">}</span><span class="p" data-group-id="0823952199-5">}</span></code></pre><p>Tuples have a fixed number of items in them. Each item in a tuple is called an
│ │ │  <em>element</em>. In the tuple <code class="inline">{moscow,{c,-10}}</code>, element 1 is <code class="inline">moscow</code> and element 2
│ │ │  is <code class="inline">{c,-10}</code>. Here <code class="inline">c</code> represents Celsius and <code class="inline">f</code> Fahrenheit.</p><h2 id="lists" class="section-heading">
│ │ │    <a href="#lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Lists</span>
│ │ │  </h2>
│ │ │  <p>Whereas tuples group things together, it is also needed to represent lists of
│ │ │  things. Lists in Erlang are surrounded by square brackets, <code class="inline">[</code> and <code class="inline">]</code>. For
│ │ │ -example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="2240913364-1">[</span><span class="p" data-group-id="2240913364-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="2240913364-3">}</span><span class="p" data-group-id="2240913364-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="2240913364-5">}</span><span class="p" data-group-id="2240913364-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="2240913364-7">}</span><span class="p" data-group-id="2240913364-6">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="2240913364-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="2240913364-9">}</span><span class="p" data-group-id="2240913364-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2240913364-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="2240913364-11">}</span><span class="p" data-group-id="2240913364-10">}</span><span class="p" data-group-id="2240913364-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │ +example, a list of the temperatures of various cities in the world can be:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4901820452-1">[</span><span class="p" data-group-id="4901820452-2">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4901820452-3">}</span><span class="p" data-group-id="4901820452-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-4">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-5">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="4901820452-5">}</span><span class="p" data-group-id="4901820452-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-6">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-7">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="4901820452-7">}</span><span class="p" data-group-id="4901820452-6">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4901820452-8">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="4901820452-9">}</span><span class="p" data-group-id="4901820452-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-10">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4901820452-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="4901820452-11">}</span><span class="p" data-group-id="4901820452-10">}</span><span class="p" data-group-id="4901820452-1">]</span></code></pre><p>Notice that this list was so long that it did not fit on one line. This does not
│ │ │  matter, Erlang allows line breaks at all &quot;sensible places&quot; but not, for example,
│ │ │  in the middle of atoms, integers, and others.</p><p>A useful way of looking at parts of lists, is by using <code class="inline">|</code>. This is best
│ │ │ -explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="8946244636-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="8946244636-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8946244636-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8946244636-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8946244636-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8946244636-3">]</span><span class="gp unselectable">
│ │ │ +explained by an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">17&gt; </span><span class="p" data-group-id="0525624875-1">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="n">TheRest</span><span class="p" data-group-id="0525624875-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0525624875-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0525624875-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0525624875-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0525624875-3">]</span><span class="gp unselectable">
│ │ │  18&gt; </span><span class="n">First</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │  19&gt; </span><span class="n">TheRest</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8946244636-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8946244636-4">]</span></code></pre><p>To separate the first elements of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ -used. <code class="inline">First</code> has got value <code class="inline">1</code> and <code class="inline">TheRest</code> has got the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="5405232909-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="5405232909-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5405232909-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5405232909-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5405232909-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5405232909-3">]</span><span class="gp unselectable">
│ │ │ +</span><span class="p" data-group-id="0525624875-4">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0525624875-4">]</span></code></pre><p>To separate the first elements of the list from the rest of the list, <code class="inline">|</code> is
│ │ │ +used. <code class="inline">First</code> has got value <code class="inline">1</code> and <code class="inline">TheRest</code> has got the value <code class="inline">[2,3,4,5]</code>.</p><p>Another example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">20&gt; </span><span class="p" data-group-id="9267596187-1">[</span><span class="n">E1</span><span class="p">,</span><span class="w"> </span><span class="n">E2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">R</span><span class="p" data-group-id="9267596187-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9267596187-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9267596187-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9267596187-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9267596187-3">]</span><span class="gp unselectable">
│ │ │  21&gt; </span><span class="n">E1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │  22&gt; </span><span class="n">E2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="gp unselectable">
│ │ │  23&gt; </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5405232909-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="5405232909-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │ +</span><span class="p" data-group-id="9267596187-4">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9267596187-4">]</span></code></pre><p>Here you see the use of <code class="inline">|</code> to get the first two elements from the list. If you
│ │ │  try to get more elements from the list than there are elements in the list, an
│ │ │  error is returned. Notice also the special case of the list with no elements,
│ │ │ -<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="5178492577-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="5178492577-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5178492577-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5178492577-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5178492577-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5178492577-3">]</span><span class="gp unselectable">
│ │ │ +<code class="inline">[]</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">24&gt; </span><span class="p" data-group-id="7341667025-1">[</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">C</span><span class="p" data-group-id="7341667025-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7341667025-2">[</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="7341667025-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7341667025-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7341667025-3">]</span><span class="gp unselectable">
│ │ │  25&gt; </span><span class="n">A</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │  26&gt; </span><span class="n">B</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">2</span><span class="gp unselectable">
│ │ │  27&gt; </span><span class="n">C</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5178492577-4">[</span><span class="p" data-group-id="5178492577-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │ +</span><span class="p" data-group-id="7341667025-4">[</span><span class="p" data-group-id="7341667025-4">]</span></code></pre><p>In the previous examples, new variable names are used, instead of reusing the
│ │ │  old ones: <code class="inline">First</code>, <code class="inline">TheRest</code>, <code class="inline">E1</code>, <code class="inline">E2</code>, <code class="inline">R</code>, <code class="inline">A</code>, <code class="inline">B</code>, and <code class="inline">C</code>. The reason for
│ │ │  this is that a variable can only be given a value once in its context (scope).
│ │ │  More about this later.</p><p>The following example shows how to find the length of a list. Enter the
│ │ │ -following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7662797270-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="7662797270-1">)</span><span class="p">.</span><span class="w">
│ │ │ +following code in a file named <code class="inline">tut4.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9064242565-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="9064242565-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7662797270-2">(</span><span class="p" data-group-id="7662797270-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7662797270-3">]</span><span class="p" data-group-id="7662797270-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9064242565-2">(</span><span class="p" data-group-id="9064242565-3">[</span><span class="ss">list_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9064242565-3">]</span><span class="p" data-group-id="9064242565-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="7662797270-4">(</span><span class="p" data-group-id="7662797270-5">[</span><span class="p" data-group-id="7662797270-5">]</span><span class="p" data-group-id="7662797270-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="9064242565-4">(</span><span class="p" data-group-id="9064242565-5">[</span><span class="p" data-group-id="9064242565-5">]</span><span class="p" data-group-id="9064242565-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">list_length</span><span class="p" data-group-id="7662797270-6">(</span><span class="p" data-group-id="7662797270-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7662797270-7">]</span><span class="p" data-group-id="7662797270-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="7662797270-8">(</span><span class="n">Rest</span><span class="p" data-group-id="7662797270-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="1459040024-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="1459040024-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1459040024-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="1459040024-2">}</span><span class="gp unselectable">
│ │ │ -29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="1459040024-3">(</span><span class="p" data-group-id="1459040024-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="1459040024-4">]</span><span class="p" data-group-id="1459040024-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="9262380792-1">(</span><span class="p" data-group-id="9262380792-2">[</span><span class="p" data-group-id="9262380792-2">]</span><span class="p" data-group-id="9262380792-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="1092868191-1">(</span><span class="p" data-group-id="1092868191-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1092868191-2">]</span><span class="p" data-group-id="1092868191-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="1092868191-3">(</span><span class="n">Rest</span><span class="p" data-group-id="1092868191-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │ +</span><span class="nf">list_length</span><span class="p" data-group-id="9064242565-6">(</span><span class="p" data-group-id="9064242565-7">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9064242565-7">]</span><span class="p" data-group-id="9064242565-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="9064242565-8">(</span><span class="n">Rest</span><span class="p" data-group-id="9064242565-8">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">28&gt; </span><span class="nf">c</span><span class="p" data-group-id="2853885330-1">(</span><span class="ss">tut4</span><span class="p" data-group-id="2853885330-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2853885330-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut4</span><span class="p" data-group-id="2853885330-2">}</span><span class="gp unselectable">
│ │ │ +29&gt; </span><span class="nc">tut4</span><span class="p">:</span><span class="nf">list_length</span><span class="p" data-group-id="2853885330-3">(</span><span class="p" data-group-id="2853885330-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="2853885330-4">]</span><span class="p" data-group-id="2853885330-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">7</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="3492293065-1">(</span><span class="p" data-group-id="3492293065-2">[</span><span class="p" data-group-id="3492293065-2">]</span><span class="p" data-group-id="3492293065-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">0</span><span class="p">;</span></code></pre><p>The length of an empty list is obviously 0.</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_length</span><span class="p" data-group-id="8822815677-1">(</span><span class="p" data-group-id="8822815677-2">[</span><span class="n">First</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8822815677-2">]</span><span class="p" data-group-id="8822815677-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nf">list_length</span><span class="p" data-group-id="8822815677-3">(</span><span class="n">Rest</span><span class="p" data-group-id="8822815677-3">)</span><span class="p">.</span></code></pre><p>The length of a list with the first element <code class="inline">First</code> and the remaining elements
│ │ │  <code class="inline">Rest</code> is 1 + the length of <code class="inline">Rest</code>.</p><p>(Advanced readers only: This is not tail recursive, there is a better way to
│ │ │  write this function.)</p><p>In general, tuples are used where &quot;records&quot; or &quot;structs&quot; are used in other
│ │ │  languages. Also, lists are used when representing things with varying sizes,
│ │ │  that is, where linked lists are used in other languages.</p><p>Erlang does not have a string data type. Instead, strings can be represented by
│ │ │  lists of Unicode characters. This implies for example that the list <code class="inline">[97,98,99]</code>
│ │ │  is equivalent to <code class="inline">&quot;abc&quot;</code>. The Erlang shell is &quot;clever&quot; and guesses what list you
│ │ │ -mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="2392102673-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="2392102673-1">]</span><span class="p">.</span><span class="w">
│ │ │ +mean and outputs it in what it thinks is the most appropriate form, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">30&gt; </span><span class="p" data-group-id="3533013680-1">[</span><span class="mi">97</span><span class="p">,</span><span class="mi">98</span><span class="p">,</span><span class="mi">99</span><span class="p" data-group-id="3533013680-1">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;abc&quot;</span></code></pre><h2 id="maps" class="section-heading">
│ │ │    <a href="#maps" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Maps</span>
│ │ │  </h2>
│ │ │  <p>Maps are a set of key to value associations. These associations are encapsulated
│ │ │ -with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7214319589-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="7214319589-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7214319589-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="7214319589-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │ +with <code class="inline">#{</code> and <code class="inline">}</code>. To create an association from <code class="inline">&quot;key&quot;</code> to value <code class="inline">42</code>:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="5108884708-1">#{</span><span class="w"> </span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p" data-group-id="5108884708-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5108884708-2">#{</span><span class="s">&quot;key&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">42</span><span class="p" data-group-id="5108884708-2">}</span></code></pre><p>Let us jump straight into the deep end with an example using some interesting
│ │ │  features.</p><p>The following example shows how to calculate alpha blending using maps to
│ │ │ -reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5481630924-1">(</span><span class="ss">color</span><span class="p" data-group-id="5481630924-1">)</span><span class="p">.</span><span class="w">
│ │ │ +reference color and alpha channels. Enter the code in a file named <code class="inline">color.erl</code>):</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9552486180-1">(</span><span class="ss">color</span><span class="p" data-group-id="9552486180-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5481630924-2">(</span><span class="p" data-group-id="5481630924-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="5481630924-3">]</span><span class="p" data-group-id="5481630924-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9552486180-2">(</span><span class="p" data-group-id="9552486180-3">[</span><span class="ss">new</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="ss">blend</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9552486180-3">]</span><span class="p" data-group-id="9552486180-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5481630924-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="5481630924-5">(</span><span class="n">V</span><span class="p" data-group-id="5481630924-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5481630924-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="5481630924-7">(</span><span class="n">V</span><span class="p" data-group-id="5481630924-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="5481630924-6">)</span><span class="p" data-group-id="5481630924-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9552486180-4">(</span><span class="nf">is_channel</span><span class="p" data-group-id="9552486180-5">(</span><span class="n">V</span><span class="p" data-group-id="9552486180-5">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9552486180-6">(</span><span class="nf">is_float</span><span class="p" data-group-id="9552486180-7">(</span><span class="n">V</span><span class="p" data-group-id="9552486180-7">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="9552486180-6">)</span><span class="p" data-group-id="9552486180-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">new</span><span class="p" data-group-id="5481630924-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="5481630924-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5481630924-9">(</span><span class="n">R</span><span class="p" data-group-id="5481630924-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5481630924-10">(</span><span class="n">G</span><span class="p" data-group-id="5481630924-10">)</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5481630924-11">(</span><span class="n">B</span><span class="p" data-group-id="5481630924-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5481630924-12">(</span><span class="n">A</span><span class="p" data-group-id="5481630924-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5481630924-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5481630924-13">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="5481630924-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5481630924-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">blend</span><span class="p" data-group-id="5481630924-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="5481630924-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5481630924-16">)</span><span class="p" data-group-id="5481630924-15">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="5481630924-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="5481630924-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="5481630924-18">#{</span><span class="w">
│ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="5481630924-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5481630924-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="5481630924-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5481630924-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="5481630924-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="5481630924-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">new</span><span class="p" data-group-id="9552486180-8">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="9552486180-8">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9552486180-9">(</span><span class="n">R</span><span class="p" data-group-id="9552486180-9">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9552486180-10">(</span><span class="n">G</span><span class="p" data-group-id="9552486180-10">)</span><span class="p">,</span><span class="w">
│ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9552486180-11">(</span><span class="n">B</span><span class="p" data-group-id="9552486180-11">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9552486180-12">(</span><span class="n">A</span><span class="p" data-group-id="9552486180-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9552486180-13">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="9552486180-13">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="9552486180-14">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9552486180-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">blend</span><span class="p" data-group-id="9552486180-15">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="nf">alpha</span><span class="p" data-group-id="9552486180-16">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9552486180-16">)</span><span class="p" data-group-id="9552486180-15">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="9552486180-17">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="9552486180-17">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="9552486180-18">#{</span><span class="w">
│ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="9552486180-19">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9552486180-19">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="9552486180-20">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9552486180-20">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="9552486180-21">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9552486180-21">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5481630924-18">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">blend</span><span class="p" data-group-id="5481630924-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5481630924-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="5481630924-23">#{</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9552486180-18">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">blend</span><span class="p" data-group-id="9552486180-22">(</span><span class="p">_</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="9552486180-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="9552486180-23">#{</span><span class="w">
│ │ │          </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="mf">0.0</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5481630924-23">}</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9552486180-23">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alpha</span><span class="p" data-group-id="5481630924-24">(</span><span class="p" data-group-id="5481630924-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5481630924-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="5481630924-26">}</span><span class="p" data-group-id="5481630924-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="5481630924-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-27">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">alpha</span><span class="p" data-group-id="9552486180-24">(</span><span class="p" data-group-id="9552486180-25">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-25">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9552486180-26">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="9552486180-26">}</span><span class="p" data-group-id="9552486180-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="9552486180-27">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-27">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">red</span><span class="p" data-group-id="5481630924-28">(</span><span class="p" data-group-id="5481630924-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5481630924-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="5481630924-30">}</span><span class="p" data-group-id="5481630924-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="5481630924-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-31">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">green</span><span class="p" data-group-id="5481630924-32">(</span><span class="p" data-group-id="5481630924-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5481630924-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="5481630924-34">}</span><span class="p" data-group-id="5481630924-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="5481630924-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-35">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">blue</span><span class="p" data-group-id="5481630924-36">(</span><span class="p" data-group-id="5481630924-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5481630924-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="5481630924-38">}</span><span class="p" data-group-id="5481630924-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="5481630924-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="5481630924-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="7856294558-1">(</span><span class="ss">color</span><span class="p" data-group-id="7856294558-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7856294558-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="7856294558-2">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="7856294558-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="7856294558-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7856294558-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="7856294558-4">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="7856294558-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="7856294558-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7856294558-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="7856294558-6">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="7856294558-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="7856294558-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7856294558-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="7856294558-8">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="7856294558-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="7856294558-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7856294558-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="7856294558-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6190970258-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="6190970258-2">(</span><span class="n">V</span><span class="p" data-group-id="6190970258-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6190970258-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="6190970258-4">(</span><span class="n">V</span><span class="p" data-group-id="6190970258-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="6190970258-3">)</span><span class="p" data-group-id="6190970258-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │ +</span><span class="nf">red</span><span class="p" data-group-id="9552486180-28">(</span><span class="p" data-group-id="9552486180-29">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-29">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9552486180-30">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="9552486180-30">}</span><span class="p" data-group-id="9552486180-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="9552486180-31">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-31">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">green</span><span class="p" data-group-id="9552486180-32">(</span><span class="p" data-group-id="9552486180-33">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-33">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9552486180-34">#{</span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="9552486180-34">}</span><span class="p" data-group-id="9552486180-32">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="9552486180-35">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-35">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">blue</span><span class="p" data-group-id="9552486180-36">(</span><span class="p" data-group-id="9552486180-37">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-37">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9552486180-38">#{</span><span class="ss">blue</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="9552486180-38">}</span><span class="p" data-group-id="9552486180-36">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="9552486180-39">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="9552486180-39">)</span><span class="p">.</span></code></pre><p>Compile and test:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">c</span><span class="p" data-group-id="1339536921-1">(</span><span class="ss">color</span><span class="p" data-group-id="1339536921-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1339536921-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">color</span><span class="p" data-group-id="1339536921-2">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">C1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1339536921-3">(</span><span class="mf">0.3</span><span class="p">,</span><span class="mf">0.4</span><span class="p">,</span><span class="mf">0.5</span><span class="p">,</span><span class="mf">1.0</span><span class="p" data-group-id="1339536921-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1339536921-4">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="1339536921-4">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">C2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">color</span><span class="p">:</span><span class="nf">new</span><span class="p" data-group-id="1339536921-5">(</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">0.8</span><span class="p">,</span><span class="mf">0.1</span><span class="p">,</span><span class="mf">0.3</span><span class="p" data-group-id="1339536921-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1339536921-6">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.1</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.8</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="1339536921-6">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="1339536921-7">(</span><span class="n">C1</span><span class="p">,</span><span class="n">C2</span><span class="p" data-group-id="1339536921-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1339536921-8">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.5</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.4</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.3</span><span class="p" data-group-id="1339536921-8">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">color</span><span class="p">:</span><span class="nf">blend</span><span class="p" data-group-id="1339536921-9">(</span><span class="n">C2</span><span class="p">,</span><span class="n">C1</span><span class="p" data-group-id="1339536921-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1339536921-10">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p">,</span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.38</span><span class="p">,</span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.52</span><span class="p">,</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mf">0.51</span><span class="p" data-group-id="1339536921-10">}</span></code></pre><p>This example warrants some explanation:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3859688146-1">(</span><span class="nf">is_channel</span><span class="p" data-group-id="3859688146-2">(</span><span class="n">V</span><span class="p" data-group-id="3859688146-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3859688146-3">(</span><span class="nf">is_float</span><span class="p" data-group-id="3859688146-4">(</span><span class="n">V</span><span class="p" data-group-id="3859688146-4">)</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="n">V</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="3859688146-3">)</span><span class="p" data-group-id="3859688146-1">)</span><span class="p">.</span></code></pre><p>First a macro <code class="inline">is_channel</code> is defined to help with the guard tests. This is only
│ │ │  here for convenience and to reduce syntax cluttering. For more information about
│ │ │ -macros, see <a href="../../doc/system/macros.html">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="9206840196-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="9206840196-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9206840196-2">(</span><span class="n">R</span><span class="p" data-group-id="9206840196-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9206840196-3">(</span><span class="n">G</span><span class="p" data-group-id="9206840196-3">)</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9206840196-4">(</span><span class="n">B</span><span class="p" data-group-id="9206840196-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="9206840196-5">(</span><span class="n">A</span><span class="p" data-group-id="9206840196-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9206840196-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="9206840196-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │ +macros, see <a href="../../doc/system/macros.html">The Preprocessor</a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">new</span><span class="p" data-group-id="5373666231-1">(</span><span class="n">R</span><span class="p">,</span><span class="n">G</span><span class="p">,</span><span class="n">B</span><span class="p">,</span><span class="n">A</span><span class="p" data-group-id="5373666231-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5373666231-2">(</span><span class="n">R</span><span class="p" data-group-id="5373666231-2">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5373666231-3">(</span><span class="n">G</span><span class="p" data-group-id="5373666231-3">)</span><span class="p">,</span><span class="w">
│ │ │ +                  </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5373666231-4">(</span><span class="n">B</span><span class="p" data-group-id="5373666231-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="nf">is_channel</span><span class="p" data-group-id="5373666231-5">(</span><span class="n">A</span><span class="p" data-group-id="5373666231-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5373666231-6">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">R</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">G</span><span class="p">,</span><span class="w"> </span><span class="ss">blue</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">A</span><span class="p" data-group-id="5373666231-6">}</span><span class="p">.</span></code></pre><p>The function <code class="inline">new/4</code> creates a new map term and lets the keys <code class="inline">red</code>, <code class="inline">green</code>,
│ │ │  <code class="inline">blue</code>, and <code class="inline">alpha</code> be associated with an initial value. In this case, only
│ │ │  float values between and including 0.0 and 1.0 are allowed, as ensured by the
│ │ │  <code class="inline">?is_channel/1</code> macro for each argument. Only the <code class="inline">=&gt;</code> operator is allowed when
│ │ │  creating a new map.</p><p>By calling <code class="inline">blend/2</code> on any color term created by <code class="inline">new/4</code>, the resulting color
│ │ │ -can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="0447261774-1">(</span><span class="p" data-group-id="0447261774-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0447261774-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0447261774-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="0447261774-3">}</span><span class="p" data-group-id="0447261774-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="0447261774-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="0447261774-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │ +can be calculated as determined by the two map terms.</p><p>The first thing <code class="inline">blend/2</code> does is to calculate the resulting alpha channel:</p><pre><code class="makeup erlang" translate="no"><span class="nf">alpha</span><span class="p" data-group-id="3597245847-1">(</span><span class="p" data-group-id="3597245847-2">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="3597245847-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3597245847-3">#{</span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="3597245847-3">}</span><span class="p" data-group-id="3597245847-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="3597245847-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="3597245847-4">)</span><span class="p">.</span></code></pre><p>The value associated with key <code class="inline">alpha</code> is fetched for both arguments using the
│ │ │  <code class="inline">:=</code> operator. The other keys in the map are ignored, only the key <code class="inline">alpha</code> is
│ │ │ -required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="3390061748-1">(</span><span class="p" data-group-id="3390061748-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="3390061748-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3390061748-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="3390061748-3">}</span><span class="p" data-group-id="3390061748-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="3390061748-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="3390061748-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ -The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="9851573896-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="9851573896-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Dst</span><span class="p" data-group-id="9851573896-2">#{</span><span class="w">
│ │ │ -        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="9851573896-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9851573896-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="9851573896-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9851573896-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="9851573896-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="9851573896-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +required and checked for.</p><p>This is also the case for functions <code class="inline">red/2</code>, <code class="inline">blue/2</code>, and <code class="inline">green/2</code>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">red</span><span class="p" data-group-id="8866315202-1">(</span><span class="p" data-group-id="8866315202-2">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8866315202-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8866315202-3">#{</span><span class="ss">red</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DV</span><span class="p">,</span><span class="w"> </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">DA</span><span class="p" data-group-id="8866315202-3">}</span><span class="p" data-group-id="8866315202-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SV</span><span class="o">*</span><span class="n">SA</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">DV</span><span class="o">*</span><span class="n">DA</span><span class="o">*</span><span class="p" data-group-id="8866315202-4">(</span><span class="mf">1.0</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">SA</span><span class="p" data-group-id="8866315202-4">)</span><span class="p">.</span></code></pre><p>The difference here is that a check is made for two keys in each map argument.
│ │ │ +The other keys are ignored.</p><p>Finally, let us return the resulting color in <code class="inline">blend/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">blend</span><span class="p" data-group-id="7121125017-1">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p">,</span><span class="n">Alpha</span><span class="p" data-group-id="7121125017-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Alpha</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mf">0.0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Dst</span><span class="p" data-group-id="7121125017-2">#{</span><span class="w">
│ │ │ +        </span><span class="ss">red</span><span class="w">   </span><span class="p">:=</span><span class="w"> </span><span class="nf">red</span><span class="p" data-group-id="7121125017-3">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7121125017-3">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">green</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="nf">green</span><span class="p" data-group-id="7121125017-4">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7121125017-4">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="ss">blue</span><span class="w">  </span><span class="p">:=</span><span class="w"> </span><span class="nf">blue</span><span class="p" data-group-id="7121125017-5">(</span><span class="n">Src</span><span class="p">,</span><span class="n">Dst</span><span class="p" data-group-id="7121125017-5">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">Alpha</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">alpha</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Alpha</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9851573896-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │ +    </span><span class="p" data-group-id="7121125017-2">}</span><span class="p">;</span></code></pre><p>The <code class="inline">Dst</code> map is updated with new channel values. The syntax for updating an
│ │ │  existing key with a new value is with the <code class="inline">:=</code> operator.</p><h2 id="standard-modules-and-manual-pages" class="section-heading">
│ │ │    <a href="#standard-modules-and-manual-pages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standard Modules and Manual Pages</span>
│ │ │  </h2>
│ │ │  <p>Erlang has many standard modules to help you do things. For example, the module
│ │ │ @@ -442,24 +442,24 @@
│ │ │    <a href="#writing-output-to-a-terminal" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Writing Output to a Terminal</span>
│ │ │  </h2>
│ │ │  <p>It is nice to be able to do formatted output in examples, so the next example
│ │ │  shows a simple way to use the <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function. Like all other exported
│ │ │ -functions, you can test the <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4380423167-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4380423167-2">[</span><span class="p" data-group-id="4380423167-2">]</span><span class="p" data-group-id="4380423167-1">)</span><span class="p">.</span><span class="w">
│ │ │ +functions, you can test the <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">31&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9982943508-1">(</span><span class="s">&quot;hello world</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9982943508-2">[</span><span class="p" data-group-id="9982943508-2">]</span><span class="p" data-group-id="9982943508-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4380423167-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4380423167-4">[</span><span class="ss">hello</span><span class="p" data-group-id="4380423167-4">]</span><span class="p" data-group-id="4380423167-3">)</span><span class="p">.</span><span class="w">
│ │ │ +32&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9982943508-3">(</span><span class="s">&quot;this outputs one Erlang term: </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9982943508-4">[</span><span class="ss">hello</span><span class="p" data-group-id="9982943508-4">]</span><span class="p" data-group-id="9982943508-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">one</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">term</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4380423167-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4380423167-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="4380423167-6">]</span><span class="p" data-group-id="4380423167-5">)</span><span class="p">.</span><span class="w">
│ │ │ +33&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9982943508-5">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9982943508-6">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="9982943508-6">]</span><span class="p" data-group-id="9982943508-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">helloworld</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4380423167-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4380423167-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="4380423167-8">]</span><span class="p" data-group-id="4380423167-7">)</span><span class="p">.</span><span class="w">
│ │ │ +34&gt; </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9982943508-7">(</span><span class="s">&quot;this outputs two Erlang terms: </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9982943508-8">[</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">world</span><span class="p" data-group-id="9982943508-8">]</span><span class="p" data-group-id="9982943508-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">this</span><span class="w"> </span><span class="ss">outputs</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="nc">terms</span><span class="p">:</span><span class="w"> </span><span class="ss">hello</span><span class="w"> </span><span class="ss">world</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>The function <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> (that is, <code class="inline">format</code> with two arguments) takes two lists.
│ │ │  The first one is nearly always a list written between <code class="inline">&quot; &quot;</code>. This list is printed
│ │ │  out as it is, except that each <code class="inline">~w</code> is replaced by a term taken in order from the
│ │ │  second list. Each ~n is replaced by a new line. The <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/2"><code class="inline">io:format/2</code></a> function
│ │ │  itself returns the atom <code class="inline">ok</code> if everything goes as planned. Like other functions
│ │ │  in Erlang, it crashes if an error occurs. This is not a fault in Erlang, it is a
│ │ │ @@ -473,34 +473,34 @@
│ │ │    <span class="text">A Larger Example</span>
│ │ │  </h2>
│ │ │  <p>Now for a larger example to consolidate what you have learnt so far. Assume that
│ │ │  you have a list of temperature readings from a number of cities in the world.
│ │ │  Some of them are in Celsius and some in Fahrenheit (as in the previous list).
│ │ │  First let us convert them all to Celsius, then let us print the data neatly.</p><pre><code class="makeup erlang" translate="no"><span class="c1">%% This module is in file tut5.erl</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7108824182-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="7108824182-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7108824182-2">(</span><span class="p" data-group-id="7108824182-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7108824182-3">]</span><span class="p" data-group-id="7108824182-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9336027877-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="9336027877-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9336027877-2">(</span><span class="p" data-group-id="9336027877-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9336027877-3">]</span><span class="p" data-group-id="9336027877-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Only this function is exported</span><span class="w">
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7108824182-4">(</span><span class="p" data-group-id="7108824182-5">[</span><span class="p" data-group-id="7108824182-5">]</span><span class="p" data-group-id="7108824182-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="9336027877-4">(</span><span class="p" data-group-id="9336027877-5">[</span><span class="p" data-group-id="9336027877-5">]</span><span class="p" data-group-id="9336027877-4">)</span><span class="p">-&gt;</span><span class="w">                        </span><span class="c1">% No output for an empty list</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="7108824182-6">(</span><span class="p" data-group-id="7108824182-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="7108824182-7">]</span><span class="p" data-group-id="7108824182-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="7108824182-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="7108824182-9">(</span><span class="n">City</span><span class="p" data-group-id="7108824182-9">)</span><span class="p" data-group-id="7108824182-8">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">format_temps</span><span class="p" data-group-id="7108824182-10">(</span><span class="n">Rest</span><span class="p" data-group-id="7108824182-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="7108824182-11">(</span><span class="p" data-group-id="7108824182-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7108824182-13">}</span><span class="p" data-group-id="7108824182-12">}</span><span class="p" data-group-id="7108824182-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7108824182-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7108824182-15">}</span><span class="p" data-group-id="7108824182-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="7108824182-16">(</span><span class="p" data-group-id="7108824182-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7108824182-18">}</span><span class="p" data-group-id="7108824182-17">}</span><span class="p" data-group-id="7108824182-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7108824182-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="7108824182-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7108824182-20">}</span><span class="p" data-group-id="7108824182-19">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="7108824182-22">(</span><span class="p" data-group-id="7108824182-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7108824182-24">}</span><span class="p" data-group-id="7108824182-23">}</span><span class="p" data-group-id="7108824182-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7108824182-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7108824182-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7108824182-26">]</span><span class="p" data-group-id="7108824182-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="1626294793-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="1626294793-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1626294793-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="1626294793-2">}</span><span class="gp unselectable">
│ │ │ -36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="1626294793-3">(</span><span class="p" data-group-id="1626294793-4">[</span><span class="p" data-group-id="1626294793-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="1626294793-6">}</span><span class="p" data-group-id="1626294793-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="1626294793-8">}</span><span class="p" data-group-id="1626294793-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1626294793-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="1626294793-10">}</span><span class="p" data-group-id="1626294793-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="1626294793-12">}</span><span class="p" data-group-id="1626294793-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1626294793-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="1626294793-14">}</span><span class="p" data-group-id="1626294793-13">}</span><span class="p" data-group-id="1626294793-4">]</span><span class="p" data-group-id="1626294793-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="9336027877-6">(</span><span class="p" data-group-id="9336027877-7">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9336027877-7">]</span><span class="p" data-group-id="9336027877-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="9336027877-8">(</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="9336027877-9">(</span><span class="n">City</span><span class="p" data-group-id="9336027877-9">)</span><span class="p" data-group-id="9336027877-8">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">format_temps</span><span class="p" data-group-id="9336027877-10">(</span><span class="n">Rest</span><span class="p" data-group-id="9336027877-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="9336027877-11">(</span><span class="p" data-group-id="9336027877-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9336027877-13">}</span><span class="p" data-group-id="9336027877-12">}</span><span class="p" data-group-id="9336027877-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% No conversion needed</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9336027877-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9336027877-15">}</span><span class="p" data-group-id="9336027877-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_to_celsius</span><span class="p" data-group-id="9336027877-16">(</span><span class="p" data-group-id="9336027877-17">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-18">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9336027877-18">}</span><span class="p" data-group-id="9336027877-17">}</span><span class="p" data-group-id="9336027877-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">  </span><span class="c1">% Do the conversion</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9336027877-19">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-20">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-21">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="9336027877-21">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="9336027877-20">}</span><span class="p" data-group-id="9336027877-19">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="9336027877-22">(</span><span class="p" data-group-id="9336027877-23">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-24">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9336027877-24">}</span><span class="p" data-group-id="9336027877-23">}</span><span class="p" data-group-id="9336027877-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9336027877-25">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9336027877-26">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9336027877-26">]</span><span class="p" data-group-id="9336027877-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">35&gt; </span><span class="nf">c</span><span class="p" data-group-id="2651761678-1">(</span><span class="ss">tut5</span><span class="p" data-group-id="2651761678-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2651761678-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut5</span><span class="p" data-group-id="2651761678-2">}</span><span class="gp unselectable">
│ │ │ +36&gt; </span><span class="nc">tut5</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="2651761678-3">(</span><span class="p" data-group-id="2651761678-4">[</span><span class="p" data-group-id="2651761678-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="2651761678-6">}</span><span class="p" data-group-id="2651761678-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="2651761678-8">}</span><span class="p" data-group-id="2651761678-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2651761678-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="2651761678-10">}</span><span class="p" data-group-id="2651761678-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="2651761678-12">}</span><span class="p" data-group-id="2651761678-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2651761678-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="2651761678-14">}</span><span class="p" data-group-id="2651761678-13">}</span><span class="p" data-group-id="2651761678-4">]</span><span class="p" data-group-id="2651761678-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Before looking at how this program works, notice that a few comments are added
│ │ │  to the code. A comment starts with a %-character and goes on to the end of the
│ │ │ @@ -528,28 +528,28 @@
│ │ │    <a href="#matching-guards-and-scope-of-variables" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Matching, Guards, and Scope of Variables</span>
│ │ │  </h2>
│ │ │  <p>It can be useful to find the maximum and minimum temperature in lists like this.
│ │ │  Before extending the program to do this, let us look at functions for finding
│ │ │ -the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7942131696-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="7942131696-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7942131696-2">(</span><span class="p" data-group-id="7942131696-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7942131696-3">]</span><span class="p" data-group-id="7942131696-2">)</span><span class="p">.</span><span class="w">
│ │ │ +the maximum value of the elements in a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2927891285-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="2927891285-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2927891285-2">(</span><span class="p" data-group-id="2927891285-3">[</span><span class="ss">list_max</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2927891285-3">]</span><span class="p" data-group-id="2927891285-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-4">(</span><span class="p" data-group-id="7942131696-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7942131696-5">]</span><span class="p" data-group-id="7942131696-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -   </span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="7942131696-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-4">(</span><span class="p" data-group-id="2927891285-5">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2927891285-5">]</span><span class="p" data-group-id="2927891285-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +   </span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-6">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="2927891285-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-7">(</span><span class="p" data-group-id="7942131696-8">[</span><span class="p" data-group-id="7942131696-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="7942131696-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-7">(</span><span class="p" data-group-id="2927891285-8">[</span><span class="p" data-group-id="2927891285-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="2927891285-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Res</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-9">(</span><span class="p" data-group-id="7942131696-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7942131696-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7942131696-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="7942131696-11">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-12">(</span><span class="p" data-group-id="7942131696-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="7942131696-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7942131696-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="7942131696-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="7942131696-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="9916139420-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="9916139420-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9916139420-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="9916139420-2">}</span><span class="gp unselectable">
│ │ │ -38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="9916139420-3">(</span><span class="p" data-group-id="9916139420-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9916139420-4">]</span><span class="p" data-group-id="9916139420-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-9">(</span><span class="p" data-group-id="2927891285-10">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2927891285-10">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2927891285-9">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-11">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Head</span><span class="p" data-group-id="2927891285-11">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-12">(</span><span class="p" data-group-id="2927891285-13">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2927891285-13">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2927891285-12">)</span><span class="w">  </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="2927891285-14">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2927891285-14">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">37&gt; </span><span class="nf">c</span><span class="p" data-group-id="4612941845-1">(</span><span class="ss">tut6</span><span class="p" data-group-id="4612941845-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4612941845-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut6</span><span class="p" data-group-id="4612941845-2">}</span><span class="gp unselectable">
│ │ │ +38&gt; </span><span class="nc">tut6</span><span class="p">:</span><span class="nf">list_max</span><span class="p" data-group-id="4612941845-3">(</span><span class="p" data-group-id="4612941845-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4612941845-4">]</span><span class="p" data-group-id="4612941845-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">7</span></code></pre><p>First notice that two functions have the same name, <code class="inline">list_max</code>. However, each of
│ │ │  these takes a different number of arguments (parameters). In Erlang these are
│ │ │  regarded as completely different functions. Where you need to distinguish
│ │ │  between these functions, you write Name/Arity, where Name is the function name
│ │ │  and Arity is the number of arguments, in this case <code class="inline">list_max/1</code> and
│ │ │  <code class="inline">list_max/2</code>.</p><p>In this example you walk through a list &quot;carrying&quot; a value, in this case
│ │ │  <code class="inline">Result_so_far</code>. <code class="inline">list_max/1</code> simply assumes that the max value of the list is
│ │ │ @@ -578,180 +578,180 @@
│ │ │  </span><span class="mi">5</span><span class="gp unselectable">
│ │ │  40&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">6</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="gp unselectable">
│ │ │  41&gt; </span><span class="n">M</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value 6</span><span class="gp unselectable">
│ │ │  42&gt; </span><span class="n">N</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">6</span></code></pre><p>The use of the match operator is particularly useful for pulling apart Erlang
│ │ │ -terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="0772382759-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="0772382759-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0772382759-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0772382759-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0772382759-3">}</span><span class="p" data-group-id="0772382759-2">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0772382759-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0772382759-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="0772382759-5">}</span><span class="p" data-group-id="0772382759-4">}</span><span class="gp unselectable">
│ │ │ +terms and creating new ones.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">43&gt; </span><span class="p" data-group-id="2614016438-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2614016438-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2614016438-2">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2614016438-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="2614016438-3">}</span><span class="p" data-group-id="2614016438-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2614016438-4">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="2614016438-5">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="2614016438-5">}</span><span class="p" data-group-id="2614016438-4">}</span><span class="gp unselectable">
│ │ │  44&gt; </span><span class="n">X</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="gp unselectable">
│ │ │  45&gt; </span><span class="n">Y</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0772382759-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="0772382759-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="7871382577-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7871382577-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7871382577-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7871382577-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7871382577-3">}</span><span class="p" data-group-id="7871382577-2">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2614016438-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">28</span><span class="p" data-group-id="2614016438-6">}</span></code></pre><p>Here <code class="inline">X</code> gets the value <code class="inline">paris</code> and <code class="inline">Y</code> the value <code class="inline">{f,28}</code>.</p><p>If you try to do the same again with another city, an error is returned:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">46&gt; </span><span class="p" data-group-id="2854374870-1">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="2854374870-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2854374870-2">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2854374870-3">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="2854374870-3">}</span><span class="p" data-group-id="2854374870-2">}</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no match of right hand side value {london,{f,36}}</span></code></pre><p>Variables can also be used to improve the readability of programs. For example,
│ │ │ -in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="2288054160-1">(</span><span class="p" data-group-id="2288054160-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="2288054160-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="2288054160-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +in function <code class="inline">list_max/2</code> above, you can write:</p><pre><code class="makeup erlang" translate="no"><span class="nf">list_max</span><span class="p" data-group-id="8834268275-1">(</span><span class="p" data-group-id="8834268275-2">[</span><span class="n">Head</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="8834268275-2">]</span><span class="p">,</span><span class="w"> </span><span class="n">Result_so_far</span><span class="p" data-group-id="8834268275-1">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Head</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Result_so_far</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">New_result_far</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Head</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">list_max</span><span class="p" data-group-id="2288054160-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="2288054160-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │ +    </span><span class="nf">list_max</span><span class="p" data-group-id="8834268275-3">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">New_result_far</span><span class="p" data-group-id="8834268275-3">)</span><span class="p">;</span></code></pre><p>This is possibly a little clearer.</p><h2 id="more-about-lists" class="section-heading">
│ │ │    <a href="#more-about-lists" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">More About Lists</span>
│ │ │  </h2>
│ │ │ -<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="2823483538-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="2823483538-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2823483538-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="2823483538-2">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2823483538-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2823483538-3">]</span><span class="gp unselectable">
│ │ │ +<p>Remember that the <code class="inline">|</code> operator can be used to get the head of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">47&gt; </span><span class="p" data-group-id="0086375187-1">[</span><span class="n">M1</span><span class="p">|</span><span class="n">T1</span><span class="p" data-group-id="0086375187-1">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0086375187-2">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="ss">rome</span><span class="p" data-group-id="0086375187-2">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0086375187-3">[</span><span class="ss">paris</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="0086375187-3">]</span><span class="gp unselectable">
│ │ │  48&gt; </span><span class="n">M1</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="gp unselectable">
│ │ │  49&gt; </span><span class="n">T1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2823483538-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2823483538-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7010206228-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7010206228-1">]</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7010206228-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7010206228-2">]</span><span class="gp unselectable">
│ │ │ +</span><span class="p" data-group-id="0086375187-4">[</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="0086375187-4">]</span></code></pre><p>The <code class="inline">|</code> operator can also be used to add a head to a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">50&gt; </span><span class="n">L1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2211168234-1">[</span><span class="ss">madrid</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="2211168234-1">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2211168234-2">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2211168234-2">]</span><span class="gp unselectable">
│ │ │  51&gt; </span><span class="n">L1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7010206228-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="7010206228-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8216110997-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="8216110997-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2211168234-3">[</span><span class="ss">madrid</span><span class="p">,</span><span class="ss">london</span><span class="p">,</span><span class="ss">rome</span><span class="p" data-group-id="2211168234-3">]</span></code></pre><p>Now an example of this when working with lists - reversing the order of a list:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8561353670-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="8561353670-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8216110997-2">(</span><span class="p" data-group-id="8216110997-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8216110997-3">]</span><span class="p" data-group-id="8216110997-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8561353670-2">(</span><span class="p" data-group-id="8561353670-3">[</span><span class="ss">reverse</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8561353670-3">]</span><span class="p" data-group-id="8561353670-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="8216110997-4">(</span><span class="n">List</span><span class="p" data-group-id="8216110997-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="8216110997-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8216110997-6">[</span><span class="p" data-group-id="8216110997-6">]</span><span class="p" data-group-id="8216110997-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="8561353670-4">(</span><span class="n">List</span><span class="p" data-group-id="8561353670-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="8561353670-5">(</span><span class="n">List</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8561353670-6">[</span><span class="p" data-group-id="8561353670-6">]</span><span class="p" data-group-id="8561353670-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="8216110997-7">(</span><span class="p" data-group-id="8216110997-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8216110997-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="8216110997-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="8216110997-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8216110997-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="8216110997-10">]</span><span class="p" data-group-id="8216110997-9">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="8216110997-11">(</span><span class="p" data-group-id="8216110997-12">[</span><span class="p" data-group-id="8216110997-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="8216110997-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="3913499010-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="3913499010-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3913499010-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="3913499010-2">}</span><span class="gp unselectable">
│ │ │ -53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="3913499010-3">(</span><span class="p" data-group-id="3913499010-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3913499010-4">]</span><span class="p" data-group-id="3913499010-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3913499010-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3913499010-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="8561353670-7">(</span><span class="p" data-group-id="8561353670-8">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8561353670-8">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="8561353670-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="8561353670-9">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8561353670-10">[</span><span class="n">Head</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="8561353670-10">]</span><span class="p" data-group-id="8561353670-9">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="8561353670-11">(</span><span class="p" data-group-id="8561353670-12">[</span><span class="p" data-group-id="8561353670-12">]</span><span class="p">,</span><span class="w"> </span><span class="n">Reversed_List</span><span class="p" data-group-id="8561353670-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Reversed_List</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">52&gt; </span><span class="nf">c</span><span class="p" data-group-id="2635423587-1">(</span><span class="ss">tut8</span><span class="p" data-group-id="2635423587-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2635423587-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut8</span><span class="p" data-group-id="2635423587-2">}</span><span class="gp unselectable">
│ │ │ +53&gt; </span><span class="nc">tut8</span><span class="p">:</span><span class="nf">reverse</span><span class="p" data-group-id="2635423587-3">(</span><span class="p" data-group-id="2635423587-4">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="2635423587-4">]</span><span class="p" data-group-id="2635423587-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2635423587-5">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="2635423587-5">]</span></code></pre><p>Consider how <code class="inline">Reversed_List</code> is built. It starts as [], then successively the
│ │ │  heads are taken off of the list to be reversed and added to the the
│ │ │ -<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="0376299716-1">(</span><span class="p" data-group-id="0376299716-2">[</span><span class="mi">1</span><span class="p">|</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0376299716-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-3">[</span><span class="p" data-group-id="0376299716-3">]</span><span class="p" data-group-id="0376299716-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="0376299716-4">(</span><span class="p" data-group-id="0376299716-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0376299716-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-6">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="0376299716-7">[</span><span class="p" data-group-id="0376299716-7">]</span><span class="p" data-group-id="0376299716-6">]</span><span class="p" data-group-id="0376299716-4">)</span><span class="w">
│ │ │ +<code class="inline">Reversed_List</code>, as shown in the following:</p><pre><code class="makeup erlang" translate="no"><span class="nf">reverse</span><span class="p" data-group-id="5774388601-1">(</span><span class="p" data-group-id="5774388601-2">[</span><span class="mi">1</span><span class="p">|</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5774388601-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-3">[</span><span class="p" data-group-id="5774388601-3">]</span><span class="p" data-group-id="5774388601-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="5774388601-4">(</span><span class="p" data-group-id="5774388601-5">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5774388601-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-6">[</span><span class="mi">1</span><span class="p">|</span><span class="p" data-group-id="5774388601-7">[</span><span class="p" data-group-id="5774388601-7">]</span><span class="p" data-group-id="5774388601-6">]</span><span class="p" data-group-id="5774388601-4">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="0376299716-8">(</span><span class="p" data-group-id="0376299716-9">[</span><span class="mi">2</span><span class="p">|</span><span class="mi">3</span><span class="p" data-group-id="0376299716-9">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-10">[</span><span class="mi">1</span><span class="p" data-group-id="0376299716-10">]</span><span class="p" data-group-id="0376299716-8">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="0376299716-11">(</span><span class="p" data-group-id="0376299716-12">[</span><span class="mi">3</span><span class="p" data-group-id="0376299716-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-13">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="0376299716-14">[</span><span class="mi">1</span><span class="p" data-group-id="0376299716-14">]</span><span class="p">)</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="5774388601-8">(</span><span class="p" data-group-id="5774388601-9">[</span><span class="mi">2</span><span class="p">|</span><span class="mi">3</span><span class="p" data-group-id="5774388601-9">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-10">[</span><span class="mi">1</span><span class="p" data-group-id="5774388601-10">]</span><span class="p" data-group-id="5774388601-8">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="5774388601-11">(</span><span class="p" data-group-id="5774388601-12">[</span><span class="mi">3</span><span class="p" data-group-id="5774388601-12">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-13">[</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="5774388601-14">[</span><span class="mi">1</span><span class="p" data-group-id="5774388601-14">]</span><span class="p">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="0376299716-15">(</span><span class="p" data-group-id="0376299716-16">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="0376299716-17">[</span><span class="p" data-group-id="0376299716-17">]</span><span class="p" data-group-id="0376299716-16">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-18">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0376299716-18">]</span><span class="p" data-group-id="0376299716-15">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">reverse</span><span class="p" data-group-id="0376299716-19">(</span><span class="p" data-group-id="0376299716-20">[</span><span class="p" data-group-id="0376299716-20">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-21">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="0376299716-22">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0376299716-22">]</span><span class="p" data-group-id="0376299716-21">]</span><span class="p" data-group-id="0376299716-19">)</span><span class="w">
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="5774388601-15">(</span><span class="p" data-group-id="5774388601-16">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="5774388601-17">[</span><span class="p" data-group-id="5774388601-17">]</span><span class="p" data-group-id="5774388601-16">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-18">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5774388601-18">]</span><span class="p" data-group-id="5774388601-15">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">reverse</span><span class="p" data-group-id="5774388601-19">(</span><span class="p" data-group-id="5774388601-20">[</span><span class="p" data-group-id="5774388601-20">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-21">[</span><span class="mi">3</span><span class="p">|</span><span class="p" data-group-id="5774388601-22">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5774388601-22">]</span><span class="p" data-group-id="5774388601-21">]</span><span class="p" data-group-id="5774388601-19">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">reverse</span><span class="p" data-group-id="0376299716-23">(</span><span class="p" data-group-id="0376299716-24">[</span><span class="p" data-group-id="0376299716-24">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0376299716-25">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0376299716-25">]</span><span class="p" data-group-id="0376299716-23">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0376299716-26">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0376299716-26">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │ +</span><span class="nf">reverse</span><span class="p" data-group-id="5774388601-23">(</span><span class="p" data-group-id="5774388601-24">[</span><span class="p" data-group-id="5774388601-24">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5774388601-25">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5774388601-25">]</span><span class="p" data-group-id="5774388601-23">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5774388601-26">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5774388601-26">]</span></code></pre><p>The module <code class="inline">lists</code> contains many functions for manipulating lists, for example,
│ │ │  for reversing them. So before writing a list-manipulating function it is a good
│ │ │  idea to check if one not already is written for you (see the <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html"><code class="inline">lists</code></a> manual
│ │ │  page in STDLIB).</p><p>Now let us get back to the cities and temperatures, but take a more structured
│ │ │ -approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9957246530-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="9957246530-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9957246530-2">(</span><span class="p" data-group-id="9957246530-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9957246530-3">]</span><span class="p" data-group-id="9957246530-2">)</span><span class="p">.</span><span class="w">
│ │ │ +approach this time. First let us convert the whole list to Celsius as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1286481954-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="1286481954-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1286481954-2">(</span><span class="p" data-group-id="1286481954-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1286481954-3">]</span><span class="p" data-group-id="1286481954-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="9957246530-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="9957246530-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9957246530-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="9957246530-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="1286481954-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="1286481954-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1286481954-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="1286481954-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9957246530-6">(</span><span class="p" data-group-id="9957246530-7">[</span><span class="p" data-group-id="9957246530-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9957246530-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="9957246530-9">}</span><span class="p" data-group-id="9957246530-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9957246530-7">]</span><span class="p" data-group-id="9957246530-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9957246530-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9957246530-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9957246530-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="9957246530-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="9957246530-11">}</span><span class="p" data-group-id="9957246530-10">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9957246530-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9957246530-14">(</span><span class="n">Rest</span><span class="p" data-group-id="9957246530-14">)</span><span class="p" data-group-id="9957246530-13">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9957246530-15">(</span><span class="p" data-group-id="9957246530-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="9957246530-16">]</span><span class="p" data-group-id="9957246530-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9957246530-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9957246530-18">(</span><span class="n">Rest</span><span class="p" data-group-id="9957246530-18">)</span><span class="p" data-group-id="9957246530-17">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="9957246530-19">(</span><span class="p" data-group-id="9957246530-20">[</span><span class="p" data-group-id="9957246530-20">]</span><span class="p" data-group-id="9957246530-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9957246530-21">[</span><span class="p" data-group-id="9957246530-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="9351606334-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="9351606334-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9351606334-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="9351606334-2">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ -55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="9351606334-3">(</span><span class="p" data-group-id="9351606334-4">[</span><span class="p" data-group-id="9351606334-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9351606334-6">}</span><span class="p" data-group-id="9351606334-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9351606334-8">}</span><span class="p" data-group-id="9351606334-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9351606334-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9351606334-10">}</span><span class="p" data-group-id="9351606334-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9351606334-12">}</span><span class="p" data-group-id="9351606334-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9351606334-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9351606334-14">}</span><span class="p" data-group-id="9351606334-13">}</span><span class="p" data-group-id="9351606334-4">]</span><span class="p" data-group-id="9351606334-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9351606334-15">[</span><span class="p" data-group-id="9351606334-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="9351606334-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9351606334-17">}</span><span class="p" data-group-id="9351606334-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9351606334-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="9351606334-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="9351606334-19">}</span><span class="p" data-group-id="9351606334-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9351606334-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="9351606334-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9351606334-21">}</span><span class="p" data-group-id="9351606334-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9351606334-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="9351606334-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="9351606334-23">}</span><span class="p" data-group-id="9351606334-22">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9351606334-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="9351606334-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="9351606334-25">}</span><span class="p" data-group-id="9351606334-24">}</span><span class="p" data-group-id="9351606334-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="7245558465-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7245558465-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7245558465-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="7245558465-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1286481954-6">(</span><span class="p" data-group-id="1286481954-7">[</span><span class="p" data-group-id="1286481954-8">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1286481954-9">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="1286481954-9">}</span><span class="p" data-group-id="1286481954-8">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1286481954-7">]</span><span class="p" data-group-id="1286481954-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1286481954-10">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1286481954-11">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1286481954-12">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="1286481954-12">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="1286481954-11">}</span><span class="p" data-group-id="1286481954-10">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1286481954-13">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1286481954-14">(</span><span class="n">Rest</span><span class="p" data-group-id="1286481954-14">)</span><span class="p" data-group-id="1286481954-13">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1286481954-15">(</span><span class="p" data-group-id="1286481954-16">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1286481954-16">]</span><span class="p" data-group-id="1286481954-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1286481954-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1286481954-18">(</span><span class="n">Rest</span><span class="p" data-group-id="1286481954-18">)</span><span class="p" data-group-id="1286481954-17">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="1286481954-19">(</span><span class="p" data-group-id="1286481954-20">[</span><span class="p" data-group-id="1286481954-20">]</span><span class="p" data-group-id="1286481954-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1286481954-21">[</span><span class="p" data-group-id="1286481954-21">]</span><span class="p">.</span></code></pre><p>Test the function:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">54&gt; </span><span class="nf">c</span><span class="p" data-group-id="5901373101-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5901373101-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5901373101-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="5901373101-2">}</span><span class="p">.</span><span class="gp unselectable">
│ │ │ +55&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5901373101-3">(</span><span class="p" data-group-id="5901373101-4">[</span><span class="p" data-group-id="5901373101-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5901373101-6">}</span><span class="p" data-group-id="5901373101-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5901373101-8">}</span><span class="p" data-group-id="5901373101-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5901373101-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5901373101-10">}</span><span class="p" data-group-id="5901373101-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5901373101-12">}</span><span class="p" data-group-id="5901373101-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5901373101-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5901373101-14">}</span><span class="p" data-group-id="5901373101-13">}</span><span class="p" data-group-id="5901373101-4">]</span><span class="p" data-group-id="5901373101-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5901373101-15">[</span><span class="p" data-group-id="5901373101-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="5901373101-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5901373101-17">}</span><span class="p" data-group-id="5901373101-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5901373101-18">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="5901373101-19">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">21.11111111111111</span><span class="p" data-group-id="5901373101-19">}</span><span class="p" data-group-id="5901373101-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5901373101-20">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="5901373101-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5901373101-21">}</span><span class="p" data-group-id="5901373101-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5901373101-22">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="5901373101-23">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="5901373101-23">}</span><span class="p" data-group-id="5901373101-22">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="5901373101-24">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="5901373101-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mf">2.2222222222222223</span><span class="p" data-group-id="5901373101-25">}</span><span class="p" data-group-id="5901373101-24">}</span><span class="p" data-group-id="5901373101-15">]</span></code></pre><p>Explanation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">format_temps</span><span class="p" data-group-id="8661199695-1">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="8661199695-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8661199695-2">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="8661199695-2">)</span><span class="p">.</span></code></pre><p>Here <code class="inline">format_temps/1</code> calls <code class="inline">convert_list_to_c/1</code>. <code class="inline">convert_list_to_c/1</code> takes
│ │ │  off the head of the <code class="inline">List_of_cities</code>, converts it to Celsius if needed. The <code class="inline">|</code>
│ │ │ -operator is used to add the (maybe) converted to the converted rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0602557302-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0602557302-2">(</span><span class="n">Rest</span><span class="p" data-group-id="0602557302-2">)</span><span class="p" data-group-id="0602557302-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3521807725-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3521807725-2">(</span><span class="n">Rest</span><span class="p" data-group-id="3521807725-2">)</span><span class="p" data-group-id="3521807725-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5420793312-1">(</span><span class="p" data-group-id="5420793312-2">[</span><span class="p" data-group-id="5420793312-2">]</span><span class="p" data-group-id="5420793312-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5420793312-3">[</span><span class="p" data-group-id="5420793312-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0567387562-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0567387562-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0567387562-2">(</span><span class="p" data-group-id="0567387562-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0567387562-3">]</span><span class="p" data-group-id="0567387562-2">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="0567387562-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="0567387562-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0567387562-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="0567387562-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="0567387562-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="0567387562-6">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0567387562-7">(</span><span class="p" data-group-id="0567387562-8">[</span><span class="p" data-group-id="0567387562-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0567387562-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0567387562-10">}</span><span class="p" data-group-id="0567387562-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0567387562-8">]</span><span class="p" data-group-id="0567387562-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0567387562-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0567387562-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0567387562-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="0567387562-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="0567387562-12">}</span><span class="p" data-group-id="0567387562-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0567387562-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0567387562-15">(</span><span class="n">Rest</span><span class="p" data-group-id="0567387562-15">)</span><span class="p" data-group-id="0567387562-14">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0567387562-16">(</span><span class="p" data-group-id="0567387562-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0567387562-17">]</span><span class="p" data-group-id="0567387562-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0567387562-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0567387562-19">(</span><span class="n">Rest</span><span class="p" data-group-id="0567387562-19">)</span><span class="p" data-group-id="0567387562-18">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0567387562-20">(</span><span class="p" data-group-id="0567387562-21">[</span><span class="p" data-group-id="0567387562-21">]</span><span class="p" data-group-id="0567387562-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0567387562-22">[</span><span class="p" data-group-id="0567387562-22">]</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="0567387562-23">(</span><span class="p" data-group-id="0567387562-24">[</span><span class="p" data-group-id="0567387562-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0567387562-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0567387562-26">}</span><span class="p" data-group-id="0567387562-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0567387562-24">]</span><span class="p" data-group-id="0567387562-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0567387562-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0567387562-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0567387562-28">]</span><span class="p" data-group-id="0567387562-27">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="0567387562-29">(</span><span class="n">Rest</span><span class="p" data-group-id="0567387562-29">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="0567387562-30">(</span><span class="p" data-group-id="0567387562-31">[</span><span class="p" data-group-id="0567387562-31">]</span><span class="p" data-group-id="0567387562-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="9204610150-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="9204610150-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9204610150-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="9204610150-2">}</span><span class="gp unselectable">
│ │ │ -57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="9204610150-3">(</span><span class="p" data-group-id="9204610150-4">[</span><span class="p" data-group-id="9204610150-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9204610150-6">}</span><span class="p" data-group-id="9204610150-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9204610150-8">}</span><span class="p" data-group-id="9204610150-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9204610150-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9204610150-10">}</span><span class="p" data-group-id="9204610150-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9204610150-12">}</span><span class="p" data-group-id="9204610150-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9204610150-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9204610150-14">}</span><span class="p" data-group-id="9204610150-13">}</span><span class="p" data-group-id="9204610150-4">]</span><span class="p" data-group-id="9204610150-3">)</span><span class="p">.</span><span class="w">
│ │ │ +operator is used to add the (maybe) converted to the converted rest of the list:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3515462827-1">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="3515462827-2">(</span><span class="n">Rest</span><span class="p" data-group-id="3515462827-2">)</span><span class="p" data-group-id="3515462827-1">]</span><span class="p">;</span></code></pre><p>or:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5828801850-1">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5828801850-2">(</span><span class="n">Rest</span><span class="p" data-group-id="5828801850-2">)</span><span class="p" data-group-id="5828801850-1">]</span><span class="p">;</span></code></pre><p>This is done until the end of the list is reached, that is, the list is empty:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_list_to_c</span><span class="p" data-group-id="2160138799-1">(</span><span class="p" data-group-id="2160138799-2">[</span><span class="p" data-group-id="2160138799-2">]</span><span class="p" data-group-id="2160138799-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2160138799-3">[</span><span class="p" data-group-id="2160138799-3">]</span><span class="p">.</span></code></pre><p>Now when the list is converted, a function to print it is added:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0420909587-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0420909587-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0420909587-2">(</span><span class="p" data-group-id="0420909587-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0420909587-3">]</span><span class="p" data-group-id="0420909587-2">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="0420909587-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="0420909587-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0420909587-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="0420909587-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="0420909587-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="0420909587-6">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0420909587-7">(</span><span class="p" data-group-id="0420909587-8">[</span><span class="p" data-group-id="0420909587-9">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420909587-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0420909587-10">}</span><span class="p" data-group-id="0420909587-9">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0420909587-8">]</span><span class="p" data-group-id="0420909587-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0420909587-11">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420909587-12">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420909587-13">(</span><span class="n">F</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="0420909587-13">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="0420909587-12">}</span><span class="p" data-group-id="0420909587-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0420909587-14">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0420909587-15">(</span><span class="n">Rest</span><span class="p" data-group-id="0420909587-15">)</span><span class="p" data-group-id="0420909587-14">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0420909587-16">(</span><span class="p" data-group-id="0420909587-17">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0420909587-17">]</span><span class="p" data-group-id="0420909587-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0420909587-18">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0420909587-19">(</span><span class="n">Rest</span><span class="p" data-group-id="0420909587-19">)</span><span class="p" data-group-id="0420909587-18">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0420909587-20">(</span><span class="p" data-group-id="0420909587-21">[</span><span class="p" data-group-id="0420909587-21">]</span><span class="p" data-group-id="0420909587-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0420909587-22">[</span><span class="p" data-group-id="0420909587-22">]</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="0420909587-23">(</span><span class="p" data-group-id="0420909587-24">[</span><span class="p" data-group-id="0420909587-25">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420909587-26">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0420909587-26">}</span><span class="p" data-group-id="0420909587-25">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0420909587-24">]</span><span class="p" data-group-id="0420909587-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0420909587-27">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0420909587-28">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0420909587-28">]</span><span class="p" data-group-id="0420909587-27">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="0420909587-29">(</span><span class="n">Rest</span><span class="p" data-group-id="0420909587-29">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="0420909587-30">(</span><span class="p" data-group-id="0420909587-31">[</span><span class="p" data-group-id="0420909587-31">]</span><span class="p" data-group-id="0420909587-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ok</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">56&gt; </span><span class="nf">c</span><span class="p" data-group-id="0330001595-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0330001595-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0330001595-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut7</span><span class="p" data-group-id="0330001595-2">}</span><span class="gp unselectable">
│ │ │ +57&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="0330001595-3">(</span><span class="p" data-group-id="0330001595-4">[</span><span class="p" data-group-id="0330001595-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0330001595-6">}</span><span class="p" data-group-id="0330001595-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0330001595-8">}</span><span class="p" data-group-id="0330001595-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0330001595-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0330001595-10">}</span><span class="p" data-group-id="0330001595-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0330001595-12">}</span><span class="p" data-group-id="0330001595-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0330001595-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0330001595-14">}</span><span class="p" data-group-id="0330001595-13">}</span><span class="p" data-group-id="0330001595-4">]</span><span class="p" data-group-id="0330001595-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Now a function has to be added to find the cities with the maximum and minimum
│ │ │  temperatures. The following program is not the most efficient way of doing this
│ │ │  as you walk through the list of cities four times. But it is better to first
│ │ │  strive for clarity and correctness and to make programs efficient only if
│ │ │ -needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8757649460-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="8757649460-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8757649460-2">(</span><span class="p" data-group-id="8757649460-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8757649460-3">]</span><span class="p" data-group-id="8757649460-2">)</span><span class="p">.</span><span class="w">
│ │ │ +needed.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0662407734-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="0662407734-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0662407734-2">(</span><span class="p" data-group-id="0662407734-3">[</span><span class="ss">format_temps</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0662407734-3">]</span><span class="p" data-group-id="0662407734-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">format_temps</span><span class="p" data-group-id="8757649460-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="8757649460-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8757649460-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="8757649460-5">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="8757649460-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="8757649460-6">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8757649460-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="8757649460-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="8757649460-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="8757649460-8">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="8757649460-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="8757649460-9">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8757649460-10">(</span><span class="p" data-group-id="8757649460-11">[</span><span class="p" data-group-id="8757649460-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8757649460-13">}</span><span class="p" data-group-id="8757649460-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8757649460-11">]</span><span class="p" data-group-id="8757649460-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8757649460-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="8757649460-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="8757649460-15">}</span><span class="p" data-group-id="8757649460-14">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8757649460-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8757649460-18">(</span><span class="n">Rest</span><span class="p" data-group-id="8757649460-18">)</span><span class="p" data-group-id="8757649460-17">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8757649460-19">(</span><span class="p" data-group-id="8757649460-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8757649460-20">]</span><span class="p" data-group-id="8757649460-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8757649460-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8757649460-22">(</span><span class="n">Rest</span><span class="p" data-group-id="8757649460-22">)</span><span class="p" data-group-id="8757649460-21">]</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8757649460-23">(</span><span class="p" data-group-id="8757649460-24">[</span><span class="p" data-group-id="8757649460-24">]</span><span class="p" data-group-id="8757649460-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8757649460-25">[</span><span class="p" data-group-id="8757649460-25">]</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="8757649460-26">(</span><span class="p" data-group-id="8757649460-27">[</span><span class="p" data-group-id="8757649460-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8757649460-29">}</span><span class="p" data-group-id="8757649460-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8757649460-27">]</span><span class="p" data-group-id="8757649460-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8757649460-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8757649460-31">]</span><span class="p" data-group-id="8757649460-30">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">print_temp</span><span class="p" data-group-id="8757649460-32">(</span><span class="n">Rest</span><span class="p" data-group-id="8757649460-32">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">print_temp</span><span class="p" data-group-id="8757649460-33">(</span><span class="p" data-group-id="8757649460-34">[</span><span class="p" data-group-id="8757649460-34">]</span><span class="p" data-group-id="8757649460-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">format_temps</span><span class="p" data-group-id="0662407734-4">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="0662407734-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_List</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0662407734-5">(</span><span class="n">List_of_cities</span><span class="p" data-group-id="0662407734-5">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="0662407734-6">(</span><span class="n">Converted_List</span><span class="p" data-group-id="0662407734-6">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0662407734-7">{</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="0662407734-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="0662407734-8">(</span><span class="n">Converted_List</span><span class="p" data-group-id="0662407734-8">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_max_and_min</span><span class="p" data-group-id="0662407734-9">(</span><span class="n">Max_city</span><span class="p">,</span><span class="w"> </span><span class="n">Min_city</span><span class="p" data-group-id="0662407734-9">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0662407734-10">(</span><span class="p" data-group-id="0662407734-11">[</span><span class="p" data-group-id="0662407734-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-13">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0662407734-13">}</span><span class="p" data-group-id="0662407734-12">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0662407734-11">]</span><span class="p" data-group-id="0662407734-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Converted_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0662407734-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-16">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="mi">32</span><span class="p" data-group-id="0662407734-16">)</span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="0662407734-15">}</span><span class="p" data-group-id="0662407734-14">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0662407734-17">[</span><span class="n">Converted_City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0662407734-18">(</span><span class="n">Rest</span><span class="p" data-group-id="0662407734-18">)</span><span class="p" data-group-id="0662407734-17">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0662407734-19">(</span><span class="p" data-group-id="0662407734-20">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0662407734-20">]</span><span class="p" data-group-id="0662407734-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0662407734-21">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0662407734-22">(</span><span class="n">Rest</span><span class="p" data-group-id="0662407734-22">)</span><span class="p" data-group-id="0662407734-21">]</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0662407734-23">(</span><span class="p" data-group-id="0662407734-24">[</span><span class="p" data-group-id="0662407734-24">]</span><span class="p" data-group-id="0662407734-23">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0662407734-25">[</span><span class="p" data-group-id="0662407734-25">]</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="0662407734-26">(</span><span class="p" data-group-id="0662407734-27">[</span><span class="p" data-group-id="0662407734-28">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-29">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0662407734-29">}</span><span class="p" data-group-id="0662407734-28">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0662407734-27">]</span><span class="p" data-group-id="0662407734-26">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0662407734-30">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> c</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-31">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0662407734-31">]</span><span class="p" data-group-id="0662407734-30">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">print_temp</span><span class="p" data-group-id="0662407734-32">(</span><span class="n">Rest</span><span class="p" data-group-id="0662407734-32">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">print_temp</span><span class="p" data-group-id="0662407734-33">(</span><span class="p" data-group-id="0662407734-34">[</span><span class="p" data-group-id="0662407734-34">]</span><span class="p" data-group-id="0662407734-33">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="8757649460-35">(</span><span class="p" data-group-id="8757649460-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8757649460-36">]</span><span class="p" data-group-id="8757649460-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="8757649460-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="8757649460-37">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="0662407734-35">(</span><span class="p" data-group-id="0662407734-36">[</span><span class="n">City</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0662407734-36">]</span><span class="p" data-group-id="0662407734-35">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="0662407734-37">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">City</span><span class="p" data-group-id="0662407734-37">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="8757649460-38">(</span><span class="p" data-group-id="8757649460-39">[</span><span class="p" data-group-id="8757649460-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8757649460-41">}</span><span class="p" data-group-id="8757649460-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="8757649460-39">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="8757649460-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="8757649460-43">}</span><span class="p" data-group-id="8757649460-42">}</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="8757649460-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="8757649460-45">}</span><span class="p" data-group-id="8757649460-44">}</span><span class="p" data-group-id="8757649460-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="0662407734-38">(</span><span class="p" data-group-id="0662407734-39">[</span><span class="p" data-group-id="0662407734-40">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-41">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0662407734-41">}</span><span class="p" data-group-id="0662407734-40">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="0662407734-39">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="0662407734-42">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-43">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="0662407734-43">}</span><span class="p" data-group-id="0662407734-42">}</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="0662407734-44">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-45">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="0662407734-45">}</span><span class="p" data-group-id="0662407734-44">}</span><span class="p" data-group-id="0662407734-38">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">Temp</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">Max_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8757649460-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8757649460-47">}</span><span class="p" data-group-id="8757649460-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0662407734-46">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-47">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0662407734-47">}</span><span class="p" data-group-id="0662407734-46">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8757649460-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="8757649460-49">}</span><span class="p" data-group-id="8757649460-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ +            </span><span class="n">Max_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0662407734-48">{</span><span class="n">Max_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-49">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_Temp</span><span class="p" data-group-id="0662407734-49">}</span><span class="p" data-group-id="0662407734-48">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │           </span><span class="n">Temp</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Min_Temp</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8757649460-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8757649460-51">}</span><span class="p" data-group-id="8757649460-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0662407734-50">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-51">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0662407734-51">}</span><span class="p" data-group-id="0662407734-50">}</span><span class="p">;</span><span class="w">           </span><span class="c1">% Change</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8757649460-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="8757649460-53">}</span><span class="p" data-group-id="8757649460-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │ +            </span><span class="n">Min_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0662407734-52">{</span><span class="n">Min_Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-53">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_Temp</span><span class="p" data-group-id="0662407734-53">}</span><span class="p" data-group-id="0662407734-52">}</span><span class="w"> </span><span class="c1">% Unchanged</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="8757649460-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="8757649460-54">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">find_max_and_min</span><span class="p" data-group-id="0662407734-54">(</span><span class="n">Rest</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="0662407734-54">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="8757649460-55">(</span><span class="p" data-group-id="8757649460-56">[</span><span class="p" data-group-id="8757649460-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="8757649460-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8757649460-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="8757649460-57">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">find_max_and_min</span><span class="p" data-group-id="0662407734-55">(</span><span class="p" data-group-id="0662407734-56">[</span><span class="p" data-group-id="0662407734-56">]</span><span class="p">,</span><span class="w"> </span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="0662407734-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0662407734-57">{</span><span class="n">Max_City</span><span class="p">,</span><span class="w"> </span><span class="n">Min_City</span><span class="p" data-group-id="0662407734-57">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="8757649460-58">(</span><span class="p" data-group-id="8757649460-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="8757649460-60">}</span><span class="p" data-group-id="8757649460-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="8757649460-62">}</span><span class="p" data-group-id="8757649460-61">}</span><span class="p" data-group-id="8757649460-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8757649460-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="8757649460-64">]</span><span class="p" data-group-id="8757649460-63">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8757649460-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8757649460-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="8757649460-66">]</span><span class="p" data-group-id="8757649460-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="7247976694-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="7247976694-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7247976694-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="7247976694-2">}</span><span class="gp unselectable">
│ │ │ -59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="7247976694-3">(</span><span class="p" data-group-id="7247976694-4">[</span><span class="p" data-group-id="7247976694-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7247976694-6">}</span><span class="p" data-group-id="7247976694-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7247976694-8">}</span><span class="p" data-group-id="7247976694-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7247976694-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7247976694-10">}</span><span class="p" data-group-id="7247976694-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7247976694-12">}</span><span class="p" data-group-id="7247976694-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7247976694-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7247976694-14">}</span><span class="p" data-group-id="7247976694-13">}</span><span class="p" data-group-id="7247976694-4">]</span><span class="p" data-group-id="7247976694-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print_max_and_min</span><span class="p" data-group-id="0662407734-58">(</span><span class="p" data-group-id="0662407734-59">{</span><span class="n">Max_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-60">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Max_temp</span><span class="p" data-group-id="0662407734-60">}</span><span class="p" data-group-id="0662407734-59">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-61">{</span><span class="n">Min_name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-62">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Min_temp</span><span class="p" data-group-id="0662407734-62">}</span><span class="p" data-group-id="0662407734-61">}</span><span class="p" data-group-id="0662407734-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0662407734-63">(</span><span class="s">&quot;Max temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-64">[</span><span class="n">Max_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Max_name</span><span class="p" data-group-id="0662407734-64">]</span><span class="p" data-group-id="0662407734-63">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0662407734-65">(</span><span class="s">&quot;Min temperature was </span><span class="si">~w</span><span class="s"> c in </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0662407734-66">[</span><span class="n">Min_temp</span><span class="p">,</span><span class="w"> </span><span class="n">Min_name</span><span class="p" data-group-id="0662407734-66">]</span><span class="p" data-group-id="0662407734-65">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">58&gt; </span><span class="nf">c</span><span class="p" data-group-id="5072153961-1">(</span><span class="ss">tut7</span><span class="p" data-group-id="5072153961-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5072153961-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">tut7</span><span class="p" data-group-id="5072153961-2">}</span><span class="gp unselectable">
│ │ │ +59&gt; </span><span class="nc">tut7</span><span class="p">:</span><span class="nf">format_temps</span><span class="p" data-group-id="5072153961-3">(</span><span class="p" data-group-id="5072153961-4">[</span><span class="p" data-group-id="5072153961-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="5072153961-6">}</span><span class="p" data-group-id="5072153961-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="5072153961-8">}</span><span class="p" data-group-id="5072153961-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5072153961-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="5072153961-10">}</span><span class="p" data-group-id="5072153961-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="5072153961-12">}</span><span class="p" data-group-id="5072153961-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5072153961-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="5072153961-14">}</span><span class="p" data-group-id="5072153961-13">}</span><span class="p" data-group-id="5072153961-4">]</span><span class="p" data-group-id="5072153961-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="o">-</span><span class="mi">4</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="o">-</span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="mf">2.2222222222222223</span><span class="w"> </span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="n">Max</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="mf">21.11111111111111</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">cape_town</span><span class="w">
│ │ │  </span><span class="n">Min</span><span class="w"> </span><span class="ss">temperature</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">moscow</span><span class="w">
│ │ │ @@ -773,88 +773,88 @@
│ │ │          Action 4
│ │ │  end</code></pre><p>Notice that there is no <code class="inline">;</code> before <code class="inline">end</code>. Conditions do the same as guards, that
│ │ │  is, tests that succeed or fail. Erlang starts at the top and tests until it
│ │ │  finds a condition that succeeds. Then it evaluates (performs) the action
│ │ │  following the condition and ignores all other conditions and actions before the
│ │ │  <code class="inline">end</code>. If no condition matches, a run-time failure occurs. A condition that
│ │ │  always succeeds is the atom <code class="inline">true</code>. This is often used last in an <code class="inline">if</code>, meaning,
│ │ │ -do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6188548197-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="6188548197-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6188548197-2">(</span><span class="p" data-group-id="6188548197-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6188548197-3">]</span><span class="p" data-group-id="6188548197-2">)</span><span class="p">.</span><span class="w">
│ │ │ +do the action following the <code class="inline">true</code> if all other conditions have failed.</p><p>The following is a short program to show the workings of <code class="inline">if</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2226950712-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="2226950712-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2226950712-2">(</span><span class="p" data-group-id="2226950712-3">[</span><span class="ss">test_if</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2226950712-3">]</span><span class="p" data-group-id="2226950712-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">test_if</span><span class="p" data-group-id="6188548197-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="6188548197-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">test_if</span><span class="p" data-group-id="2226950712-4">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="2226950712-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6188548197-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6188548197-6">[</span><span class="p" data-group-id="6188548197-6">]</span><span class="p" data-group-id="6188548197-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2226950712-5">(</span><span class="s">&quot;A == 5</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2226950712-6">[</span><span class="p" data-group-id="2226950712-6">]</span><span class="p" data-group-id="2226950712-5">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">a_equals_5</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6188548197-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6188548197-8">[</span><span class="p" data-group-id="6188548197-8">]</span><span class="p" data-group-id="6188548197-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2226950712-7">(</span><span class="s">&quot;B == 6</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2226950712-8">[</span><span class="p" data-group-id="2226950712-8">]</span><span class="p" data-group-id="2226950712-7">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">b_equals_6</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                      </span><span class="c1">%That is A equals 2 and B equals 3</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6188548197-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6188548197-10">[</span><span class="p" data-group-id="6188548197-10">]</span><span class="p" data-group-id="6188548197-9">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2226950712-9">(</span><span class="s">&quot;A == 2, B == 3</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2226950712-10">[</span><span class="p" data-group-id="2226950712-10">]</span><span class="p" data-group-id="2226950712-9">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">a_equals_2_b_equals_3</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">                     </span><span class="c1">%That is A equals 1 or B equals 7</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6188548197-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6188548197-12">[</span><span class="p" data-group-id="6188548197-12">]</span><span class="p" data-group-id="6188548197-11">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2226950712-11">(</span><span class="s">&quot;A == 1 ; B == 7</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2226950712-12">[</span><span class="p" data-group-id="2226950712-12">]</span><span class="p" data-group-id="2226950712-11">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="3728172878-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="3728172878-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3728172878-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="3728172878-2">}</span><span class="gp unselectable">
│ │ │ -61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3728172878-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="3728172878-3">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><p>Testing this program gives:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">60&gt; </span><span class="nf">c</span><span class="p" data-group-id="7807561817-1">(</span><span class="ss">tut9</span><span class="p" data-group-id="7807561817-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7807561817-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut9</span><span class="p" data-group-id="7807561817-2">}</span><span class="gp unselectable">
│ │ │ +61&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7807561817-3">(</span><span class="mi">5</span><span class="p">,</span><span class="mi">33</span><span class="p" data-group-id="7807561817-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="ss">a_equals_5</span><span class="gp unselectable">
│ │ │ -62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3728172878-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3728172878-4">)</span><span class="p">.</span><span class="w">
│ │ │ +62&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7807561817-4">(</span><span class="mi">33</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7807561817-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">6</span><span class="w">
│ │ │  </span><span class="ss">b_equals_6</span><span class="gp unselectable">
│ │ │ -63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3728172878-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3728172878-5">)</span><span class="p">.</span><span class="w">
│ │ │ +63&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7807561817-5">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7807561817-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="w">
│ │ │  </span><span class="ss">a_equals_2_b_equals_3</span><span class="gp unselectable">
│ │ │ -64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3728172878-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="3728172878-6">)</span><span class="p">.</span><span class="w">
│ │ │ +64&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7807561817-6">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="7807561817-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="gp unselectable">
│ │ │ -65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3728172878-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="3728172878-7">)</span><span class="p">.</span><span class="w">
│ │ │ +65&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7807561817-7">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p" data-group-id="7807561817-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">A</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">;</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">7</span><span class="w">
│ │ │  </span><span class="ss">a_equals_1_or_b_equals_7</span><span class="gp unselectable">
│ │ │ -66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="3728172878-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="3728172878-8">)</span><span class="p">.</span><span class="w">
│ │ │ +66&gt; </span><span class="nc">tut9</span><span class="p">:</span><span class="nf">test_if</span><span class="p" data-group-id="7807561817-8">(</span><span class="mi">33</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="7807561817-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: no true branch found when evaluating an if expression
│ │ │       in function  tut9:test_if/2 (tut9.erl, line 5)</span></code></pre><p>Notice that <code class="inline">tut9:test_if(33,33)</code> does not cause any condition to succeed. This
│ │ │  leads to the run time error <code class="inline">if_clause</code>, here nicely formatted by the shell. See
│ │ │  <a href="../../doc/system/expressions.html">Guard Sequences</a> for details of the many guard tests
│ │ │  available.</p><p><code class="inline">case</code> is another construct in Erlang. Recall that the <code class="inline">convert_length</code> function
│ │ │ -was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="6658022403-1">(</span><span class="p" data-group-id="6658022403-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="6658022403-2">}</span><span class="p" data-group-id="6658022403-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6658022403-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="6658022403-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="6658022403-4">(</span><span class="p" data-group-id="6658022403-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="6658022403-5">}</span><span class="p" data-group-id="6658022403-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6658022403-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="6658022403-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7935816484-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="7935816484-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7935816484-2">(</span><span class="p" data-group-id="7935816484-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7935816484-3">]</span><span class="p" data-group-id="7935816484-2">)</span><span class="p">.</span><span class="w">
│ │ │ +was written as:</p><pre><code class="makeup erlang" translate="no"><span class="nf">convert_length</span><span class="p" data-group-id="4667857948-1">(</span><span class="p" data-group-id="4667857948-2">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="4667857948-2">}</span><span class="p" data-group-id="4667857948-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4667857948-3">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="4667857948-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="4667857948-4">(</span><span class="p" data-group-id="4667857948-5">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="4667857948-5">}</span><span class="p" data-group-id="4667857948-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4667857948-6">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="4667857948-6">}</span><span class="p">.</span></code></pre><p>The same program can also be written as:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9923899460-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="9923899460-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9923899460-2">(</span><span class="p" data-group-id="9923899460-3">[</span><span class="ss">convert_length</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9923899460-3">]</span><span class="p" data-group-id="9923899460-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_length</span><span class="p" data-group-id="7935816484-4">(</span><span class="n">Length</span><span class="p" data-group-id="7935816484-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">convert_length</span><span class="p" data-group-id="9923899460-4">(</span><span class="n">Length</span><span class="p" data-group-id="9923899460-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7935816484-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="7935816484-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7935816484-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7935816484-6">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="7935816484-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="7935816484-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7935816484-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="7935816484-8">}</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="3315692308-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="3315692308-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3315692308-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="3315692308-2">}</span><span class="gp unselectable">
│ │ │ -68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="3315692308-3">(</span><span class="p" data-group-id="3315692308-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="3315692308-4">}</span><span class="p" data-group-id="3315692308-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3315692308-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="3315692308-5">}</span><span class="gp unselectable">
│ │ │ -69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="3315692308-6">(</span><span class="p" data-group-id="3315692308-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="3315692308-7">}</span><span class="p" data-group-id="3315692308-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3315692308-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="3315692308-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │ +        </span><span class="p" data-group-id="9923899460-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p" data-group-id="9923899460-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9923899460-6">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9923899460-6">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9923899460-7">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p" data-group-id="9923899460-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9923899460-8">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mf">2.54</span><span class="p" data-group-id="9923899460-8">}</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">67&gt; </span><span class="nf">c</span><span class="p" data-group-id="2966474999-1">(</span><span class="ss">tut10</span><span class="p" data-group-id="2966474999-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2966474999-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut10</span><span class="p" data-group-id="2966474999-2">}</span><span class="gp unselectable">
│ │ │ +68&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2966474999-3">(</span><span class="p" data-group-id="2966474999-4">{</span><span class="ss">inch</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p" data-group-id="2966474999-4">}</span><span class="p" data-group-id="2966474999-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2966474999-5">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="mf">15.24</span><span class="p" data-group-id="2966474999-5">}</span><span class="gp unselectable">
│ │ │ +69&gt; </span><span class="nc">tut10</span><span class="p">:</span><span class="nf">convert_length</span><span class="p" data-group-id="2966474999-6">(</span><span class="p" data-group-id="2966474999-7">{</span><span class="ss">centimeter</span><span class="p">,</span><span class="w"> </span><span class="mf">2.5</span><span class="p" data-group-id="2966474999-7">}</span><span class="p" data-group-id="2966474999-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2966474999-8">{</span><span class="ss">inch</span><span class="p">,</span><span class="mf">0.984251968503937</span><span class="p" data-group-id="2966474999-8">}</span></code></pre><p>Both <code class="inline">case</code> and <code class="inline">if</code> have <em>return values</em>, that is, in the above example <code class="inline">case</code>
│ │ │  returned either <code class="inline">{inch,X/2.54}</code> or <code class="inline">{centimeter,Y*2.54}</code>. The behaviour of
│ │ │  <code class="inline">case</code> can also be modified by using guards. The following example clarifies
│ │ │  this. It tells us the length of a month, given the year. The year must be known,
│ │ │ -since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3451331216-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="3451331216-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3451331216-2">(</span><span class="p" data-group-id="3451331216-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3451331216-3">]</span><span class="p" data-group-id="3451331216-2">)</span><span class="p">.</span><span class="w">
│ │ │ +since February has 29 days in a leap year.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1916951697-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="1916951697-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1916951697-2">(</span><span class="p" data-group-id="1916951697-3">[</span><span class="ss">month_length</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="1916951697-3">]</span><span class="p" data-group-id="1916951697-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">month_length</span><span class="p" data-group-id="3451331216-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="3451331216-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">month_length</span><span class="p" data-group-id="1916951697-4">(</span><span class="n">Year</span><span class="p">,</span><span class="w"> </span><span class="n">Month</span><span class="p" data-group-id="1916951697-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% All years divisible by 400 are leap</span><span class="w">
│ │ │      </span><span class="c1">%% Years divisible by 100 are not leap (except the 400 rule above)</span><span class="w">
│ │ │      </span><span class="c1">%% Years divisible by 4 are leap (except the 100 rule above)</span><span class="w">
│ │ │      </span><span class="n">Leap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">if</span><span class="w">
│ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="3451331216-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="3451331216-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="1916951697-5">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="1916951697-5">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="3451331216-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="3451331216-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="1916951697-6">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">100</span><span class="p" data-group-id="1916951697-6">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">100</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_leap</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">trunc</span><span class="p" data-group-id="3451331216-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3451331216-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nf">trunc</span><span class="p" data-group-id="1916951697-7">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="1916951697-7">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">leap</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">not_leap</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Month</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">sep</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">apr</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w">
│ │ │ @@ -865,152 +865,152 @@
│ │ │          </span><span class="ss">jan</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">mar</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">may</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">jul</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">aug</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">oct</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="ss">dec</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">31</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="2624619834-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="2624619834-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2624619834-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="2624619834-2">}</span><span class="gp unselectable">
│ │ │ -71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2624619834-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="2624619834-3">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">70&gt; </span><span class="nf">c</span><span class="p" data-group-id="7804403245-1">(</span><span class="ss">tut11</span><span class="p" data-group-id="7804403245-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7804403245-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut11</span><span class="p" data-group-id="7804403245-2">}</span><span class="gp unselectable">
│ │ │ +71&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="7804403245-3">(</span><span class="mi">2004</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="7804403245-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">29</span><span class="gp unselectable">
│ │ │ -72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2624619834-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="2624619834-4">)</span><span class="p">.</span><span class="w">
│ │ │ +72&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="7804403245-4">(</span><span class="mi">2003</span><span class="p">,</span><span class="w"> </span><span class="ss">feb</span><span class="p" data-group-id="7804403245-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">28</span><span class="gp unselectable">
│ │ │ -73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="2624619834-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="2624619834-5">)</span><span class="p">.</span><span class="w">
│ │ │ +73&gt; </span><span class="nc">tut11</span><span class="p">:</span><span class="nf">month_length</span><span class="p" data-group-id="7804403245-5">(</span><span class="mi">1947</span><span class="p">,</span><span class="w"> </span><span class="ss">aug</span><span class="p" data-group-id="7804403245-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">31</span></code></pre><h2 id="built-in-functions-bifs" class="section-heading">
│ │ │    <a href="#built-in-functions-bifs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Built-In Functions (BIFs)</span>
│ │ │  </h2>
│ │ │  <p>BIFs are functions that for some reason are built-in to the Erlang virtual
│ │ │  machine. BIFs often implement functionality that is impossible or is too
│ │ │  inefficient to implement in Erlang. Some BIFs can be called using the function
│ │ │  name only but they are by default belonging to the <code class="inline">erlang</code> module. For example,
│ │ │  the call to the BIF <code class="inline">trunc</code> below is equivalent to a call to <code class="inline">erlang:trunc</code>.</p><p>As shown, first it is checked if a year is leap. If a year is divisible by 400,
│ │ │  it is a leap year. To determine this, first divide the year by 400 and use the
│ │ │  BIF <code class="inline">trunc</code> (more about this later) to cut off any decimals. Then multiply by
│ │ │  400 again and see if the same value is returned again. For example, year 2004:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2004</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.01</span><span class="w">
│ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="5274729974-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="5274729974-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="3586698304-1">(</span><span class="mf">5.01</span><span class="p" data-group-id="3586698304-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>2000 is not the same as 2004, so 2004 is not divisible by 400. Year 2000:</p><pre><code class="makeup erlang" translate="no"><span class="mi">2000</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">5.0</span><span class="w">
│ │ │ -</span><span class="nf">trunc</span><span class="p" data-group-id="7640628376-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="7640628376-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │ +</span><span class="nf">trunc</span><span class="p" data-group-id="4032290701-1">(</span><span class="mf">5.0</span><span class="p" data-group-id="4032290701-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="mi">5</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2000</span></code></pre><p>That is, a leap year. The next two <code class="inline">trunc</code>-tests evaluate if the year is
│ │ │  divisible by 100 or 4 in the same way. The first <code class="inline">if</code> returns <code class="inline">leap</code> or
│ │ │  <code class="inline">not_leap</code>, which lands up in the variable <code class="inline">Leap</code>. This variable is used in the
│ │ │  guard for <code class="inline">feb</code> in the following <code class="inline">case</code> that tells us how long the month is.</p><p>This example showed the use of <code class="inline">trunc</code>. It is easier to use the Erlang operator
│ │ │  <code class="inline">rem</code> that gives the remainder after division, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">74&gt; </span><span class="mi">2004</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="1642034730-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="1642034730-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="mi">4</span></code></pre><p>So instead of writing:</p><pre><code class="makeup erlang" translate="no"><span class="nf">trunc</span><span class="p" data-group-id="0342977338-1">(</span><span class="n">Year</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">400</span><span class="p" data-group-id="0342977338-1">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Year</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>it can be written:</p><pre><code class="makeup erlang" translate="no"><span class="n">Year</span><span class="w"> </span><span class="ow">rem</span><span class="w"> </span><span class="mi">400</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">leap</span><span class="p">;</span></code></pre><p>There are many other BIFs such as <code class="inline">trunc</code>. Only a few BIFs can be used in
│ │ │  guards, and you cannot use functions you have defined yourself in guards. (see
│ │ │  <a href="../../doc/system/expressions.html">Guard Sequences</a>) (For advanced readers: This is to
│ │ │  ensure that guards do not have side effects.) Let us play with a few of these
│ │ │ -functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="4281648313-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="4281648313-1">)</span><span class="p">.</span><span class="w">
│ │ │ +functions in the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">75&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="1419246472-1">(</span><span class="mf">5.6</span><span class="p" data-group-id="1419246472-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">5</span><span class="gp unselectable">
│ │ │ -76&gt; </span><span class="nf">round</span><span class="p" data-group-id="4281648313-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="4281648313-2">)</span><span class="p">.</span><span class="w">
│ │ │ +76&gt; </span><span class="nf">round</span><span class="p" data-group-id="1419246472-2">(</span><span class="mf">5.6</span><span class="p" data-group-id="1419246472-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">6</span><span class="gp unselectable">
│ │ │ -77&gt; </span><span class="nf">length</span><span class="p" data-group-id="4281648313-3">(</span><span class="p" data-group-id="4281648313-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="4281648313-4">]</span><span class="p" data-group-id="4281648313-3">)</span><span class="p">.</span><span class="w">
│ │ │ +77&gt; </span><span class="nf">length</span><span class="p" data-group-id="1419246472-3">(</span><span class="p" data-group-id="1419246472-4">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p">,</span><span class="ss">d</span><span class="p" data-group-id="1419246472-4">]</span><span class="p" data-group-id="1419246472-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span><span class="gp unselectable">
│ │ │ -78&gt; </span><span class="nf">float</span><span class="p" data-group-id="4281648313-5">(</span><span class="mi">5</span><span class="p" data-group-id="4281648313-5">)</span><span class="p">.</span><span class="w">
│ │ │ +78&gt; </span><span class="nf">float</span><span class="p" data-group-id="1419246472-5">(</span><span class="mi">5</span><span class="p" data-group-id="1419246472-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">5.0</span><span class="gp unselectable">
│ │ │ -79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="4281648313-6">(</span><span class="ss">hello</span><span class="p" data-group-id="4281648313-6">)</span><span class="p">.</span><span class="w">
│ │ │ +79&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="1419246472-6">(</span><span class="ss">hello</span><span class="p" data-group-id="1419246472-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="4281648313-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="4281648313-7">)</span><span class="p">.</span><span class="w">
│ │ │ +80&gt; </span><span class="nf">is_atom</span><span class="p" data-group-id="1419246472-7">(</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1419246472-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="4281648313-8">(</span><span class="p" data-group-id="4281648313-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4281648313-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="4281648313-10">}</span><span class="p" data-group-id="4281648313-9">}</span><span class="p" data-group-id="4281648313-8">)</span><span class="p">.</span><span class="w">
│ │ │ +81&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="1419246472-8">(</span><span class="p" data-group-id="1419246472-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1419246472-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="1419246472-10">}</span><span class="p" data-group-id="1419246472-9">}</span><span class="p" data-group-id="1419246472-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="4281648313-11">(</span><span class="p" data-group-id="4281648313-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4281648313-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="4281648313-13">}</span><span class="p" data-group-id="4281648313-12">]</span><span class="p" data-group-id="4281648313-11">)</span><span class="p">.</span><span class="w">
│ │ │ +82&gt; </span><span class="nf">is_tuple</span><span class="p" data-group-id="1419246472-11">(</span><span class="p" data-group-id="1419246472-12">[</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1419246472-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p" data-group-id="1419246472-13">}</span><span class="p" data-group-id="1419246472-12">]</span><span class="p" data-group-id="1419246472-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre><p>All of these can be used in guards. Now for some BIFs that cannot be used in
│ │ │ -guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="2544534467-1">(</span><span class="ss">hello</span><span class="p" data-group-id="2544534467-1">)</span><span class="p">.</span><span class="w">
│ │ │ +guards:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">83&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="5045543561-1">(</span><span class="ss">hello</span><span class="p" data-group-id="5045543561-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;hello&quot;</span><span class="gp unselectable">
│ │ │ -84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="2544534467-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="2544534467-2">)</span><span class="p">.</span><span class="w">
│ │ │ +84&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="5045543561-2">(</span><span class="s">&quot;goodbye&quot;</span><span class="p" data-group-id="5045543561-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">goodbye</span><span class="gp unselectable">
│ │ │ -85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="2544534467-3">(</span><span class="mi">22</span><span class="p" data-group-id="2544534467-3">)</span><span class="p">.</span><span class="w">
│ │ │ +85&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="5045543561-3">(</span><span class="mi">22</span><span class="p" data-group-id="5045543561-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;22&quot;</span></code></pre><p>These three BIFs do conversions that would be difficult (or impossible) to do in
│ │ │  Erlang.</p><h2 id="higher-order-functions-funs" class="section-heading">
│ │ │    <a href="#higher-order-functions-funs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Higher-Order Functions (Funs)</span>
│ │ │  </h2>
│ │ │  <p>Erlang, like most modern functional programming languages, has higher-order
│ │ │ -functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="6055410913-1">(</span><span class="n">X</span><span class="p" data-group-id="6055410913-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +functions. Here is an example using the shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">86&gt; </span><span class="n">Xf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="2337165971-1">(</span><span class="n">X</span><span class="p" data-group-id="2337165971-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="6055410913-2">(</span><span class="mi">5</span><span class="p" data-group-id="6055410913-2">)</span><span class="p">.</span><span class="w">
│ │ │ +87&gt; </span><span class="n">Xf</span><span class="p" data-group-id="2337165971-2">(</span><span class="mi">5</span><span class="p" data-group-id="2337165971-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span></code></pre><p>Here is defined a function that doubles the value of a number and assigned this
│ │ │  function to a variable. Thus <code class="inline">Xf(5)</code> returns value 10. Two useful functions when
│ │ │ -working with lists are <code class="inline">foreach</code> and <code class="inline">map</code>, which are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="1813299669-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1813299669-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1813299669-2">]</span><span class="p" data-group-id="1813299669-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">Fun</span><span class="p" data-group-id="1813299669-3">(</span><span class="n">First</span><span class="p" data-group-id="1813299669-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">foreach</span><span class="p" data-group-id="1813299669-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="1813299669-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">foreach</span><span class="p" data-group-id="1813299669-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1813299669-6">[</span><span class="p" data-group-id="1813299669-6">]</span><span class="p" data-group-id="1813299669-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +working with lists are <code class="inline">foreach</code> and <code class="inline">map</code>, which are defined as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">foreach</span><span class="p" data-group-id="3559558619-1">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3559558619-2">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="3559558619-2">]</span><span class="p" data-group-id="3559558619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">Fun</span><span class="p" data-group-id="3559558619-3">(</span><span class="n">First</span><span class="p" data-group-id="3559558619-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">foreach</span><span class="p" data-group-id="3559558619-4">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="n">Rest</span><span class="p" data-group-id="3559558619-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">foreach</span><span class="p" data-group-id="3559558619-5">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3559558619-6">[</span><span class="p" data-group-id="3559558619-6">]</span><span class="p" data-group-id="3559558619-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="1813299669-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1813299669-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="1813299669-8">]</span><span class="p" data-group-id="1813299669-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1813299669-9">[</span><span class="n">Fun</span><span class="p" data-group-id="1813299669-10">(</span><span class="n">First</span><span class="p" data-group-id="1813299669-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="1813299669-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="1813299669-11">)</span><span class="p" data-group-id="1813299669-9">]</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">map</span><span class="p" data-group-id="1813299669-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1813299669-13">[</span><span class="p" data-group-id="1813299669-13">]</span><span class="p" data-group-id="1813299669-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1813299669-14">[</span><span class="p" data-group-id="1813299669-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="3559558619-7">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3559558619-8">[</span><span class="n">First</span><span class="p">|</span><span class="n">Rest</span><span class="p" data-group-id="3559558619-8">]</span><span class="p" data-group-id="3559558619-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3559558619-9">[</span><span class="n">Fun</span><span class="p" data-group-id="3559558619-10">(</span><span class="n">First</span><span class="p" data-group-id="3559558619-10">)</span><span class="p">|</span><span class="nf">map</span><span class="p" data-group-id="3559558619-11">(</span><span class="n">Fun</span><span class="p">,</span><span class="n">Rest</span><span class="p" data-group-id="3559558619-11">)</span><span class="p" data-group-id="3559558619-9">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">map</span><span class="p" data-group-id="3559558619-12">(</span><span class="n">Fun</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3559558619-13">[</span><span class="p" data-group-id="3559558619-13">]</span><span class="p" data-group-id="3559558619-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3559558619-14">[</span><span class="p" data-group-id="3559558619-14">]</span><span class="p">.</span></code></pre><p>These two functions are provided in the standard module <code class="inline">lists</code>. <code class="inline">foreach</code> takes
│ │ │  a list and applies a fun to every element in the list. <code class="inline">map</code> creates a new list
│ │ │  by applying a fun to every element in a list. Going back to the shell, <code class="inline">map</code> is
│ │ │ -used and a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9229107552-1">(</span><span class="n">X</span><span class="p" data-group-id="9229107552-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +used and a fun to add 3 to every element of a list:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">88&gt; </span><span class="n">Add_3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3635206930-1">(</span><span class="n">X</span><span class="p" data-group-id="3635206930-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9229107552-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9229107552-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9229107552-3">]</span><span class="p" data-group-id="9229107552-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9229107552-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9229107552-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9647952912-1">(</span><span class="p" data-group-id="9647952912-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9647952912-3">}</span><span class="p" data-group-id="9647952912-2">}</span><span class="p" data-group-id="9647952912-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9647952912-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9647952912-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="9647952912-5">]</span><span class="p" data-group-id="9647952912-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +89&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3635206930-2">(</span><span class="n">Add_3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3635206930-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3635206930-3">]</span><span class="p" data-group-id="3635206930-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3635206930-4">[</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3635206930-4">]</span></code></pre><p>Let us (again) print the temperatures in a list of cities:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">90&gt; </span><span class="n">Print_City</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8739650992-1">(</span><span class="p" data-group-id="8739650992-2">{</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-3">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8739650992-3">}</span><span class="p" data-group-id="8739650992-2">}</span><span class="p" data-group-id="8739650992-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8739650992-4">(</span><span class="s">&quot;</span><span class="si">~-</span><span class="s">15w </span><span class="si">~w</span><span class="s"> </span><span class="si">~w</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8739650992-5">[</span><span class="n">City</span><span class="p">,</span><span class="w"> </span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="8739650992-5">]</span><span class="p" data-group-id="8739650992-4">)</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">5.123085357</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="9647952912-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-7">[</span><span class="p" data-group-id="9647952912-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="9647952912-9">}</span><span class="p" data-group-id="9647952912-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="9647952912-11">}</span><span class="p" data-group-id="9647952912-10">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9647952912-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="9647952912-13">}</span><span class="p" data-group-id="9647952912-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9647952912-15">}</span><span class="p" data-group-id="9647952912-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9647952912-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="9647952912-17">}</span><span class="p" data-group-id="9647952912-16">}</span><span class="p" data-group-id="9647952912-7">]</span><span class="p" data-group-id="9647952912-6">)</span><span class="p">.</span><span class="w">
│ │ │ +91&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="8739650992-6">(</span><span class="n">Print_City</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-7">[</span><span class="p" data-group-id="8739650992-8">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-9">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8739650992-9">}</span><span class="p" data-group-id="8739650992-8">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-10">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-11">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8739650992-11">}</span><span class="p" data-group-id="8739650992-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8739650992-12">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="8739650992-13">}</span><span class="p" data-group-id="8739650992-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-14">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-15">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8739650992-15">}</span><span class="p" data-group-id="8739650992-14">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-16">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8739650992-17">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="8739650992-17">}</span><span class="p" data-group-id="8739650992-16">}</span><span class="p" data-group-id="8739650992-7">]</span><span class="p" data-group-id="8739650992-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">moscow</span><span class="w">          </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="w">
│ │ │  </span><span class="ss">cape_town</span><span class="w">       </span><span class="ss">f</span><span class="w"> </span><span class="mi">70</span><span class="w">
│ │ │  </span><span class="ss">stockholm</span><span class="w">       </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="w">
│ │ │  </span><span class="ss">paris</span><span class="w">           </span><span class="ss">f</span><span class="w"> </span><span class="mi">28</span><span class="w">
│ │ │  </span><span class="ss">london</span><span class="w">          </span><span class="ss">f</span><span class="w"> </span><span class="mi">36</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Let us now define a fun that can be used to go through a list of cities and
│ │ │ -temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7634532335-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="7634532335-1">)</span><span class="p">.</span><span class="w">
│ │ │ +temperatures and transform them all to Celsius.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="5577806229-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="5577806229-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7634532335-2">(</span><span class="p" data-group-id="7634532335-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7634532335-3">]</span><span class="p" data-group-id="7634532335-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5577806229-2">(</span><span class="p" data-group-id="5577806229-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="5577806229-3">]</span><span class="p" data-group-id="5577806229-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="7634532335-4">(</span><span class="p" data-group-id="7634532335-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634532335-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7634532335-6">}</span><span class="p" data-group-id="7634532335-5">}</span><span class="p" data-group-id="7634532335-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7634532335-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634532335-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="7634532335-9">(</span><span class="p" data-group-id="7634532335-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="7634532335-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="7634532335-9">)</span><span class="p" data-group-id="7634532335-8">}</span><span class="p" data-group-id="7634532335-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="7634532335-11">(</span><span class="p" data-group-id="7634532335-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634532335-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7634532335-13">}</span><span class="p" data-group-id="7634532335-12">}</span><span class="p" data-group-id="7634532335-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7634532335-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7634532335-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="7634532335-15">}</span><span class="p" data-group-id="7634532335-14">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7634532335-16">(</span><span class="n">List</span><span class="p" data-group-id="7634532335-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7634532335-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="7634532335-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0811640572-1">(</span><span class="p" data-group-id="0811640572-2">[</span><span class="p" data-group-id="0811640572-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0811640572-4">}</span><span class="p" data-group-id="0811640572-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="0811640572-6">}</span><span class="p" data-group-id="0811640572-5">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0811640572-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0811640572-8">}</span><span class="p" data-group-id="0811640572-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="0811640572-10">}</span><span class="p" data-group-id="0811640572-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0811640572-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="0811640572-12">}</span><span class="p" data-group-id="0811640572-11">}</span><span class="p" data-group-id="0811640572-2">]</span><span class="p" data-group-id="0811640572-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0811640572-13">[</span><span class="p" data-group-id="0811640572-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="0811640572-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="0811640572-15">}</span><span class="p" data-group-id="0811640572-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0811640572-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="0811640572-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="0811640572-17">}</span><span class="p" data-group-id="0811640572-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0811640572-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="0811640572-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="0811640572-19">}</span><span class="p" data-group-id="0811640572-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0811640572-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="0811640572-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="0811640572-21">}</span><span class="p" data-group-id="0811640572-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0811640572-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="0811640572-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0811640572-23">}</span><span class="p" data-group-id="0811640572-22">}</span><span class="p" data-group-id="0811640572-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0428710787-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="0428710787-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="5577806229-4">(</span><span class="p" data-group-id="5577806229-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5577806229-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5577806229-6">}</span><span class="p" data-group-id="5577806229-5">}</span><span class="p" data-group-id="5577806229-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5577806229-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5577806229-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="5577806229-9">(</span><span class="p" data-group-id="5577806229-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="5577806229-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="5577806229-9">)</span><span class="p" data-group-id="5577806229-8">}</span><span class="p" data-group-id="5577806229-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="5577806229-11">(</span><span class="p" data-group-id="5577806229-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5577806229-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5577806229-13">}</span><span class="p" data-group-id="5577806229-12">}</span><span class="p" data-group-id="5577806229-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5577806229-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5577806229-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="5577806229-15">}</span><span class="p" data-group-id="5577806229-14">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="5577806229-16">(</span><span class="n">List</span><span class="p" data-group-id="5577806229-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="5577806229-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="5577806229-17">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">92&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="7085668679-1">(</span><span class="p" data-group-id="7085668679-2">[</span><span class="p" data-group-id="7085668679-3">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-4">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7085668679-4">}</span><span class="p" data-group-id="7085668679-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-5">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="7085668679-6">}</span><span class="p" data-group-id="7085668679-5">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7085668679-7">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7085668679-8">}</span><span class="p" data-group-id="7085668679-7">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-9">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-10">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="7085668679-10">}</span><span class="p" data-group-id="7085668679-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-11">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7085668679-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="7085668679-12">}</span><span class="p" data-group-id="7085668679-11">}</span><span class="p" data-group-id="7085668679-2">]</span><span class="p" data-group-id="7085668679-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7085668679-13">[</span><span class="p" data-group-id="7085668679-14">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="7085668679-15">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="7085668679-15">}</span><span class="p" data-group-id="7085668679-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7085668679-16">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="7085668679-17">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="7085668679-17">}</span><span class="p" data-group-id="7085668679-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7085668679-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="7085668679-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="7085668679-19">}</span><span class="p" data-group-id="7085668679-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7085668679-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="7085668679-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="7085668679-21">}</span><span class="p" data-group-id="7085668679-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7085668679-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="7085668679-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7085668679-23">}</span><span class="p" data-group-id="7085668679-22">}</span><span class="p" data-group-id="7085668679-13">]</span></code></pre><p>The <code class="inline">convert_to_c</code> function is the same as before, but here it is used as a fun:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2917417651-1">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="2917417651-1">)</span></code></pre><p>When a function defined elsewhere is used as a fun, it can be referred to as
│ │ │  <code class="inline">Function/Arity</code> (remember that <code class="inline">Arity</code> = number of arguments). So in the
│ │ │  <code class="inline">map</code>-call <code class="inline">lists:map(fun convert_to_c/1, List)</code> is written. As shown,
│ │ │  <code class="inline">convert_list_to_c</code> becomes much shorter and easier to understand.</p><p>The standard module <code class="inline">lists</code> also contains a function <code class="inline">sort(Fun, List)</code> where
│ │ │  <code class="inline">Fun</code> is a fun with two arguments. This fun returns <code class="inline">true</code> if the first argument
│ │ │  is less than the second argument, or else <code class="inline">false</code>. Sorting is added to the
│ │ │ -<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6800601004-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="6800601004-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">convert_list_to_c</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0920441393-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="0920441393-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6800601004-2">(</span><span class="p" data-group-id="6800601004-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6800601004-3">]</span><span class="p" data-group-id="6800601004-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0920441393-2">(</span><span class="p" data-group-id="0920441393-3">[</span><span class="ss">convert_list_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="0920441393-3">]</span><span class="p" data-group-id="0920441393-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="6800601004-4">(</span><span class="p" data-group-id="6800601004-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="6800601004-6">}</span><span class="p" data-group-id="6800601004-5">}</span><span class="p" data-group-id="6800601004-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6800601004-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="6800601004-9">(</span><span class="p" data-group-id="6800601004-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="6800601004-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="6800601004-9">)</span><span class="p" data-group-id="6800601004-8">}</span><span class="p" data-group-id="6800601004-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">convert_to_c</span><span class="p" data-group-id="6800601004-11">(</span><span class="p" data-group-id="6800601004-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="6800601004-13">}</span><span class="p" data-group-id="6800601004-12">}</span><span class="p" data-group-id="6800601004-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6800601004-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="6800601004-15">}</span><span class="p" data-group-id="6800601004-14">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="6800601004-16">(</span><span class="n">List</span><span class="p" data-group-id="6800601004-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="6800601004-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="6800601004-17">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="6800601004-18">(</span><span class="nf">fun</span><span class="p" data-group-id="6800601004-19">(</span><span class="p" data-group-id="6800601004-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="6800601004-21">}</span><span class="p" data-group-id="6800601004-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6800601004-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="6800601004-23">}</span><span class="p" data-group-id="6800601004-22">}</span><span class="p" data-group-id="6800601004-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="6800601004-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="8694127986-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="8694127986-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8694127986-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="8694127986-2">}</span><span class="gp unselectable">
│ │ │ -94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="8694127986-3">(</span><span class="p" data-group-id="8694127986-4">[</span><span class="p" data-group-id="8694127986-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8694127986-6">}</span><span class="p" data-group-id="8694127986-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="8694127986-8">}</span><span class="p" data-group-id="8694127986-7">}</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8694127986-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="8694127986-10">}</span><span class="p" data-group-id="8694127986-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="8694127986-12">}</span><span class="p" data-group-id="8694127986-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8694127986-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="8694127986-14">}</span><span class="p" data-group-id="8694127986-13">}</span><span class="p" data-group-id="8694127986-4">]</span><span class="p" data-group-id="8694127986-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8694127986-15">[</span><span class="p" data-group-id="8694127986-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="8694127986-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="8694127986-17">}</span><span class="p" data-group-id="8694127986-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8694127986-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="8694127986-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="8694127986-19">}</span><span class="p" data-group-id="8694127986-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8694127986-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="8694127986-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="8694127986-21">}</span><span class="p" data-group-id="8694127986-20">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8694127986-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="8694127986-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="8694127986-23">}</span><span class="p" data-group-id="8694127986-22">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8694127986-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="8694127986-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="8694127986-25">}</span><span class="p" data-group-id="8694127986-24">}</span><span class="p" data-group-id="8694127986-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="6310979071-1">(</span><span class="p" data-group-id="6310979071-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6310979071-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="6310979071-3">}</span><span class="p" data-group-id="6310979071-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6310979071-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6310979071-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="6310979071-5">}</span><span class="p" data-group-id="6310979071-4">}</span><span class="p" data-group-id="6310979071-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="0920441393-4">(</span><span class="p" data-group-id="0920441393-5">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-6">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0920441393-6">}</span><span class="p" data-group-id="0920441393-5">}</span><span class="p" data-group-id="0920441393-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0920441393-7">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-8">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="nf">trunc</span><span class="p" data-group-id="0920441393-9">(</span><span class="p" data-group-id="0920441393-10">(</span><span class="n">Temp</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">32</span><span class="p" data-group-id="0920441393-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="0920441393-9">)</span><span class="p" data-group-id="0920441393-8">}</span><span class="p" data-group-id="0920441393-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">convert_to_c</span><span class="p" data-group-id="0920441393-11">(</span><span class="p" data-group-id="0920441393-12">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-13">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0920441393-13">}</span><span class="p" data-group-id="0920441393-12">}</span><span class="p" data-group-id="0920441393-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0920441393-14">{</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-15">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp</span><span class="p" data-group-id="0920441393-15">}</span><span class="p" data-group-id="0920441393-14">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="0920441393-16">(</span><span class="n">List</span><span class="p" data-group-id="0920441393-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">New_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="0920441393-17">(</span><span class="k">fun</span><span class="w"> </span><span class="ss">convert_to_c</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">List</span><span class="p" data-group-id="0920441393-17">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="0920441393-18">(</span><span class="nf">fun</span><span class="p" data-group-id="0920441393-19">(</span><span class="p" data-group-id="0920441393-20">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-21">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="0920441393-21">}</span><span class="p" data-group-id="0920441393-20">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-22">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0920441393-23">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="0920441393-23">}</span><span class="p" data-group-id="0920441393-22">}</span><span class="p" data-group-id="0920441393-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                       </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">New_list</span><span class="p" data-group-id="0920441393-18">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">93&gt; </span><span class="nf">c</span><span class="p" data-group-id="4422024929-1">(</span><span class="ss">tut13</span><span class="p" data-group-id="4422024929-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4422024929-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">tut13</span><span class="p" data-group-id="4422024929-2">}</span><span class="gp unselectable">
│ │ │ +94&gt; </span><span class="nc">tut13</span><span class="p">:</span><span class="nf">convert_list_to_c</span><span class="p" data-group-id="4422024929-3">(</span><span class="p" data-group-id="4422024929-4">[</span><span class="p" data-group-id="4422024929-5">{</span><span class="ss">moscow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-6">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4422024929-6">}</span><span class="p" data-group-id="4422024929-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-7">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-8">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">70</span><span class="p" data-group-id="4422024929-8">}</span><span class="p" data-group-id="4422024929-7">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4422024929-9">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-10">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="4422024929-10">}</span><span class="p" data-group-id="4422024929-9">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-11">{</span><span class="ss">paris</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-12">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="4422024929-12">}</span><span class="p" data-group-id="4422024929-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-13">{</span><span class="ss">london</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4422024929-14">{</span><span class="ss">f</span><span class="p">,</span><span class="w"> </span><span class="mi">36</span><span class="p" data-group-id="4422024929-14">}</span><span class="p" data-group-id="4422024929-13">}</span><span class="p" data-group-id="4422024929-4">]</span><span class="p" data-group-id="4422024929-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4422024929-15">[</span><span class="p" data-group-id="4422024929-16">{</span><span class="ss">moscow</span><span class="p">,</span><span class="p" data-group-id="4422024929-17">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">10</span><span class="p" data-group-id="4422024929-17">}</span><span class="p" data-group-id="4422024929-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4422024929-18">{</span><span class="ss">stockholm</span><span class="p">,</span><span class="p" data-group-id="4422024929-19">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">4</span><span class="p" data-group-id="4422024929-19">}</span><span class="p" data-group-id="4422024929-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4422024929-20">{</span><span class="ss">paris</span><span class="p">,</span><span class="p" data-group-id="4422024929-21">{</span><span class="ss">c</span><span class="p">,</span><span class="o">-</span><span class="mi">2</span><span class="p" data-group-id="4422024929-21">}</span><span class="p" data-group-id="4422024929-20">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4422024929-22">{</span><span class="ss">london</span><span class="p">,</span><span class="p" data-group-id="4422024929-23">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4422024929-23">}</span><span class="p" data-group-id="4422024929-22">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4422024929-24">{</span><span class="ss">cape_town</span><span class="p">,</span><span class="p" data-group-id="4422024929-25">{</span><span class="ss">c</span><span class="p">,</span><span class="mi">21</span><span class="p" data-group-id="4422024929-25">}</span><span class="p" data-group-id="4422024929-24">}</span><span class="p" data-group-id="4422024929-15">]</span></code></pre><p>In <code class="inline">sort</code> the fun is used:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="p" data-group-id="5350749573-1">(</span><span class="p" data-group-id="5350749573-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5350749573-3">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp1</span><span class="p" data-group-id="5350749573-3">}</span><span class="p" data-group-id="5350749573-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5350749573-4">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5350749573-5">{</span><span class="ss">c</span><span class="p">,</span><span class="w"> </span><span class="n">Temp2</span><span class="p" data-group-id="5350749573-5">}</span><span class="p" data-group-id="5350749573-4">}</span><span class="p" data-group-id="5350749573-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Temp1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Temp2</span><span class="w"> </span><span class="k">end</span><span class="p">,</span></code></pre><p>Here the concept of an <em>anonymous variable</em> <code class="inline">_</code> is introduced. This is simply
│ │ │  shorthand for a variable that gets a value, but the value is ignored. This can
│ │ │  be used anywhere suitable, not just in funs. <code class="inline">Temp1 &lt; Temp2</code> returns <code class="inline">true</code> if
│ │ │  <code class="inline">Temp1</code> is less than <code class="inline">Temp2</code>.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/spec_proc.html
│ │ │ @@ -123,72 +123,72 @@
│ │ │    <a href="#simple-debugging" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simple Debugging</span>
│ │ │  </h2>
│ │ │  <p>The <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html"><code class="inline">sys</code></a> module has functions for simple debugging of processes implemented
│ │ │  using behaviours. The <code class="inline">code_lock</code> example from
│ │ │ -<a href="statem.html#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="1414696403-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="1414696403-1">]</span><span class="w"> </span><span class="p" data-group-id="1414696403-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="1414696403-2">]</span><span class="w"> </span><span class="p" data-group-id="1414696403-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="1414696403-3">]</span><span class="w"> </span><span class="p" data-group-id="1414696403-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="1414696403-4">]</span><span class="w"> </span><span class="p" data-group-id="1414696403-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="1414696403-5">]</span><span class="w"> </span><span class="p" data-group-id="1414696403-6">[</span><span class="ss">jit</span><span class="p" data-group-id="1414696403-6">]</span><span class="w">
│ │ │ +<a href="statem.html#example">gen_statem Behaviour</a> is used to illustrate this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="9563849706-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="9563849706-1">]</span><span class="w"> </span><span class="p" data-group-id="9563849706-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="9563849706-2">]</span><span class="w"> </span><span class="p" data-group-id="9563849706-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9563849706-3">]</span><span class="w"> </span><span class="p" data-group-id="9563849706-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="9563849706-4">]</span><span class="w"> </span><span class="p" data-group-id="9563849706-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="9563849706-5">]</span><span class="w"> </span><span class="p" data-group-id="9563849706-6">[</span><span class="ss">jit</span><span class="p" data-group-id="9563849706-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="1414696403-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="1414696403-8">(</span><span class="p" data-group-id="1414696403-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="1414696403-7">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1414696403-9">(</span><span class="p" data-group-id="1414696403-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1414696403-10">]</span><span class="p" data-group-id="1414696403-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="9563849706-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="9563849706-8">(</span><span class="p" data-group-id="9563849706-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="9563849706-7">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9563849706-9">(</span><span class="p" data-group-id="9563849706-10">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9563849706-10">]</span><span class="p" data-group-id="9563849706-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1414696403-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1414696403-11">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="1414696403-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1414696403-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9563849706-11">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9563849706-11">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9563849706-12">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9563849706-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="1414696403-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1414696403-13">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="9563849706-13">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9563849706-13">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="1414696403-14">(</span><span class="mi">1</span><span class="p" data-group-id="1414696403-14">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1414696403-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9563849706-14">(</span><span class="mi">1</span><span class="p" data-group-id="9563849706-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-15">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9563849706-15">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1414696403-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="1414696403-17">(</span><span class="mi">2</span><span class="p" data-group-id="1414696403-17">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1414696403-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-16">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9563849706-16">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ +5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9563849706-17">(</span><span class="mi">2</span><span class="p" data-group-id="9563849706-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-18">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9563849706-18">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1414696403-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="1414696403-20">(</span><span class="mi">3</span><span class="p" data-group-id="1414696403-20">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1414696403-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-19">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9563849706-19">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ +6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9563849706-20">(</span><span class="mi">3</span><span class="p" data-group-id="9563849706-20">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-21">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9563849706-21">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1414696403-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="1414696403-23">(</span><span class="mi">4</span><span class="p" data-group-id="1414696403-23">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1414696403-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-22">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9563849706-22">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ +7&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="9563849706-23">(</span><span class="mi">4</span><span class="p" data-group-id="9563849706-23">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-24">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9563849706-24">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="n">Unlock</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="1414696403-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1414696403-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="1414696403-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="1414696403-27">[</span><span class="p" data-group-id="1414696403-27">]</span><span class="p" data-group-id="1414696403-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">cast</span><span class="w"> </span><span class="p" data-group-id="9563849706-25">{</span><span class="ss">button</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9563849706-25">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="nb">start_timer</span><span class="w"> </span><span class="p" data-group-id="9563849706-26">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10000</span><span class="p">,</span><span class="ss">lock</span><span class="p">,</span><span class="p" data-group-id="9563849706-27">[</span><span class="p" data-group-id="9563849706-27">]</span><span class="p" data-group-id="9563849706-26">}</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w">
│ │ │  </span><span class="n">Lock</span><span class="w">
│ │ │  </span><span class="o">*</span><span class="n">DBG</span><span class="o">*</span><span class="w"> </span><span class="ss">code_lock</span><span class="w"> </span><span class="ss">consume</span><span class="w"> </span><span class="ss">state_timeout</span><span class="w"> </span><span class="ss">lock</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">open</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">locked</span><span class="gp unselectable">
│ │ │ -8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="1414696403-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="1414696403-28">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1414696403-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1414696403-30">[</span><span class="p" data-group-id="1414696403-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="1414696403-32">{</span><span class="p" data-group-id="1414696403-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1414696403-33">}</span><span class="p">,</span><span class="p" data-group-id="1414696403-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1414696403-34">}</span><span class="p" data-group-id="1414696403-32">}</span><span class="p" data-group-id="1414696403-31">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1414696403-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="1414696403-36">{</span><span class="p" data-group-id="1414696403-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1414696403-37">}</span><span class="p">,</span><span class="p" data-group-id="1414696403-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="1414696403-38">}</span><span class="p" data-group-id="1414696403-36">}</span><span class="p" data-group-id="1414696403-35">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1414696403-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="1414696403-39">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1414696403-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1414696403-40">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1414696403-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="1414696403-41">}</span><span class="p" data-group-id="1414696403-30">]</span><span class="p" data-group-id="1414696403-29">}</span><span class="gp unselectable">
│ │ │ -9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="1414696403-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="1414696403-42">)</span><span class="p">.</span><span class="w">
│ │ │ +8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9563849706-28">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="9563849706-28">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9563849706-29">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="9563849706-30">[</span><span class="p" data-group-id="9563849706-31">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="9563849706-32">{</span><span class="p" data-group-id="9563849706-33">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9563849706-33">}</span><span class="p">,</span><span class="p" data-group-id="9563849706-34">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9563849706-34">}</span><span class="p" data-group-id="9563849706-32">}</span><span class="p" data-group-id="9563849706-31">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9563849706-35">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="9563849706-36">{</span><span class="p" data-group-id="9563849706-37">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9563849706-37">}</span><span class="p">,</span><span class="p" data-group-id="9563849706-38">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">48</span><span class="p" data-group-id="9563849706-38">}</span><span class="p" data-group-id="9563849706-36">}</span><span class="p" data-group-id="9563849706-35">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9563849706-39">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">4098</span><span class="p" data-group-id="9563849706-39">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9563849706-40">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9563849706-40">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9563849706-41">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="9563849706-41">}</span><span class="p" data-group-id="9563849706-30">]</span><span class="p" data-group-id="9563849706-29">}</span><span class="gp unselectable">
│ │ │ +9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9563849706-42">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="9563849706-42">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="1414696403-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="1414696403-43">)</span><span class="p">.</span><span class="w">
│ │ │ +10&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="9563849706-43">(</span><span class="ss">code_lock</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="9563849706-43">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="1414696403-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="1414696403-44">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1414696403-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1414696403-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="1414696403-46">}</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1414696403-47">[</span><span class="p" data-group-id="1414696403-48">[</span><span class="p" data-group-id="1414696403-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="1414696403-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1414696403-50">}</span><span class="p" data-group-id="1414696403-49">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="1414696403-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="1414696403-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1414696403-52">]</span><span class="p" data-group-id="1414696403-51">}</span><span class="p" data-group-id="1414696403-48">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="1414696403-53">[</span><span class="p" data-group-id="1414696403-53">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="1414696403-54">[</span><span class="p" data-group-id="1414696403-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="1414696403-55">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="1414696403-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="1414696403-57">[</span><span class="p" data-group-id="1414696403-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="1414696403-58">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="1414696403-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="1414696403-59">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="1414696403-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="1414696403-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="1414696403-61">]</span><span class="p" data-group-id="1414696403-60">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="1414696403-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="1414696403-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="1414696403-64">[</span><span class="p" data-group-id="1414696403-64">]</span><span class="p" data-group-id="1414696403-63">}</span><span class="p" data-group-id="1414696403-62">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="1414696403-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="1414696403-66">[</span><span class="p" data-group-id="1414696403-66">]</span><span class="p" data-group-id="1414696403-65">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="1414696403-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="1414696403-68">[</span><span class="p" data-group-id="1414696403-68">]</span><span class="p" data-group-id="1414696403-67">}</span><span class="p" data-group-id="1414696403-57">]</span><span class="p" data-group-id="1414696403-56">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="1414696403-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="1414696403-70">[</span><span class="p" data-group-id="1414696403-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="p" data-group-id="1414696403-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="1414696403-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1414696403-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1414696403-74">]</span><span class="p">,</span><span class="w">
│ │ │ -                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1414696403-75">[</span><span class="p" data-group-id="1414696403-75">]</span><span class="p" data-group-id="1414696403-73">}</span><span class="p" data-group-id="1414696403-72">}</span><span class="p" data-group-id="1414696403-71">}</span><span class="p" data-group-id="1414696403-70">]</span><span class="p" data-group-id="1414696403-69">}</span><span class="p" data-group-id="1414696403-54">]</span><span class="p" data-group-id="1414696403-47">]</span><span class="p" data-group-id="1414696403-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │ +11&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="9563849706-44">(</span><span class="ss">code_lock</span><span class="p" data-group-id="9563849706-44">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9563849706-45">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9563849706-46">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">gen_statem</span><span class="p" data-group-id="9563849706-46">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9563849706-47">[</span><span class="p" data-group-id="9563849706-48">[</span><span class="p" data-group-id="9563849706-49">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="9563849706-50">{</span><span class="ss">code_lock</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9563849706-50">}</span><span class="p" data-group-id="9563849706-49">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="9563849706-51">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="9563849706-52">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9563849706-52">]</span><span class="p" data-group-id="9563849706-51">}</span><span class="p" data-group-id="9563849706-48">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="9563849706-53">[</span><span class="p" data-group-id="9563849706-53">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="9563849706-54">[</span><span class="p" data-group-id="9563849706-55">{</span><span class="ss">header</span><span class="p">,</span><span class="s">&quot;Status for state machine code_lock&quot;</span><span class="p" data-group-id="9563849706-55">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="9563849706-56">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="9563849706-57">[</span><span class="p" data-group-id="9563849706-58">{</span><span class="s">&quot;Status&quot;</span><span class="p">,</span><span class="ss">running</span><span class="p" data-group-id="9563849706-58">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="9563849706-59">{</span><span class="s">&quot;Parent&quot;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9563849706-59">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="9563849706-60">{</span><span class="s">&quot;Modules&quot;</span><span class="p">,</span><span class="p" data-group-id="9563849706-61">[</span><span class="ss">code_lock</span><span class="p" data-group-id="9563849706-61">]</span><span class="p" data-group-id="9563849706-60">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="9563849706-62">{</span><span class="s">&quot;Time-outs&quot;</span><span class="p">,</span><span class="p" data-group-id="9563849706-63">{</span><span class="mi">0</span><span class="p">,</span><span class="p" data-group-id="9563849706-64">[</span><span class="p" data-group-id="9563849706-64">]</span><span class="p" data-group-id="9563849706-63">}</span><span class="p" data-group-id="9563849706-62">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="9563849706-65">{</span><span class="s">&quot;Logged Events&quot;</span><span class="p">,</span><span class="p" data-group-id="9563849706-66">[</span><span class="p" data-group-id="9563849706-66">]</span><span class="p" data-group-id="9563849706-65">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="9563849706-67">{</span><span class="s">&quot;Postponed&quot;</span><span class="p">,</span><span class="p" data-group-id="9563849706-68">[</span><span class="p" data-group-id="9563849706-68">]</span><span class="p" data-group-id="9563849706-67">}</span><span class="p" data-group-id="9563849706-57">]</span><span class="p" data-group-id="9563849706-56">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="9563849706-69">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="9563849706-70">[</span><span class="p" data-group-id="9563849706-71">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="w">
│ │ │ +                  </span><span class="p" data-group-id="9563849706-72">{</span><span class="ss">locked</span><span class="p">,</span><span class="p" data-group-id="9563849706-73">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9563849706-74">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9563849706-74">]</span><span class="p">,</span><span class="w">
│ │ │ +                            </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9563849706-75">[</span><span class="p" data-group-id="9563849706-75">]</span><span class="p" data-group-id="9563849706-73">}</span><span class="p" data-group-id="9563849706-72">}</span><span class="p" data-group-id="9563849706-71">}</span><span class="p" data-group-id="9563849706-70">]</span><span class="p" data-group-id="9563849706-69">}</span><span class="p" data-group-id="9563849706-54">]</span><span class="p" data-group-id="9563849706-47">]</span><span class="p" data-group-id="9563849706-45">}</span></code></pre><h2 id="special-processes" class="section-heading">
│ │ │    <a href="#special-processes" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Special Processes</span>
│ │ │  </h2>
│ │ │  <p>This section describes how to write a process that complies to the OTP design
│ │ │  principles, without using a standard behaviour. Such a process is to:</p><ul><li>Be started in a way that makes the process fit into a supervision tree</li><li>Support the <code class="inline">sys</code> <a href="spec_proc.html#debug">debug facilities</a></li><li>Take care of <a href="spec_proc.html#msg">system messages</a>.</li></ul><p>System messages are messages with a special meaning, used in the supervision
│ │ │ @@ -198,238 +198,238 @@
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h3>
│ │ │  <p>Here follows the simple server from
│ │ │  <a href="design_principles.html#ch1">Overview</a>,
│ │ │ -implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3169506375-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="3169506375-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3169506375-2">(</span><span class="p" data-group-id="3169506375-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3169506375-3">]</span><span class="p" data-group-id="3169506375-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3169506375-4">(</span><span class="p" data-group-id="3169506375-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3169506375-5">]</span><span class="p" data-group-id="3169506375-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3169506375-6">(</span><span class="p" data-group-id="3169506375-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3169506375-7">]</span><span class="p" data-group-id="3169506375-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3169506375-8">(</span><span class="p" data-group-id="3169506375-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │ +implemented using <code class="inline">sys</code> and <code class="inline">proc_lib</code> to fit into a supervision tree:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7682378346-1">(</span><span class="ss">ch4</span><span class="p" data-group-id="7682378346-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7682378346-2">(</span><span class="p" data-group-id="7682378346-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7682378346-3">]</span><span class="p" data-group-id="7682378346-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7682378346-4">(</span><span class="p" data-group-id="7682378346-5">[</span><span class="ss">alloc</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">free</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7682378346-5">]</span><span class="p" data-group-id="7682378346-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7682378346-6">(</span><span class="p" data-group-id="7682378346-7">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7682378346-7">]</span><span class="p" data-group-id="7682378346-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7682378346-8">(</span><span class="p" data-group-id="7682378346-9">[</span><span class="ss">system_continue</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="ss">system_terminate</span><span class="p">/</span><span class="mi">4</span><span class="p">,</span><span class="w">
│ │ │           </span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3169506375-9">]</span><span class="p" data-group-id="3169506375-8">)</span><span class="p">.</span><span class="w">
│ │ │ +         </span><span class="ss">system_get_state</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">system_replace_state</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7682378346-9">]</span><span class="p" data-group-id="7682378346-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="3169506375-10">(</span><span class="p" data-group-id="3169506375-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3169506375-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-12">[</span><span class="nf">self</span><span class="p" data-group-id="3169506375-13">(</span><span class="p" data-group-id="3169506375-13">)</span><span class="p" data-group-id="3169506375-12">]</span><span class="p" data-group-id="3169506375-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="7682378346-10">(</span><span class="p" data-group-id="7682378346-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7682378346-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-12">[</span><span class="nf">self</span><span class="p" data-group-id="7682378346-13">(</span><span class="p" data-group-id="7682378346-13">)</span><span class="p" data-group-id="7682378346-12">]</span><span class="p" data-group-id="7682378346-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">alloc</span><span class="p" data-group-id="3169506375-14">(</span><span class="p" data-group-id="3169506375-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3169506375-15">{</span><span class="nf">self</span><span class="p" data-group-id="3169506375-16">(</span><span class="p" data-group-id="3169506375-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3169506375-15">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">alloc</span><span class="p" data-group-id="7682378346-14">(</span><span class="p" data-group-id="7682378346-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7682378346-15">{</span><span class="nf">self</span><span class="p" data-group-id="7682378346-16">(</span><span class="p" data-group-id="7682378346-16">)</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="7682378346-15">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3169506375-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="3169506375-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7682378346-17">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Res</span><span class="p" data-group-id="7682378346-17">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Res</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">free</span><span class="p" data-group-id="3169506375-18">(</span><span class="n">Ch</span><span class="p" data-group-id="3169506375-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3169506375-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3169506375-19">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">free</span><span class="p" data-group-id="7682378346-18">(</span><span class="n">Ch</span><span class="p" data-group-id="7682378346-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">ch4</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7682378346-19">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7682378346-19">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="3169506375-20">(</span><span class="n">Parent</span><span class="p" data-group-id="3169506375-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="3169506375-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3169506375-22">(</span><span class="p" data-group-id="3169506375-22">)</span><span class="p" data-group-id="3169506375-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="3169506375-23">(</span><span class="p" data-group-id="3169506375-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="3169506375-24">(</span><span class="p" data-group-id="3169506375-25">[</span><span class="p" data-group-id="3169506375-25">]</span><span class="p" data-group-id="3169506375-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="3169506375-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3169506375-28">(</span><span class="p" data-group-id="3169506375-28">)</span><span class="p" data-group-id="3169506375-27">}</span><span class="p" data-group-id="3169506375-26">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3169506375-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3169506375-29">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7682378346-20">(</span><span class="n">Parent</span><span class="p" data-group-id="7682378346-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="7682378346-21">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7682378346-22">(</span><span class="p" data-group-id="7682378346-22">)</span><span class="p" data-group-id="7682378346-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Chs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">channels</span><span class="p" data-group-id="7682378346-23">(</span><span class="p" data-group-id="7682378346-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="7682378346-24">(</span><span class="p" data-group-id="7682378346-25">[</span><span class="p" data-group-id="7682378346-25">]</span><span class="p" data-group-id="7682378346-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="7682378346-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7682378346-28">(</span><span class="p" data-group-id="7682378346-28">)</span><span class="p" data-group-id="7682378346-27">}</span><span class="p" data-group-id="7682378346-26">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7682378346-29">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="7682378346-29">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="3169506375-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3169506375-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="7682378346-30">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="7682378346-30">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3169506375-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3169506375-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3169506375-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="3169506375-33">}</span><span class="p" data-group-id="3169506375-32">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3169506375-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3169506375-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="3169506375-35">(</span><span class="n">Chs</span><span class="p" data-group-id="3169506375-35">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3169506375-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3169506375-36">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3169506375-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3169506375-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="3169506375-38">}</span><span class="p" data-group-id="3169506375-37">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="3169506375-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="3169506375-40">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3169506375-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3169506375-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3169506375-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3169506375-44">}</span><span class="p" data-group-id="3169506375-43">}</span><span class="p" data-group-id="3169506375-42">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="3169506375-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3169506375-45">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="3169506375-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="3169506375-46">)</span><span class="p">;</span><span class="w">
│ │ │ -
│ │ │ -        </span><span class="p" data-group-id="3169506375-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="3169506375-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="3169506375-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3169506375-48">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7682378346-31">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="7682378346-31">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="7682378346-32">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-33">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="7682378346-33">}</span><span class="p" data-group-id="7682378346-32">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="7682378346-34">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="7682378346-34">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="7682378346-35">(</span><span class="n">Chs</span><span class="p" data-group-id="7682378346-35">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="7682378346-36">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7682378346-36">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="7682378346-37">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-38">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-39">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7682378346-39">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="7682378346-38">}</span><span class="p" data-group-id="7682378346-37">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="7682378346-40">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="7682378346-40">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7682378346-41">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7682378346-41">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="7682378346-42">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-43">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-44">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="7682378346-44">}</span><span class="p" data-group-id="7682378346-43">}</span><span class="p" data-group-id="7682378346-42">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="7682378346-45">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7682378346-45">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="7682378346-46">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="7682378346-46">)</span><span class="p">;</span><span class="w">
│ │ │ +
│ │ │ +        </span><span class="p" data-group-id="7682378346-47">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="7682378346-47">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="7682378346-48">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7682378346-48">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="3169506375-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3169506375-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3169506375-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3169506375-50">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="7682378346-49">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7682378346-49">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="7682378346-50">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="7682378346-50">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="3169506375-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="3169506375-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="3169506375-52">(</span><span class="n">Reason</span><span class="p" data-group-id="3169506375-52">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="7682378346-51">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Chs</span><span class="p" data-group-id="7682378346-51">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="7682378346-52">(</span><span class="n">Reason</span><span class="p" data-group-id="7682378346-52">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="3169506375-53">(</span><span class="n">Chs</span><span class="p" data-group-id="3169506375-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3169506375-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3169506375-54">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="7682378346-53">(</span><span class="n">Chs</span><span class="p" data-group-id="7682378346-53">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7682378346-54">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7682378346-54">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="3169506375-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3169506375-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="3169506375-56">(</span><span class="n">Chs</span><span class="p" data-group-id="3169506375-56">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3169506375-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="3169506375-57">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="7682378346-55">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="7682378346-55">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="7682378346-56">(</span><span class="n">Chs</span><span class="p" data-group-id="7682378346-56">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7682378346-57">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="7682378346-57">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="3169506375-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3169506375-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3169506375-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3169506375-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="3169506375-60">]</span><span class="p" data-group-id="3169506375-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="7682378346-58">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="7682378346-58">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7682378346-59">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7682378346-60">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="7682378346-60">]</span><span class="p" data-group-id="7682378346-59">)</span><span class="p">.</span></code></pre><p id="ex">As it is not relevant to the example, the channel handling functions have been
│ │ │  omitted. To compile this example, the
│ │ │  <a href="design_principles.html#channels-implementation">implementation of channel handling</a>
│ │ │  needs to be added to the module.</p><p>Here is an example showing how the debugging functions in the <code class="inline">sys</code>
│ │ │  module can be used for <code class="inline">ch4</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="5068612744-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="5068612744-1">]</span><span class="w"> </span><span class="p" data-group-id="5068612744-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="5068612744-2">]</span><span class="w"> </span><span class="p" data-group-id="5068612744-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="5068612744-3">]</span><span class="w"> </span><span class="p" data-group-id="5068612744-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="5068612744-4">]</span><span class="w"> </span><span class="p" data-group-id="5068612744-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="5068612744-5">]</span><span class="w"> </span><span class="p" data-group-id="5068612744-6">[</span><span class="ss">jit</span><span class="p" data-group-id="5068612744-6">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">27</span><span class="w"> </span><span class="p" data-group-id="9889761867-1">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">15.0</span><span class="p" data-group-id="9889761867-1">]</span><span class="w"> </span><span class="p" data-group-id="9889761867-2">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="9889761867-2">]</span><span class="w"> </span><span class="p" data-group-id="9889761867-3">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="9889761867-3">]</span><span class="w"> </span><span class="p" data-group-id="9889761867-4">[</span><span class="nc">ds</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="9889761867-4">]</span><span class="w"> </span><span class="p" data-group-id="9889761867-5">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">1</span><span class="p" data-group-id="9889761867-5">]</span><span class="w"> </span><span class="p" data-group-id="9889761867-6">[</span><span class="ss">jit</span><span class="p" data-group-id="9889761867-6">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="5068612744-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="5068612744-8">(</span><span class="p" data-group-id="5068612744-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="5068612744-7">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5068612744-9">(</span><span class="p" data-group-id="5068612744-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5068612744-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5068612744-10">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="5068612744-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5068612744-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V15</span><span class="p">.</span><span class="mi">0</span><span class="w"> </span><span class="p" data-group-id="9889761867-7">(</span><span class="ss">press</span><span class="w"> </span><span class="n">Ctrl</span><span class="o">+</span><span class="n">G</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="nf">help</span><span class="p" data-group-id="9889761867-8">(</span><span class="p" data-group-id="9889761867-8">)</span><span class="p">.</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">help</span><span class="p" data-group-id="9889761867-7">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9889761867-9">(</span><span class="p" data-group-id="9889761867-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9889761867-10">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9889761867-10">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9889761867-11">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9889761867-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="5068612744-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5068612744-12">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="9889761867-12">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9889761867-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="5068612744-13">(</span><span class="p" data-group-id="5068612744-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5068612744-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5068612744-14">}</span><span class="w">
│ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5068612744-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="5068612744-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5068612744-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5068612744-15">}</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">alloc</span><span class="p" data-group-id="9889761867-13">(</span><span class="p" data-group-id="9889761867-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9889761867-14">{</span><span class="ss">in</span><span class="p">,</span><span class="ss">alloc</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9889761867-14">}</span><span class="w">
│ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9889761867-15">{</span><span class="ss">out</span><span class="p">,</span><span class="p" data-group-id="9889761867-16">{</span><span class="ss">ch4</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9889761867-16">}</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9889761867-15">}</span><span class="w">
│ │ │  </span><span class="mi">1</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="5068612744-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="5068612744-17">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5068612744-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="5068612744-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="5068612744-19">}</span><span class="p" data-group-id="5068612744-18">}</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">ch4</span><span class="p">:</span><span class="nf">free</span><span class="p" data-group-id="9889761867-17">(</span><span class="ss">ch1</span><span class="p" data-group-id="9889761867-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">ch4</span><span class="w"> </span><span class="ss">event</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9889761867-18">{</span><span class="ss">in</span><span class="p">,</span><span class="p" data-group-id="9889761867-19">{</span><span class="ss">free</span><span class="p">,</span><span class="ss">ch1</span><span class="p" data-group-id="9889761867-19">}</span><span class="p" data-group-id="9889761867-18">}</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="5068612744-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="5068612744-20">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5068612744-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="5068612744-22">[</span><span class="p" data-group-id="5068612744-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="5068612744-24">{</span><span class="p" data-group-id="5068612744-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5068612744-25">}</span><span class="p">,</span><span class="p" data-group-id="5068612744-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="5068612744-26">}</span><span class="p" data-group-id="5068612744-24">}</span><span class="p" data-group-id="5068612744-23">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5068612744-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="5068612744-28">{</span><span class="p" data-group-id="5068612744-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5068612744-29">}</span><span class="p">,</span><span class="p" data-group-id="5068612744-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="5068612744-30">}</span><span class="p" data-group-id="5068612744-28">}</span><span class="p" data-group-id="5068612744-27">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5068612744-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="5068612744-31">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5068612744-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5068612744-32">}</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5068612744-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5068612744-33">}</span><span class="p" data-group-id="5068612744-22">]</span><span class="p" data-group-id="5068612744-21">}</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="5068612744-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5068612744-34">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9889761867-20">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="nb">get</span><span class="p" data-group-id="9889761867-20">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9889761867-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="9889761867-22">[</span><span class="p" data-group-id="9889761867-23">{</span><span class="ss">start_time</span><span class="p">,</span><span class="p" data-group-id="9889761867-24">{</span><span class="p" data-group-id="9889761867-25">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9889761867-25">}</span><span class="p">,</span><span class="p" data-group-id="9889761867-26">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">13</span><span class="p" data-group-id="9889761867-26">}</span><span class="p" data-group-id="9889761867-24">}</span><span class="p" data-group-id="9889761867-23">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9889761867-27">{</span><span class="ss">current_time</span><span class="p">,</span><span class="p" data-group-id="9889761867-28">{</span><span class="p" data-group-id="9889761867-29">{</span><span class="mi">2024</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9889761867-29">}</span><span class="p">,</span><span class="p" data-group-id="9889761867-30">{</span><span class="mi">8</span><span class="p">,</span><span class="mi">26</span><span class="p">,</span><span class="mi">49</span><span class="p" data-group-id="9889761867-30">}</span><span class="p" data-group-id="9889761867-28">}</span><span class="p" data-group-id="9889761867-27">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9889761867-31">{</span><span class="ss">reductions</span><span class="p">,</span><span class="mi">202</span><span class="p" data-group-id="9889761867-31">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9889761867-32">{</span><span class="ss">messages_in</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9889761867-32">}</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9889761867-33">{</span><span class="ss">messages_out</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9889761867-33">}</span><span class="p" data-group-id="9889761867-22">]</span><span class="p" data-group-id="9889761867-21">}</span><span class="gp unselectable">
│ │ │ +7&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9889761867-34">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="9889761867-34">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="5068612744-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="5068612744-35">)</span><span class="p">.</span><span class="w">
│ │ │ +8&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="9889761867-35">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">false</span><span class="p" data-group-id="9889761867-35">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="5068612744-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="5068612744-36">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5068612744-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5068612744-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="5068612744-38">}</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5068612744-39">[</span><span class="p" data-group-id="5068612744-40">[</span><span class="p" data-group-id="5068612744-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="5068612744-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="5068612744-42">}</span><span class="p" data-group-id="5068612744-41">}</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="5068612744-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="5068612744-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5068612744-44">]</span><span class="p" data-group-id="5068612744-43">}</span><span class="p" data-group-id="5068612744-40">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="5068612744-45">[</span><span class="p" data-group-id="5068612744-45">]</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="5068612744-46">{</span><span class="p" data-group-id="5068612744-47">[</span><span class="mi">1</span><span class="p" data-group-id="5068612744-47">]</span><span class="p">,</span><span class="p" data-group-id="5068612744-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5068612744-48">]</span><span class="p" data-group-id="5068612744-46">}</span><span class="p" data-group-id="5068612744-39">]</span><span class="p" data-group-id="5068612744-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │ +9&gt; </span><span class="nc">sys</span><span class="p">:</span><span class="nf">get_status</span><span class="p" data-group-id="9889761867-36">(</span><span class="ss">ch4</span><span class="p" data-group-id="9889761867-36">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9889761867-37">{</span><span class="ss">status</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.90</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9889761867-38">{</span><span class="ss">module</span><span class="p">,</span><span class="ss">ch4</span><span class="p" data-group-id="9889761867-38">}</span><span class="p">,</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9889761867-39">[</span><span class="p" data-group-id="9889761867-40">[</span><span class="p" data-group-id="9889761867-41">{</span><span class="ss">&#39;$initial_call&#39;</span><span class="p">,</span><span class="p" data-group-id="9889761867-42">{</span><span class="ss">ch4</span><span class="p">,</span><span class="ss">init</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9889761867-42">}</span><span class="p" data-group-id="9889761867-41">}</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="9889761867-43">{</span><span class="ss">&#39;$ancestors&#39;</span><span class="p">,</span><span class="p" data-group-id="9889761867-44">[</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.87</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.70</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.65</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.69</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +                         </span><span class="o">&lt;</span><span class="mf">0.64</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">kernel_sup</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.47</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="9889761867-44">]</span><span class="p" data-group-id="9889761867-43">}</span><span class="p" data-group-id="9889761867-40">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="ss">running</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.88</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="p" data-group-id="9889761867-45">[</span><span class="p" data-group-id="9889761867-45">]</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="9889761867-46">{</span><span class="p" data-group-id="9889761867-47">[</span><span class="mi">1</span><span class="p" data-group-id="9889761867-47">]</span><span class="p">,</span><span class="p" data-group-id="9889761867-48">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">,</span><span class="mi">11</span><span class="p">,</span><span class="mi">12</span><span class="p">,</span><span class="mi">13</span><span class="p">,</span><span class="mi">14</span><span class="p">,</span><span class="mi">15</span><span class="p">,</span><span class="mi">16</span><span class="p">,</span><span class="mi">17</span><span class="p">,</span><span class="mi">18</span><span class="p">,</span><span class="mi">19</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="9889761867-48">]</span><span class="p" data-group-id="9889761867-46">}</span><span class="p" data-group-id="9889761867-39">]</span><span class="p" data-group-id="9889761867-37">}</span></code></pre><h3 id="starting-the-process" class="section-heading">
│ │ │    <a href="#starting-the-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting the Process</span>
│ │ │  </h3>
│ │ │  <p>A function in the <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html"><code class="inline">proc_lib</code></a> module is to be used to start the process. Several
│ │ │  functions are available, for example,
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#spawn_link/4"><code class="inline">proc_lib:spawn_link/3,4</code></a>
│ │ │  for asynchronous start and
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#start_link/5"><code class="inline">proc_lib:start_link/3,4,5</code></a> for synchronous start.</p><p>Information necessary for a process within a supervision tree, such as
│ │ │  details on ancestors and the initial call, is stored when a process
│ │ │  is started through one of these functions.</p><p>If the process terminates with a reason other than <code class="inline">normal</code> or <code class="inline">shutdown</code>, a
│ │ │  crash report is generated. For more information about the crash report, see
│ │ │  <a href="../../lib/kernel-10.2.7.2/doc/html/logger_chapter.html">Logging</a> in Kernel User's Guide.</p><p>In the example, synchronous start is used. The process starts by calling
│ │ │ -<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="5138642828-1">(</span><span class="p" data-group-id="5138642828-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5138642828-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5138642828-3">[</span><span class="nf">self</span><span class="p" data-group-id="5138642828-4">(</span><span class="p" data-group-id="5138642828-4">)</span><span class="p" data-group-id="5138642828-3">]</span><span class="p" data-group-id="5138642828-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │ +<code class="inline">ch4:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="5220360712-1">(</span><span class="p" data-group-id="5220360712-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5220360712-2">(</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5220360712-3">[</span><span class="nf">self</span><span class="p" data-group-id="5220360712-4">(</span><span class="p" data-group-id="5220360712-4">)</span><span class="p" data-group-id="5220360712-3">]</span><span class="p" data-group-id="5220360712-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch4:start_link/0</code> calls <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>, which takes a module
│ │ │  name, a function name, and an argument list as arguments. It then
│ │ │  spawns a new process and establishes a link. The new process starts
│ │ │  by executing the given function, here <code class="inline">ch4:init(Pid)</code>, where <code class="inline">Pid</code> is
│ │ │  the pid of the parent process (obtained by the call to
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#self/0"><code class="inline">self()</code></a> in the call to <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a>).</p><p>All initialization, including name registration, is done in <code class="inline">init/1</code>. The new
│ │ │ -process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="7695655953-1">(</span><span class="n">Parent</span><span class="p" data-group-id="7695655953-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +process has to acknowledge that it has been started to the parent:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3769971564-1">(</span><span class="n">Parent</span><span class="p" data-group-id="3769971564-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="7695655953-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7695655953-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="7695655953-4">(</span><span class="p" data-group-id="7695655953-4">)</span><span class="p" data-group-id="7695655953-3">}</span><span class="p" data-group-id="7695655953-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="7695655953-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7695655953-5">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="3769971564-2">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3769971564-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3769971564-4">(</span><span class="p" data-group-id="3769971564-4">)</span><span class="p" data-group-id="3769971564-3">}</span><span class="p" data-group-id="3769971564-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="3769971564-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="3769971564-5">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#start_link/3"><code class="inline">proc_lib:start_link/3</code></a> is synchronous and does not return until
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#init_ack/2"><code class="inline">proc_lib:init_ack/1,2</code></a> or
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#init_fail/3"><code class="inline">proc_lib:init_fail/2,3</code></a> has been called,
│ │ │  or the process has exited.</p><p><a href="" id="debug"></a></p><h3 id="debugging" class="section-heading">
│ │ │    <a href="#debugging" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Debugging</span>
│ │ │  </h3>
│ │ │  <p>To support the debug facilities in <code class="inline">sys</code>, a <em>debug structure</em> is needed. The
│ │ │ -<code class="inline">Deb</code> term is initialized using <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3484728978-1">(</span><span class="n">Parent</span><span class="p" data-group-id="3484728978-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<code class="inline">Deb</code> term is initialized using <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2446710049-1">(</span><span class="n">Parent</span><span class="p" data-group-id="2446710049-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="3484728978-2">(</span><span class="p" data-group-id="3484728978-3">[</span><span class="p" data-group-id="3484728978-3">]</span><span class="p" data-group-id="3484728978-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Deb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="2446710049-2">(</span><span class="p" data-group-id="2446710049-3">[</span><span class="p" data-group-id="2446710049-3">]</span><span class="p" data-group-id="2446710049-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3484728978-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3484728978-4">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2446710049-4">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="2446710049-4">)</span><span class="p">.</span></code></pre><p><a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a> takes a list of options. Given an empty list as in this
│ │ │  example means that debugging is initially disabled. For information about the
│ │ │  possible options, see <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html"><code class="inline">sys</code></a> in STDLIB.</p><p>For each <em>system event</em> to be logged or traced, the following function
│ │ │ -is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3715572181-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="3715572181-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the follow meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │ +is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="1483127931-1">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Func</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="1483127931-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Deb1</span></code></pre><p>The arguments have the follow meaning:</p><ul><li><code class="inline">Deb</code> is the debug structure as returned from <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#debug_options/1"><code class="inline">sys:debug_options/1</code></a>.</li><li><code class="inline">Func</code> is a fun specifying a (user-defined) function used to format trace
│ │ │  output. For each system event, the format function is called as
│ │ │  <code class="inline">Func(Dev, Event, Info)</code>, where:<ul><li><code class="inline">Dev</code> is the I/O device to which the output is to be printed. See <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html"><code class="inline">io</code></a>
│ │ │  in STDLIB.</li><li><code class="inline">Event</code> and <code class="inline">Info</code> are passed as-is from the call to <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a>.</li></ul></li><li><code class="inline">Info</code> is used to pass more information to <code class="inline">Func</code>. It can be any term, and it
│ │ │  is passed as-is.</li><li><code class="inline">Event</code> is the system event. It is up to the user to define what a system
│ │ │  event is and how it is to be represented. Typically, at least incoming and
│ │ │  outgoing messages are considered system events and represented by the tuples
│ │ │  <code class="inline">{in,Msg[,From]}</code> and <code class="inline">{out,Msg,To[,State]}</code>, respectively.</li></ul><p><a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> returns an updated debug structure <code class="inline">Deb1</code>.</p><p>In the example, <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_debug/4"><code class="inline">sys:handle_debug/4</code></a> is called for each incoming and
│ │ │  outgoing message. The format function <code class="inline">Func</code> is the function
│ │ │ -<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="5111122971-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="5111122971-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +<code class="inline">ch4:write_debug/3</code>, which prints the message using <a href="../../lib/stdlib-6.2.2.2/doc/html/io.html#format/3"><code class="inline">io:format/3</code></a>.</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="3770190686-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="3770190686-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5111122971-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="5111122971-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5111122971-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5111122971-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="5111122971-4">}</span><span class="p" data-group-id="5111122971-3">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5111122971-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="5111122971-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="5111122971-6">(</span><span class="n">Chs</span><span class="p" data-group-id="5111122971-6">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5111122971-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5111122971-7">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5111122971-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5111122971-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5111122971-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5111122971-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="5111122971-9">}</span><span class="p" data-group-id="5111122971-8">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="5111122971-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="5111122971-11">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5111122971-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5111122971-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="5111122971-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5111122971-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5111122971-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="5111122971-15">}</span><span class="p" data-group-id="5111122971-14">}</span><span class="p" data-group-id="5111122971-13">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="5111122971-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="5111122971-16">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">loop</span><span class="p" data-group-id="5111122971-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="5111122971-17">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3770190686-2">{</span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p" data-group-id="3770190686-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3770190686-3">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3770190686-4">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="ss">alloc</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="3770190686-4">}</span><span class="p" data-group-id="3770190686-3">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3770190686-5">{</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs2</span><span class="p" data-group-id="3770190686-5">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alloc</span><span class="p" data-group-id="3770190686-6">(</span><span class="n">Chs</span><span class="p" data-group-id="3770190686-6">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3770190686-7">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3770190686-7">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Deb3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3770190686-8">(</span><span class="n">Deb2</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3770190686-9">{</span><span class="ss">out</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3770190686-10">{</span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3770190686-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p" data-group-id="3770190686-9">}</span><span class="p" data-group-id="3770190686-8">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3770190686-11">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb3</span><span class="p" data-group-id="3770190686-11">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3770190686-12">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3770190686-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Deb2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_debug</span><span class="p" data-group-id="3770190686-13">(</span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="nc">ch4</span><span class="p">:</span><span class="ss">write_debug</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3770190686-14">{</span><span class="ss">in</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3770190686-15">{</span><span class="ss">free</span><span class="p">,</span><span class="w"> </span><span class="n">Ch</span><span class="p" data-group-id="3770190686-15">}</span><span class="p" data-group-id="3770190686-14">}</span><span class="p" data-group-id="3770190686-13">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">Chs2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">free</span><span class="p" data-group-id="3770190686-16">(</span><span class="n">Ch</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="3770190686-16">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">loop</span><span class="p" data-group-id="3770190686-17">(</span><span class="n">Chs2</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb2</span><span class="p" data-group-id="3770190686-17">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">write_debug</span><span class="p" data-group-id="5111122971-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="5111122971-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5111122971-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5111122971-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="5111122971-20">]</span><span class="p" data-group-id="5111122971-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │ +</span><span class="nf">write_debug</span><span class="p" data-group-id="3770190686-18">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p" data-group-id="3770190686-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3770190686-19">(</span><span class="n">Dev</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;</span><span class="si">~p</span><span class="s"> event = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3770190686-20">[</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="3770190686-20">]</span><span class="p" data-group-id="3770190686-19">)</span><span class="p">.</span></code></pre><p><a href="" id="msg"></a></p><h3 id="handling-system-messages" class="section-heading">
│ │ │    <a href="#handling-system-messages" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling System Messages</span>
│ │ │  </h3>
│ │ │  <p><em>System messages</em> are received as:</p><pre><code class="text">{system, From, Request}</code></pre><p>The content and meaning of these messages are not to be interpreted by the
│ │ │ -process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="9808819173-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="9808819173-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │ +process. Instead the following function is to be called:</p><pre><code class="makeup erlang" translate="no"><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="4878828290-1">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4878828290-1">)</span></code></pre><p>The arguments have the following meaning:</p><ul><li><code class="inline">Request</code> and <code class="inline">From</code> from the received system message are to be
│ │ │  passed as-is to the call to <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a>.</li><li><code class="inline">Parent</code> is the pid of the parent process.</li><li><code class="inline">Module</code> is the name of the module implementing the speciall process.</li><li><code class="inline">Deb</code> is the debug structure.</li><li><code class="inline">State</code> is a term describing the internal state and is passed on to
│ │ │  <code class="inline">Module:system_continue/3</code>, <code class="inline">Module:system_terminate/4</code>/
│ │ │  <code class="inline">Module:system_get_state/1</code>, and <code class="inline">Module:system_replace_state/2</code>.</li></ul><p><a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> does not return. It handles the system
│ │ │  message and <em>eventually</em> calls either of the following functions:</p><ul><li><p><code class="inline">Module:system_continue(Parent, Deb, State)</code> - if process execution is to
│ │ │  continue.</p></li><li><p><code class="inline">Module:system_terminate(Reason, Parent, Deb, State)</code> - if the
│ │ │  process is to terminate.</p></li></ul><p>While handling the system message, <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#handle_system_msg/6"><code class="inline">sys:handle_system_msg/6</code></a> can call
│ │ │  one of the following functions:</p><ul><li><p><code class="inline">Module:system_get_state(State)</code> - if the process is to return its state.</p></li><li><p><code class="inline">Module:system_replace_state(StateFun, State)</code> - if the process is
│ │ │  to replace its state using the fun <code class="inline">StateFun</code> fun. See <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#replace_state/3"><code class="inline">sys:replace_state/3</code></a>
│ │ │  for more information.</p></li><li><p><code class="inline">system_code_change(Misc, Module, OldVsn, Extra)</code> - if the process is to
│ │ │  perform a code change.</p></li></ul><p>A process in a supervision tree is expected to terminate with the same reason as
│ │ │ -its parent.</p><p>In the example, system messages are handed by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="8481683077-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="8481683077-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +its parent.</p><p>In the example, system messages are handed by the following code:</p><pre><code class="makeup erlang" translate="no"><span class="nf">loop</span><span class="p" data-group-id="2074955515-1">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="2074955515-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -        </span><span class="p" data-group-id="8481683077-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="8481683077-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="8481683077-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ -                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8481683077-3">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2074955515-2">{</span><span class="ss">system</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="2074955515-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">sys</span><span class="p">:</span><span class="nf">handle_system_msg</span><span class="p" data-group-id="2074955515-3">(</span><span class="n">Request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w">
│ │ │ +                                  </span><span class="ss">ch4</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2074955515-3">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_continue</span><span class="p" data-group-id="8481683077-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8481683077-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8481683077-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="8481683077-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_continue</span><span class="p" data-group-id="2074955515-4">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2074955515-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="2074955515-5">(</span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p" data-group-id="2074955515-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_terminate</span><span class="p" data-group-id="8481683077-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8481683077-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">exit</span><span class="p" data-group-id="8481683077-7">(</span><span class="n">Reason</span><span class="p" data-group-id="8481683077-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_terminate</span><span class="p" data-group-id="2074955515-6">(</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2074955515-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">exit</span><span class="p" data-group-id="2074955515-7">(</span><span class="n">Reason</span><span class="p" data-group-id="2074955515-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_get_state</span><span class="p" data-group-id="8481683077-8">(</span><span class="n">Chs</span><span class="p" data-group-id="8481683077-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8481683077-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8481683077-9">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">system_get_state</span><span class="p" data-group-id="2074955515-8">(</span><span class="n">Chs</span><span class="p" data-group-id="2074955515-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2074955515-9">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2074955515-9">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">system_replace_state</span><span class="p" data-group-id="8481683077-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="8481683077-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="8481683077-11">(</span><span class="n">Chs</span><span class="p" data-group-id="8481683077-11">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8481683077-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="8481683077-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │ +</span><span class="nf">system_replace_state</span><span class="p" data-group-id="2074955515-10">(</span><span class="n">StateFun</span><span class="p">,</span><span class="w"> </span><span class="n">Chs</span><span class="p" data-group-id="2074955515-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">NChs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">StateFun</span><span class="p" data-group-id="2074955515-11">(</span><span class="n">Chs</span><span class="p" data-group-id="2074955515-11">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2074955515-12">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p">,</span><span class="w"> </span><span class="n">NChs</span><span class="p" data-group-id="2074955515-12">}</span><span class="p">.</span></code></pre><p>If a special process is configured to trap exits, it must take notice
│ │ │  of 'EXIT' messages from its parent process and terminate using the
│ │ │ -same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3739094373-1">(</span><span class="n">Parent</span><span class="p" data-group-id="3739094373-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +same exit reason once the parent process has terminated.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0122552933-1">(</span><span class="n">Parent</span><span class="p" data-group-id="0122552933-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="3739094373-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3739094373-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="0122552933-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="0122552933-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="3739094373-3">(</span><span class="n">Parent</span><span class="p" data-group-id="3739094373-3">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="0122552933-3">(</span><span class="n">Parent</span><span class="p" data-group-id="0122552933-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">loop</span><span class="p" data-group-id="3739094373-4">(</span><span class="n">Parent</span><span class="p" data-group-id="3739094373-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">loop</span><span class="p" data-group-id="0122552933-4">(</span><span class="n">Parent</span><span class="p" data-group-id="0122552933-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3739094373-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="3739094373-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0122552933-5">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="0122552933-5">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="c1">%% Clean up here, if needed.</span><span class="w">
│ │ │ -            </span><span class="nf">exit</span><span class="p" data-group-id="3739094373-6">(</span><span class="n">Reason</span><span class="p" data-group-id="3739094373-6">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="nf">exit</span><span class="p" data-group-id="0122552933-6">(</span><span class="n">Reason</span><span class="p" data-group-id="0122552933-6">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><h2 id="user-defined-behaviours" class="section-heading">
│ │ │    <a href="#user-defined-behaviours" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">User-Defined Behaviours</span>
│ │ │  </h2>
│ │ │ @@ -448,71 +448,71 @@
│ │ │  function. Note that the <code class="inline">-optional_callbacks</code> attribute is to be used together
│ │ │  with the <code class="inline">-callback</code> attribute; it cannot be combined with the
│ │ │  <code class="inline">behaviour_info()</code> function described below.</p><p>Tools that need to know about optional callback functions can call
│ │ │  <code class="inline">Behaviour:behaviour_info(optional_callbacks)</code> to get a list of all optional
│ │ │  callback functions.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>We recommend using the <code class="inline">-callback</code> attribute rather than the
│ │ │  <code class="inline">behaviour_info()</code> function. The reason is that the extra type information can
│ │ │  be used by tools to produce documentation or find discrepancies.</p></section><p>As an alternative to the <code class="inline">-callback</code> and <code class="inline">-optional_callbacks</code> attributes you
│ │ │ -may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="0842446243-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="0842446243-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0842446243-2">[</span><span class="p" data-group-id="0842446243-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="0842446243-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="0842446243-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="0842446243-4">}</span><span class="p" data-group-id="0842446243-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │ +may directly implement and export <code class="inline">behaviour_info()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">behaviour_info</span><span class="p" data-group-id="5045677884-1">(</span><span class="ss">callbacks</span><span class="p" data-group-id="5045677884-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5045677884-2">[</span><span class="p" data-group-id="5045677884-3">{</span><span class="n">Name1</span><span class="p">,</span><span class="w"> </span><span class="n">Arity1</span><span class="p" data-group-id="5045677884-3">}</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="p" data-group-id="5045677884-4">{</span><span class="n">NameN</span><span class="p">,</span><span class="w"> </span><span class="n">ArityN</span><span class="p" data-group-id="5045677884-4">}</span><span class="p" data-group-id="5045677884-2">]</span><span class="p">.</span></code></pre><p>where each <code class="inline">{Name, Arity}</code> specifies the name and arity of a callback function.
│ │ │  This function is otherwise automatically generated by the compiler using the
│ │ │  <code class="inline">-callback</code> attributes.</p><p>When the compiler encounters the module attribute <code class="inline">-behaviour(Behaviour).</code> in a
│ │ │  module <code class="inline">Mod</code>, it calls <code class="inline">Behaviour:behaviour_info(callbacks)</code> and compares the
│ │ │  result with the set of functions actually exported from <code class="inline">Mod</code>, and issues a
│ │ │  warning if any callback function is missing.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">%% User-defined behaviour module</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8660250967-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="8660250967-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8660250967-2">(</span><span class="p" data-group-id="8660250967-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8660250967-3">]</span><span class="p" data-group-id="8660250967-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6079987009-1">(</span><span class="ss">simple_server</span><span class="p" data-group-id="6079987009-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6079987009-2">(</span><span class="p" data-group-id="6079987009-3">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6079987009-3">]</span><span class="p" data-group-id="6079987009-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="8660250967-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8660250967-5">(</span><span class="p" data-group-id="8660250967-5">)</span><span class="p" data-group-id="8660250967-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="8660250967-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8660250967-7">(</span><span class="p" data-group-id="8660250967-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8660250967-8">(</span><span class="p" data-group-id="8660250967-8">)</span><span class="p" data-group-id="8660250967-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8660250967-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8660250967-10">(</span><span class="p" data-group-id="8660250967-10">)</span><span class="p" data-group-id="8660250967-9">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="8660250967-11">(</span><span class="p" data-group-id="8660250967-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="8660250967-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8660250967-13">(</span><span class="p" data-group-id="8660250967-13">)</span><span class="p" data-group-id="8660250967-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8660250967-14">(</span><span class="p" data-group-id="8660250967-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">init</span><span class="p" data-group-id="6079987009-4">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6079987009-5">(</span><span class="p" data-group-id="6079987009-5">)</span><span class="p" data-group-id="6079987009-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="6079987009-6">(</span><span class="n">Req</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6079987009-7">(</span><span class="p" data-group-id="6079987009-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6079987009-8">(</span><span class="p" data-group-id="6079987009-8">)</span><span class="p" data-group-id="6079987009-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="6079987009-9">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Reply</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6079987009-10">(</span><span class="p" data-group-id="6079987009-10">)</span><span class="p" data-group-id="6079987009-9">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">terminate</span><span class="p" data-group-id="6079987009-11">(</span><span class="p" data-group-id="6079987009-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">&#39;ok&#39;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">callback</span><span class="w"> </span><span class="nf">format_state</span><span class="p" data-group-id="6079987009-12">(</span><span class="n">State</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6079987009-13">(</span><span class="p" data-group-id="6079987009-13">)</span><span class="p" data-group-id="6079987009-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="6079987009-14">(</span><span class="p" data-group-id="6079987009-14">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="8660250967-15">(</span><span class="p" data-group-id="8660250967-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8660250967-16">]</span><span class="p" data-group-id="8660250967-15">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">optional_callbacks</span><span class="p" data-group-id="6079987009-15">(</span><span class="p" data-group-id="6079987009-16">[</span><span class="ss">format_state</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="6079987009-16">]</span><span class="p" data-group-id="6079987009-15">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Alternatively you may define:</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% -export([behaviour_info/1]).</span><span class="w">
│ │ │  </span><span class="c1">%% behaviour_info(callbacks) -&gt;</span><span class="w">
│ │ │  </span><span class="c1">%%     [{init,1},</span><span class="w">
│ │ │  </span><span class="c1">%%      {handle_req,2},</span><span class="w">
│ │ │  </span><span class="c1">%%      {terminate,0}].</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="8660250967-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8660250967-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8660250967-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8660250967-19">[</span><span class="nf">self</span><span class="p" data-group-id="8660250967-20">(</span><span class="p" data-group-id="8660250967-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8660250967-19">]</span><span class="p" data-group-id="8660250967-18">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="6079987009-17">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="6079987009-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6079987009-18">(</span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6079987009-19">[</span><span class="nf">self</span><span class="p" data-group-id="6079987009-20">(</span><span class="p" data-group-id="6079987009-20">)</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="6079987009-19">]</span><span class="p" data-group-id="6079987009-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8660250967-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="8660250967-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">register</span><span class="p" data-group-id="8660250967-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8660250967-23">(</span><span class="p" data-group-id="8660250967-23">)</span><span class="p" data-group-id="8660250967-22">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="6079987009-21">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p" data-group-id="6079987009-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">register</span><span class="p" data-group-id="6079987009-22">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6079987009-23">(</span><span class="p" data-group-id="6079987009-23">)</span><span class="p" data-group-id="6079987009-22">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="8660250967-24">(</span><span class="p" data-group-id="8660250967-25">[</span><span class="p" data-group-id="8660250967-25">]</span><span class="p" data-group-id="8660250967-24">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="8660250967-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8660250967-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="8660250967-28">(</span><span class="p" data-group-id="8660250967-28">)</span><span class="p" data-group-id="8660250967-27">}</span><span class="p" data-group-id="8660250967-26">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">loop</span><span class="p" data-group-id="8660250967-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8660250967-29">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="n">Dbg</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">sys</span><span class="p">:</span><span class="nf">debug_options</span><span class="p" data-group-id="6079987009-24">(</span><span class="p" data-group-id="6079987009-25">[</span><span class="p" data-group-id="6079987009-25">]</span><span class="p" data-group-id="6079987009-24">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">proc_lib</span><span class="p">:</span><span class="nf">init_ack</span><span class="p" data-group-id="6079987009-26">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6079987009-27">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="6079987009-28">(</span><span class="p" data-group-id="6079987009-28">)</span><span class="p" data-group-id="6079987009-27">}</span><span class="p" data-group-id="6079987009-26">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">loop</span><span class="p" data-group-id="6079987009-29">(</span><span class="n">Parent</span><span class="p">,</span><span class="w"> </span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Deb</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6079987009-29">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9020872552-1">(</span><span class="ss">db</span><span class="p" data-group-id="9020872552-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9020872552-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="9020872552-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>In a callback module:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6507553806-1">(</span><span class="ss">db</span><span class="p" data-group-id="6507553806-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6507553806-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="6507553806-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9020872552-3">(</span><span class="p" data-group-id="9020872552-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9020872552-4">]</span><span class="p" data-group-id="9020872552-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6507553806-3">(</span><span class="p" data-group-id="6507553806-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6507553806-4">]</span><span class="p" data-group-id="6507553806-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The contracts specified with <code class="inline">-callback</code> attributes in behaviour modules can be
│ │ │  further refined by adding <code class="inline">-spec</code> attributes in callback modules. This can be
│ │ │  useful as <code class="inline">-callback</code> contracts are usually generic. The same callback module
│ │ │ -with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0000527867-1">(</span><span class="ss">db</span><span class="p" data-group-id="0000527867-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="0000527867-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="0000527867-2">)</span><span class="p">.</span><span class="w">
│ │ │ +with contracts for the callbacks:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3595703011-1">(</span><span class="ss">db</span><span class="p" data-group-id="3595703011-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3595703011-2">(</span><span class="ss">simple_server</span><span class="p" data-group-id="3595703011-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0000527867-3">(</span><span class="p" data-group-id="0000527867-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="0000527867-4">]</span><span class="p" data-group-id="0000527867-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3595703011-3">(</span><span class="p" data-group-id="3595703011-4">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">handle_req</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">terminate</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3595703011-4">]</span><span class="p" data-group-id="3595703011-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0000527867-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0000527867-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0000527867-7">[</span><span class="nf">atom</span><span class="p" data-group-id="0000527867-8">(</span><span class="p" data-group-id="0000527867-8">)</span><span class="p" data-group-id="0000527867-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="0000527867-9">(</span><span class="p" data-group-id="0000527867-9">)</span><span class="p" data-group-id="0000527867-6">}</span><span class="p" data-group-id="0000527867-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3595703011-5">(</span><span class="ss">state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3595703011-6">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3595703011-7">[</span><span class="nf">atom</span><span class="p" data-group-id="3595703011-8">(</span><span class="p" data-group-id="3595703011-8">)</span><span class="p" data-group-id="3595703011-7">]</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3595703011-9">(</span><span class="p" data-group-id="3595703011-9">)</span><span class="p" data-group-id="3595703011-6">}</span><span class="p" data-group-id="3595703011-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="0000527867-10">(</span><span class="p" data-group-id="0000527867-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="0000527867-11">{</span><span class="p" data-group-id="0000527867-11">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="0000527867-12">(</span><span class="p" data-group-id="0000527867-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="0000527867-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="0000527867-14">(</span><span class="p" data-group-id="0000527867-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="0000527867-15">(</span><span class="p" data-group-id="0000527867-15">)</span><span class="p" data-group-id="0000527867-13">}</span><span class="p">;</span><span class="w">
│ │ │ -                   </span><span class="p" data-group-id="0000527867-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="0000527867-17">(</span><span class="p" data-group-id="0000527867-17">)</span><span class="p" data-group-id="0000527867-16">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="3595703011-10">(</span><span class="p" data-group-id="3595703011-10">)</span><span class="w">   </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">state</span><span class="p" data-group-id="3595703011-11">{</span><span class="p" data-group-id="3595703011-11">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">request</span><span class="p" data-group-id="3595703011-12">(</span><span class="p" data-group-id="3595703011-12">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3595703011-13">{</span><span class="ss">&#39;store&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3595703011-14">(</span><span class="p" data-group-id="3595703011-14">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3595703011-15">(</span><span class="p" data-group-id="3595703011-15">)</span><span class="p" data-group-id="3595703011-13">}</span><span class="p">;</span><span class="w">
│ │ │ +                   </span><span class="p" data-group-id="3595703011-16">{</span><span class="ss">&#39;lookup&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3595703011-17">(</span><span class="p" data-group-id="3595703011-17">)</span><span class="p" data-group-id="3595703011-16">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="0000527867-18">(</span><span class="nf">request</span><span class="p" data-group-id="0000527867-19">(</span><span class="p" data-group-id="0000527867-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="0000527867-20">(</span><span class="p" data-group-id="0000527867-20">)</span><span class="p" data-group-id="0000527867-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0000527867-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="0000527867-22">(</span><span class="p" data-group-id="0000527867-22">)</span><span class="p" data-group-id="0000527867-21">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">handle_req</span><span class="p" data-group-id="3595703011-18">(</span><span class="nf">request</span><span class="p" data-group-id="3595703011-19">(</span><span class="p" data-group-id="3595703011-19">)</span><span class="p">,</span><span class="w"> </span><span class="nf">state</span><span class="p" data-group-id="3595703011-20">(</span><span class="p" data-group-id="3595703011-20">)</span><span class="p" data-group-id="3595703011-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3595703011-21">{</span><span class="ss">&#39;ok&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3595703011-22">(</span><span class="p" data-group-id="3595703011-22">)</span><span class="p" data-group-id="3595703011-21">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Each <code class="inline">-spec</code> contract is to be a subtype of the respective <code class="inline">-callback</code> contract.</p>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/statem.html
│ │ │ @@ -124,15 +124,15 @@
│ │ │  </h2>
│ │ │  <p>Established Automata Theory does not deal much with how a <em>state transition</em>
│ │ │  is triggered, but assumes that the output is a function of the input
│ │ │  (and the state) and that they are some kind of values.</p><p>For an Event-Driven State Machine, the input is an <em>event</em> that triggers
│ │ │  a <em>state transition</em> and the output is actions executed during
│ │ │  the <em>state transition</em>.  Analogously to the mathematical model
│ │ │  of a Finite State Machine, it can be described as a set of relations
│ │ │ -of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="4963987036-1">(</span><span class="n">S</span><span class="p" data-group-id="4963987036-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="4963987036-2">(</span><span class="n">E</span><span class="p" data-group-id="4963987036-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="4963987036-3">(</span><span class="n">A</span><span class="p" data-group-id="4963987036-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="4963987036-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="4963987036-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │ +of the following form:</p><pre><code class="makeup erlang" translate="no"><span class="n">State</span><span class="p" data-group-id="6487780747-1">(</span><span class="n">S</span><span class="p" data-group-id="6487780747-1">)</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">Event</span><span class="p" data-group-id="6487780747-2">(</span><span class="n">E</span><span class="p" data-group-id="6487780747-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Actions</span><span class="p" data-group-id="6487780747-3">(</span><span class="n">A</span><span class="p" data-group-id="6487780747-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p" data-group-id="6487780747-4">(</span><span class="n">S</span><span class="err">&#39;</span><span class="p" data-group-id="6487780747-4">)</span></code></pre><p>These relations are interpreted as follows: if we are in state <code class="inline">S</code>,
│ │ │  and event <code class="inline">E</code> occurs, we are to perform actions <code class="inline">A</code>, and make a transition
│ │ │  to state <code class="inline">S'</code>.  Notice that <code class="inline">S'</code> can be equal to <code class="inline">S</code>,
│ │ │  and that <code class="inline">A</code> can be empty.</p><p>In <code class="inline">gen_statem</code> we define a <em>state change</em> as a <em>state transition</em> in which the
│ │ │  new state <code class="inline">S'</code> is different from the current state <code class="inline">S</code>, where &quot;different&quot; means
│ │ │  Erlang's strict inequality: <code class="inline">=/=</code> also known as &quot;does not match&quot;. <code class="inline">gen_statem</code>
│ │ │  does more things during <em>state changes</em> than during other <em>state transitions</em>.</p><p>As <code class="inline">A</code> and <code class="inline">S'</code> depend only on <code class="inline">S</code> and <code class="inline">E</code>, the kind of state machine described
│ │ │  here is a Mealy machine (see, for example, the Wikipedia article
│ │ │ @@ -405,20 +405,20 @@
│ │ │    </a>
│ │ │    <span class="text">State Enter Calls</span>
│ │ │  </h2>
│ │ │  <p>The <code class="inline">gen_statem</code> behaviour can, if this is enabled, regardless of <em>callback
│ │ │  mode</em>, automatically call the <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:state_enter/0"><em>state callback</em></a>
│ │ │  with special arguments whenever the state changes, so you can write
│ │ │  state enter actions near the rest of the <em>state transition</em> rules.
│ │ │ -It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="2570145576-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2570145576-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +It typically looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">StateName</span><span class="p" data-group-id="3871821971-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3871821971-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">state</span><span class="w"> </span><span class="ss">enter</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2570145576-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="2570145576-2">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">StateName</span><span class="p" data-group-id="2570145576-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2570145576-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3871821971-2">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="3871821971-2">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="n">StateName</span><span class="p" data-group-id="3871821971-3">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3871821971-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">actions</span><span class="w"> </span><span class="ss">here</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2570145576-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="2570145576-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │ +    </span><span class="p" data-group-id="3871821971-4">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="n">NewStateName</span><span class="p">,</span><span class="w"> </span><span class="n">NewData</span><span class="p" data-group-id="3871821971-4">}</span><span class="p">.</span></code></pre><p>Since the <em>state enter call</em> is not an event there are restrictions on the
│ │ │  allowed return value and state <a href="#transition-actions"><em>transition actions</em></a>.
│ │ │  You must not change the state, <a href="#postponing-events">postpone</a> this non-event,
│ │ │  <a href="#inserted-events">insert any events</a>, or change the
│ │ │  <a href="#callback-module"><em>callback module</em></a>.</p><p>The first state that is entered after <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#c:init/1"><code class="inline">gen_statem:init/1</code></a> will get
│ │ │  a <em>state enter call</em> with <code class="inline">OldState</code> equal to the current state.</p><p>You may repeat the <em>state enter call</em> using the <code class="inline">{repeat_state,...}</code> return
│ │ │  value from the <a href="#state-callback"><em>state callback</em></a>. In this case
│ │ │  <code class="inline">OldState</code> will also be equal to the current state.</p><p>Depending on how your state machine is specified, this can be a very useful
│ │ │ @@ -499,72 +499,72 @@
│ │ │  
│ │ │      locked      --&gt; check_code : {button, Button}\n* Collect Buttons
│ │ │      check_code  --&gt; locked     : Incorrect code
│ │ │      check_code  --&gt; open       : Correct code\n* do_unlock()\n* Clear Buttons\n* Set state_timeout 10 s
│ │ │  
│ │ │      open        --&gt; open   : {button, Digit}
│ │ │      open        --&gt; locked : state_timeout\n* do_lock()</code></pre><p>This code lock state machine can be implemented using <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a> with
│ │ │ -the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8657495598-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="8657495598-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="8657495598-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="8657495598-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="8657495598-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="8657495598-3">)</span><span class="p">.</span><span class="w">
│ │ │ +the following <em>callback module</em>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7615048127-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="7615048127-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7615048127-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="7615048127-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="7615048127-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock</span><span class="p" data-group-id="7615048127-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8657495598-4">(</span><span class="p" data-group-id="8657495598-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8657495598-5">]</span><span class="p" data-group-id="8657495598-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8657495598-6">(</span><span class="p" data-group-id="8657495598-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="8657495598-7">]</span><span class="p" data-group-id="8657495598-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8657495598-8">(</span><span class="p" data-group-id="8657495598-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="8657495598-9">]</span><span class="p" data-group-id="8657495598-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8657495598-10">(</span><span class="p" data-group-id="8657495598-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="8657495598-11">]</span><span class="p" data-group-id="8657495598-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="8657495598-12">(</span><span class="n">Code</span><span class="p" data-group-id="8657495598-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8657495598-13">(</span><span class="p" data-group-id="8657495598-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="8657495598-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8657495598-15">[</span><span class="p" data-group-id="8657495598-15">]</span><span class="p" data-group-id="8657495598-13">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="8657495598-16">(</span><span class="n">Button</span><span class="p" data-group-id="8657495598-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="8657495598-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8657495598-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8657495598-18">}</span><span class="p" data-group-id="8657495598-17">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="8657495598-19">(</span><span class="n">Code</span><span class="p" data-group-id="8657495598-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="8657495598-20">(</span><span class="p" data-group-id="8657495598-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8657495598-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="8657495598-22">(</span><span class="n">Code</span><span class="p" data-group-id="8657495598-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="8657495598-23">[</span><span class="p" data-group-id="8657495598-23">]</span><span class="p" data-group-id="8657495598-21">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="8657495598-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8657495598-24">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="8657495598-25">(</span><span class="p" data-group-id="8657495598-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="7390698501-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7390698501-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7390698501-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7390698501-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7390698501-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7390698501-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7615048127-4">(</span><span class="p" data-group-id="7615048127-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7615048127-5">]</span><span class="p" data-group-id="7615048127-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7615048127-6">(</span><span class="p" data-group-id="7615048127-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7615048127-7">]</span><span class="p" data-group-id="7615048127-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7615048127-8">(</span><span class="p" data-group-id="7615048127-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7615048127-9">]</span><span class="p" data-group-id="7615048127-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7615048127-10">(</span><span class="p" data-group-id="7615048127-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="7615048127-11">]</span><span class="p" data-group-id="7615048127-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="7615048127-12">(</span><span class="n">Code</span><span class="p" data-group-id="7615048127-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7615048127-13">(</span><span class="p" data-group-id="7615048127-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="7615048127-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615048127-15">[</span><span class="p" data-group-id="7615048127-15">]</span><span class="p" data-group-id="7615048127-13">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="7615048127-16">(</span><span class="n">Button</span><span class="p" data-group-id="7615048127-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="7615048127-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7615048127-18">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7615048127-18">}</span><span class="p" data-group-id="7615048127-17">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7615048127-19">(</span><span class="n">Code</span><span class="p" data-group-id="7615048127-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="7615048127-20">(</span><span class="p" data-group-id="7615048127-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7615048127-21">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="7615048127-22">(</span><span class="n">Code</span><span class="p" data-group-id="7615048127-22">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7615048127-23">[</span><span class="p" data-group-id="7615048127-23">]</span><span class="p" data-group-id="7615048127-21">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7615048127-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7615048127-24">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="7615048127-25">(</span><span class="p" data-group-id="7615048127-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9250514663-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9250514663-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9250514663-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9250514663-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9250514663-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9250514663-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="7390698501-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="7390698501-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="9250514663-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="9250514663-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="7390698501-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="7390698501-5">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7390698501-6">[</span><span class="n">Button</span><span class="p" data-group-id="7390698501-6">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="9250514663-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="9250514663-5">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9250514663-6">[</span><span class="n">Button</span><span class="p" data-group-id="9250514663-6">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7390698501-7">(</span><span class="p" data-group-id="7390698501-7">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7390698501-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7390698501-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7390698501-10">[</span><span class="p" data-group-id="7390698501-10">]</span><span class="p" data-group-id="7390698501-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="7390698501-11">[</span><span class="p" data-group-id="7390698501-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7390698501-12">}</span><span class="p" data-group-id="7390698501-11">]</span><span class="p" data-group-id="7390698501-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9250514663-7">(</span><span class="p" data-group-id="9250514663-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9250514663-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9250514663-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9250514663-10">[</span><span class="p" data-group-id="9250514663-10">]</span><span class="p" data-group-id="9250514663-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9250514663-11">[</span><span class="p" data-group-id="9250514663-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9250514663-12">}</span><span class="p" data-group-id="9250514663-11">]</span><span class="p" data-group-id="9250514663-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7390698501-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7390698501-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="7390698501-14">}</span><span class="p" data-group-id="7390698501-13">}</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="5133753528-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="5133753528-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="5133753528-2">(</span><span class="p" data-group-id="5133753528-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5133753528-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5133753528-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="5133753528-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5133753528-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5133753528-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5133753528-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5133753528-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5133753528-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="4399002815-1">(</span><span class="p" data-group-id="4399002815-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4399002815-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4399002815-3">[</span><span class="p" data-group-id="4399002815-3">]</span><span class="p" data-group-id="4399002815-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="4399002815-4">(</span><span class="p" data-group-id="4399002815-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4399002815-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4399002815-6">[</span><span class="p" data-group-id="4399002815-6">]</span><span class="p" data-group-id="4399002815-5">)</span><span class="p">.</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9250514663-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9250514663-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9250514663-14">}</span><span class="p" data-group-id="9250514663-13">}</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="3463191382-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="3463191382-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3463191382-2">(</span><span class="p" data-group-id="3463191382-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3463191382-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3463191382-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3463191382-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3463191382-5">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3463191382-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3463191382-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3463191382-6">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3463191382-6">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="5575650006-1">(</span><span class="p" data-group-id="5575650006-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5575650006-2">(</span><span class="s">&quot;Lock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5575650006-3">[</span><span class="p" data-group-id="5575650006-3">]</span><span class="p" data-group-id="5575650006-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="5575650006-4">(</span><span class="p" data-group-id="5575650006-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5575650006-5">(</span><span class="s">&quot;Unlock</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5575650006-6">[</span><span class="p" data-group-id="5575650006-6">]</span><span class="p" data-group-id="5575650006-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="4399002815-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4399002815-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="4399002815-8">(</span><span class="p" data-group-id="4399002815-8">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="5575650006-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5575650006-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="5575650006-8">(</span><span class="p" data-group-id="5575650006-8">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><p>The code is explained in the next sections.</p><h2 id="starting-gen_statem" class="section-heading">
│ │ │    <a href="#starting-gen_statem" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting gen_statem</span>
│ │ │  </h2>
│ │ │  <p>In the example in the previous section, <code class="inline">gen_statem</code> is started by calling
│ │ │ -<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="8235403177-1">(</span><span class="n">Code</span><span class="p" data-group-id="8235403177-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="8235403177-2">(</span><span class="p" data-group-id="8235403177-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="8235403177-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8235403177-4">[</span><span class="p" data-group-id="8235403177-4">]</span><span class="p" data-group-id="8235403177-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │ +<code class="inline">code_lock:start_link(Code)</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="7867963033-1">(</span><span class="n">Code</span><span class="p" data-group-id="7867963033-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7867963033-2">(</span><span class="p" data-group-id="7867963033-3">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="7867963033-3">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7867963033-4">[</span><span class="p" data-group-id="7867963033-4">]</span><span class="p" data-group-id="7867963033-2">)</span><span class="p">.</span></code></pre><p><code class="inline">start_link/1</code> calls function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/4</code></a>,
│ │ │  which spawns and links to a new process, a <code class="inline">gen_statem</code>.</p><ul><li><p>The first argument, <code class="inline">{local,?NAME}</code>, specifies the name. In this case, the
│ │ │  <code class="inline">gen_statem</code> is locally registered as <code class="inline">code_lock</code> through the macro <code class="inline">?NAME</code>.</p><p>If the name is omitted, the <code class="inline">gen_statem</code> is not registered. Instead its pid
│ │ │  must be used. The name can also be specified as <code class="inline">{global, Name}</code>, then the
│ │ │  <code class="inline">gen_statem</code> is registered using <a href="../../lib/kernel-10.2.7.2/doc/html/global.html#register_name/2"><code class="inline">global:register_name/2</code></a> in Kernel.</p></li><li><p>The second argument, <code class="inline">?MODULE</code>, is the name of the <em>callback module</em>,
│ │ │  that is, the module where the callback functions are located,
│ │ │  which is this module.</p><p>The interface functions (<code class="inline">start_link/1</code> and <code class="inline">button/1</code>) are located in the
│ │ │  same module as the callback functions (<code class="inline">init/1</code>, <code class="inline">locked/3</code>, and <code class="inline">open/3</code>).
│ │ │ @@ -574,184 +574,184 @@
│ │ │  see <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3</code></a>.</p></li></ul><p>If name registration succeeds, the new <code class="inline">gen_statem</code> process calls callback
│ │ │  function <code class="inline">code_lock:init(Code)</code>. This function is expected to return
│ │ │  <code class="inline">{ok, State, Data}</code>, where <code class="inline">State</code> is the initial state of the <code class="inline">gen_statem</code>,
│ │ │  in this case <code class="inline">locked</code>; assuming that the door is locked to begin with.
│ │ │  <code class="inline">Data</code> is the internal server data of the <code class="inline">gen_statem</code>. Here the server data
│ │ │  is a <a href="../../lib/stdlib-6.2.2.2/doc/html/maps.html"><code class="inline">map()</code></a> with key <code class="inline">code</code> that stores the correct
│ │ │  button sequence, key <code class="inline">length</code> store its length, and key <code class="inline">buttons</code>
│ │ │ -that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="0499134568-1">(</span><span class="n">Code</span><span class="p" data-group-id="0499134568-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="0499134568-2">(</span><span class="p" data-group-id="0499134568-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0499134568-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="0499134568-4">(</span><span class="n">Code</span><span class="p" data-group-id="0499134568-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="0499134568-5">[</span><span class="p" data-group-id="0499134568-5">]</span><span class="p" data-group-id="0499134568-3">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0499134568-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0499134568-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │ +that stores the collected buttons up to the same length.</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2984541959-1">(</span><span class="n">Code</span><span class="p" data-group-id="2984541959-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="2984541959-2">(</span><span class="p" data-group-id="2984541959-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2984541959-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="2984541959-4">(</span><span class="n">Code</span><span class="p" data-group-id="2984541959-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2984541959-5">[</span><span class="p" data-group-id="2984541959-5">]</span><span class="p" data-group-id="2984541959-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2984541959-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2984541959-6">}</span><span class="p">.</span></code></pre><p>Function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │  is synchronous. It does not return until the <code class="inline">gen_statem</code> is initialized
│ │ │  and is ready to receive events.</p><p>Function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/3"><code class="inline">gen_statem:start_link/3,4</code></a>
│ │ │  must be used if the <code class="inline">gen_statem</code> is part of a supervision tree, that is,
│ │ │  started by a supervisor.  Function,
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start/3"><code class="inline">gen_statem:start/3,4</code></a> can be used to start
│ │ │  a standalone <code class="inline">gen_statem</code>, meaning it is not part of a supervision tree.</p><p>Function <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">Module:callback_mode/0</code></a> selects
│ │ │  the <a href="#callback-modes"><code class="inline">CallbackMode</code></a> for the <em>callback module</em>,
│ │ │  in this case <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">state_functions</code></a>.
│ │ │ -That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="2645735364-1">(</span><span class="p" data-group-id="2645735364-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +That is, each state has its own handler function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="0611330581-1">(</span><span class="p" data-group-id="0611330581-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">state_functions</span><span class="p">.</span></code></pre><h2 id="handling-events" class="section-heading">
│ │ │    <a href="#handling-events" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Handling Events</span>
│ │ │  </h2>
│ │ │  <p>The function notifying the code lock about a button event is implemented using
│ │ │ -<a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="3002126777-1">(</span><span class="n">Button</span><span class="p" data-group-id="3002126777-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3002126777-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3002126777-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3002126777-3">}</span><span class="p" data-group-id="3002126777-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │ +<a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#cast/2"><code class="inline">gen_statem:cast/2</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">button</span><span class="p" data-group-id="8157924699-1">(</span><span class="n">Button</span><span class="p" data-group-id="8157924699-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="8157924699-2">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8157924699-3">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8157924699-3">}</span><span class="p" data-group-id="8157924699-2">)</span><span class="p">.</span></code></pre><p>The first argument is the name of the <code class="inline">gen_statem</code> and must agree with
│ │ │  the name used to start it. So, we use the same macro <code class="inline">?NAME</code> as when starting.
│ │ │  <code class="inline">{button, Button}</code> is the event content.</p><p>The event is sent to the <code class="inline">gen_statem</code>. When the event is received, the
│ │ │  <code class="inline">gen_statem</code> calls <code class="inline">StateName(cast, Event, Data)</code>, which is expected
│ │ │  to return a tuple <code class="inline">{next_state, NewStateName, NewData}</code>, or
│ │ │  <code class="inline">{next_state, NewStateName, NewData, Actions}</code>. <code class="inline">StateName</code> is the name
│ │ │  of the current state and <code class="inline">NewStateName</code> is the name of the next state.
│ │ │  <code class="inline">NewData</code> is a new value for the server data of the <code class="inline">gen_statem</code>,
│ │ │ -and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9092848500-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9092848500-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9092848500-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9092848500-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9092848500-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9092848500-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +and <code class="inline">Actions</code> is a list of actions to be performed by the <code class="inline">gen_statem</code> engine.</p><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9845655489-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9845655489-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9845655489-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="9845655489-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9845655489-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9845655489-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="9092848500-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="9092848500-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="9845655489-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="9845655489-4">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="9092848500-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="9092848500-5">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9092848500-6">[</span><span class="n">Button</span><span class="p" data-group-id="9092848500-6">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="9845655489-5">(</span><span class="n">Buttons</span><span class="p" data-group-id="9845655489-5">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9845655489-6">[</span><span class="n">Button</span><span class="p" data-group-id="9845655489-6">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9092848500-7">(</span><span class="p" data-group-id="9092848500-7">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9092848500-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9092848500-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9092848500-10">[</span><span class="p" data-group-id="9092848500-10">]</span><span class="p" data-group-id="9092848500-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="9092848500-11">[</span><span class="p" data-group-id="9092848500-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9092848500-12">}</span><span class="p" data-group-id="9092848500-11">]</span><span class="p" data-group-id="9092848500-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9845655489-7">(</span><span class="p" data-group-id="9845655489-7">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9845655489-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9845655489-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9845655489-10">[</span><span class="p" data-group-id="9845655489-10">]</span><span class="p" data-group-id="9845655489-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9845655489-11">[</span><span class="p" data-group-id="9845655489-12">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="9845655489-12">}</span><span class="p" data-group-id="9845655489-11">]</span><span class="p" data-group-id="9845655489-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9092848500-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9092848500-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9092848500-14">}</span><span class="p" data-group-id="9092848500-13">}</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9845655489-13">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9845655489-14">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9845655489-14">}</span><span class="p" data-group-id="9845655489-13">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>In state <code class="inline">locked</code>, when a button is pressed, it is collected with the
│ │ │  previously pressed buttons up to the length of the correct code, then
│ │ │  compared with the correct code. Depending on the result, the door is
│ │ │  either unlocked and the <code class="inline">gen_statem</code> goes to state <code class="inline">open</code>, or the door
│ │ │  remains in state <code class="inline">locked</code>.</p><p>When changing to state <code class="inline">open</code>, the collected buttons are reset, the lock
│ │ │ -unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="3075711861-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3075711861-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3075711861-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3075711861-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3075711861-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3075711861-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │ +unlocked, and a <em>state time-out</em> for 10 seconds is started.</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="7019576317-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7019576317-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7019576317-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7019576317-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7019576317-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7019576317-3">}</span><span class="p">.</span></code></pre><p>In state <code class="inline">open</code>, a button event is ignored by staying in the same state.
│ │ │  This can also be done by returning <code class="inline">{keep_state, Data}</code>, or in this case
│ │ │  since <code class="inline">Data</code> is unchanged, by returning <code class="inline">keep_state_and_data</code>.</p><h2 id="state-time-outs" class="section-heading">
│ │ │    <a href="#state-time-outs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">State Time-Outs</span>
│ │ │  </h2>
│ │ │  <p>When a correct code has been given, the door is unlocked and the following
│ │ │ -tuple is returned from <code class="inline">locked/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0874076618-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0874076618-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0874076618-3">[</span><span class="p" data-group-id="0874076618-3">]</span><span class="p" data-group-id="0874076618-2">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="0874076618-4">[</span><span class="p" data-group-id="0874076618-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0874076618-5">}</span><span class="p" data-group-id="0874076618-4">]</span><span class="p" data-group-id="0874076618-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │ +tuple is returned from <code class="inline">locked/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7875115950-1">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7875115950-2">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7875115950-3">[</span><span class="p" data-group-id="7875115950-3">]</span><span class="p" data-group-id="7875115950-2">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7875115950-4">[</span><span class="p" data-group-id="7875115950-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7875115950-5">}</span><span class="p" data-group-id="7875115950-4">]</span><span class="p" data-group-id="7875115950-1">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span></code></pre><p>10,000 is a time-out value in milliseconds. After this time (10 seconds),
│ │ │  a time-out occurs. Then, <code class="inline">StateName(state_timeout, lock, Data)</code> is called.
│ │ │  The time-out occurs when the door has been in state <code class="inline">open</code> for 10 seconds.
│ │ │ -After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="6600831172-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="6600831172-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6600831172-2">(</span><span class="p" data-group-id="6600831172-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6600831172-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6600831172-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │ +After that the door is locked again:</p><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="8681823057-1">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w">  </span><span class="n">Data</span><span class="p" data-group-id="8681823057-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8681823057-2">(</span><span class="p" data-group-id="8681823057-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8681823057-3">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8681823057-3">}</span><span class="p">;</span></code></pre><p>The timer for a <em>state time-out</em> is automatically canceled when
│ │ │  the state machine does a <em>state change</em>.</p><p>You can restart, cancel, or update a <em>state time-out</em>. See section
│ │ │  <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="all-state-events" class="section-heading">
│ │ │    <a href="#all-state-events" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">All State Events</span>
│ │ │  </h2>
│ │ │  <p>Sometimes events can arrive in any state of the <code class="inline">gen_statem</code>. It is convenient
│ │ │  to handle these in a common state handler function that all state functions
│ │ │  call for events not specific to the state.</p><p>Consider a <code class="inline">code_length/0</code> function that returns the length
│ │ │  of the correct code.  We dispatch all events that are not state-specific
│ │ │  to the common function <code class="inline">handle_common/3</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1177349864-1">(</span><span class="p" data-group-id="1177349864-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1177349864-2">]</span><span class="p" data-group-id="1177349864-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="5372161384-1">(</span><span class="p" data-group-id="5372161384-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="5372161384-2">]</span><span class="p" data-group-id="5372161384-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="1177349864-3">(</span><span class="p" data-group-id="1177349864-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1177349864-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="1177349864-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="5372161384-3">(</span><span class="p" data-group-id="5372161384-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="5372161384-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="5372161384-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1177349864-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1177349864-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1177349864-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1177349864-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="1177349864-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1177349864-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="5372161384-5">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5372161384-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="5372161384-6">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5372161384-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="5372161384-7">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5372161384-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1177349864-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1177349864-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1177349864-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1177349864-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">handle_common</span><span class="p" data-group-id="1177349864-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1177349864-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="1177349864-11">(</span><span class="p" data-group-id="1177349864-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="1177349864-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1177349864-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1177349864-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1177349864-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1177349864-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1177349864-15">[</span><span class="p" data-group-id="1177349864-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="1177349864-17">(</span><span class="n">Code</span><span class="p" data-group-id="1177349864-17">)</span><span class="p" data-group-id="1177349864-16">}</span><span class="p" data-group-id="1177349864-15">]</span><span class="p" data-group-id="1177349864-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1687389202-1">(</span><span class="p" data-group-id="1687389202-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1687389202-2">]</span><span class="p" data-group-id="1687389202-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="5372161384-8">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="5372161384-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="5372161384-9">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5372161384-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">handle_common</span><span class="p" data-group-id="5372161384-10">(</span><span class="n">EventType</span><span class="p">,</span><span class="w"> </span><span class="n">EventContent</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5372161384-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="5372161384-11">(</span><span class="p" data-group-id="5372161384-12">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="5372161384-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5372161384-13">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="5372161384-13">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5372161384-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5372161384-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="5372161384-15">[</span><span class="p" data-group-id="5372161384-16">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="5372161384-17">(</span><span class="n">Code</span><span class="p" data-group-id="5372161384-17">)</span><span class="p" data-group-id="5372161384-16">}</span><span class="p" data-group-id="5372161384-15">]</span><span class="p" data-group-id="5372161384-14">}</span><span class="p">.</span></code></pre><p>Another way to do it is through a convenience macro <code class="inline">?HANDLE_COMMON/0</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4600608871-1">(</span><span class="p" data-group-id="4600608871-2">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4600608871-2">]</span><span class="p" data-group-id="4600608871-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="1687389202-3">(</span><span class="p" data-group-id="1687389202-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="1687389202-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="1687389202-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="4600608871-3">(</span><span class="p" data-group-id="4600608871-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4600608871-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="4600608871-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="1687389202-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="1687389202-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="1687389202-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="1687389202-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="1687389202-7">)</span><span class="p" data-group-id="1687389202-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4600608871-5">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="4600608871-6">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="4600608871-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="4600608871-7">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="4600608871-7">)</span><span class="p" data-group-id="4600608871-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="1687389202-8">(</span><span class="p" data-group-id="1687389202-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="1687389202-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1687389202-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="1687389202-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1687389202-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1687389202-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1687389202-12">[</span><span class="p" data-group-id="1687389202-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="1687389202-14">(</span><span class="n">Code</span><span class="p" data-group-id="1687389202-14">)</span><span class="p" data-group-id="1687389202-13">}</span><span class="p" data-group-id="1687389202-12">]</span><span class="p" data-group-id="1687389202-11">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="4600608871-8">(</span><span class="p" data-group-id="4600608871-9">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4600608871-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4600608871-10">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="4600608871-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4600608871-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4600608871-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4600608871-12">[</span><span class="p" data-group-id="4600608871-13">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="4600608871-14">(</span><span class="n">Code</span><span class="p" data-group-id="4600608871-14">)</span><span class="p" data-group-id="4600608871-13">}</span><span class="p" data-group-id="4600608871-12">]</span><span class="p" data-group-id="4600608871-11">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1687389202-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1687389202-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4600608871-15">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4600608871-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1687389202-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="1687389202-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="4600608871-16">(</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4600608871-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><p>This example uses <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#call/2"><code class="inline">gen_statem:call/2</code></a>, which waits for a reply from the server.
│ │ │  The reply is sent with a <code class="inline">{reply, From, Reply}</code> tuple in an action list in the
│ │ │  <code class="inline">{keep_state, ...}</code> tuple that retains the current state. This return form is
│ │ │  convenient when you want to stay in the current state but do not know or care
│ │ │  about what it is.</p><p>If the common <em>state callback</em> needs to know the current state a function
│ │ │ -<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3823955867-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="3823955867-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="3823955867-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="3823955867-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="3823955867-3">)</span><span class="p" data-group-id="3823955867-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │ +<code class="inline">handle_common/4</code> can be used instead:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3829008171-1">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="3829008171-2">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="3829008171-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="3829008171-3">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="3829008171-3">)</span><span class="p" data-group-id="3829008171-1">)</span><span class="p">.</span></code></pre><h2 id="one-state-callback" class="section-heading">
│ │ │    <a href="#one-state-callback" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">One State Callback</span>
│ │ │  </h2>
│ │ │  <p>If <a href="#callback-modes"><em>callback mode</em></a> <code class="inline">handle_event_function</code> is used,
│ │ │  all events are handled in
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#c:handle_event/4"><code class="inline">Module:handle_event/4</code></a> and we can
│ │ │  (but do not have to) use an event-centered approach where we first branch
│ │ │  depending on event and then depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7267312769-1">(</span><span class="p" data-group-id="7267312769-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="7267312769-2">]</span><span class="p" data-group-id="7267312769-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8568384323-1">(</span><span class="p" data-group-id="8568384323-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="8568384323-2">]</span><span class="p" data-group-id="8568384323-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="7267312769-3">(</span><span class="p" data-group-id="7267312769-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="8568384323-3">(</span><span class="p" data-group-id="8568384323-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">handle_event_function</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7267312769-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7267312769-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="7267312769-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7267312769-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7267312769-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7267312769-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8568384323-4">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8568384323-5">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="8568384323-5">}</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8568384323-6">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8568384323-6">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8568384323-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">State</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │  	</span><span class="ss">locked</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="7267312769-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="7267312769-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8568384323-7">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="8568384323-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="7267312769-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="7267312769-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="8568384323-8">(</span><span class="n">Buttons</span><span class="p" data-group-id="8568384323-8">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="7267312769-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="7267312769-9">)</span><span class="w">
│ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="7267312769-10">[</span><span class="n">Button</span><span class="p" data-group-id="7267312769-10">]</span><span class="p">,</span><span class="w">
│ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="8568384323-9">(</span><span class="n">Buttons</span><span class="p" data-group-id="8568384323-9">)</span><span class="w">
│ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="8568384323-10">[</span><span class="n">Button</span><span class="p" data-group-id="8568384323-10">]</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="k">if</span><span class="w">
│ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7267312769-11">(</span><span class="p" data-group-id="7267312769-11">)</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="7267312769-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7267312769-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="7267312769-14">[</span><span class="p" data-group-id="7267312769-14">]</span><span class="p" data-group-id="7267312769-13">}</span><span class="p">,</span><span class="w">
│ │ │ -                     </span><span class="p" data-group-id="7267312769-15">[</span><span class="p" data-group-id="7267312769-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7267312769-16">}</span><span class="p" data-group-id="7267312769-15">]</span><span class="p" data-group-id="7267312769-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8568384323-11">(</span><span class="p" data-group-id="8568384323-11">)</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="8568384323-12">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8568384323-13">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="8568384323-14">[</span><span class="p" data-group-id="8568384323-14">]</span><span class="p" data-group-id="8568384323-13">}</span><span class="p">,</span><span class="w">
│ │ │ +                     </span><span class="p" data-group-id="8568384323-15">[</span><span class="p" data-group-id="8568384323-16">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8568384323-16">}</span><span class="p" data-group-id="8568384323-15">]</span><span class="p" data-group-id="8568384323-12">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="7267312769-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7267312769-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="7267312769-18">}</span><span class="p" data-group-id="7267312769-17">}</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="8568384323-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8568384323-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="8568384323-18">}</span><span class="p" data-group-id="8568384323-17">}</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">open</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7267312769-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7267312769-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="7267312769-20">(</span><span class="p" data-group-id="7267312769-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7267312769-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7267312769-21">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="7267312769-22">(</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="7267312769-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="7267312769-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7267312769-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="7267312769-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7267312769-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7267312769-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="7267312769-26">[</span><span class="p" data-group-id="7267312769-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="7267312769-28">(</span><span class="n">Code</span><span class="p" data-group-id="7267312769-28">)</span><span class="p" data-group-id="7267312769-27">}</span><span class="p" data-group-id="7267312769-26">]</span><span class="p" data-group-id="7267312769-25">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8568384323-19">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8568384323-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="8568384323-20">(</span><span class="p" data-group-id="8568384323-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8568384323-21">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8568384323-21">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8568384323-22">(</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8568384323-23">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="8568384323-23">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8568384323-24">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="8568384323-24">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8568384323-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8568384323-25">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="8568384323-26">[</span><span class="p" data-group-id="8568384323-27">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="8568384323-28">(</span><span class="n">Code</span><span class="p" data-group-id="8568384323-28">)</span><span class="p" data-group-id="8568384323-27">}</span><span class="p" data-group-id="8568384323-26">]</span><span class="p" data-group-id="8568384323-25">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><h2 id="stopping" class="section-heading">
│ │ │    <a href="#stopping" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Stopping</span>
│ │ │  </h2>
│ │ │ @@ -763,59 +763,59 @@
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_statem</code> is part of a supervision tree, no stop function is needed.
│ │ │  The <code class="inline">gen_statem</code> is automatically terminated by its supervisor. Exactly how
│ │ │  this is done is defined by a <a href="sup_princ.html#shutdown">shutdown strategy</a>
│ │ │  set in the supervisor.</p><p>If it is necessary to clean up before termination, the shutdown strategy
│ │ │  must be a time-out value and the <code class="inline">gen_statem</code> must in function <code class="inline">init/1</code>
│ │ │  set itself to trap exit signals by calling
│ │ │ -<a href="../../erts-15.2.7.2/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="3027290800-1">(</span><span class="n">Args</span><span class="p" data-group-id="3027290800-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="3027290800-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3027290800-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="3027290800-3">(</span><span class="p" data-group-id="3027290800-3">)</span><span class="p">,</span><span class="w">
│ │ │ +<a href="../../erts-15.2.7.2/doc/html/erlang.html#process_flag/2"><code class="inline">process_flag(trap_exit, true)</code></a>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="6026392222-1">(</span><span class="n">Args</span><span class="p" data-group-id="6026392222-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="6026392222-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="6026392222-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="6026392222-3">(</span><span class="p" data-group-id="6026392222-3">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>When ordered to shut down, the <code class="inline">gen_statem</code> then calls callback function
│ │ │  <code class="inline">terminate(shutdown, State, Data)</code>.</p><p>In this example, function <code class="inline">terminate/3</code> locks the door if it is open,
│ │ │  so we do not accidentally leave the door open
│ │ │ -when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="5190839495-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5190839495-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="5190839495-2">(</span><span class="p" data-group-id="5190839495-2">)</span><span class="p">,</span><span class="w">
│ │ │ +when the supervision tree terminates:</p><pre><code class="makeup erlang" translate="no"><span class="nf">terminate</span><span class="p" data-group-id="0180593955-1">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="0180593955-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="0180593955-2">(</span><span class="p" data-group-id="0180593955-2">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="standalone-gen_statem" class="section-heading">
│ │ │    <a href="#standalone-gen_statem" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Standalone gen_statem</span>
│ │ │  </h3>
│ │ │  <p>If the <code class="inline">gen_statem</code> is not part of a supervision tree, it can be stopped
│ │ │  using <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#stop/1"><code class="inline">gen_statem:stop/1</code></a>, preferably through
│ │ │  an API function:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3574233685-1">(</span><span class="p" data-group-id="3574233685-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3574233685-2">]</span><span class="p" data-group-id="3574233685-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2684288672-1">(</span><span class="p" data-group-id="2684288672-2">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="2684288672-2">]</span><span class="p" data-group-id="2684288672-1">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="3574233685-3">(</span><span class="p" data-group-id="3574233685-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3574233685-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="3574233685-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="2684288672-3">(</span><span class="p" data-group-id="2684288672-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="2684288672-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="2684288672-4">)</span><span class="p">.</span></code></pre><p>This makes the <code class="inline">gen_statem</code> call callback function <code class="inline">terminate/3</code> just like
│ │ │  for a supervised server and waits for the process to terminate.</p><h2 id="event-time-outs" class="section-heading">
│ │ │    <a href="#event-time-outs" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Event Time-Outs</span>
│ │ │  </h2>
│ │ │  <p>A time-out feature inherited from <code class="inline">gen_statem</code>'s predecessor <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_fsm.html"><code class="inline">gen_fsm</code></a>,
│ │ │  is an <em>event time-out</em>, that is, if an event arrives the timer is canceled.
│ │ │  You get either an event or a time-out, but not both.</p><p>It is ordered by the
│ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">{timeout, Time, EventContent}</code>,
│ │ │  or just an integer <code class="inline">Time</code>, even without the enclosing actions list (the latter
│ │ │  is a form inherited from <code class="inline">gen_fsm</code>).</p><p>This type of time-out is useful, for example, to act on inactivity.
│ │ │  Let's restart the code sequence if no button is pressed for say 30 seconds:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="3468544897-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3468544897-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3468544897-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3468544897-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3468544897-4">[</span><span class="p" data-group-id="3468544897-4">]</span><span class="p" data-group-id="3468544897-3">}</span><span class="p" data-group-id="3468544897-2">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="3468544897-5">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3468544897-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3468544897-6">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3468544897-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3468544897-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3468544897-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2832751860-1">(</span><span class="ss">timeout</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2832751860-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="2832751860-2">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2832751860-3">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2832751860-4">[</span><span class="p" data-group-id="2832751860-4">]</span><span class="p" data-group-id="2832751860-3">}</span><span class="p" data-group-id="2832751860-2">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="2832751860-5">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2832751860-6">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2832751860-6">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="2832751860-7">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2832751860-7">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2832751860-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3468544897-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3468544897-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="3468544897-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="3468544897-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="2832751860-8">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2832751860-9">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2832751860-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p" data-group-id="2832751860-8">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Whenever we receive a button event we start an <em>event time-out</em> of 30 seconds,
│ │ │  and if we get an <em>event type</em> of <code class="inline">timeout</code> we reset the remaining
│ │ │  code sequence.</p><p>An <em>event time-out</em> is canceled by any other event so you either get
│ │ │  some other event or the time-out event. Therefore, canceling,
│ │ │  restarting, or updating an <em>event time-out</em> is neither possible nor
│ │ │  necessary. Whatever event you act on has already canceled
│ │ │  the <em>event time-out</em>, so there is never a running <em>event time-out</em>
│ │ │ @@ -834,30 +834,30 @@
│ │ │  another, maybe cancel the time-out without changing states, or perhaps run
│ │ │  multiple time-outs in parallel. All this can be accomplished with
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:generic_timeout/0"><em>generic time-outs</em></a>. They may look a little
│ │ │  bit like <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:event_timeout/0"><em>event time-outs</em></a> but contain
│ │ │  a name to allow for any number of them simultaneously and they are
│ │ │  not automatically canceled.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │  by instead using a <em>generic time-out</em> named for example <code class="inline">open</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="0806063658-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0806063658-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0806063658-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0806063658-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0806063658-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0806063658-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="3109640424-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3109640424-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3109640424-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3109640424-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3109640424-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3109640424-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0806063658-4">(</span><span class="p" data-group-id="0806063658-4">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="0806063658-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0806063658-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0806063658-7">[</span><span class="p" data-group-id="0806063658-7">]</span><span class="p" data-group-id="0806063658-6">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="0806063658-8">[</span><span class="p" data-group-id="0806063658-9">{</span><span class="p" data-group-id="0806063658-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="0806063658-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0806063658-9">}</span><span class="p" data-group-id="0806063658-8">]</span><span class="p" data-group-id="0806063658-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3109640424-4">(</span><span class="p" data-group-id="3109640424-4">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="3109640424-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3109640424-6">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3109640424-7">[</span><span class="p" data-group-id="3109640424-7">]</span><span class="p" data-group-id="3109640424-6">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="3109640424-8">[</span><span class="p" data-group-id="3109640424-9">{</span><span class="p" data-group-id="3109640424-10">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="3109640424-10">}</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3109640424-9">}</span><span class="p" data-group-id="3109640424-8">]</span><span class="p" data-group-id="3109640424-5">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="0806063658-11">(</span><span class="p" data-group-id="0806063658-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="0806063658-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0806063658-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="0806063658-13">(</span><span class="p" data-group-id="0806063658-13">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0806063658-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="0806063658-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="0806063658-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0806063658-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0806063658-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0806063658-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0806063658-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="0806063658-17">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3109640424-11">(</span><span class="p" data-group-id="3109640424-12">{</span><span class="ss">timeout</span><span class="p">,</span><span class="ss">open</span><span class="p" data-group-id="3109640424-12">}</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3109640424-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="3109640424-13">(</span><span class="p" data-group-id="3109640424-13">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3109640424-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3109640424-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="3109640424-15">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3109640424-16">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3109640424-16">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3109640424-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3109640424-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3109640424-17">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Specific <em>generic time-outs</em> can just as <a href="#state-time-outs"><em>state time-outs</em></a>
│ │ │  be restarted or canceled by setting it to a new time or <code class="inline">infinity</code>.</p><p>In this particular case we do not need to cancel the time-out since
│ │ │  the time-out event is the only possible reason to do a <em>state change</em>
│ │ │  from <code class="inline">open</code> to <code class="inline">locked</code>.</p><p>Instead of bothering with when to cancel a time-out, a late time-out event
│ │ │  can be handled by ignoring it if it arrives in a state
│ │ │  where it is known to be late.</p><p>You can restart, cancel, or update a <em>generic time-out</em>.
│ │ │  See section <a href="#time-outs"><em>Time-Outs</em></a> for details.</p><h2 id="erlang-timers" class="section-heading">
│ │ │ @@ -869,32 +869,32 @@
│ │ │  <p>The most versatile way to handle time-outs is to use Erlang Timers; see
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#start_timer/4"><code class="inline">erlang:start_timer/3,4</code></a>. Most time-out tasks
│ │ │  can be performed with the time-out features in <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html"><code class="inline">gen_statem</code></a>,
│ │ │  but an example of one that cannot is if you should need the return value
│ │ │  from <a href="../../erts-15.2.7.2/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>, that is,
│ │ │  the remaining time of the timer.</p><p>Here is how to accomplish the <em>state time-out</em> in the previous example
│ │ │  by instead using an Erlang Timer:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="3108330331-1">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3108330331-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3108330331-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3108330331-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="3108330331-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3108330331-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="0509910015-1">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0509910015-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0509910015-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="0509910015-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0509910015-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0509910015-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="3108330331-4">(</span><span class="p" data-group-id="3108330331-4">)</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0509910015-4">(</span><span class="p" data-group-id="0509910015-4">)</span><span class="p">,</span><span class="w">
│ │ │  	    </span><span class="n">Tref</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="3108330331-5">(</span><span class="w">
│ │ │ -                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3108330331-6">(</span><span class="p" data-group-id="3108330331-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="3108330331-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3108330331-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3108330331-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="3108330331-9">[</span><span class="p" data-group-id="3108330331-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="3108330331-8">}</span><span class="p" data-group-id="3108330331-7">}</span><span class="p">;</span><span class="w">
│ │ │ +                 </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">start_timer</span><span class="p" data-group-id="0509910015-5">(</span><span class="w">
│ │ │ +                     </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="0509910015-6">(</span><span class="p" data-group-id="0509910015-6">)</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p" data-group-id="0509910015-5">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0509910015-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0509910015-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="0509910015-9">[</span><span class="p" data-group-id="0509910015-9">]</span><span class="p">,</span><span class="w"> </span><span class="ss">timer</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="0509910015-8">}</span><span class="p" data-group-id="0509910015-7">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="3108330331-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3108330331-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="3108330331-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3108330331-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="3108330331-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3108330331-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="3108330331-13">(</span><span class="p" data-group-id="3108330331-13">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3108330331-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="3108330331-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3108330331-15">)</span><span class="p" data-group-id="3108330331-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="3108330331-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3108330331-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="3108330331-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3108330331-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3108330331-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="3108330331-18">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0509910015-10">(</span><span class="ss">info</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0509910015-11">{</span><span class="ss">timeout</span><span class="p">,</span><span class="n">Tref</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="0509910015-11">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0509910015-12">#{</span><span class="ss">timer</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Tref</span><span class="p" data-group-id="0509910015-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0509910015-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="0509910015-13">(</span><span class="p" data-group-id="0509910015-13">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0509910015-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="ss">locked</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="0509910015-15">(</span><span class="ss">timer</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0509910015-15">)</span><span class="p" data-group-id="0509910015-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0509910015-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0509910015-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0509910015-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0509910015-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0509910015-18">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="0509910015-18">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Removing the <code class="inline">timer</code> key from the map when we do a <em>state change</em> to <code class="inline">locked</code>
│ │ │  is not strictly necessary since we can only get into state <code class="inline">open</code>
│ │ │  with an updated <code class="inline">timer</code> map value. But it can be nice to not have
│ │ │  outdated values in the state <code class="inline">Data</code>.</p><p>If you need to cancel a timer because of some other event, you can use
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#cancel_timer/2"><code class="inline">erlang:cancel_timer(Tref)</code></a>. Note that no time-out
│ │ │  message will arrive after this (because the timer has been
│ │ │  explicitly canceled), unless you have already postponed one earlier
│ │ │ @@ -910,16 +910,16 @@
│ │ │    <span class="text">Postponing Events</span>
│ │ │  </h2>
│ │ │  <p>If you want to ignore a particular event in the current state and handle it
│ │ │  in a future state, you can postpone the event. A postponed event
│ │ │  is retried after a <em>state change</em>, that is, <code class="inline">OldState =/= NewState</code>.</p><p>Postponing is ordered by the
│ │ │  <a href="#transition-actions"><em>transition action</em></a> <code class="inline">postpone</code>.</p><p>In this example, instead of ignoring button events while in the <code class="inline">open</code> state,
│ │ │  we can postpone them handle them later in the <code class="inline">locked</code> state:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1652070123-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1652070123-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1652070123-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1652070123-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1652070123-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="1652070123-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="1652070123-4">]</span><span class="p" data-group-id="1652070123-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="0843660537-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0843660537-2">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="0843660537-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0843660537-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0843660537-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="0843660537-4">[</span><span class="ss">postpone</span><span class="p" data-group-id="0843660537-4">]</span><span class="p" data-group-id="0843660537-3">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>Since a postponed event is only retried after a <em>state change</em>, you have to
│ │ │  think about where to keep a state data item. You can keep it in the server
│ │ │  <code class="inline">Data</code> or in the <code class="inline">State</code> itself, for example by having two more or less
│ │ │  identical states to keep a boolean value, or by using a complex state (see
│ │ │  section <a href="#complex-state"><em>Complex State</em></a>) with
│ │ │  <a href="#callback-modes"><em>callback mode</em></a>
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:callback_mode/0"><code class="inline">handle_event_function</code></a>. If a change
│ │ │ @@ -940,55 +940,55 @@
│ │ │    <a href="#selective-receive" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Selective Receive</span>
│ │ │  </h3>
│ │ │  <p>Erlang's selective <code class="inline">receive</code> statement is often used to describe simple state
│ │ │  machine examples in straightforward Erlang code. The following is a possible
│ │ │ -implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2297600631-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="2297600631-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2297600631-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="2297600631-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2297600631-3">(</span><span class="p" data-group-id="2297600631-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="2297600631-4">]</span><span class="p" data-group-id="2297600631-3">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="2297600631-5">(</span><span class="n">Code</span><span class="p" data-group-id="2297600631-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">spawn</span><span class="p" data-group-id="2297600631-6">(</span><span class="w">
│ │ │ -      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2297600631-7">(</span><span class="p" data-group-id="2297600631-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="2297600631-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="2297600631-9">(</span><span class="p" data-group-id="2297600631-9">)</span><span class="p" data-group-id="2297600631-8">)</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="nf">do_lock</span><span class="p" data-group-id="2297600631-10">(</span><span class="p" data-group-id="2297600631-10">)</span><span class="p">,</span><span class="w">
│ │ │ -	      </span><span class="nf">locked</span><span class="p" data-group-id="2297600631-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="2297600631-12">(</span><span class="n">Code</span><span class="p" data-group-id="2297600631-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2297600631-13">[</span><span class="p" data-group-id="2297600631-13">]</span><span class="p" data-group-id="2297600631-11">)</span><span class="w">
│ │ │ -      </span><span class="k">end</span><span class="p" data-group-id="2297600631-6">)</span><span class="p">.</span><span class="w">
│ │ │ +implementation of the first example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3098690156-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="3098690156-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3098690156-2">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_1</span><span class="p" data-group-id="3098690156-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3098690156-3">(</span><span class="p" data-group-id="3098690156-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3098690156-4">]</span><span class="p" data-group-id="3098690156-3">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="3098690156-5">(</span><span class="n">Code</span><span class="p" data-group-id="3098690156-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">spawn</span><span class="p" data-group-id="3098690156-6">(</span><span class="w">
│ │ │ +      </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3098690156-7">(</span><span class="p" data-group-id="3098690156-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +	      </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">register</span><span class="p" data-group-id="3098690156-8">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="3098690156-9">(</span><span class="p" data-group-id="3098690156-9">)</span><span class="p" data-group-id="3098690156-8">)</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="nf">do_lock</span><span class="p" data-group-id="3098690156-10">(</span><span class="p" data-group-id="3098690156-10">)</span><span class="p">,</span><span class="w">
│ │ │ +	      </span><span class="nf">locked</span><span class="p" data-group-id="3098690156-11">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="3098690156-12">(</span><span class="n">Code</span><span class="p" data-group-id="3098690156-12">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3098690156-13">[</span><span class="p" data-group-id="3098690156-13">]</span><span class="p" data-group-id="3098690156-11">)</span><span class="w">
│ │ │ +      </span><span class="k">end</span><span class="p" data-group-id="3098690156-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="2297600631-14">(</span><span class="n">Button</span><span class="p" data-group-id="2297600631-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2297600631-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2297600631-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="0786083371-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="0786083371-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="3098690156-14">(</span><span class="n">Button</span><span class="p" data-group-id="3098690156-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">NAME</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="3098690156-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3098690156-15">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9206447648-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9206447648-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0786083371-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0786083371-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9206447648-2">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9206447648-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │                  </span><span class="k">if</span><span class="w">
│ │ │ -                    </span><span class="nf">length</span><span class="p" data-group-id="0786083371-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="0786083371-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                    </span><span class="nf">length</span><span class="p" data-group-id="9206447648-3">(</span><span class="n">Buttons</span><span class="p" data-group-id="9206447648-3">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                          </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │                      </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                        </span><span class="nf">tl</span><span class="p" data-group-id="0786083371-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="0786083371-4">)</span><span class="w">
│ │ │ -                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="0786083371-5">[</span><span class="n">Button</span><span class="p" data-group-id="0786083371-5">]</span><span class="p">,</span><span class="w">
│ │ │ +                        </span><span class="nf">tl</span><span class="p" data-group-id="9206447648-4">(</span><span class="n">Buttons</span><span class="p" data-group-id="9206447648-4">)</span><span class="w">
│ │ │ +                </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9206447648-5">[</span><span class="n">Button</span><span class="p" data-group-id="9206447648-5">]</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="k">if</span><span class="w">
│ │ │                  </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="0786083371-6">(</span><span class="p" data-group-id="0786083371-6">)</span><span class="p">,</span><span class="w">
│ │ │ -		    </span><span class="nf">open</span><span class="p" data-group-id="0786083371-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="0786083371-7">)</span><span class="p">;</span><span class="w">
│ │ │ +                    </span><span class="nf">do_unlock</span><span class="p" data-group-id="9206447648-6">(</span><span class="p" data-group-id="9206447648-6">)</span><span class="p">,</span><span class="w">
│ │ │ +		    </span><span class="nf">open</span><span class="p" data-group-id="9206447648-7">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="9206447648-7">)</span><span class="p">;</span><span class="w">
│ │ │                  </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -                    </span><span class="nf">locked</span><span class="p" data-group-id="0786083371-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="0786083371-8">)</span><span class="w">
│ │ │ +                    </span><span class="nf">locked</span><span class="p" data-group-id="9206447648-8">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9206447648-8">)</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="w">
│ │ │ -    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="4266077001-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="4266077001-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">end</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="1570905128-1">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="1570905128-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -	    </span><span class="nf">do_lock</span><span class="p" data-group-id="4266077001-2">(</span><span class="p" data-group-id="4266077001-2">)</span><span class="p">,</span><span class="w">
│ │ │ -	    </span><span class="nf">locked</span><span class="p" data-group-id="4266077001-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4266077001-4">[</span><span class="p" data-group-id="4266077001-4">]</span><span class="p" data-group-id="4266077001-3">)</span><span class="w">
│ │ │ +	    </span><span class="nf">do_lock</span><span class="p" data-group-id="1570905128-2">(</span><span class="p" data-group-id="1570905128-2">)</span><span class="p">,</span><span class="w">
│ │ │ +	    </span><span class="nf">locked</span><span class="p" data-group-id="1570905128-3">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1570905128-4">[</span><span class="p" data-group-id="1570905128-4">]</span><span class="p" data-group-id="1570905128-3">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="4266077001-5">(</span><span class="p" data-group-id="4266077001-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4266077001-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4266077001-7">[</span><span class="p" data-group-id="4266077001-7">]</span><span class="p" data-group-id="4266077001-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="4266077001-8">(</span><span class="p" data-group-id="4266077001-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4266077001-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4266077001-10">[</span><span class="p" data-group-id="4266077001-10">]</span><span class="p" data-group-id="4266077001-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="1570905128-5">(</span><span class="p" data-group-id="1570905128-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1570905128-6">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1570905128-7">[</span><span class="p" data-group-id="1570905128-7">]</span><span class="p" data-group-id="1570905128-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="1570905128-8">(</span><span class="p" data-group-id="1570905128-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1570905128-9">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1570905128-10">[</span><span class="p" data-group-id="1570905128-10">]</span><span class="p" data-group-id="1570905128-9">)</span><span class="p">.</span></code></pre><p>The selective receive in this case causes <code class="inline">open</code> to implicitly postpone any
│ │ │  events to the <code class="inline">locked</code> state.</p><p>A catch-all receive should never be used from a <code class="inline">gen_statem</code> behaviour
│ │ │  (or from any <code class="inline">gen_*</code> behaviour), as the receive statement is within
│ │ │  the <code class="inline">gen_*</code> engine itself. <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html"><code class="inline">sys</code></a>-compatible behaviours must respond to
│ │ │  system messages and therefore do that in their engine receive loop,
│ │ │  passing non-system messages to the <em>callback module</em>. Using a catch-all
│ │ │  receive can result in system messages being discarded, which in turn
│ │ │  can lead to unexpected behaviour. If a selective receive must be used,
│ │ │ @@ -1011,40 +1011,40 @@
│ │ │  section), especially if only one or a few states have state enter actions,
│ │ │  this is a perfect use case for the built in
│ │ │  <a href="#state-enter-calls"><em>state enter calls</em></a>.</p><p>You return a list containing <code class="inline">state_enter</code> from your
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#c:callback_mode/0"><code class="inline">callback_mode/0</code></a> function and the
│ │ │  <code class="inline">gen_statem</code> engine will call your <em>state callback</em> once with an event
│ │ │  <code class="inline">(enter, OldState, ...)</code> whenever it does a <em>state change</em>. Then you
│ │ │  just need to handle these event-like calls in all states.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="1959614372-1">(</span><span class="n">Code</span><span class="p" data-group-id="1959614372-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="1959614372-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1959614372-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1959614372-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1959614372-4">(</span><span class="n">Code</span><span class="p" data-group-id="1959614372-4">)</span><span class="p" data-group-id="1959614372-3">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1959614372-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1959614372-5">}</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="1959614372-6">(</span><span class="p" data-group-id="1959614372-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1959614372-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="1959614372-7">]</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1959614372-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1959614372-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="1959614372-9">(</span><span class="p" data-group-id="1959614372-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1959614372-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1959614372-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1959614372-12">[</span><span class="p" data-group-id="1959614372-12">]</span><span class="p" data-group-id="1959614372-11">}</span><span class="p" data-group-id="1959614372-10">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1959614372-13">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1959614372-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1959614372-14">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1959614372-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1959614372-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1959614372-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="5442576482-1">(</span><span class="n">Code</span><span class="p" data-group-id="5442576482-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="5442576482-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5442576482-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5442576482-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5442576482-4">(</span><span class="n">Code</span><span class="p" data-group-id="5442576482-4">)</span><span class="p" data-group-id="5442576482-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5442576482-5">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5442576482-5">}</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="5442576482-6">(</span><span class="p" data-group-id="5442576482-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5442576482-7">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="5442576482-7">]</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="5442576482-8">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5442576482-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="5442576482-9">(</span><span class="p" data-group-id="5442576482-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5442576482-10">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="5442576482-11">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5442576482-12">[</span><span class="p" data-group-id="5442576482-12">]</span><span class="p" data-group-id="5442576482-11">}</span><span class="p" data-group-id="5442576482-10">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="5442576482-13">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5442576482-14">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5442576482-14">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5442576482-15">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="5442576482-15">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5442576482-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="1959614372-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1959614372-16">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="5442576482-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5442576482-16">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1959614372-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1959614372-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1959614372-18">(</span><span class="p" data-group-id="1959614372-18">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1959614372-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1959614372-20">[</span><span class="p" data-group-id="1959614372-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1959614372-21">}</span><span class="p" data-group-id="1959614372-20">]</span><span class="p" data-group-id="1959614372-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1959614372-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1959614372-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1959614372-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1959614372-23">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="5442576482-17">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5442576482-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5442576482-18">(</span><span class="p" data-group-id="5442576482-18">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5442576482-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="5442576482-20">[</span><span class="p" data-group-id="5442576482-21">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5442576482-21">}</span><span class="p" data-group-id="5442576482-20">]</span><span class="p" data-group-id="5442576482-19">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="5442576482-22">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5442576482-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5442576482-23">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5442576482-23">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>You can repeat the state enter code by returning one of
│ │ │  <code class="inline">{repeat_state, ...}</code>,<code class="inline">{repeat_state_and_data, _}</code>,
│ │ │  or <code class="inline">repeat_state_and_data</code> that otherwise behaves exactly like their
│ │ │  <code class="inline">keep_state</code> siblings.  See the type
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:state_callback_result/2"><code class="inline">state_callback_result()</code></a>
│ │ │  in the Reference Manual.</p><h2 id="inserted-events" class="section-heading">
│ │ │    <a href="#inserted-events" class="hover-link">
│ │ │ @@ -1066,44 +1066,44 @@
│ │ │  to dispatch pre-processed events as internal events to the main state
│ │ │  machine.</p><p>Using internal events also can make it easier to synchronize the state
│ │ │  machines.</p><p>A variant of this is to use a <a href="#complex-state">complex state</a> with
│ │ │  <a href="#one-state-callback">one state callback</a>, modeling the state
│ │ │  with, for example, a tuple <code class="inline">{MainFSMState, SubFSMState}</code>.</p><p>To illustrate this we make up an example where the buttons instead generate
│ │ │  down and up (press and release) events, and the lock responds
│ │ │  to an up event only after the corresponding down event.</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1105333633-1">(</span><span class="p" data-group-id="1105333633-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1105333633-2">]</span><span class="p" data-group-id="1105333633-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4191937327-1">(</span><span class="p" data-group-id="4191937327-2">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4191937327-2">]</span><span class="p" data-group-id="4191937327-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="1105333633-3">(</span><span class="n">Button</span><span class="p" data-group-id="1105333633-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1105333633-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1105333633-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1105333633-5">}</span><span class="p" data-group-id="1105333633-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="4191937327-3">(</span><span class="n">Button</span><span class="p" data-group-id="4191937327-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4191937327-4">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191937327-5">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4191937327-5">}</span><span class="p" data-group-id="4191937327-4">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="1105333633-6">(</span><span class="n">Button</span><span class="p" data-group-id="1105333633-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="1105333633-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1105333633-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1105333633-8">}</span><span class="p" data-group-id="1105333633-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="4191937327-6">(</span><span class="n">Button</span><span class="p" data-group-id="4191937327-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4191937327-7">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191937327-8">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4191937327-8">}</span><span class="p" data-group-id="4191937327-7">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1105333633-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1105333633-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="1105333633-10">(</span><span class="p" data-group-id="1105333633-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1105333633-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="1105333633-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1105333633-13">[</span><span class="p" data-group-id="1105333633-13">]</span><span class="p" data-group-id="1105333633-12">}</span><span class="p" data-group-id="1105333633-11">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="1105333633-14">(</span><span class="w">
│ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1105333633-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1105333633-15">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1105333633-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1105333633-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1105333633-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="2719948789-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2719948789-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2719948789-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2719948789-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2719948789-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2719948789-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="2719948789-4">}</span><span class="p" data-group-id="2719948789-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="2719948789-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2719948789-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2719948789-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2719948789-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4191937327-9">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4191937327-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="4191937327-10">(</span><span class="p" data-group-id="4191937327-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4191937327-11">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="4191937327-12">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4191937327-13">[</span><span class="p" data-group-id="4191937327-13">]</span><span class="p" data-group-id="4191937327-12">}</span><span class="p" data-group-id="4191937327-11">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="4191937327-14">(</span><span class="w">
│ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4191937327-15">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4191937327-15">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4191937327-16">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="4191937327-16">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4191937327-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">handle_common</span><span class="p" data-group-id="1002070955-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1002070955-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1002070955-2">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1002070955-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1002070955-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1002070955-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="1002070955-4">}</span><span class="p" data-group-id="1002070955-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="1002070955-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1002070955-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1002070955-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1002070955-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2719948789-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="2719948789-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2719948789-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="2719948789-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2719948789-9">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="2719948789-10">[</span><span class="p" data-group-id="2719948789-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="2719948789-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2719948789-12">}</span><span class="p" data-group-id="2719948789-11">}</span><span class="p" data-group-id="2719948789-10">]</span><span class="p" data-group-id="2719948789-8">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2719948789-13">#{</span><span class="p" data-group-id="2719948789-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1002070955-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="1002070955-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1002070955-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="1002070955-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1002070955-9">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="1002070955-10">[</span><span class="p" data-group-id="1002070955-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="1002070955-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1002070955-12">}</span><span class="p" data-group-id="1002070955-11">}</span><span class="p" data-group-id="1002070955-10">]</span><span class="p" data-group-id="1002070955-8">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1002070955-13">#{</span><span class="p" data-group-id="1002070955-13">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="2719948789-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2719948789-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2719948789-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2719948789-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2719948789-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="2719948789-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="2719948789-17">]</span><span class="p" data-group-id="2719948789-16">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="1002070955-14">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1002070955-15">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1002070955-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1002070955-14">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1002070955-16">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="n">Data</span><span class="p">,</span><span class="p" data-group-id="1002070955-17">[</span><span class="ss">postpone</span><span class="p" data-group-id="1002070955-17">]</span><span class="p" data-group-id="1002070955-16">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>If you start this program with <code class="inline">code_lock:start([17])</code> you can unlock with
│ │ │  <code class="inline">code_lock:down(17), code_lock:up(17).</code></p><h2 id="example-revisited" class="section-heading">
│ │ │    <a href="#example-revisited" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example Revisited</span>
│ │ │  </h2>
│ │ │ @@ -1131,152 +1131,152 @@
│ │ │  Also, the state diagram does not show that the <code class="inline">code_length/0</code> call
│ │ │  must be handled in every state.</p><h3 id="callback-mode-state_functions" class="section-heading">
│ │ │    <a href="#callback-mode-state_functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Callback Mode: state_functions</span>
│ │ │  </h3>
│ │ │ -<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3583810642-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="3583810642-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="3583810642-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="3583810642-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3583810642-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="3583810642-3">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Using state functions:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6721216133-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="6721216133-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="6721216133-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="6721216133-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="6721216133-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_2</span><span class="p" data-group-id="6721216133-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3583810642-4">(</span><span class="p" data-group-id="3583810642-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3583810642-5">]</span><span class="p" data-group-id="3583810642-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3583810642-6">(</span><span class="p" data-group-id="3583810642-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3583810642-7">]</span><span class="p" data-group-id="3583810642-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3583810642-8">(</span><span class="p" data-group-id="3583810642-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="3583810642-9">]</span><span class="p" data-group-id="3583810642-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3583810642-10">(</span><span class="p" data-group-id="3583810642-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="3583810642-11">]</span><span class="p" data-group-id="3583810642-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="3583810642-12">(</span><span class="n">Code</span><span class="p" data-group-id="3583810642-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3583810642-13">(</span><span class="p" data-group-id="3583810642-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="3583810642-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3583810642-15">[</span><span class="p" data-group-id="3583810642-15">]</span><span class="p" data-group-id="3583810642-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="3583810642-16">(</span><span class="p" data-group-id="3583810642-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="3583810642-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="3583810642-17">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">down</span><span class="p" data-group-id="3583810642-18">(</span><span class="n">Button</span><span class="p" data-group-id="3583810642-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3583810642-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3583810642-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3583810642-20">}</span><span class="p" data-group-id="3583810642-19">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">up</span><span class="p" data-group-id="3583810642-21">(</span><span class="n">Button</span><span class="p" data-group-id="3583810642-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="3583810642-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3583810642-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="3583810642-23">}</span><span class="p" data-group-id="3583810642-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">code_length</span><span class="p" data-group-id="3583810642-24">(</span><span class="p" data-group-id="3583810642-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="3583810642-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="3583810642-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="5201795778-1">(</span><span class="n">Code</span><span class="p" data-group-id="5201795778-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="5201795778-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="5201795778-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5201795778-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5201795778-4">(</span><span class="n">Code</span><span class="p" data-group-id="5201795778-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5201795778-5">[</span><span class="p" data-group-id="5201795778-5">]</span><span class="p" data-group-id="5201795778-3">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5201795778-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5201795778-6">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6721216133-4">(</span><span class="p" data-group-id="6721216133-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6721216133-5">]</span><span class="p" data-group-id="6721216133-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6721216133-6">(</span><span class="p" data-group-id="6721216133-7">[</span><span class="ss">down</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">up</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">code_length</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6721216133-7">]</span><span class="p" data-group-id="6721216133-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6721216133-8">(</span><span class="p" data-group-id="6721216133-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6721216133-9">]</span><span class="p" data-group-id="6721216133-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6721216133-10">(</span><span class="p" data-group-id="6721216133-11">[</span><span class="ss">locked</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">open</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="6721216133-11">]</span><span class="p" data-group-id="6721216133-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="6721216133-12">(</span><span class="n">Code</span><span class="p" data-group-id="6721216133-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6721216133-13">(</span><span class="p" data-group-id="6721216133-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6721216133-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6721216133-15">[</span><span class="p" data-group-id="6721216133-15">]</span><span class="p" data-group-id="6721216133-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="6721216133-16">(</span><span class="p" data-group-id="6721216133-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="6721216133-17">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="6721216133-17">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">down</span><span class="p" data-group-id="6721216133-18">(</span><span class="n">Button</span><span class="p" data-group-id="6721216133-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6721216133-19">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6721216133-20">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6721216133-20">}</span><span class="p" data-group-id="6721216133-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">up</span><span class="p" data-group-id="6721216133-21">(</span><span class="n">Button</span><span class="p" data-group-id="6721216133-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="6721216133-22">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6721216133-23">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6721216133-23">}</span><span class="p" data-group-id="6721216133-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">code_length</span><span class="p" data-group-id="6721216133-24">(</span><span class="p" data-group-id="6721216133-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="6721216133-25">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p" data-group-id="6721216133-25">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9458033815-1">(</span><span class="n">Code</span><span class="p" data-group-id="9458033815-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="9458033815-2">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="9458033815-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9458033815-3">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="9458033815-4">(</span><span class="n">Code</span><span class="p" data-group-id="9458033815-4">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9458033815-5">[</span><span class="p" data-group-id="9458033815-5">]</span><span class="p" data-group-id="9458033815-3">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9458033815-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9458033815-6">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="5201795778-7">(</span><span class="p" data-group-id="5201795778-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5201795778-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="5201795778-8">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="9458033815-7">(</span><span class="p" data-group-id="9458033815-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9458033815-8">[</span><span class="ss">state_functions</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="9458033815-8">]</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="5201795778-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="5201795778-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="5201795778-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="5201795778-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="5201795778-11">)</span><span class="p" data-group-id="5201795778-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9458033815-9">(</span><span class="n">HANDLE_COMMON</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">?</span><span class="n">FUNCTION_NAME</span><span class="p" data-group-id="9458033815-10">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="9458033815-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">handle_common</span><span class="p" data-group-id="9458033815-11">(</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="9458033815-11">)</span><span class="p" data-group-id="9458033815-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="5201795778-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5201795778-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5201795778-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5201795778-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5201795778-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5201795778-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="5201795778-15">}</span><span class="p" data-group-id="5201795778-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="5201795778-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5201795778-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5201795778-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5201795778-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9458033815-12">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9458033815-13">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9458033815-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9458033815-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9458033815-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9458033815-15">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9458033815-15">}</span><span class="p" data-group-id="9458033815-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9458033815-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9458033815-17">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9458033815-17">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9458033815-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5201795778-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="5201795778-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="5201795778-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="5201795778-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5201795778-20">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="5201795778-21">[</span><span class="p" data-group-id="5201795778-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="5201795778-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="5201795778-23">}</span><span class="p" data-group-id="5201795778-22">}</span><span class="p" data-group-id="5201795778-21">]</span><span class="p" data-group-id="5201795778-19">}</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5201795778-24">#{</span><span class="p" data-group-id="5201795778-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9458033815-18">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="9458033815-18">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="9458033815-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="9458033815-20">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9458033815-20">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9458033815-21">[</span><span class="p" data-group-id="9458033815-22">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="9458033815-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9458033815-23">}</span><span class="p" data-group-id="9458033815-22">}</span><span class="p" data-group-id="9458033815-21">]</span><span class="p" data-group-id="9458033815-19">}</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9458033815-24">#{</span><span class="p" data-group-id="9458033815-24">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_common</span><span class="p" data-group-id="5201795778-25">(</span><span class="p" data-group-id="5201795778-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="5201795778-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5201795778-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="5201795778-27">}</span><span class="p" data-group-id="5201795778-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5201795778-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5201795778-29">[</span><span class="p" data-group-id="5201795778-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="5201795778-31">(</span><span class="n">Code</span><span class="p" data-group-id="5201795778-31">)</span><span class="p" data-group-id="5201795778-30">}</span><span class="p" data-group-id="5201795778-29">]</span><span class="p" data-group-id="5201795778-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="9369807761-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="9369807761-2">(</span><span class="p" data-group-id="9369807761-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9369807761-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9369807761-5">[</span><span class="p" data-group-id="9369807761-5">]</span><span class="p" data-group-id="9369807761-4">}</span><span class="p" data-group-id="9369807761-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9369807761-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9369807761-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="9369807761-9">[</span><span class="p" data-group-id="9369807761-9">]</span><span class="p" data-group-id="9369807761-8">}</span><span class="p" data-group-id="9369807761-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">locked</span><span class="p" data-group-id="9369807761-10">(</span><span class="w">
│ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9369807761-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9369807761-11">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9369807761-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="9369807761-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_common</span><span class="p" data-group-id="9458033815-25">(</span><span class="p" data-group-id="9458033815-26">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="9458033815-26">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9458033815-27">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="9458033815-27">}</span><span class="p" data-group-id="9458033815-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9458033815-28">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="9458033815-29">[</span><span class="p" data-group-id="9458033815-30">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="nf">length</span><span class="p" data-group-id="9458033815-31">(</span><span class="n">Code</span><span class="p" data-group-id="9458033815-31">)</span><span class="p" data-group-id="9458033815-30">}</span><span class="p" data-group-id="9458033815-29">]</span><span class="p" data-group-id="9458033815-28">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">locked</span><span class="p" data-group-id="1367173233-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1367173233-2">(</span><span class="p" data-group-id="1367173233-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1367173233-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1367173233-5">[</span><span class="p" data-group-id="1367173233-5">]</span><span class="p" data-group-id="1367173233-4">}</span><span class="p" data-group-id="1367173233-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="1367173233-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1367173233-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1367173233-9">[</span><span class="p" data-group-id="1367173233-9">]</span><span class="p" data-group-id="1367173233-8">}</span><span class="p" data-group-id="1367173233-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">locked</span><span class="p" data-group-id="1367173233-10">(</span><span class="w">
│ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1367173233-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1367173233-11">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1367173233-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1367173233-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="9369807761-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="9369807761-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1367173233-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="1367173233-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="9369807761-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="9369807761-14">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="9369807761-15">[</span><span class="n">Button</span><span class="p" data-group-id="9369807761-15">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1367173233-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="1367173233-14">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1367173233-15">[</span><span class="n">Button</span><span class="p" data-group-id="1367173233-15">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9369807761-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-16">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1367173233-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-16">}</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9369807761-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9369807761-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="9369807761-18">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="9369807761-19">[</span><span class="p" data-group-id="9369807761-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="9369807761-20">}</span><span class="p" data-group-id="9369807761-19">]</span><span class="p" data-group-id="9369807761-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1367173233-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1367173233-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1367173233-18">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="1367173233-19">[</span><span class="p" data-group-id="1367173233-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="1367173233-20">}</span><span class="p" data-group-id="1367173233-19">]</span><span class="p" data-group-id="1367173233-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="1112599365-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1112599365-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1112599365-2">(</span><span class="p" data-group-id="1112599365-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1112599365-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="1112599365-4">[</span><span class="p" data-group-id="1112599365-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1112599365-5">}</span><span class="p" data-group-id="1112599365-4">]</span><span class="p" data-group-id="1112599365-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1112599365-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1112599365-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1112599365-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1112599365-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">open</span><span class="p" data-group-id="1112599365-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1112599365-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1112599365-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="1112599365-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="1112599365-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1112599365-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="1112599365-11">]</span><span class="p" data-group-id="1112599365-10">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">open</span><span class="p" data-group-id="7110002467-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="7110002467-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="7110002467-2">(</span><span class="p" data-group-id="7110002467-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7110002467-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="7110002467-4">[</span><span class="p" data-group-id="7110002467-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="7110002467-5">}</span><span class="p" data-group-id="7110002467-4">]</span><span class="p" data-group-id="7110002467-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="7110002467-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7110002467-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7110002467-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="7110002467-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">open</span><span class="p" data-group-id="7110002467-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7110002467-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="7110002467-9">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7110002467-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7110002467-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7110002467-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="7110002467-11">]</span><span class="p" data-group-id="7110002467-10">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">?</span><span class="n">HANDLE_COMMON</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">do_lock</span><span class="p" data-group-id="1112599365-12">(</span><span class="p" data-group-id="1112599365-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1112599365-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1112599365-14">[</span><span class="p" data-group-id="1112599365-14">]</span><span class="p" data-group-id="1112599365-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="1112599365-15">(</span><span class="p" data-group-id="1112599365-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1112599365-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1112599365-17">[</span><span class="p" data-group-id="1112599365-17">]</span><span class="p" data-group-id="1112599365-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_lock</span><span class="p" data-group-id="7110002467-12">(</span><span class="p" data-group-id="7110002467-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7110002467-13">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7110002467-14">[</span><span class="p" data-group-id="7110002467-14">]</span><span class="p" data-group-id="7110002467-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="7110002467-15">(</span><span class="p" data-group-id="7110002467-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7110002467-16">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7110002467-17">[</span><span class="p" data-group-id="7110002467-17">]</span><span class="p" data-group-id="7110002467-16">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="1112599365-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1112599365-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="1112599365-19">(</span><span class="p" data-group-id="1112599365-19">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="7110002467-18">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="7110002467-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="7110002467-19">(</span><span class="p" data-group-id="7110002467-19">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h3 id="callback-mode-handle_event_function" class="section-heading">
│ │ │    <a href="#callback-mode-handle_event_function" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Callback Mode: handle_event_function</span>
│ │ │  </h3>
│ │ │  <p>This section describes what to change in the example to use one
│ │ │  <code class="inline">handle_event/4</code> function.  The previously used approach to first branch
│ │ │  depending on event does not work that well here because of
│ │ │ -the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8004033530-1">(</span><span class="p" data-group-id="8004033530-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="8004033530-2">]</span><span class="p" data-group-id="8004033530-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="0004869829-1">(</span><span class="p" data-group-id="0004869829-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0004869829-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="0004869829-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ +the <em>state enter calls</em>, so this example first branches depending on state:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1665910065-1">(</span><span class="p" data-group-id="1665910065-2">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="1665910065-2">]</span><span class="p" data-group-id="1665910065-1">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">callback_mode</span><span class="p" data-group-id="3758121251-1">(</span><span class="p" data-group-id="3758121251-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3758121251-2">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="3758121251-2">]</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6849661091-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="6849661091-2">(</span><span class="p" data-group-id="6849661091-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6849661091-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6849661091-5">[</span><span class="p" data-group-id="6849661091-5">]</span><span class="p" data-group-id="6849661091-4">}</span><span class="p" data-group-id="6849661091-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6849661091-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6849661091-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="6849661091-9">[</span><span class="p" data-group-id="6849661091-9">]</span><span class="p" data-group-id="6849661091-8">}</span><span class="p" data-group-id="6849661091-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6849661091-10">(</span><span class="w">
│ │ │ -  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6849661091-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6849661091-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="6849661091-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="6849661091-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1375612489-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1375612489-2">(</span><span class="p" data-group-id="1375612489-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1375612489-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-4">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1375612489-5">[</span><span class="p" data-group-id="1375612489-5">]</span><span class="p" data-group-id="1375612489-4">}</span><span class="p" data-group-id="1375612489-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1375612489-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1375612489-7">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-8">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1375612489-9">[</span><span class="p" data-group-id="1375612489-9">]</span><span class="p" data-group-id="1375612489-8">}</span><span class="p" data-group-id="1375612489-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1375612489-10">(</span><span class="w">
│ │ │ +  </span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1375612489-11">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1375612489-11">}</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1375612489-12">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1375612489-12">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="6849661091-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="6849661091-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1375612489-13">(</span><span class="n">Buttons</span><span class="p" data-group-id="1375612489-13">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="6849661091-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="6849661091-14">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="6849661091-15">[</span><span class="n">Button</span><span class="p" data-group-id="6849661091-15">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1375612489-14">(</span><span class="n">Buttons</span><span class="p" data-group-id="1375612489-14">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1375612489-15">[</span><span class="n">Button</span><span class="p" data-group-id="1375612489-15">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6849661091-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-16">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1375612489-16">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-16">}</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6849661091-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6849661091-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="6849661091-18">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="6849661091-19">[</span><span class="p" data-group-id="6849661091-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="6849661091-20">}</span><span class="p" data-group-id="6849661091-19">]</span><span class="p" data-group-id="6849661091-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1375612489-17">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1375612489-18">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1375612489-18">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="1375612489-19">[</span><span class="p" data-group-id="1375612489-20">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="1375612489-20">}</span><span class="p" data-group-id="1375612489-19">]</span><span class="p" data-group-id="1375612489-17">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5297024338-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5297024338-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5297024338-2">(</span><span class="p" data-group-id="5297024338-2">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5297024338-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5297024338-4">[</span><span class="p" data-group-id="5297024338-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5297024338-5">}</span><span class="p" data-group-id="5297024338-4">]</span><span class="p" data-group-id="5297024338-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5297024338-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5297024338-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5297024338-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5297024338-7">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5297024338-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5297024338-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5297024338-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5297024338-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5297024338-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="5297024338-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="5297024338-11">]</span><span class="p" data-group-id="5297024338-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6204755739-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6204755739-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6204755739-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6204755739-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6204755739-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6204755739-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="6204755739-4">}</span><span class="p" data-group-id="6204755739-3">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6204755739-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6204755739-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6204755739-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6204755739-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8233412565-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="8233412565-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="8233412565-2">(</span><span class="p" data-group-id="8233412565-2">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8233412565-3">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="8233412565-4">[</span><span class="p" data-group-id="8233412565-5">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="8233412565-5">}</span><span class="p" data-group-id="8233412565-4">]</span><span class="p" data-group-id="8233412565-3">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8233412565-6">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8233412565-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8233412565-7">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="ss">locked</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="8233412565-7">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="8233412565-8">(</span><span class="ss">internal</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8233412565-9">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="8233412565-9">}</span><span class="p">,</span><span class="w"> </span><span class="ss">open</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8233412565-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8233412565-10">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="8233412565-11">[</span><span class="ss">postpone</span><span class="p" data-group-id="8233412565-11">]</span><span class="p" data-group-id="8233412565-10">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%% Common events</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0492484466-1">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0492484466-2">{</span><span class="ss">down</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0492484466-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0492484466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0492484466-3">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0492484466-4">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0492484466-4">}</span><span class="p" data-group-id="0492484466-3">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0492484466-5">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0492484466-6">{</span><span class="ss">up</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0492484466-6">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0492484466-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Data</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6204755739-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="6204755739-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="6204755739-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="6204755739-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="6204755739-9">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="6204755739-10">[</span><span class="p" data-group-id="6204755739-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="6204755739-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="6204755739-12">}</span><span class="p" data-group-id="6204755739-11">}</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="6204755739-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="6204755739-13">}</span><span class="p" data-group-id="6204755739-10">]</span><span class="p" data-group-id="6204755739-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="6204755739-14">#{</span><span class="p" data-group-id="6204755739-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0492484466-7">#{</span><span class="ss">button</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Button</span><span class="p" data-group-id="0492484466-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0492484466-8">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">remove</span><span class="p" data-group-id="0492484466-9">(</span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0492484466-9">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="0492484466-10">[</span><span class="p" data-group-id="0492484466-11">{</span><span class="ss">next_event</span><span class="p">,</span><span class="ss">internal</span><span class="p">,</span><span class="p" data-group-id="0492484466-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="0492484466-12">}</span><span class="p" data-group-id="0492484466-11">}</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="0492484466-13">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="0492484466-13">}</span><span class="p" data-group-id="0492484466-10">]</span><span class="p" data-group-id="0492484466-8">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0492484466-14">#{</span><span class="p" data-group-id="0492484466-14">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">keep_state_and_data</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="6204755739-15">(</span><span class="p" data-group-id="6204755739-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="6204755739-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6204755739-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="6204755739-17">}</span><span class="p" data-group-id="6204755739-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6204755739-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="6204755739-19">[</span><span class="p" data-group-id="6204755739-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="6204755739-20">}</span><span class="p" data-group-id="6204755739-19">]</span><span class="p" data-group-id="6204755739-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="0492484466-15">(</span><span class="p" data-group-id="0492484466-16">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="0492484466-16">}</span><span class="p">,</span><span class="w"> </span><span class="ss">code_length</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0492484466-17">#{</span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="0492484466-17">}</span><span class="p" data-group-id="0492484466-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0492484466-18">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="0492484466-19">[</span><span class="p" data-group-id="0492484466-20">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">Length</span><span class="p" data-group-id="0492484466-20">}</span><span class="p" data-group-id="0492484466-19">]</span><span class="p" data-group-id="0492484466-18">}</span><span class="p">.</span></code></pre><p>Notice that postponing buttons from the <code class="inline">open</code> state to the <code class="inline">locked</code> state
│ │ │  seems like a strange thing to do for a code lock, but it at least
│ │ │  illustrates event postponing.</p><h2 id="filter-the-state" class="section-heading">
│ │ │    <a href="#filter-the-state" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Filter the State</span>
│ │ │  </h2>
│ │ │ @@ -1286,30 +1286,30 @@
│ │ │  and which digits that remain to unlock.</p><p>This state data can be regarded as sensitive, and maybe not what you want
│ │ │  in the error log because of some unpredictable event.</p><p>Another reason to filter the state can be that the state is too large to print,
│ │ │  as it fills the error log with uninteresting details.</p><p>To avoid this, you can format the internal state that gets in the error log
│ │ │  and gets returned from <a href="../../lib/stdlib-6.2.2.2/doc/html/sys.html#get_status/1"><code class="inline">sys:get_status/1,2</code></a>
│ │ │  by implementing function
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a>,
│ │ │  for example like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9771919143-1">(</span><span class="p" data-group-id="9771919143-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9771919143-2">]</span><span class="p" data-group-id="9771919143-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9708158772-1">(</span><span class="p" data-group-id="9708158772-2">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="ss">format_status</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="9708158772-2">]</span><span class="p" data-group-id="9708158772-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">format_status</span><span class="p" data-group-id="9771919143-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9771919143-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9771919143-4">]</span><span class="p" data-group-id="9771919143-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">format_status</span><span class="p" data-group-id="9708158772-3">(</span><span class="n">Opt</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9708158772-4">[</span><span class="p">_</span><span class="n">PDict</span><span class="p">,</span><span class="n">State</span><span class="p">,</span><span class="n">Data</span><span class="p" data-group-id="9708158772-4">]</span><span class="p" data-group-id="9708158772-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">StateData</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -	</span><span class="p" data-group-id="9771919143-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ -	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9771919143-6">(</span><span class="w">
│ │ │ -	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9771919143-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9771919143-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ -	       </span><span class="p" data-group-id="9771919143-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9771919143-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │ +	</span><span class="p" data-group-id="9708158772-5">{</span><span class="n">State</span><span class="p">,</span><span class="w">
│ │ │ +	 </span><span class="nc">maps</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="9708158772-6">(</span><span class="w">
│ │ │ +	   </span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9708158772-7">(</span><span class="ss">code</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9708158772-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">false</span><span class="p">;</span><span class="w">
│ │ │ +	       </span><span class="p" data-group-id="9708158772-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="9708158772-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">true</span><span class="w">
│ │ │  	   </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -	   </span><span class="n">Data</span><span class="p" data-group-id="9771919143-6">)</span><span class="p" data-group-id="9771919143-5">}</span><span class="p">,</span><span class="w">
│ │ │ +	   </span><span class="n">Data</span><span class="p" data-group-id="9708158772-6">)</span><span class="p" data-group-id="9708158772-5">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">Opt</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │  	</span><span class="ss">terminate</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  	    </span><span class="n">StateData</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">normal</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -	    </span><span class="p" data-group-id="9771919143-9">[</span><span class="p" data-group-id="9771919143-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="9771919143-11">[</span><span class="p" data-group-id="9771919143-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="9771919143-12">}</span><span class="p" data-group-id="9771919143-11">]</span><span class="p" data-group-id="9771919143-10">}</span><span class="p" data-group-id="9771919143-9">]</span><span class="w">
│ │ │ +	    </span><span class="p" data-group-id="9708158772-9">[</span><span class="p" data-group-id="9708158772-10">{</span><span class="ss">data</span><span class="p">,</span><span class="p" data-group-id="9708158772-11">[</span><span class="p" data-group-id="9708158772-12">{</span><span class="s">&quot;State&quot;</span><span class="p">,</span><span class="n">StateData</span><span class="p" data-group-id="9708158772-12">}</span><span class="p" data-group-id="9708158772-11">]</span><span class="p" data-group-id="9708158772-10">}</span><span class="p" data-group-id="9708158772-9">]</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>It is not mandatory to implement a
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#c:format_status/2"><code class="inline">Module:format_status/2</code></a> function.
│ │ │  If you do not, a default implementation is used that does the same
│ │ │  as this example function without filtering the <code class="inline">Data</code> term, that is,
│ │ │  <code class="inline">StateData = {State, Data}</code>, in this example containing sensitive information.</p><h2 id="complex-state" class="section-heading">
│ │ │    <a href="#complex-state" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -1322,104 +1322,104 @@
│ │ │  like a tuple.</p><p>One reason to use this is when you have a state item that when changed
│ │ │  should cancel the <a href="#state-time-outs"><em>state time-out</em></a>, or one that affects
│ │ │  the event handling in combination with postponing events. We will go for
│ │ │  the latter and complicate the previous example by introducing
│ │ │  a configurable lock button (this is the state item in question),
│ │ │  which in the <code class="inline">open</code> state immediately locks the door, and an API function
│ │ │  <code class="inline">set_lock_button/1</code> to set the lock button.</p><p>Suppose now that we call <code class="inline">set_lock_button</code> while the door is open,
│ │ │ -and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="5608154657-1">(</span><span class="p" data-group-id="5608154657-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="5608154657-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="5608154657-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5608154657-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5608154657-3">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5608154657-4">(</span><span class="ss">a</span><span class="p" data-group-id="5608154657-4">)</span><span class="p">.</span><span class="w">
│ │ │ +and we have already postponed a button event that was the new lock button:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3320480387-1">(</span><span class="p" data-group-id="3320480387-2">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="3320480387-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">x</span><span class="p" data-group-id="3320480387-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3320480387-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.666</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="3320480387-3">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3320480387-4">(</span><span class="ss">a</span><span class="p" data-group-id="3320480387-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5608154657-5">(</span><span class="ss">b</span><span class="p" data-group-id="5608154657-5">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3320480387-5">(</span><span class="ss">b</span><span class="p" data-group-id="3320480387-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5608154657-6">(</span><span class="ss">c</span><span class="p" data-group-id="5608154657-6">)</span><span class="p">.</span><span class="w">
│ │ │ +4&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3320480387-6">(</span><span class="ss">c</span><span class="p" data-group-id="3320480387-6">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="w">
│ │ │  </span><span class="n">Open</span><span class="gp unselectable">
│ │ │ -5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="5608154657-7">(</span><span class="ss">y</span><span class="p" data-group-id="5608154657-7">)</span><span class="p">.</span><span class="w">
│ │ │ +5&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">button</span><span class="p" data-group-id="3320480387-7">(</span><span class="ss">y</span><span class="p" data-group-id="3320480387-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="5608154657-8">(</span><span class="ss">y</span><span class="p" data-group-id="5608154657-8">)</span><span class="p">.</span><span class="w">
│ │ │ +6&gt; </span><span class="nc">code_lock</span><span class="p">:</span><span class="nf">set_lock_button</span><span class="p" data-group-id="3320480387-8">(</span><span class="ss">y</span><span class="p" data-group-id="3320480387-8">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="c1">% What should happen here?  Immediate lock or nothing?</span></code></pre><p>We could say that the button was pressed too early so it should not be
│ │ │  recognized as the lock button. Or we can make the lock button part of
│ │ │  the state so when we then change the lock button in the locked state,
│ │ │  the change becomes a <em>state change</em> and all postponed events are retried,
│ │ │  therefore the lock is immediately locked!</p><p>We define the state as <code class="inline">{StateName, LockButton}</code>, where <code class="inline">StateName</code>
│ │ │ -is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4184853955-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="4184853955-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4184853955-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="4184853955-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="4184853955-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="4184853955-3">)</span><span class="p">.</span><span class="w">
│ │ │ +is as before and <code class="inline">LockButton</code> is the current lock button:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9785671729-1">(</span><span class="ss">code_lock</span><span class="p" data-group-id="9785671729-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="9785671729-2">(</span><span class="ss">gen_statem</span><span class="p" data-group-id="9785671729-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="9785671729-3">(</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="ss">code_lock_3</span><span class="p" data-group-id="9785671729-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4184853955-4">(</span><span class="p" data-group-id="4184853955-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4184853955-5">]</span><span class="p" data-group-id="4184853955-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4184853955-6">(</span><span class="p" data-group-id="4184853955-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4184853955-7">]</span><span class="p" data-group-id="4184853955-6">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4184853955-8">(</span><span class="p" data-group-id="4184853955-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="4184853955-9">]</span><span class="p" data-group-id="4184853955-8">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4184853955-10">(</span><span class="p" data-group-id="4184853955-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="4184853955-11">]</span><span class="p" data-group-id="4184853955-10">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="4184853955-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="4184853955-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4184853955-13">(</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="4184853955-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="4184853955-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4184853955-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4184853955-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4184853955-16">[</span><span class="p" data-group-id="4184853955-16">]</span><span class="p" data-group-id="4184853955-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">stop</span><span class="p" data-group-id="4184853955-17">(</span><span class="p" data-group-id="4184853955-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="4184853955-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="4184853955-18">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">button</span><span class="p" data-group-id="4184853955-19">(</span><span class="n">Button</span><span class="p" data-group-id="4184853955-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="4184853955-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4184853955-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="4184853955-21">}</span><span class="p" data-group-id="4184853955-20">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">set_lock_button</span><span class="p" data-group-id="4184853955-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="4184853955-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="4184853955-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4184853955-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4184853955-24">}</span><span class="p" data-group-id="4184853955-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="2283846610-1">(</span><span class="p" data-group-id="2283846610-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="2283846610-2">}</span><span class="p" data-group-id="2283846610-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">process_flag</span><span class="p" data-group-id="2283846610-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="2283846610-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2283846610-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="2283846610-5">(</span><span class="n">Code</span><span class="p" data-group-id="2283846610-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="2283846610-6">[</span><span class="p" data-group-id="2283846610-6">]</span><span class="p" data-group-id="2283846610-4">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2283846610-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283846610-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="2283846610-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-7">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9785671729-4">(</span><span class="p" data-group-id="9785671729-5">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">2</span><span class="p">,</span><span class="ss">stop</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="9785671729-5">]</span><span class="p" data-group-id="9785671729-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9785671729-6">(</span><span class="p" data-group-id="9785671729-7">[</span><span class="ss">button</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">set_lock_button</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9785671729-7">]</span><span class="p" data-group-id="9785671729-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9785671729-8">(</span><span class="p" data-group-id="9785671729-9">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="ss">callback_mode</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="ss">terminate</span><span class="p">/</span><span class="mi">3</span><span class="p" data-group-id="9785671729-9">]</span><span class="p" data-group-id="9785671729-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9785671729-10">(</span><span class="p" data-group-id="9785671729-11">[</span><span class="ss">handle_event</span><span class="p">/</span><span class="mi">4</span><span class="p" data-group-id="9785671729-11">]</span><span class="p" data-group-id="9785671729-10">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="9785671729-12">(</span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="n">LockButton</span><span class="p" data-group-id="9785671729-12">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="9785671729-13">(</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9785671729-14">{</span><span class="ss">local</span><span class="p">,</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="9785671729-14">}</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9785671729-15">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="9785671729-15">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9785671729-16">[</span><span class="p" data-group-id="9785671729-16">]</span><span class="p" data-group-id="9785671729-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">stop</span><span class="p" data-group-id="9785671729-17">(</span><span class="p" data-group-id="9785671729-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">stop</span><span class="p" data-group-id="9785671729-18">(</span><span class="o">?</span><span class="n">NAME</span><span class="p" data-group-id="9785671729-18">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">button</span><span class="p" data-group-id="9785671729-19">(</span><span class="n">Button</span><span class="p" data-group-id="9785671729-19">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">cast</span><span class="p" data-group-id="9785671729-20">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9785671729-21">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="9785671729-21">}</span><span class="p" data-group-id="9785671729-20">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">set_lock_button</span><span class="p" data-group-id="9785671729-22">(</span><span class="n">LockButton</span><span class="p" data-group-id="9785671729-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">gen_statem</span><span class="p">:</span><span class="nf">call</span><span class="p" data-group-id="9785671729-23">(</span><span class="o">?</span><span class="n">NAME</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9785671729-24">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="9785671729-24">}</span><span class="p" data-group-id="9785671729-23">)</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="1309283022-1">(</span><span class="p" data-group-id="1309283022-2">{</span><span class="n">Code</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1309283022-2">}</span><span class="p" data-group-id="1309283022-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">process_flag</span><span class="p" data-group-id="1309283022-3">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="1309283022-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">Data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1309283022-4">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1309283022-5">(</span><span class="n">Code</span><span class="p" data-group-id="1309283022-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1309283022-6">[</span><span class="p" data-group-id="1309283022-6">]</span><span class="p" data-group-id="1309283022-4">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1309283022-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309283022-8">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1309283022-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-7">}</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">callback_mode</span><span class="p" data-group-id="2283846610-9">(</span><span class="p" data-group-id="2283846610-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2283846610-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="2283846610-10">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">callback_mode</span><span class="p" data-group-id="1309283022-9">(</span><span class="p" data-group-id="1309283022-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1309283022-10">[</span><span class="ss">handle_event_function</span><span class="p">,</span><span class="ss">state_enter</span><span class="p" data-group-id="1309283022-10">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% State: locked</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2283846610-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283846610-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2283846610-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_lock</span><span class="p" data-group-id="2283846610-13">(</span><span class="p" data-group-id="2283846610-13">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2283846610-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2283846610-16">[</span><span class="p" data-group-id="2283846610-16">]</span><span class="p" data-group-id="2283846610-15">}</span><span class="p" data-group-id="2283846610-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2283846610-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283846610-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="2283846610-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2283846610-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="2283846610-21">[</span><span class="p" data-group-id="2283846610-21">]</span><span class="p" data-group-id="2283846610-20">}</span><span class="p" data-group-id="2283846610-19">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="2283846610-22">(</span><span class="w">
│ │ │ -  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283846610-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="2283846610-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283846610-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="2283846610-24">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="2283846610-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="2283846610-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1309283022-11">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309283022-12">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1309283022-12">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_lock</span><span class="p" data-group-id="1309283022-13">(</span><span class="p" data-group-id="1309283022-13">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1309283022-14">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-15">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1309283022-16">[</span><span class="p" data-group-id="1309283022-16">]</span><span class="p" data-group-id="1309283022-15">}</span><span class="p" data-group-id="1309283022-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1309283022-17">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">button</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309283022-18">{</span><span class="ss">locked</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1309283022-18">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-17">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1309283022-19">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-20">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="p" data-group-id="1309283022-21">[</span><span class="p" data-group-id="1309283022-21">]</span><span class="p" data-group-id="1309283022-20">}</span><span class="p" data-group-id="1309283022-19">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1309283022-22">(</span><span class="w">
│ │ │ +  </span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309283022-23">{</span><span class="ss">button</span><span class="p">,</span><span class="n">Button</span><span class="p" data-group-id="1309283022-23">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309283022-24">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1309283022-24">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="1309283022-25">#{</span><span class="ss">code</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Code</span><span class="p">,</span><span class="w"> </span><span class="nb">length</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Length</span><span class="p">,</span><span class="w"> </span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Buttons</span><span class="p" data-group-id="1309283022-25">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │          </span><span class="k">if</span><span class="w">
│ │ │ -            </span><span class="nf">length</span><span class="p" data-group-id="2283846610-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="2283846610-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">length</span><span class="p" data-group-id="1309283022-26">(</span><span class="n">Buttons</span><span class="p" data-group-id="1309283022-26">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">Length</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                  </span><span class="n">Buttons</span><span class="p">;</span><span class="w">
│ │ │              </span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                </span><span class="nf">tl</span><span class="p" data-group-id="2283846610-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="2283846610-27">)</span><span class="w">
│ │ │ -        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="2283846610-28">[</span><span class="n">Button</span><span class="p" data-group-id="2283846610-28">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="nf">tl</span><span class="p" data-group-id="1309283022-27">(</span><span class="n">Buttons</span><span class="p" data-group-id="1309283022-27">)</span><span class="w">
│ │ │ +        </span><span class="k">end</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="p" data-group-id="1309283022-28">[</span><span class="n">Button</span><span class="p" data-group-id="1309283022-28">]</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">if</span><span class="w">
│ │ │          </span><span class="n">NewButtons</span><span class="w"> </span><span class="o">=:=</span><span class="w"> </span><span class="n">Code</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Correct</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2283846610-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2283846610-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="2283846610-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-29">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1309283022-29">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309283022-30">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="1309283022-30">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-29">}</span><span class="p">;</span><span class="w">
│ │ │  	</span><span class="ss">true</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="c1">% Incomplete | Incorrect</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="2283846610-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="2283846610-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="2283846610-32">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="2283846610-33">[</span><span class="p" data-group-id="2283846610-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="2283846610-34">}</span><span class="p" data-group-id="2283846610-33">]</span><span class="p" data-group-id="2283846610-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="1309283022-31">{</span><span class="ss">keep_state</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="1309283022-32">#{</span><span class="ss">buttons</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">NewButtons</span><span class="p" data-group-id="1309283022-32">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="1309283022-33">[</span><span class="p" data-group-id="1309283022-34">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">30</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">button</span><span class="p" data-group-id="1309283022-34">}</span><span class="p" data-group-id="1309283022-33">]</span><span class="p" data-group-id="1309283022-31">}</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5722384399-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5722384399-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5722384399-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5722384399-3">(</span><span class="p" data-group-id="5722384399-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5722384399-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5722384399-5">[</span><span class="p" data-group-id="5722384399-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5722384399-6">}</span><span class="p" data-group-id="5722384399-5">]</span><span class="p" data-group-id="5722384399-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5722384399-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5722384399-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5722384399-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5722384399-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5722384399-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5722384399-9">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5722384399-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5722384399-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5722384399-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5722384399-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5722384399-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="5722384399-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="5722384399-14">}</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5722384399-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5722384399-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5722384399-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5722384399-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5722384399-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5722384399-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="5722384399-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="5722384399-20">]</span><span class="p" data-group-id="5722384399-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4062713020-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4062713020-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4062713020-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="4062713020-3">(</span><span class="p" data-group-id="4062713020-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4062713020-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4062713020-5">[</span><span class="p" data-group-id="4062713020-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="4062713020-6">}</span><span class="p" data-group-id="4062713020-5">]</span><span class="p" data-group-id="4062713020-4">}</span><span class="p">;</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4062713020-7">(</span><span class="ss">state_timeout</span><span class="p">,</span><span class="w"> </span><span class="ss">lock</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-8">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4062713020-8">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4062713020-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4062713020-9">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-10">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4062713020-10">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4062713020-9">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4062713020-11">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-12">{</span><span class="ss">button</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4062713020-12">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-13">{</span><span class="ss">open</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4062713020-13">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4062713020-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4062713020-14">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-15">{</span><span class="ss">locked</span><span class="p">,</span><span class="n">LockButton</span><span class="p" data-group-id="4062713020-15">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4062713020-14">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4062713020-16">(</span><span class="ss">cast</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-17">{</span><span class="ss">button</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4062713020-17">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4062713020-18">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="4062713020-18">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="4062713020-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4062713020-19">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="p" data-group-id="4062713020-20">[</span><span class="ss">postpone</span><span class="p" data-group-id="4062713020-20">]</span><span class="p" data-group-id="4062713020-19">}</span><span class="p">;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% Common events</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="3504908086-1">(</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3504908086-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="3504908086-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3504908086-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="3504908086-3">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="3504908086-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="3504908086-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3504908086-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3504908086-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3504908086-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="3504908086-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="3504908086-7">[</span><span class="p" data-group-id="3504908086-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="3504908086-8">}</span><span class="p" data-group-id="3504908086-7">]</span><span class="p" data-group-id="3504908086-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="8078702219-1">(</span><span class="p" data-group-id="8078702219-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8078702219-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8078702219-3">[</span><span class="p" data-group-id="8078702219-3">]</span><span class="p" data-group-id="8078702219-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">do_unlock</span><span class="p" data-group-id="8078702219-4">(</span><span class="p" data-group-id="8078702219-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8078702219-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8078702219-6">[</span><span class="p" data-group-id="8078702219-6">]</span><span class="p" data-group-id="8078702219-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="4976236147-1">(</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4976236147-2">{</span><span class="ss">call</span><span class="p">,</span><span class="n">From</span><span class="p" data-group-id="4976236147-2">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4976236147-3">{</span><span class="ss">set_lock_button</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="4976236147-3">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="4976236147-4">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="4976236147-4">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4976236147-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4976236147-5">{</span><span class="ss">next_state</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4976236147-6">{</span><span class="n">StateName</span><span class="p">,</span><span class="n">NewLockButton</span><span class="p" data-group-id="4976236147-6">}</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="4976236147-7">[</span><span class="p" data-group-id="4976236147-8">{</span><span class="ss">reply</span><span class="p">,</span><span class="n">From</span><span class="p">,</span><span class="n">OldLockButton</span><span class="p" data-group-id="4976236147-8">}</span><span class="p" data-group-id="4976236147-7">]</span><span class="p" data-group-id="4976236147-5">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">do_lock</span><span class="p" data-group-id="9006249832-1">(</span><span class="p" data-group-id="9006249832-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9006249832-2">(</span><span class="s">&quot;Locked</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9006249832-3">[</span><span class="p" data-group-id="9006249832-3">]</span><span class="p" data-group-id="9006249832-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">do_unlock</span><span class="p" data-group-id="9006249832-4">(</span><span class="p" data-group-id="9006249832-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="9006249832-5">(</span><span class="s">&quot;Open</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9006249832-6">[</span><span class="p" data-group-id="9006249832-6">]</span><span class="p" data-group-id="9006249832-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">terminate</span><span class="p" data-group-id="8078702219-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="8078702219-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="8078702219-8">(</span><span class="p" data-group-id="8078702219-8">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">terminate</span><span class="p" data-group-id="9006249832-7">(</span><span class="p">_</span><span class="n">Reason</span><span class="p">,</span><span class="w"> </span><span class="n">State</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="9006249832-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">State</span><span class="w"> </span><span class="o">=/=</span><span class="w"> </span><span class="ss">locked</span><span class="w"> </span><span class="ow">andalso</span><span class="w"> </span><span class="nf">do_lock</span><span class="p" data-group-id="9006249832-8">(</span><span class="p" data-group-id="9006249832-8">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="ss">ok</span><span class="p">.</span></code></pre><h2 id="hibernation" class="section-heading">
│ │ │    <a href="#hibernation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Hibernation</span>
│ │ │  </h2>
│ │ │  <p>If you have many servers in one node and they have some state(s) in their
│ │ │ @@ -1428,19 +1428,19 @@
│ │ │  footprint of a server can be minimized by hibernating it through
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/proc_lib.html#hibernate/3"><code class="inline">proc_lib:hibernate/3</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is rather costly to hibernate a process; see <a href="../../erts-15.2.7.2/doc/html/erlang.html#hibernate/3"><code class="inline">erlang:hibernate/3</code></a>. It is
│ │ │  not something you want to do after every event.</p></section><p>We can in this example hibernate in the <code class="inline">{open, _}</code> state,
│ │ │  because what normally occurs in that state is that the <em>state time-out</em>
│ │ │  after a while triggers a transition to <code class="inline">{locked, _}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% State: open</span><span class="w">
│ │ │ -</span><span class="nf">handle_event</span><span class="p" data-group-id="5526588264-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5526588264-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="5526588264-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="5526588264-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">do_unlock</span><span class="p" data-group-id="5526588264-3">(</span><span class="p" data-group-id="5526588264-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5526588264-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ -     </span><span class="p" data-group-id="5526588264-5">[</span><span class="p" data-group-id="5526588264-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="5526588264-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ -      </span><span class="ss">hibernate</span><span class="p" data-group-id="5526588264-5">]</span><span class="p" data-group-id="5526588264-4">}</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">handle_event</span><span class="p" data-group-id="1309739866-1">(</span><span class="ss">enter</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">OldState</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1309739866-2">{</span><span class="ss">open</span><span class="p">,</span><span class="p">_</span><span class="p" data-group-id="1309739866-2">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Data</span><span class="p" data-group-id="1309739866-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">do_unlock</span><span class="p" data-group-id="1309739866-3">(</span><span class="p" data-group-id="1309739866-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1309739866-4">{</span><span class="ss">keep_state_and_data</span><span class="p">,</span><span class="w">
│ │ │ +     </span><span class="p" data-group-id="1309739866-5">[</span><span class="p" data-group-id="1309739866-6">{</span><span class="ss">state_timeout</span><span class="p">,</span><span class="mi">10</span><span class="p">_</span><span class="mi">000</span><span class="p">,</span><span class="ss">lock</span><span class="p" data-group-id="1309739866-6">}</span><span class="p">,</span><span class="w"> </span><span class="c1">% Time in milliseconds</span><span class="w">
│ │ │ +      </span><span class="ss">hibernate</span><span class="p" data-group-id="1309739866-5">]</span><span class="p" data-group-id="1309739866-4">}</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span></code></pre><p>The atom <a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#t:hibernate/0"><code class="inline">hibernate</code></a> in the action list on the
│ │ │  last line when entering the <code class="inline">{open, _}</code> state is the only change. If any event
│ │ │  arrives in the <code class="inline">{open, _},</code> state, we do not bother to rehibernate,
│ │ │  so the server stays awake after any event.</p><p>To change that we would need to insert action <code class="inline">hibernate</code> in more places.
│ │ │  For example, the state-independent <code class="inline">set_lock_button</code> operation
│ │ │  would have to use <code class="inline">hibernate</code> but only in the <code class="inline">{open, _}</code> state,
│ │ │  which would clutter the code.</p><p>Another not uncommon scenario is to use the
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/sup_princ.html
│ │ │ @@ -128,48 +128,48 @@
│ │ │  the order specified by this list, and are terminated in the reverse order.</p><h2 id="example" class="section-heading">
│ │ │    <a href="#example" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Example</span>
│ │ │  </h2>
│ │ │  <p>The callback module for a supervisor starting the server from
│ │ │ -<a href="gen_server_concepts.html#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7107622703-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="7107622703-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7107622703-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="7107622703-2">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="gen_server_concepts.html#ex">gen_server Behaviour</a> can look as follows:</p><p><a href="" id="ex"></a></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1194931489-1">(</span><span class="ss">ch_sup</span><span class="p" data-group-id="1194931489-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="1194931489-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="1194931489-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7107622703-3">(</span><span class="p" data-group-id="7107622703-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7107622703-4">]</span><span class="p" data-group-id="7107622703-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7107622703-5">(</span><span class="p" data-group-id="7107622703-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7107622703-6">]</span><span class="p" data-group-id="7107622703-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1194931489-3">(</span><span class="p" data-group-id="1194931489-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1194931489-4">]</span><span class="p" data-group-id="1194931489-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1194931489-5">(</span><span class="p" data-group-id="1194931489-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="1194931489-6">]</span><span class="p" data-group-id="1194931489-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="7107622703-7">(</span><span class="p" data-group-id="7107622703-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7107622703-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7107622703-9">[</span><span class="p" data-group-id="7107622703-9">]</span><span class="p" data-group-id="7107622703-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="1194931489-7">(</span><span class="p" data-group-id="1194931489-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="1194931489-8">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1194931489-9">[</span><span class="p" data-group-id="1194931489-9">]</span><span class="p" data-group-id="1194931489-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="7107622703-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7107622703-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7107622703-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="7107622703-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7107622703-12">[</span><span class="p" data-group-id="7107622703-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7107622703-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7107622703-15">[</span><span class="p" data-group-id="7107622703-15">]</span><span class="p" data-group-id="7107622703-14">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="1194931489-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="1194931489-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1194931489-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">one_for_one</span><span class="p">,</span><span class="w"> </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5</span><span class="p" data-group-id="1194931489-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1194931489-12">[</span><span class="p" data-group-id="1194931489-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1194931489-14">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1194931489-15">[</span><span class="p" data-group-id="1194931489-15">]</span><span class="p" data-group-id="1194931489-14">}</span><span class="p">,</span><span class="w">
│ │ │                      </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │                      </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │                      </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7107622703-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="7107622703-16">]</span><span class="p" data-group-id="7107622703-13">}</span><span class="p" data-group-id="7107622703-12">]</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="7107622703-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7107622703-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="7107622703-18">}</span><span class="p" data-group-id="7107622703-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │ +                    </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1194931489-16">[</span><span class="ss">ch3</span><span class="p" data-group-id="1194931489-16">]</span><span class="p" data-group-id="1194931489-13">}</span><span class="p" data-group-id="1194931489-12">]</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="1194931489-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1194931489-18">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="1194931489-18">}</span><span class="p" data-group-id="1194931489-17">}</span><span class="p">.</span></code></pre><p>The <code class="inline">SupFlags</code> variable in the return value from <code class="inline">init/1</code> represents the
│ │ │  <a href="sup_princ.html#flags">supervisor flags</a>.</p><p>The <code class="inline">ChildSpecs</code> variable in the return value from <code class="inline">init/1</code> is a list of
│ │ │  <a href="sup_princ.html#spec">child specifications</a>.</p><p><a href="" id="flags"></a></p><h2 id="supervisor-flags" class="section-heading">
│ │ │    <a href="#supervisor-flags" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Supervisor Flags</span>
│ │ │  </h2>
│ │ │ -<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="0751067201-1">(</span><span class="p" data-group-id="0751067201-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0751067201-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="0751067201-3">(</span><span class="p" data-group-id="0751067201-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ -                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0751067201-4">(</span><span class="p" data-group-id="0751067201-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ -                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="0751067201-5">(</span><span class="p" data-group-id="0751067201-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ -                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="0751067201-6">(</span><span class="p" data-group-id="0751067201-6">)</span><span class="p" data-group-id="0751067201-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ -    </span><span class="nf">strategy</span><span class="p" data-group-id="0751067201-7">(</span><span class="p" data-group-id="0751067201-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │ +<p>This is the type definition for the supervisor flags:</p><pre><code class="makeup erlang" translate="no"><span class="nf">sup_flags</span><span class="p" data-group-id="5984031929-1">(</span><span class="p" data-group-id="5984031929-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5984031929-2">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">strategy</span><span class="p" data-group-id="5984031929-3">(</span><span class="p" data-group-id="5984031929-3">)</span><span class="p">,</span><span class="w">           </span><span class="c1">% optional</span><span class="w">
│ │ │ +                </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="5984031929-4">(</span><span class="p" data-group-id="5984031929-4">)</span><span class="p">,</span><span class="w">   </span><span class="c1">% optional</span><span class="w">
│ │ │ +                </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="5984031929-5">(</span><span class="p" data-group-id="5984031929-5">)</span><span class="p">,</span><span class="w">          </span><span class="c1">% optional</span><span class="w">
│ │ │ +                </span><span class="ss">auto_shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="5984031929-6">(</span><span class="p" data-group-id="5984031929-6">)</span><span class="p" data-group-id="5984031929-2">}</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ +    </span><span class="nf">strategy</span><span class="p" data-group-id="5984031929-7">(</span><span class="p" data-group-id="5984031929-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">one_for_all</span><span class="w">
│ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">one_for_one</span><span class="w">
│ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">rest_for_one</span><span class="w">
│ │ │                 </span><span class="p">|</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="w">
│ │ │ -    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="0751067201-8">(</span><span class="p" data-group-id="0751067201-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │ +    </span><span class="nf">auto_shutdown</span><span class="p" data-group-id="5984031929-8">(</span><span class="p" data-group-id="5984031929-8">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">never</span><span class="w">
│ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">any_significant</span><span class="w">
│ │ │                      </span><span class="p">|</span><span class="w"> </span><span class="ss">all_significant</span></code></pre><ul><li><code class="inline">strategy</code> specifies the <a href="sup_princ.html#strategy">restart strategy</a>.</li><li><code class="inline">intensity</code> and <code class="inline">period</code> specify the
│ │ │  <a href="sup_princ.html#max_intensity">maximum restart intensity</a>.</li><li><code class="inline">auto_shutdown</code> specifies whether and when a supervisor should
│ │ │  <a href="sup_princ.html#automatic-shutdown">automatically shut itself down</a>.</li></ul><p><a href="" id="strategy"></a></p><h2 id="restart-strategy" class="section-heading">
│ │ │    <a href="#restart-strategy" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -408,28 +408,28 @@
│ │ │  exhaust the <a href="sup_princ.html#max_intensity">Maximum Restart Intensity</a> of the
│ │ │  parent supervisor.</p></section><p><a href="" id="spec"></a></p><h2 id="child-specification" class="section-heading">
│ │ │    <a href="#child-specification" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Child Specification</span>
│ │ │  </h2>
│ │ │ -<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="9821757127-1">(</span><span class="p" data-group-id="9821757127-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9821757127-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="9821757127-3">(</span><span class="p" data-group-id="9821757127-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ -                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="9821757127-4">(</span><span class="p" data-group-id="9821757127-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ -                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="9821757127-5">(</span><span class="p" data-group-id="9821757127-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="9821757127-6">(</span><span class="p" data-group-id="9821757127-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="9821757127-7">(</span><span class="p" data-group-id="9821757127-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="9821757127-8">(</span><span class="p" data-group-id="9821757127-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ -                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="9821757127-9">(</span><span class="p" data-group-id="9821757127-9">)</span><span class="p" data-group-id="9821757127-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ -    </span><span class="nf">child_id</span><span class="p" data-group-id="9821757127-10">(</span><span class="p" data-group-id="9821757127-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="9821757127-11">(</span><span class="p" data-group-id="9821757127-11">)</span><span class="w">
│ │ │ -    </span><span class="nf">mfargs</span><span class="p" data-group-id="9821757127-12">(</span><span class="p" data-group-id="9821757127-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9821757127-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="9821757127-14">(</span><span class="p" data-group-id="9821757127-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="9821757127-15">(</span><span class="p" data-group-id="9821757127-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="9821757127-16">[</span><span class="nf">term</span><span class="p" data-group-id="9821757127-17">(</span><span class="p" data-group-id="9821757127-17">)</span><span class="p" data-group-id="9821757127-16">]</span><span class="p" data-group-id="9821757127-13">}</span><span class="w">
│ │ │ -    </span><span class="nf">modules</span><span class="p" data-group-id="9821757127-18">(</span><span class="p" data-group-id="9821757127-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9821757127-19">[</span><span class="nf">module</span><span class="p" data-group-id="9821757127-20">(</span><span class="p" data-group-id="9821757127-20">)</span><span class="p" data-group-id="9821757127-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ -    </span><span class="nf">restart</span><span class="p" data-group-id="9821757127-21">(</span><span class="p" data-group-id="9821757127-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ -    </span><span class="nf">significant</span><span class="p" data-group-id="9821757127-22">(</span><span class="p" data-group-id="9821757127-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="9821757127-23">(</span><span class="p" data-group-id="9821757127-23">)</span><span class="w">
│ │ │ -    </span><span class="nf">shutdown</span><span class="p" data-group-id="9821757127-24">(</span><span class="p" data-group-id="9821757127-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="9821757127-25">(</span><span class="p" data-group-id="9821757127-25">)</span><span class="w">
│ │ │ -    </span><span class="nf">worker</span><span class="p" data-group-id="9821757127-26">(</span><span class="p" data-group-id="9821757127-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │ +<p>The type definition for a child specification is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="nf">child_spec</span><span class="p" data-group-id="3804437219-1">(</span><span class="p" data-group-id="3804437219-1">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3804437219-2">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">child_id</span><span class="p" data-group-id="3804437219-3">(</span><span class="p" data-group-id="3804437219-3">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% mandatory</span><span class="w">
│ │ │ +                 </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">mfargs</span><span class="p" data-group-id="3804437219-4">(</span><span class="p" data-group-id="3804437219-4">)</span><span class="p">,</span><span class="w">            </span><span class="c1">% mandatory</span><span class="w">
│ │ │ +                 </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">restart</span><span class="p" data-group-id="3804437219-5">(</span><span class="p" data-group-id="3804437219-5">)</span><span class="p">,</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">significant</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">significant</span><span class="p" data-group-id="3804437219-6">(</span><span class="p" data-group-id="3804437219-6">)</span><span class="p">,</span><span class="w"> </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">shutdown</span><span class="p" data-group-id="3804437219-7">(</span><span class="p" data-group-id="3804437219-7">)</span><span class="p">,</span><span class="w">       </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">worker</span><span class="p" data-group-id="3804437219-8">(</span><span class="p" data-group-id="3804437219-8">)</span><span class="p">,</span><span class="w">             </span><span class="c1">% optional</span><span class="w">
│ │ │ +                 </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="nf">modules</span><span class="p" data-group-id="3804437219-9">(</span><span class="p" data-group-id="3804437219-9">)</span><span class="p" data-group-id="3804437219-2">}</span><span class="w">         </span><span class="c1">% optional</span><span class="w">
│ │ │ +    </span><span class="nf">child_id</span><span class="p" data-group-id="3804437219-10">(</span><span class="p" data-group-id="3804437219-10">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="3804437219-11">(</span><span class="p" data-group-id="3804437219-11">)</span><span class="w">
│ │ │ +    </span><span class="nf">mfargs</span><span class="p" data-group-id="3804437219-12">(</span><span class="p" data-group-id="3804437219-12">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3804437219-13">{</span><span class="n">M</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="3804437219-14">(</span><span class="p" data-group-id="3804437219-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="3804437219-15">(</span><span class="p" data-group-id="3804437219-15">)</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3804437219-16">[</span><span class="nf">term</span><span class="p" data-group-id="3804437219-17">(</span><span class="p" data-group-id="3804437219-17">)</span><span class="p" data-group-id="3804437219-16">]</span><span class="p" data-group-id="3804437219-13">}</span><span class="w">
│ │ │ +    </span><span class="nf">modules</span><span class="p" data-group-id="3804437219-18">(</span><span class="p" data-group-id="3804437219-18">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3804437219-19">[</span><span class="nf">module</span><span class="p" data-group-id="3804437219-20">(</span><span class="p" data-group-id="3804437219-20">)</span><span class="p" data-group-id="3804437219-19">]</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">dynamic</span><span class="w">
│ │ │ +    </span><span class="nf">restart</span><span class="p" data-group-id="3804437219-21">(</span><span class="p" data-group-id="3804437219-21">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">permanent</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">transient</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">temporary</span><span class="w">
│ │ │ +    </span><span class="nf">significant</span><span class="p" data-group-id="3804437219-22">(</span><span class="p" data-group-id="3804437219-22">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="3804437219-23">(</span><span class="p" data-group-id="3804437219-23">)</span><span class="w">
│ │ │ +    </span><span class="nf">shutdown</span><span class="p" data-group-id="3804437219-24">(</span><span class="p" data-group-id="3804437219-24">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">timeout</span><span class="p" data-group-id="3804437219-25">(</span><span class="p" data-group-id="3804437219-25">)</span><span class="w">
│ │ │ +    </span><span class="nf">worker</span><span class="p" data-group-id="3804437219-26">(</span><span class="p" data-group-id="3804437219-26">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">worker</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">supervisor</span></code></pre><ul><li><p><code class="inline">id</code> is used to identify the child specification internally by the supervisor.</p><p>The <code class="inline">id</code> key is mandatory.</p><p>Note that this identifier occasionally has been called &quot;name&quot;. As far as
│ │ │  possible, the terms &quot;identifier&quot; or &quot;id&quot; are now used but in order to keep
│ │ │  backwards compatibility, some occurrences of &quot;name&quot; can still be found, for
│ │ │  example in error messages.</p></li><li><p><code class="inline">start</code> defines the function call used to start the child process. It is a
│ │ │  module-function-arguments tuple used as <a href="../../erts-15.2.7.2/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A)</code></a>.</p><p>It is to be (or result in) a call to any of the following:</p><ul><li><a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/2,3</code></a></li><li><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_server.html#start_link/4"><code class="inline">gen_server:start_link/3,4</code></a></li><li><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_statem.html#start_link/4"><code class="inline">gen_statem:start_link/3,4</code></a></li><li><a href="../../lib/stdlib-6.2.2.2/doc/html/gen_event.html#start_link/2"><code class="inline">gen_event:start_link/0,1,2</code></a></li><li>A function compliant with these functions. For details, see
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html"><code class="inline">supervisor</code></a>.</li></ul><p>The <code class="inline">start</code> key is mandatory.</p></li><li><p><a href="" id="restart"></a> <code class="inline">restart</code> defines when a terminated child process is to be
│ │ │  restarted.</p><ul><li>A <code class="inline">permanent</code> child process is always restarted.</li><li>A <code class="inline">temporary</code> child process is never restarted (not even when the supervisor
│ │ │  restart strategy is <code class="inline">rest_for_one</code> or <code class="inline">one_for_all</code> and a sibling death
│ │ │ @@ -457,53 +457,53 @@
│ │ │  <code class="inline">supervisor</code>, the default value <code class="inline">infinity</code> will be used.</p></li><li><p><code class="inline">type</code> specifies whether the child process is a supervisor or a worker.</p><p>The <code class="inline">type</code> key is optional. If it is not given, the default value <code class="inline">worker</code>
│ │ │  will be used.</p></li><li><p><code class="inline">modules</code> has to be a list consisting of a single element. The value
│ │ │  of that element depends on the behaviour of the process:</p><ul><li>If the child process is a <code class="inline">gen_event</code>, the element has to be the atom
│ │ │  <code class="inline">dynamic</code>.</li><li>Otherwise, the element should be <code class="inline">Module</code>, where <code class="inline">Module</code> is the
│ │ │  name of the callback module.</li></ul><p>This information is used by the release handler during upgrades and
│ │ │  downgrades; see <a href="release_handling.html">Release Handling</a>.</p><p>The <code class="inline">modules</code> key is optional. If it is not given, it defaults to <code class="inline">[M]</code>, where
│ │ │  <code class="inline">M</code> comes from the child's start <code class="inline">{M,F,A}</code>.</p></li></ul><p><em>Example:</em> The child specification to start the server <code class="inline">ch3</code> in the previous
│ │ │ -example look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1197798116-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1197798116-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197798116-3">[</span><span class="p" data-group-id="1197798116-3">]</span><span class="p" data-group-id="1197798116-2">}</span><span class="p">,</span><span class="w">
│ │ │ +example look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5701338563-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5701338563-2">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5701338563-3">[</span><span class="p" data-group-id="5701338563-3">]</span><span class="p" data-group-id="5701338563-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">permanent</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">worker</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="1197798116-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="1197798116-4">]</span><span class="p" data-group-id="1197798116-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="5701338563-4">[</span><span class="ss">ch3</span><span class="p" data-group-id="5701338563-4">]</span><span class="p" data-group-id="5701338563-1">}</span></code></pre><p>or simplified, relying on the default values:</p><pre><code class="text">#{id =&gt; ch3,
│ │ │    start =&gt; {ch3, start_link, []},
│ │ │    shutdown =&gt; brutal_kill}</code></pre><p>Example: A child specification to start the event manager from the chapter about
│ │ │ -<a href="events.html#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7111968532-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7111968532-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7111968532-3">[</span><span class="p" data-group-id="7111968532-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="7111968532-4">}</span><span class="p" data-group-id="7111968532-3">]</span><span class="p" data-group-id="7111968532-2">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="7111968532-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │ +<a href="events.html#mgr">gen_event</a>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4271304612-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">error_man</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4271304612-2">{</span><span class="ss">gen_event</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4271304612-3">[</span><span class="p" data-group-id="4271304612-4">{</span><span class="ss">local</span><span class="p">,</span><span class="w"> </span><span class="ss">error_man</span><span class="p" data-group-id="4271304612-4">}</span><span class="p" data-group-id="4271304612-3">]</span><span class="p" data-group-id="4271304612-2">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">modules</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">dynamic</span><span class="p" data-group-id="4271304612-1">}</span></code></pre><p>Both server and event manager are registered processes which can be expected to
│ │ │  be always accessible. Thus they are specified to be <code class="inline">permanent</code>.</p><p><code class="inline">ch3</code> does not need to do any cleaning up before termination. Thus, no shutdown
│ │ │  time is needed, but <code class="inline">brutal_kill</code> is sufficient. <code class="inline">error_man</code> can need some time
│ │ │  for the event handlers to clean up, thus the shutdown time is set to 5000 ms
│ │ │ -(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3241732151-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3241732151-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3241732151-3">[</span><span class="p" data-group-id="3241732151-3">]</span><span class="p" data-group-id="3241732151-2">}</span><span class="p">,</span><span class="w">
│ │ │ +(which is the default value).</p><p>Example: A child specification to start another supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3192510690-1">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">sup</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="3192510690-2">{</span><span class="ss">sup</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3192510690-3">[</span><span class="p" data-group-id="3192510690-3">]</span><span class="p" data-group-id="3192510690-2">}</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="ss">restart</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">transient</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3241732151-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │ +  </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">supervisor</span><span class="p" data-group-id="3192510690-1">}</span><span class="w"> </span><span class="c1">% will cause default shutdown=&gt;infinity</span></code></pre><p><a href="" id="super_tree"></a></p><h2 id="starting-a-supervisor" class="section-heading">
│ │ │    <a href="#starting-a-supervisor" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Starting a Supervisor</span>
│ │ │  </h2>
│ │ │  <p>In the previous example, the supervisor is started by calling
│ │ │ -<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="6006954840-1">(</span><span class="p" data-group-id="6006954840-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="6006954840-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6006954840-3">[</span><span class="p" data-group-id="6006954840-3">]</span><span class="p" data-group-id="6006954840-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │ +<code class="inline">ch_sup:start_link()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">start_link</span><span class="p" data-group-id="3149351466-1">(</span><span class="p" data-group-id="3149351466-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="3149351466-2">(</span><span class="ss">ch_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3149351466-3">[</span><span class="p" data-group-id="3149351466-3">]</span><span class="p" data-group-id="3149351466-2">)</span><span class="p">.</span></code></pre><p><code class="inline">ch_sup:start_link</code> calls function <a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_link/2"><code class="inline">supervisor:start_link/2</code></a>, which spawns and
│ │ │  links to a new process, a supervisor.</p><ul><li>The first argument, <code class="inline">ch_sup</code>, is the name of the callback module, that is, the
│ │ │  module where the <code class="inline">init</code> callback function is located.</li><li>The second argument, <code class="inline">[]</code>, is a term that is passed as is to the callback
│ │ │  function <code class="inline">init</code>. Here, <code class="inline">init</code> does not need any data and ignores the argument.</li></ul><p>In this case, the supervisor is not registered. Instead its pid must be used. A
│ │ │  name can be specified by calling
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({local, Name}, Module, Args)</code></a>
│ │ │  or
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link({global, Name}, Module, Args)</code></a>.</p><p>The new supervisor process calls the callback function <code class="inline">ch_sup:init([])</code>. <code class="inline">init</code>
│ │ │ -has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="9171661268-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="9171661268-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9171661268-2">#{</span><span class="p" data-group-id="9171661268-2">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9171661268-3">[</span><span class="p" data-group-id="9171661268-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="9171661268-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9171661268-6">[</span><span class="p" data-group-id="9171661268-6">]</span><span class="p" data-group-id="9171661268-5">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="9171661268-4">}</span><span class="p" data-group-id="9171661268-3">]</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9171661268-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9171661268-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="9171661268-8">}</span><span class="p" data-group-id="9171661268-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │ +has to return <code class="inline">{ok, {SupFlags, ChildSpecs}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">init</span><span class="p" data-group-id="4861722125-1">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4861722125-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4861722125-2">#{</span><span class="p" data-group-id="4861722125-2">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4861722125-3">[</span><span class="p" data-group-id="4861722125-4">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">ch3</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4861722125-5">{</span><span class="ss">ch3</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4861722125-6">[</span><span class="p" data-group-id="4861722125-6">]</span><span class="p" data-group-id="4861722125-5">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="4861722125-4">}</span><span class="p" data-group-id="4861722125-3">]</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4861722125-7">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4861722125-8">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="4861722125-8">}</span><span class="p" data-group-id="4861722125-7">}</span><span class="p">.</span></code></pre><p>Subsequently, the supervisor starts its child processes according to the child
│ │ │  specifications in the start specification. In this case there is a single child
│ │ │  process, called <code class="inline">ch3</code>.</p><p><a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_link/3"><code class="inline">supervisor:start_link/3</code></a> is synchronous. It does not return until all child
│ │ │  processes have been started.</p><h2 id="adding-a-child-process" class="section-heading">
│ │ │    <a href="#adding-a-child-process" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Adding a Child Process</span>
│ │ │ @@ -532,31 +532,31 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Simplified one_for_one Supervisors</span>
│ │ │  </h2>
│ │ │  <p>A supervisor with restart strategy <code class="inline">simple_one_for_one</code> is a simplified
│ │ │  <code class="inline">one_for_one</code> supervisor, where all child processes are dynamically added
│ │ │  instances of the same process.</p><p>The following is an example of a callback module for a <code class="inline">simple_one_for_one</code>
│ │ │ -supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="4376024164-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="4376024164-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="4376024164-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="4376024164-2">)</span><span class="p">.</span><span class="w">
│ │ │ +supervisor:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7498401785-1">(</span><span class="ss">simple_sup</span><span class="p" data-group-id="7498401785-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">behaviour</span><span class="p" data-group-id="7498401785-2">(</span><span class="ss">supervisor</span><span class="p" data-group-id="7498401785-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4376024164-3">(</span><span class="p" data-group-id="4376024164-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="4376024164-4">]</span><span class="p" data-group-id="4376024164-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="4376024164-5">(</span><span class="p" data-group-id="4376024164-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="4376024164-6">]</span><span class="p" data-group-id="4376024164-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7498401785-3">(</span><span class="p" data-group-id="7498401785-4">[</span><span class="ss">start_link</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="7498401785-4">]</span><span class="p" data-group-id="7498401785-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7498401785-5">(</span><span class="p" data-group-id="7498401785-6">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="7498401785-6">]</span><span class="p" data-group-id="7498401785-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">start_link</span><span class="p" data-group-id="4376024164-7">(</span><span class="p" data-group-id="4376024164-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="4376024164-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4376024164-9">[</span><span class="p" data-group-id="4376024164-9">]</span><span class="p" data-group-id="4376024164-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">start_link</span><span class="p" data-group-id="7498401785-7">(</span><span class="p" data-group-id="7498401785-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">supervisor</span><span class="p">:</span><span class="nf">start_link</span><span class="p" data-group-id="7498401785-8">(</span><span class="ss">simple_sup</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7498401785-9">[</span><span class="p" data-group-id="7498401785-9">]</span><span class="p" data-group-id="7498401785-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="4376024164-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="4376024164-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4376024164-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="7498401785-10">(</span><span class="p">_</span><span class="n">Args</span><span class="p" data-group-id="7498401785-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">SupFlags</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7498401785-11">#{</span><span class="ss">strategy</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">simple_one_for_one</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">intensity</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4376024164-11">}</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4376024164-12">[</span><span class="p" data-group-id="4376024164-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4376024164-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4376024164-15">[</span><span class="p" data-group-id="4376024164-15">]</span><span class="p" data-group-id="4376024164-14">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="4376024164-13">}</span><span class="p" data-group-id="4376024164-12">]</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="4376024164-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4376024164-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="4376024164-17">}</span><span class="p" data-group-id="4376024164-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │ +                 </span><span class="ss">period</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="7498401785-11">}</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ChildSpecs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7498401785-12">[</span><span class="p" data-group-id="7498401785-13">#{</span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">call</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">start</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="7498401785-14">{</span><span class="ss">call</span><span class="p">,</span><span class="w"> </span><span class="ss">start_link</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7498401785-15">[</span><span class="p" data-group-id="7498401785-15">]</span><span class="p" data-group-id="7498401785-14">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="ss">shutdown</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">brutal_kill</span><span class="p" data-group-id="7498401785-13">}</span><span class="p" data-group-id="7498401785-12">]</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="7498401785-16">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7498401785-17">{</span><span class="n">SupFlags</span><span class="p">,</span><span class="w"> </span><span class="n">ChildSpecs</span><span class="p" data-group-id="7498401785-17">}</span><span class="p" data-group-id="7498401785-16">}</span><span class="p">.</span></code></pre><p>When started, the supervisor does not start any child
│ │ │  processes. Instead, all child processes need to be added dynamically by
│ │ │  calling <a href="../../lib/stdlib-6.2.2.2/doc/html/supervisor.html#start_child/2"><code class="inline">supervisor:start_child(Sup, List)</code></a>.</p><p><code class="inline">Sup</code> is the pid, or name, of the supervisor. <code class="inline">List</code> is an arbitrary list of
│ │ │  terms, which are added to the list of arguments specified in the child
│ │ │  specification. If the start function is specified as <code class="inline">{M, F, A}</code>, the child
│ │ │  process is started by calling <a href="../../erts-15.2.7.2/doc/html/erlang.html#apply/3"><code class="inline">apply(M, F, A++List)</code></a>.</p><p>For example, adding a child to <code class="inline">simple_sup</code> above:</p><pre><code class="text">supervisor:start_child(Pid, [id1])</code></pre><p>The result is that the child process is started by calling
│ │ │  <a href="../../erts-15.2.7.2/doc/html/erlang.html#apply/3"><code class="inline">apply(call, start_link, []++[id1])</code></a>, or actually:</p><pre><code class="text">call:start_link(id1)</code></pre><p>A child under a <code class="inline">simple_one_for_one</code> supervisor can be terminated with the
│ │ │  following:</p><pre><code class="text">supervisor:terminate_child(Sup, Pid)</code></pre><p><code class="inline">Sup</code> is the pid, or name, of the supervisor and <code class="inline">Pid</code> is the pid of the child.</p><p>Because a <code class="inline">simple_one_for_one</code> supervisor can have many children, it shuts them
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/tablesdatabases.html
│ │ │ @@ -146,73 +146,73 @@
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Deleting an Element</span>
│ │ │  </h3>
│ │ │  <p>The <code class="inline">delete</code> operation is considered successful if the element was not present
│ │ │  in the table. Hence all attempts to check that the element is present in the
│ │ │  Ets/Mnesia table before deletion are unnecessary. Here follows an example for
│ │ │ -Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2037440153-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2037440153-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2037440153-2">[</span><span class="p" data-group-id="2037440153-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +Ets tables:</p><p><strong>DO</strong></p><pre><code class="text">ets:delete(Tab, Key),</code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6584374177-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6584374177-1">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6584374177-2">[</span><span class="p" data-group-id="6584374177-2">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2037440153-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="2037440153-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="2037440153-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="2037440153-4">)</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6584374177-3">[</span><span class="p">_</span><span class="p">|</span><span class="p">_</span><span class="p" data-group-id="6584374177-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">ets</span><span class="p">:</span><span class="nf">delete</span><span class="p" data-group-id="6584374177-4">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="6584374177-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span><span class="p">,</span></code></pre><h3 id="fetching-data" class="section-heading">
│ │ │    <a href="#fetching-data" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Fetching Data</span>
│ │ │  </h3>
│ │ │  <p>Do not fetch data that you already have.</p><p>Consider that you have a module that handles the abstract data type <code class="inline">Person</code>.
│ │ │  You export the interface function <code class="inline">print_person/1</code>, which uses the internal
│ │ │  functions <code class="inline">print_name/1</code>, <code class="inline">print_age/1</code>, and <code class="inline">print_occupation/1</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If the function <code class="inline">print_name/1</code>, and so on, had been interface functions, the
│ │ │  situation would have been different, as you do not want the user of the
│ │ │  interface to know about the internal data representation.</p></section><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="0042776266-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="0042776266-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="3928382836-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="3928382836-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="0042776266-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="0042776266-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0042776266-3">[</span><span class="n">Person</span><span class="p" data-group-id="0042776266-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="0042776266-4">(</span><span class="n">Person</span><span class="p" data-group-id="0042776266-4">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="0042776266-5">(</span><span class="n">Person</span><span class="p" data-group-id="0042776266-5">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="0042776266-6">(</span><span class="n">Person</span><span class="p" data-group-id="0042776266-6">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0042776266-7">[</span><span class="p" data-group-id="0042776266-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0042776266-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0042776266-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="0042776266-9">]</span><span class="p" data-group-id="0042776266-8">)</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3928382836-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3928382836-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3928382836-3">[</span><span class="n">Person</span><span class="p" data-group-id="3928382836-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="3928382836-4">(</span><span class="n">Person</span><span class="p" data-group-id="3928382836-4">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="3928382836-5">(</span><span class="n">Person</span><span class="p" data-group-id="3928382836-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="3928382836-6">(</span><span class="n">Person</span><span class="p" data-group-id="3928382836-6">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3928382836-7">[</span><span class="p" data-group-id="3928382836-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3928382836-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928382836-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="3928382836-9">]</span><span class="p" data-group-id="3928382836-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="0042776266-10">(</span><span class="n">Person</span><span class="p" data-group-id="0042776266-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0042776266-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0042776266-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="0042776266-12">]</span><span class="p" data-group-id="0042776266-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="3928382836-10">(</span><span class="n">Person</span><span class="p" data-group-id="3928382836-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3928382836-11">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928382836-12">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="3928382836-12">]</span><span class="p" data-group-id="3928382836-11">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="0042776266-13">(</span><span class="n">Person</span><span class="p" data-group-id="0042776266-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0042776266-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0042776266-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="0042776266-15">]</span><span class="p" data-group-id="0042776266-14">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="3928382836-13">(</span><span class="n">Person</span><span class="p" data-group-id="3928382836-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3928382836-14">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928382836-15">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3928382836-15">]</span><span class="p" data-group-id="3928382836-14">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="0042776266-16">(</span><span class="n">Person</span><span class="p" data-group-id="0042776266-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0042776266-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0042776266-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="0042776266-18">]</span><span class="p" data-group-id="0042776266-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ -</span><span class="nf">print_person</span><span class="p" data-group-id="3593551243-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="3593551243-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="3928382836-16">(</span><span class="n">Person</span><span class="p" data-group-id="3928382836-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3928382836-17">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3928382836-18">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="3928382836-18">]</span><span class="p" data-group-id="3928382836-17">)</span><span class="p">.</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="c1">%%% Interface function</span><span class="w">
│ │ │ +</span><span class="nf">print_person</span><span class="p" data-group-id="6020571945-1">(</span><span class="n">PersonId</span><span class="p" data-group-id="6020571945-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% Look up the person in the named table person,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3593551243-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3593551243-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3593551243-3">[</span><span class="n">Person</span><span class="p" data-group-id="3593551243-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">print_name</span><span class="p" data-group-id="3593551243-4">(</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-4">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_age</span><span class="p" data-group-id="3593551243-5">(</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-5">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">print_occupation</span><span class="p" data-group-id="3593551243-6">(</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-6">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3593551243-7">[</span><span class="p" data-group-id="3593551243-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3593551243-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3593551243-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-9">]</span><span class="p" data-group-id="3593551243-8">)</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6020571945-2">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="6020571945-2">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6020571945-3">[</span><span class="n">Person</span><span class="p" data-group-id="6020571945-3">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">print_name</span><span class="p" data-group-id="6020571945-4">(</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-4">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_age</span><span class="p" data-group-id="6020571945-5">(</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-5">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">print_occupation</span><span class="p" data-group-id="6020571945-6">(</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-6">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="6020571945-7">[</span><span class="p" data-group-id="6020571945-7">]</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6020571945-8">(</span><span class="s">&quot;No person with ID = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6020571945-9">[</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-9">]</span><span class="p" data-group-id="6020571945-8">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%%% Internal functions</span><span class="w">
│ │ │ -</span><span class="nf">print_name</span><span class="p" data-group-id="3593551243-10">(</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3593551243-11">[</span><span class="n">Person</span><span class="p" data-group-id="3593551243-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3593551243-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3593551243-12">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3593551243-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3593551243-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="3593551243-14">]</span><span class="p" data-group-id="3593551243-13">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_age</span><span class="p" data-group-id="3593551243-15">(</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3593551243-16">[</span><span class="n">Person</span><span class="p" data-group-id="3593551243-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3593551243-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3593551243-17">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3593551243-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3593551243-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="3593551243-19">]</span><span class="p" data-group-id="3593551243-18">)</span><span class="p">.</span><span class="w">
│ │ │ -
│ │ │ -</span><span class="nf">print_occupation</span><span class="p" data-group-id="3593551243-20">(</span><span class="n">PersonID</span><span class="p" data-group-id="3593551243-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3593551243-21">[</span><span class="n">Person</span><span class="p" data-group-id="3593551243-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="3593551243-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="3593551243-22">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3593551243-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3593551243-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="3593551243-24">]</span><span class="p" data-group-id="3593551243-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │ +</span><span class="nf">print_name</span><span class="p" data-group-id="6020571945-10">(</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6020571945-11">[</span><span class="n">Person</span><span class="p" data-group-id="6020571945-11">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6020571945-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="6020571945-12">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6020571945-13">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6020571945-14">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="p" data-group-id="6020571945-14">]</span><span class="p" data-group-id="6020571945-13">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_age</span><span class="p" data-group-id="6020571945-15">(</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-15">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6020571945-16">[</span><span class="n">Person</span><span class="p" data-group-id="6020571945-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6020571945-17">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="6020571945-17">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6020571945-18">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6020571945-19">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="6020571945-19">]</span><span class="p" data-group-id="6020571945-18">)</span><span class="p">.</span><span class="w">
│ │ │ +
│ │ │ +</span><span class="nf">print_occupation</span><span class="p" data-group-id="6020571945-20">(</span><span class="n">PersonID</span><span class="p" data-group-id="6020571945-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="6020571945-21">[</span><span class="n">Person</span><span class="p" data-group-id="6020571945-21">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="6020571945-22">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="n">PersonId</span><span class="p" data-group-id="6020571945-22">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6020571945-23">(</span><span class="s">&quot;No person </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6020571945-24">[</span><span class="n">Person</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">occupation</span><span class="p" data-group-id="6020571945-24">]</span><span class="p" data-group-id="6020571945-23">)</span><span class="p">.</span></code></pre><h3 id="non-persistent-database-storage" class="section-heading">
│ │ │    <a href="#non-persistent-database-storage" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Non-Persistent Database Storage</span>
│ │ │  </h3>
│ │ │  <p>For non-persistent database storage, prefer Ets tables over Mnesia
│ │ │  <code class="inline">local_content</code> tables. Even the Mnesia <code class="inline">dirty_write</code> operations carry a fixed
│ │ │ @@ -226,38 +226,38 @@
│ │ │  </h3>
│ │ │  <p>Assuming an Ets table that uses <code class="inline">idno</code> as key and contains the following:</p><pre><code class="text">[#person{idno = 1, name = &quot;Adam&quot;,  age = 31, occupation = &quot;mailman&quot;},
│ │ │   #person{idno = 2, name = &quot;Bryan&quot;, age = 31, occupation = &quot;cashier&quot;},
│ │ │   #person{idno = 3, name = &quot;Bryan&quot;, age = 35, occupation = &quot;banker&quot;},
│ │ │   #person{idno = 4, name = &quot;Carl&quot;,  age = 25, occupation = &quot;mailman&quot;}]</code></pre><p>If you <em>must</em> return all data stored in the Ets table, you can use
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a>. However, usually you are only interested in a subset of the
│ │ │  information in which case <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#tab2list/1"><code class="inline">ets:tab2list/1</code></a> is expensive. If you only want to
│ │ │ -extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="5865706775-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5865706775-2">[</span><span class="p" data-group-id="5865706775-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5865706775-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ +extract one field from each record, for example, the age of every person, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="9774452698-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9774452698-2">[</span><span class="p" data-group-id="9774452698-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="9774452698-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5865706775-4">}</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="5865706775-5">[</span><span class="p" data-group-id="5865706775-5">]</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="5865706775-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="5865706775-6">]</span><span class="p" data-group-id="5865706775-3">}</span><span class="p" data-group-id="5865706775-2">]</span><span class="p" data-group-id="5865706775-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="4213978155-1">(</span><span class="n">Tab</span><span class="p" data-group-id="4213978155-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="4213978155-2">(</span><span class="nf">fun</span><span class="p" data-group-id="4213978155-3">(</span><span class="n">X</span><span class="p" data-group-id="4213978155-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="4213978155-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="6121893107-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6121893107-2">[</span><span class="p" data-group-id="6121893107-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="6121893107-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="9774452698-4">}</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="9774452698-5">[</span><span class="p" data-group-id="9774452698-5">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="9774452698-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="9774452698-6">]</span><span class="p" data-group-id="9774452698-3">}</span><span class="p" data-group-id="9774452698-2">]</span><span class="p" data-group-id="9774452698-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="8191270779-1">(</span><span class="n">Tab</span><span class="p" data-group-id="8191270779-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="8191270779-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8191270779-3">(</span><span class="n">X</span><span class="p" data-group-id="8191270779-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="8191270779-2">)</span><span class="p">,</span></code></pre><p>If you are only interested in the age of all persons named &quot;Bryan&quot;, then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="8088209803-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8088209803-2">[</span><span class="p" data-group-id="8088209803-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8088209803-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;$1&#39;</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="6121893107-4">}</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="6121893107-5">[</span><span class="p" data-group-id="6121893107-5">]</span><span class="p">,</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="6121893107-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="6121893107-6">]</span><span class="p" data-group-id="6121893107-3">}</span><span class="p" data-group-id="6121893107-2">]</span><span class="p" data-group-id="6121893107-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="5572853622-1">(</span><span class="n">Tab</span><span class="p" data-group-id="5572853622-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="5572853622-2">(</span><span class="nf">fun</span><span class="p" data-group-id="5572853622-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5572853622-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="8088209803-4">}</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="8088209803-5">[</span><span class="p" data-group-id="8088209803-5">]</span><span class="p">,</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="8088209803-6">[</span><span class="ss">&#39;$1&#39;</span><span class="p" data-group-id="8088209803-6">]</span><span class="p" data-group-id="8088209803-3">}</span><span class="p" data-group-id="8088209803-2">]</span><span class="p" data-group-id="8088209803-1">)</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="2543098586-1">(</span><span class="n">Tab</span><span class="p" data-group-id="2543098586-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="2543098586-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2543098586-3">(</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="2543098586-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │                                  </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                    </span><span class="p" data-group-id="5572853622-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="5572853622-4">]</span><span class="p">;</span><span class="w">
│ │ │ +                                    </span><span class="p" data-group-id="2543098586-4">[</span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p">|</span><span class="n">Acc</span><span class="p" data-group-id="2543098586-4">]</span><span class="p">;</span><span class="w">
│ │ │                                   </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                                       </span><span class="n">Acc</span><span class="w">
│ │ │                             </span><span class="k">end</span><span class="w">
│ │ │ -             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5572853622-5">[</span><span class="p" data-group-id="5572853622-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="5572853622-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ -then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="5945599080-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5945599080-2">[</span><span class="p" data-group-id="5945599080-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="5945599080-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2543098586-5">[</span><span class="p" data-group-id="2543098586-5">]</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="2543098586-2">)</span></code></pre><p>If you need all information stored in the Ets table about persons named &quot;Bryan&quot;,
│ │ │ +then:</p><p><strong>DO</strong></p><pre><code class="makeup erlang" translate="no"><span class="nc">ets</span><span class="p">:</span><span class="nf">select</span><span class="p" data-group-id="3188843551-1">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3188843551-2">[</span><span class="p" data-group-id="3188843551-3">{</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="3188843551-4">{</span><span class="ss">idno</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">name</span><span class="o">=</span><span class="s">&quot;Bryan&quot;</span><span class="p">,</span><span class="w">
│ │ │                            </span><span class="ss">age</span><span class="o">=</span><span class="ss">&#39;_&#39;</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="5945599080-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5945599080-5">[</span><span class="p" data-group-id="5945599080-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5945599080-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="5945599080-6">]</span><span class="p" data-group-id="5945599080-3">}</span><span class="p" data-group-id="5945599080-2">]</span><span class="p" data-group-id="5945599080-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="6384902004-1">(</span><span class="n">Tab</span><span class="p" data-group-id="6384902004-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="6384902004-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6384902004-3">(</span><span class="n">X</span><span class="p" data-group-id="6384902004-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="6384902004-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │ +                          </span><span class="ss">occupation</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="3188843551-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3188843551-5">[</span><span class="p" data-group-id="3188843551-5">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3188843551-6">[</span><span class="ss">&#39;$_&#39;</span><span class="p" data-group-id="3188843551-6">]</span><span class="p" data-group-id="3188843551-3">}</span><span class="p" data-group-id="3188843551-2">]</span><span class="p" data-group-id="3188843551-1">)</span><span class="p">,</span></code></pre><p><strong>DO NOT</strong></p><pre><code class="makeup erlang" translate="no"><span class="n">TabList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">tab2list</span><span class="p" data-group-id="6726790959-1">(</span><span class="n">Tab</span><span class="p" data-group-id="6726790959-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">filter</span><span class="p" data-group-id="6726790959-2">(</span><span class="nf">fun</span><span class="p" data-group-id="6726790959-3">(</span><span class="n">X</span><span class="p" data-group-id="6726790959-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">name</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">&quot;Bryan&quot;</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">TabList</span><span class="p" data-group-id="6726790959-2">)</span><span class="p">,</span></code></pre><h3 id="ordered_set-tables" class="section-heading">
│ │ │    <a href="#ordered_set-tables" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text"><code class="inline">ordered_set</code> Tables</span>
│ │ │  </h3>
│ │ │  <p>If the data in the table is to be accessed so that the order of the keys in the
│ │ │  table is significant, the table type <code class="inline">ordered_set</code> can be used instead of the
│ │ │ @@ -293,20 +293,20 @@
│ │ │  Clearly, the second table would have to be kept consistent with the master
│ │ │  table. Mnesia can do this for you, but a home-brew index table can be very
│ │ │  efficient compared to the overhead involved in using Mnesia.</p><p>An index table for the table in the previous examples would have to be a bag (as
│ │ │  keys would appear more than once) and can have the following contents:</p><pre><code class="text">[#index_entry{name=&quot;Adam&quot;, idno=1},
│ │ │   #index_entry{name=&quot;Bryan&quot;, idno=2},
│ │ │   #index_entry{name=&quot;Bryan&quot;, idno=3},
│ │ │   #index_entry{name=&quot;Carl&quot;, idno=4}]</code></pre><p>Given this index table, a lookup of the <code class="inline">age</code> fields for all persons named
│ │ │ -&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2375801930-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="2375801930-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="2375801930-2">(</span><span class="nf">fun</span><span class="p" data-group-id="2375801930-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="2375801930-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="2375801930-4">}</span><span class="p" data-group-id="2375801930-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="2375801930-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2375801930-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="2375801930-6">}</span><span class="p" data-group-id="2375801930-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="2375801930-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="2375801930-7">)</span><span class="p">,</span><span class="w">
│ │ │ +&quot;Bryan&quot; can be done as follows:</p><pre><code class="makeup erlang" translate="no"><span class="n">MatchingIDs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7772529879-1">(</span><span class="n">IndexTable</span><span class="p">,</span><span class="s">&quot;Bryan&quot;</span><span class="p" data-group-id="7772529879-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7772529879-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7772529879-3">(</span><span class="o">#</span><span class="ss">index_entry</span><span class="p" data-group-id="7772529879-4">{</span><span class="ss">idno</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="7772529879-4">}</span><span class="p" data-group-id="7772529879-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="7772529879-5">[</span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="7772529879-6">{</span><span class="ss">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Age</span><span class="p" data-group-id="7772529879-6">}</span><span class="p" data-group-id="7772529879-5">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">ets</span><span class="p">:</span><span class="nf">lookup</span><span class="p" data-group-id="7772529879-7">(</span><span class="n">PersonTable</span><span class="p">,</span><span class="w"> </span><span class="n">ID</span><span class="p" data-group-id="7772529879-7">)</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="n">Age</span><span class="w">
│ │ │            </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="2375801930-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │ +          </span><span class="n">MatchingIDs</span><span class="p" data-group-id="7772529879-2">)</span><span class="p">,</span></code></pre><p>Notice that this code does not use <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#match/2"><code class="inline">ets:match/2</code></a>, but instead uses the
│ │ │  <a href="../../lib/stdlib-6.2.2.2/doc/html/ets.html#lookup/2"><code class="inline">ets:lookup/2</code></a> call. The <a href="../../lib/stdlib-6.2.2.2/doc/html/lists.html#map/2"><code class="inline">lists:map/2</code></a> call is only used to traverse the <code class="inline">idno</code>s
│ │ │  matching the name &quot;Bryan&quot; in the table; thus the number of lookups in the master
│ │ │  table is minimized.</p><p>Keeping an index table introduces some overhead when inserting records in the
│ │ │  table. The number of operations gained from the table must therefore be compared
│ │ │  against the number of operations inserting objects in the table. However, notice
│ │ │  that the gain is significant when the key can be used to lookup elements.</p><h2 id="mnesia" class="section-heading">
│ │ │    <a href="#mnesia" class="hover-link">
│ │ │ @@ -321,51 +321,51 @@
│ │ │    <span class="text">Secondary Index</span>
│ │ │  </h3>
│ │ │  <p>If you frequently do lookups on a field that is not the key of the table, you
│ │ │  lose performance using <a href="../../lib/mnesia-4.23.5/doc/html/mnesia.html#select/3">mnesia:select()</a> or
│ │ │  <a href="../../lib/mnesia-4.23.5/doc/html/mnesia.html#match_object/1"><code class="inline">mnesia:match_object()</code></a> as these function traverse
│ │ │  the whole table. Instead, you can create a secondary index and use
│ │ │  <a href="../../lib/mnesia-4.23.5/doc/html/mnesia.html#index_read/3"><code class="inline">mnesia:index_read/3</code></a> to get faster access at the expense of using more
│ │ │ -memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0388558552-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0388558552-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="0388558552-2">}</span><span class="p" data-group-id="0388558552-1">)</span><span class="p">.</span><span class="w">
│ │ │ +memory.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0404764662-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0404764662-2">{</span><span class="ss">idno</span><span class="p">,</span><span class="w"> </span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p">,</span><span class="w"> </span><span class="ss">occupation</span><span class="p" data-group-id="0404764662-2">}</span><span class="p" data-group-id="0404764662-1">)</span><span class="p">.</span><span class="w">
│ │ │          </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0388558552-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="0388558552-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="0388558552-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0388558552-5">[</span><span class="p" data-group-id="0388558552-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="0388558552-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="0388558552-7">]</span><span class="p" data-group-id="0388558552-6">}</span><span class="p">,</span><span class="w">
│ │ │ -                              </span><span class="p" data-group-id="0388558552-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ -                                    </span><span class="nf">record_info</span><span class="p" data-group-id="0388558552-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="0388558552-9">)</span><span class="p" data-group-id="0388558552-8">}</span><span class="p" data-group-id="0388558552-5">]</span><span class="p" data-group-id="0388558552-4">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0388558552-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="0388558552-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="0388558552-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="0388558552-11">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0404764662-3">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="0404764662-3">}</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ +</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">create_table</span><span class="p" data-group-id="0404764662-4">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0404764662-5">[</span><span class="p" data-group-id="0404764662-6">{</span><span class="ss">index</span><span class="p">,</span><span class="p" data-group-id="0404764662-7">[</span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="0404764662-7">]</span><span class="p" data-group-id="0404764662-6">}</span><span class="p">,</span><span class="w">
│ │ │ +                              </span><span class="p" data-group-id="0404764662-8">{</span><span class="ss">attributes</span><span class="p">,</span><span class="w">
│ │ │ +                                    </span><span class="nf">record_info</span><span class="p" data-group-id="0404764662-9">(</span><span class="ss">fields</span><span class="p">,</span><span class="w"> </span><span class="ss">person</span><span class="p" data-group-id="0404764662-9">)</span><span class="p" data-group-id="0404764662-8">}</span><span class="p" data-group-id="0404764662-5">]</span><span class="p" data-group-id="0404764662-4">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0404764662-10">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p" data-group-id="0404764662-10">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">add_table_index</span><span class="p" data-group-id="0404764662-11">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="ss">age</span><span class="p" data-group-id="0404764662-11">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="n">PersonsAge42</span><span class="w"> </span><span class="o">=</span><span class="w">
│ │ │ -     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="0388558552-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="0388558552-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │ +     </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_index_read</span><span class="p" data-group-id="0404764662-12">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p">.</span><span class="ss">age</span><span class="p" data-group-id="0404764662-12">)</span><span class="p">,</span></code></pre><h3 id="transactions" class="section-heading">
│ │ │    <a href="#transactions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Transactions</span>
│ │ │  </h3>
│ │ │  <p>Using transactions is a way to guarantee that the distributed Mnesia database
│ │ │  remains consistent, even when many different processes update it in parallel.
│ │ │  However, if you have real-time requirements it is recommended to use dirtry
│ │ │  operations instead of transactions. When using dirty operations, you lose the
│ │ │  consistency guarantee; this is usually solved by only letting one process update
│ │ │  the table. Other processes must send update requests to that process.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="c1">%% Using transaction</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9894978013-1">(</span><span class="p" data-group-id="9894978013-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="9894978013-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9894978013-3">(</span><span class="p" data-group-id="9894978013-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9894978013-4">}</span><span class="p" data-group-id="9894978013-3">)</span><span class="p">,</span><span class="w">
│ │ │ -           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9894978013-5">(</span><span class="p" data-group-id="9894978013-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9894978013-6">}</span><span class="p" data-group-id="9894978013-5">)</span><span class="p" data-group-id="9894978013-2">]</span><span class="w">
│ │ │ +</span><span class="n">Fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="9764855055-1">(</span><span class="p" data-group-id="9764855055-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="9764855055-2">[</span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9764855055-3">(</span><span class="p" data-group-id="9764855055-4">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9764855055-4">}</span><span class="p" data-group-id="9764855055-3">)</span><span class="p">,</span><span class="w">
│ │ │ +           </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">read</span><span class="p" data-group-id="9764855055-5">(</span><span class="p" data-group-id="9764855055-6">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9764855055-6">}</span><span class="p" data-group-id="9764855055-5">)</span><span class="p" data-group-id="9764855055-2">]</span><span class="w">
│ │ │        </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="9894978013-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9894978013-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="9894978013-8">]</span><span class="p" data-group-id="9894978013-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="9894978013-9">(</span><span class="n">Fun</span><span class="p" data-group-id="9894978013-9">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9764855055-7">{</span><span class="ss">atomic</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9764855055-8">[</span><span class="n">Result1</span><span class="p">,</span><span class="w"> </span><span class="n">Result2</span><span class="p" data-group-id="9764855055-8">]</span><span class="p" data-group-id="9764855055-7">}</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">transaction</span><span class="p" data-group-id="9764855055-9">(</span><span class="n">Fun</span><span class="p" data-group-id="9764855055-9">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │  </span><span class="c1">%% Same thing using dirty operations</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9894978013-10">(</span><span class="p" data-group-id="9894978013-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9894978013-11">}</span><span class="p" data-group-id="9894978013-10">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9894978013-12">(</span><span class="p" data-group-id="9894978013-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9894978013-13">}</span><span class="p" data-group-id="9894978013-12">)</span><span class="p">,</span></code></pre>
│ │ │ +</span><span class="n">Result1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9764855055-10">(</span><span class="p" data-group-id="9764855055-11">{</span><span class="n">Table</span><span class="p">,</span><span class="w"> </span><span class="n">Key</span><span class="p" data-group-id="9764855055-11">}</span><span class="p" data-group-id="9764855055-10">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Result2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">mnesia</span><span class="p">:</span><span class="nf">dirty_read</span><span class="p" data-group-id="9764855055-12">(</span><span class="p" data-group-id="9764855055-13">{</span><span class="n">Table2</span><span class="p">,</span><span class="w"> </span><span class="n">Key2</span><span class="p" data-group-id="9764855055-13">}</span><span class="p" data-group-id="9764855055-12">)</span><span class="p">,</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="eff_guide_functions.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/system/typespec.html
│ │ │ @@ -238,124 +238,124 @@
│ │ │  and optional <code class="inline">(=&gt;)</code> association types. If an association type is mandatory, an
│ │ │  association with that type needs to be present. In the case of an optional
│ │ │  association type it is not required for the key type to be present.</p><p>The notation <code class="inline">#{}</code> specifies the singleton type for the empty map. Note that
│ │ │  this notation is not a shorthand for the <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a> type.</p><p>For convenience, the following types are also built-in. They can be thought as
│ │ │  predefined aliases for the type unions also shown in the table.</p><p><a href="" id="builtin_types"></a></p><table><thead><tr><th style="text-align: left;"><em>Built-in type</em></th><th style="text-align: left;"><em>Defined as</em></th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:binary/0"><code class="inline">binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:nonempty_binary/0"><code class="inline">nonempty_binary/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:8, _:_*8&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:bitstring/0"><code class="inline">bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:nonempty_bitstring/0"><code class="inline">nonempty_bitstring/0</code></a></td><td style="text-align: left;"><code class="inline">&lt;&lt;_:1, _:_*1&gt;&gt;</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a></td><td style="text-align: left;"><code class="inline">'false'</code> | <code class="inline">'true'</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:byte/0"><code class="inline">byte/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:char/0"><code class="inline">char/0</code></a></td><td style="text-align: left;"><code class="inline">0..16#10ffff</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:nil/0"><code class="inline">nil/0</code></a></td><td style="text-align: left;"><code class="inline">[]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:number/0"><code class="inline">number/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:integer/0"><code class="inline">integer/0</code></a> | <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:float/0"><code class="inline">float/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:list/0"><code class="inline">list/0</code></a></td><td style="text-align: left;"><code class="inline">[any()]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:maybe_improper_list/0"><code class="inline">maybe_improper_list/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:maybe_improper_list/2"><code class="inline">maybe_improper_list(any(), any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:nonempty_list/0"><code class="inline">nonempty_list/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:nonempty_list/1"><code class="inline">nonempty_list(any())</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:string/0"><code class="inline">string/0</code></a></td><td style="text-align: left;"><code class="inline">[char()]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:nonempty_string/0"><code class="inline">nonempty_string/0</code></a></td><td style="text-align: left;"><code class="inline">[char(),...]</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:iodata/0"><code class="inline">iodata/0</code></a></td><td style="text-align: left;"><code class="inline">iolist()</code> | <code class="inline">binary()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:iolist/0"><code class="inline">iolist/0</code></a></td><td style="text-align: left;"><code class="inline">maybe_improper_list(byte()</code> | <code class="inline">binary()</code> | <code class="inline">iolist(), binary()</code> | <code class="inline">[])</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:map/0"><code class="inline">map/0</code></a></td><td style="text-align: left;"><code class="inline">#{any() =&gt; any()}</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:function/0"><code class="inline">function/0</code></a></td><td style="text-align: left;"><code class="inline">fun()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:module/0"><code class="inline">module/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:mfa/0"><code class="inline">mfa/0</code></a></td><td style="text-align: left;"><code class="inline">{module(),atom(),arity()}</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:arity/0"><code class="inline">arity/0</code></a></td><td style="text-align: left;"><code class="inline">0..255</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:identifier/0"><code class="inline">identifier/0</code></a></td><td style="text-align: left;"><code class="inline">pid()</code> | <code class="inline">port()</code> | <code class="inline">reference()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#node/0"><code class="inline">node/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:atom/0"><code class="inline">atom/0</code></a></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:timeout/0"><code class="inline">timeout/0</code></a></td><td style="text-align: left;"><code class="inline">'infinity'</code> | <code class="inline">non_neg_integer()</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a></td><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:none/0"><code class="inline">none/0</code></a></td></tr></tbody></table><p><em>Table: Built-in types, predefined aliases</em></p><p>In addition, the following three built-in types exist and can be thought as
│ │ │  defined below, though strictly their &quot;type definition&quot; is not valid syntax
│ │ │  according to the type language defined above.</p><table><thead><tr><th style="text-align: left;"><em>Built-in type</em></th><th style="text-align: left;"><em>Can be thought defined by the syntax</em></th></tr></thead><tbody><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:non_neg_integer/0"><code class="inline">non_neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">0..</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:pos_integer/0"><code class="inline">pos_integer/0</code></a></td><td style="text-align: left;"><code class="inline">1..</code></td></tr><tr><td style="text-align: left;"><a href="../../erts-15.2.7.2/doc/html/erlang.html#t:neg_integer/0"><code class="inline">neg_integer/0</code></a></td><td style="text-align: left;"><code class="inline">..-1</code></td></tr></tbody></table><p><em>Table: Additional built-in types</em></p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The following built-in list types also exist, but they are expected to be
│ │ │ -rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="0717561296-1">(</span><span class="p" data-group-id="0717561296-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="0717561296-2">(</span><span class="nf">any</span><span class="p" data-group-id="0717561296-3">(</span><span class="p" data-group-id="0717561296-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="0717561296-4">(</span><span class="p" data-group-id="0717561296-4">)</span><span class="p" data-group-id="0717561296-2">)</span><span class="w">
│ │ │ -</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="0717561296-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="0717561296-5">)</span><span class="w">
│ │ │ -</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="0717561296-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="0717561296-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ -shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="3730791028-1">{</span><span class="p" data-group-id="3730791028-1">}</span><span class="w">
│ │ │ -        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="3730791028-2">{</span><span class="n">Fields</span><span class="p" data-group-id="3730791028-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │ +rarely used. Hence, they have long names:</p></section><pre><code class="makeup erlang" translate="no"><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="4964948147-1">(</span><span class="p" data-group-id="4964948147-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="4964948147-2">(</span><span class="nf">any</span><span class="p" data-group-id="4964948147-3">(</span><span class="p" data-group-id="4964948147-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="4964948147-4">(</span><span class="p" data-group-id="4964948147-4">)</span><span class="p" data-group-id="4964948147-2">)</span><span class="w">
│ │ │ +</span><span class="nf">nonempty_improper_list</span><span class="p" data-group-id="4964948147-5">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="4964948147-5">)</span><span class="w">
│ │ │ +</span><span class="nf">nonempty_maybe_improper_list</span><span class="p" data-group-id="4964948147-6">(</span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="n">Type2</span><span class="p" data-group-id="4964948147-6">)</span></code></pre><p>where the last two types define the set of Erlang terms one would expect.</p><p>Also for convenience, record notation is allowed to be used. Records are
│ │ │ +shorthands for the corresponding tuples:</p><pre><code class="makeup erlang" translate="no"><span class="n">Record</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="0392404077-1">{</span><span class="p" data-group-id="0392404077-1">}</span><span class="w">
│ │ │ +        </span><span class="p">|</span><span class="w"> </span><span class="p">#</span><span class="n">Erlang_Atom</span><span class="p" data-group-id="0392404077-2">{</span><span class="n">Fields</span><span class="p" data-group-id="0392404077-2">}</span></code></pre><p>Records are extended to possibly contain type information. This is described in
│ │ │  <a href="typespec.html#typeinrecords">Type Information in Record Declarations</a>.</p><h3 id="redefining-built-in-types" class="section-heading">
│ │ │    <a href="#redefining-built-in-types" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Redefining built-in types</span>
│ │ │  </h3>
│ │ │  <section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Starting from Erlang/OTP 26, it is permitted to define a type having the same
│ │ │  name as a built-in type.</p></section><p>It is recommended to avoid deliberately reusing built-in names because it can be
│ │ │  confusing. However, when an Erlang/OTP release introduces a new type, code that
│ │ │  happened to define its own type having the same name will continue to work.</p><p>As an example, imagine that the Erlang/OTP 42 release introduces a new type
│ │ │ -<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="1627294340-1">(</span><span class="p" data-group-id="1627294340-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1627294340-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="1627294340-3">(</span><span class="p" data-group-id="1627294340-3">)</span><span class="p" data-group-id="1627294340-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ -for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="3849699237-1">(</span><span class="p" data-group-id="3849699237-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="3849699237-2">#{</span><span class="p" data-group-id="3849699237-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │ +<code class="inline">gadget()</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="1571110865-1">(</span><span class="p" data-group-id="1571110865-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1571110865-2">{</span><span class="ss">&#39;gadget&#39;</span><span class="p">,</span><span class="w"> </span><span class="nf">reference</span><span class="p" data-group-id="1571110865-3">(</span><span class="p" data-group-id="1571110865-3">)</span><span class="p" data-group-id="1571110865-2">}</span><span class="p">.</span></code></pre><p>Further imagine that some code has its own (different) definition of <code class="inline">gadget()</code>,
│ │ │ +for example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">gadget</span><span class="p" data-group-id="7832441075-1">(</span><span class="p" data-group-id="7832441075-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7832441075-2">#{</span><span class="p" data-group-id="7832441075-2">}</span><span class="p">.</span></code></pre><p>Since redefinitions are allowed, the code will still compile (but with a
│ │ │  warning), and Dialyzer will not emit any additional warnings.</p><h2 id="type-declarations-of-user-defined-types" class="section-heading">
│ │ │    <a href="#type-declarations-of-user-defined-types" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Declarations of User-Defined Types</span>
│ │ │  </h2>
│ │ │  <p>As seen, the basic syntax of a type is an atom followed by closed parentheses.
│ │ │  New types are declared using <code class="inline">-type</code> and <code class="inline">-opaque</code> attributes as in the
│ │ │ -following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="8776425779-1">(</span><span class="p" data-group-id="8776425779-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="8776425779-2">(</span><span class="p" data-group-id="8776425779-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │ +following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">my_struct_type</span><span class="p" data-group-id="0336348019-1">(</span><span class="p" data-group-id="0336348019-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">opaque</span><span class="w"> </span><span class="nf">my_opaq_type</span><span class="p" data-group-id="0336348019-2">(</span><span class="p" data-group-id="0336348019-2">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type</span><span class="p">.</span></code></pre><p>The type name is the atom <code class="inline">my_struct_type</code>, followed by parentheses. <code class="inline">Type</code> is a
│ │ │  type as defined in the previous section. A current restriction is that <code class="inline">Type</code>
│ │ │  can contain only predefined types, or user-defined types which are either of the
│ │ │  following:</p><ul><li>Module-local type, that is, with a definition that is present in the code of
│ │ │  the module</li><li>Remote type, that is, type defined in, and exported by, other modules; more
│ │ │  about this soon.</li></ul><p>For module-local types, the restriction that their definition exists in the
│ │ │  module is enforced by the compiler and results in a compilation error. (A
│ │ │  similar restriction currently exists for records.)</p><p>Type declarations can also be parameterized by including type variables between
│ │ │  the parentheses. The syntax of type variables is the same as Erlang variables,
│ │ │  that is, starts with an upper-case letter. These variables is to
│ │ │ -appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="2472926185-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="2472926185-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="2472926185-2">[</span><span class="p" data-group-id="2472926185-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="2472926185-3">}</span><span class="p" data-group-id="2472926185-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ -refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="5243696261-1">(</span><span class="p" data-group-id="5243696261-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="5243696261-2">]</span><span class="p" data-group-id="5243696261-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arguments.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="6998162220-1">(</span><span class="p" data-group-id="6998162220-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6998162220-2">]</span><span class="p" data-group-id="6998162220-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ -them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="2491953016-1">(</span><span class="p" data-group-id="2491953016-1">)</span><span class="w">
│ │ │ -</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="2491953016-2">(</span><span class="nf">atom</span><span class="p" data-group-id="2491953016-3">(</span><span class="p" data-group-id="2491953016-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="2491953016-4">(</span><span class="p" data-group-id="2491953016-4">)</span><span class="p" data-group-id="2491953016-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │ +appear on the RHS of the definition. A concrete example follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">orddict</span><span class="p" data-group-id="1838313069-1">(</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="1838313069-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="1838313069-2">[</span><span class="p" data-group-id="1838313069-3">{</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">Val</span><span class="p" data-group-id="1838313069-3">}</span><span class="p" data-group-id="1838313069-2">]</span><span class="p">.</span></code></pre><p>A module can export some types to declare that other modules are allowed to
│ │ │ +refer to them as <em>remote types</em>. This declaration has the following form:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="1776482898-1">(</span><span class="p" data-group-id="1776482898-2">[</span><span class="n">T1</span><span class="o">/</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p">,</span><span class="w"> </span><span class="n">Tk</span><span class="o">/</span><span class="n">Ak</span><span class="p" data-group-id="1776482898-2">]</span><span class="p" data-group-id="1776482898-1">)</span><span class="p">.</span></code></pre><p>Here the <code class="inline">Ti</code>s are atoms (the name of the type) and the <code class="inline">Ai</code>s are their arguments.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">export_type</span><span class="p" data-group-id="4128607128-1">(</span><span class="p" data-group-id="4128607128-2">[</span><span class="ss">my_struct_type</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">orddict</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="4128607128-2">]</span><span class="p" data-group-id="4128607128-1">)</span><span class="p">.</span></code></pre><p>Assuming that these types are exported from module <code class="inline">'mod'</code>, you can refer to
│ │ │ +them from other modules using remote type expressions like the following:</p><pre><code class="makeup erlang" translate="no"><span class="nc">mod</span><span class="p">:</span><span class="nf">my_struct_type</span><span class="p" data-group-id="1667187202-1">(</span><span class="p" data-group-id="1667187202-1">)</span><span class="w">
│ │ │ +</span><span class="nc">mod</span><span class="p">:</span><span class="nf">orddict</span><span class="p" data-group-id="1667187202-2">(</span><span class="nf">atom</span><span class="p" data-group-id="1667187202-3">(</span><span class="p" data-group-id="1667187202-3">)</span><span class="p">,</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="1667187202-4">(</span><span class="p" data-group-id="1667187202-4">)</span><span class="p" data-group-id="1667187202-2">)</span></code></pre><p>It is not allowed to refer to types that are not declared as exported.</p><p>Types declared as <code class="inline">opaque</code> represent sets of terms whose structure is not
│ │ │  supposed to be visible from outside of their defining module. That is, only the
│ │ │  module defining them is allowed to depend on their term structure. Consequently,
│ │ │  such types do not make much sense as module local - module local types are not
│ │ │  accessible by other modules anyway - and is always to be exported.</p><p>Read more on <a href="opaques.html">Opaques</a></p><p><a href="" id="typeinrecords"></a></p><h2 id="type-information-in-record-declarations" class="section-heading">
│ │ │    <a href="#type-information-in-record-declarations" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Type Information in Record Declarations</span>
│ │ │  </h2>
│ │ │  <p>The types of record fields can be specified in the declaration of the record.
│ │ │ -The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="6622956258-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6622956258-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="6622956258-2">}</span><span class="p" data-group-id="6622956258-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ -previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1429982901-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1429982901-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="1429982901-3">(</span><span class="p" data-group-id="1429982901-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="1429982901-2">}</span><span class="p" data-group-id="1429982901-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ -the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="3250459529-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3250459529-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3250459529-3">[</span><span class="p" data-group-id="3250459529-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="3250459529-2">}</span><span class="p" data-group-id="3250459529-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │ +The syntax for this is as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0703561824-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0703561824-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="0703561824-2">}</span><span class="p" data-group-id="0703561824-1">)</span><span class="p">.</span></code></pre><p>For fields without type annotations, their type defaults to <code class="inline">any()</code>. That is, the
│ │ │ +previous example is a shorthand for the following:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8057022182-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8057022182-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">any</span><span class="p" data-group-id="8057022182-3">(</span><span class="p" data-group-id="8057022182-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="8057022182-2">}</span><span class="p" data-group-id="8057022182-1">)</span><span class="p">.</span></code></pre><p>In the presence of initial values for fields, the type must be declared after
│ │ │ +the initialization, as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7688867118-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7688867118-2">{</span><span class="ss">field1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7688867118-3">[</span><span class="p" data-group-id="7688867118-3">]</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type1</span><span class="p">,</span><span class="w"> </span><span class="ss">field2</span><span class="p">,</span><span class="w"> </span><span class="ss">field3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="n">Type3</span><span class="p" data-group-id="7688867118-2">}</span><span class="p" data-group-id="7688867118-1">)</span><span class="p">.</span></code></pre><p>The initial values for fields are to be compatible with (that is, a member of)
│ │ │  the corresponding types. This is checked by the compiler and results in a
│ │ │  compilation error if a violation is detected.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Before Erlang/OTP 19, for fields without initial values, the singleton type
│ │ │  <code class="inline">'undefined'</code> was added to all declared types. In other words, the following
│ │ │ -two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5039385642-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5039385642-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5039385642-3">(</span><span class="p" data-group-id="5039385642-3">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="5039385642-4">(</span><span class="p" data-group-id="5039385642-4">)</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="5039385642-2">}</span><span class="p" data-group-id="5039385642-1">)</span><span class="p">.</span><span class="w">
│ │ │ +two record declarations had identical effects:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7598713094-1">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7598713094-2">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7598713094-3">(</span><span class="p" data-group-id="7598713094-3">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="7598713094-4">(</span><span class="p" data-group-id="7598713094-4">)</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="7598713094-2">}</span><span class="p" data-group-id="7598713094-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="5039385642-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5039385642-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="5039385642-7">(</span><span class="p" data-group-id="5039385642-7">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="5039385642-8">(</span><span class="p" data-group-id="5039385642-8">)</span><span class="p">,</span><span class="w">
│ │ │ -              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="5039385642-6">}</span><span class="p" data-group-id="5039385642-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="7598713094-5">(</span><span class="ss">rec</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7598713094-6">{</span><span class="ss">f1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">42</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="7598713094-7">(</span><span class="p" data-group-id="7598713094-7">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="ss">f2</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">float</span><span class="p" data-group-id="7598713094-8">(</span><span class="p" data-group-id="7598713094-8">)</span><span class="p">,</span><span class="w">
│ │ │ +              </span><span class="ss">f3</span><span class="w">      </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">&#39;undefined&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;a&#39;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;b&#39;</span><span class="p" data-group-id="7598713094-6">}</span><span class="p" data-group-id="7598713094-5">)</span><span class="p">.</span></code></pre><p>This is no longer the case. If you require <code class="inline">'undefined'</code> in your record field
│ │ │  type, you must explicitly add it to the typespec, as in the 2nd example.</p></section><p>Any record, containing type information or not, once defined, can be used as a
│ │ │  type using the following syntax:</p><pre><code class="text">#rec{}</code></pre><p>In addition, the record fields can be further specified when using a record type
│ │ │  by adding type information about the field as follows:</p><pre><code class="text">#rec{some_field :: Type}</code></pre><p>Any unspecified fields are assumed to have the type in the original record
│ │ │  declaration.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>When records are used to create patterns for ETS and Mnesia match functions,
│ │ │ -Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="0569598529-1">(</span><span class="p" data-group-id="0569598529-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="0569598529-2">(</span><span class="p" data-group-id="0569598529-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="0569598529-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0569598529-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="0569598529-5">(</span><span class="p" data-group-id="0569598529-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="0569598529-6">(</span><span class="p" data-group-id="0569598529-6">)</span><span class="p" data-group-id="0569598529-4">}</span><span class="p" data-group-id="0569598529-3">)</span><span class="p">.</span><span class="w">
│ │ │ +Dialyzer may need some help not to emit bad warnings. For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1651736653-1">(</span><span class="p" data-group-id="1651736653-1">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="1651736653-2">(</span><span class="p" data-group-id="1651736653-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="1651736653-3">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1651736653-4">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="1651736653-5">(</span><span class="p" data-group-id="1651736653-5">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="1651736653-6">(</span><span class="p" data-group-id="1651736653-6">)</span><span class="p" data-group-id="1651736653-4">}</span><span class="p" data-group-id="1651736653-3">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">lookup</span><span class="p" data-group-id="0569598529-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="0569598529-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="0569598529-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="0569598529-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="0569598529-9">}</span><span class="p" data-group-id="0569598529-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │ +</span><span class="nf">lookup</span><span class="p" data-group-id="1651736653-7">(</span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="n">Tab</span><span class="p" data-group-id="1651736653-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">ets</span><span class="p">:</span><span class="nf">match_object</span><span class="p" data-group-id="1651736653-8">(</span><span class="n">Tab</span><span class="p">,</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="1651736653-9">{</span><span class="ss">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Name</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="1651736653-9">}</span><span class="p" data-group-id="1651736653-8">)</span><span class="p">.</span></code></pre><p>Dialyzer will emit a warning since <code class="inline">'_'</code> is not in the type of record field
│ │ │  <code class="inline">height</code>.</p><p>The recommended way of dealing with this is to declare the smallest record
│ │ │  field types to accommodate all your needs, and then create refinements as
│ │ │ -needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="2485790840-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2485790840-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="2485790840-3">(</span><span class="p" data-group-id="2485790840-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2485790840-4">(</span><span class="p" data-group-id="2485790840-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="2485790840-2">}</span><span class="p" data-group-id="2485790840-1">)</span><span class="p">.</span><span class="w">
│ │ │ +needed. The modified example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">record</span><span class="p" data-group-id="8803984304-1">(</span><span class="ss">person</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8803984304-2">{</span><span class="ss">name</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="8803984304-3">(</span><span class="p" data-group-id="8803984304-3">)</span><span class="p">,</span><span class="w"> </span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="8803984304-4">(</span><span class="p" data-group-id="8803984304-4">)</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">&#39;_&#39;</span><span class="p" data-group-id="8803984304-2">}</span><span class="p" data-group-id="8803984304-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="2485790840-5">(</span><span class="p" data-group-id="2485790840-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="2485790840-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="2485790840-7">(</span><span class="p" data-group-id="2485790840-7">)</span><span class="p" data-group-id="2485790840-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │ +</span><span class="p">-</span><span class="na">type</span><span class="w"> </span><span class="nf">person</span><span class="p" data-group-id="8803984304-5">(</span><span class="p" data-group-id="8803984304-5">)</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="o">#</span><span class="ss">person</span><span class="p" data-group-id="8803984304-6">{</span><span class="ss">height</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">height</span><span class="p" data-group-id="8803984304-7">(</span><span class="p" data-group-id="8803984304-7">)</span><span class="p" data-group-id="8803984304-6">}</span><span class="p">.</span></code></pre><p>In specifications and type declarations the type <code class="inline">person()</code> is to be preferred
│ │ │  before <code class="inline">#person{}</code>.</p></section><h2 id="specifications-for-functions" class="section-heading">
│ │ │    <a href="#specifications-for-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Specifications for Functions</span>
│ │ │  </h2>
│ │ │  <p>A specification (or contract) for a function is given using the <code class="inline">-spec</code>
│ │ │  attribute. The general format is as follows:</p><pre><code class="text">-spec Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>An implementation of the function with the same name <code class="inline">Function</code> must exist in
│ │ │  the current module, and the arity of the function must match the number of
│ │ │  arguments, otherwise the compilation fails.</p><p>The following longer format with module name is also valid as long as <code class="inline">Module</code>
│ │ │  is the name of the current module. This can be useful for documentation
│ │ │  purposes.</p><pre><code class="text">-spec Module:Function(ArgType1, ..., ArgTypeN) -&gt; ReturnType.</code></pre><p>Also, for documentation purposes, argument names can be given:</p><pre><code class="text">-spec Function(ArgName1 :: Type1, ..., ArgNameN :: TypeN) -&gt; RT.</code></pre><p>A function specification can be overloaded. That is, it can have several types,
│ │ │ -separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="0200504032-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="0200504032-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="0200504032-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="0200504032-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │ +separated by a semicolon (<code class="inline">;</code>). For example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8042591904-1">(</span><span class="n">T1</span><span class="p">,</span><span class="w"> </span><span class="n">T2</span><span class="p" data-group-id="8042591904-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T3</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="8042591904-2">(</span><span class="n">T4</span><span class="p">,</span><span class="w"> </span><span class="n">T5</span><span class="p" data-group-id="8042591904-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">T6</span><span class="p">.</span></code></pre><p>A current restriction, which currently results in a warning by Dialyzer, is that
│ │ │  the domains of the argument types cannot overlap. For example, the following
│ │ │ -specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3415517219-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="3415517219-2">(</span><span class="p" data-group-id="3415517219-2">)</span><span class="p" data-group-id="3415517219-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="3415517219-3">(</span><span class="p" data-group-id="3415517219-3">)</span><span class="p">;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="3415517219-4">(</span><span class="nf">integer</span><span class="p" data-group-id="3415517219-5">(</span><span class="p" data-group-id="3415517219-5">)</span><span class="p" data-group-id="3415517219-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3415517219-6">(</span><span class="p" data-group-id="3415517219-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │ +specification results in a warning:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8868330259-1">(</span><span class="nf">pos_integer</span><span class="p" data-group-id="8868330259-2">(</span><span class="p" data-group-id="8868330259-2">)</span><span class="p" data-group-id="8868330259-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="8868330259-3">(</span><span class="p" data-group-id="8868330259-3">)</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="8868330259-4">(</span><span class="nf">integer</span><span class="p" data-group-id="8868330259-5">(</span><span class="p" data-group-id="8868330259-5">)</span><span class="p" data-group-id="8868330259-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8868330259-6">(</span><span class="p" data-group-id="8868330259-6">)</span><span class="p">.</span></code></pre><p>Type variables can be used in specifications to specify relations for the input
│ │ │  and output arguments of a function. For example, the following specification
│ │ │  defines the type of a polymorphic identity function:</p><pre><code class="text">-spec id(X) -&gt; X.</code></pre><p>Notice that the above specification does not restrict the input and output type
│ │ │  in any way. These types can be constrained by guard-like subtype constraints and
│ │ │ -provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="2946267697-1">(</span><span class="n">X</span><span class="p" data-group-id="2946267697-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="2946267697-2">(</span><span class="p" data-group-id="2946267697-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │ +provide bounded quantification:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="5519537224-1">(</span><span class="n">X</span><span class="p" data-group-id="5519537224-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="5519537224-2">(</span><span class="p" data-group-id="5519537224-2">)</span><span class="p">.</span></code></pre><p>Currently, the <code class="inline">::</code> constraint (read as &quot;is a subtype of&quot;) is the only guard
│ │ │  constraint that can be used in the <code class="inline">when</code> part of a <code class="inline">-spec</code> attribute.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The above function specification uses multiple occurrences of the same type
│ │ │  variable. That provides more type information than the following function
│ │ │ -specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="3582495619-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="3582495619-2">(</span><span class="p" data-group-id="3582495619-2">)</span><span class="p" data-group-id="3582495619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="3582495619-3">(</span><span class="p" data-group-id="3582495619-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │ +specification, where the type variables are missing:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">id</span><span class="p" data-group-id="5035702983-1">(</span><span class="nf">tuple</span><span class="p" data-group-id="5035702983-2">(</span><span class="p" data-group-id="5035702983-2">)</span><span class="p" data-group-id="5035702983-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">tuple</span><span class="p" data-group-id="5035702983-3">(</span><span class="p" data-group-id="5035702983-3">)</span><span class="p">.</span></code></pre><p>The latter specification says that the function takes some tuple and returns
│ │ │  some tuple. The specification with the <code class="inline">X</code> type variable specifies that the
│ │ │  function takes a tuple and returns <em>the same</em> tuple.</p><p>However, it is up to the tools that process the specifications to choose
│ │ │  whether to take this extra information into account or not.</p></section><p>The scope of a <code class="inline">::</code> constraint is the <code class="inline">(...) -&gt; RetType</code> specification after
│ │ │  which it appears. To avoid confusion, it is suggested that different variables
│ │ │  are used in different constituents of an overloaded contract, as shown in the
│ │ │ -following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="8525113354-1">(</span><span class="p" data-group-id="8525113354-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="8525113354-3">(</span><span class="p" data-group-id="8525113354-3">)</span><span class="p" data-group-id="8525113354-2">}</span><span class="p" data-group-id="8525113354-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="8525113354-4">(</span><span class="p" data-group-id="8525113354-4">)</span><span class="p">;</span><span class="w">
│ │ │ -         </span><span class="p" data-group-id="8525113354-5">(</span><span class="p" data-group-id="8525113354-6">[</span><span class="n">Y</span><span class="p" data-group-id="8525113354-6">]</span><span class="p" data-group-id="8525113354-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="8525113354-7">(</span><span class="p" data-group-id="8525113354-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │ +following example:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3946506246-1">(</span><span class="p" data-group-id="3946506246-2">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="3946506246-3">(</span><span class="p" data-group-id="3946506246-3">)</span><span class="p" data-group-id="3946506246-2">}</span><span class="p" data-group-id="3946506246-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">X</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">atom</span><span class="p" data-group-id="3946506246-4">(</span><span class="p" data-group-id="3946506246-4">)</span><span class="p">;</span><span class="w">
│ │ │ +         </span><span class="p" data-group-id="3946506246-5">(</span><span class="p" data-group-id="3946506246-6">[</span><span class="n">Y</span><span class="p" data-group-id="3946506246-6">]</span><span class="p" data-group-id="3946506246-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">number</span><span class="p" data-group-id="3946506246-7">(</span><span class="p" data-group-id="3946506246-7">)</span><span class="p">.</span></code></pre><p>Some functions in Erlang are not meant to return; either because they define
│ │ │  servers or because they are used to throw exceptions, as in the following
│ │ │ -function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="0634941035-1">(</span><span class="n">Err</span><span class="p" data-group-id="0634941035-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="0634941035-2">(</span><span class="p" data-group-id="0634941035-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="0634941035-3">}</span><span class="p" data-group-id="0634941035-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │ +function:</p><pre><code class="makeup erlang" translate="no"><span class="nf">my_error</span><span class="p" data-group-id="5666658599-1">(</span><span class="n">Err</span><span class="p" data-group-id="5666658599-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="5666658599-2">(</span><span class="p" data-group-id="5666658599-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Err</span><span class="p" data-group-id="5666658599-3">}</span><span class="p" data-group-id="5666658599-2">)</span><span class="p">.</span></code></pre><p>For such functions, it is recommended to use the special <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:no_return/0"><code class="inline">no_return/0</code></a> type
│ │ │  for their &quot;return&quot;, through a contract of the following form:</p><pre><code class="text">-spec my_error(term()) -&gt; no_return().</code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Erlang uses the shorthand version <code class="inline">_</code> as an anonymous type variable equivalent
│ │ │  to <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:term/0"><code class="inline">term/0</code></a> or <a href="../../erts-15.2.7.2/doc/html/erlang.html#t:any/0"><code class="inline">any/0</code></a>. For example, the following function</p><pre><code class="text">-spec Function(string(), _) -&gt; string().</code></pre><p>is equivalent to:</p><pre><code class="text">-spec Function(string(), any()) -&gt; string().</code></pre></section>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ ├── ./usr/share/doc/erlang-doc/html/doc/upcoming_incompatibilities.html
│ │ │ @@ -149,45 +149,45 @@
│ │ │  occurrences of <code class="inline">maybe</code> without quotes.</p><p><a href="" id="float_matching"></a></p><h3 id="0-0-and-0-0-will-no-longer-be-exactly-equal" class="section-heading">
│ │ │    <a href="#0-0-and-0-0-will-no-longer-be-exactly-equal" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">0.0 and -0.0 will no longer be exactly equal</span>
│ │ │  </h3>
│ │ │  <p>Currently, the floating point numbers <code class="inline">0.0</code> and <code class="inline">-0.0</code> have distinct internal
│ │ │ -representations. That can be seen if they are converted to binaries:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="5429953235-1">&lt;&lt;</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="5429953235-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5429953235-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="5429953235-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="p" data-group-id="5429953235-3">&lt;&lt;</span><span class="o">-</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="5429953235-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5429953235-4">&lt;&lt;</span><span class="mi">128</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="5429953235-4">&gt;&gt;</span></code></pre><p>However, when they are matched against each other or compared using the <code class="inline">=:=</code>
│ │ │ +representations. That can be seen if they are converted to binaries:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="p" data-group-id="9126846203-1">&lt;&lt;</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="9126846203-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9126846203-2">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="9126846203-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="p" data-group-id="9126846203-3">&lt;&lt;</span><span class="o">-</span><span class="mf">0.0</span><span class="o">/</span><span class="nb">float</span><span class="p" data-group-id="9126846203-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9126846203-4">&lt;&lt;</span><span class="mi">128</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="9126846203-4">&gt;&gt;</span></code></pre><p>However, when they are matched against each other or compared using the <code class="inline">=:=</code>
│ │ │  operator, they are considered to be equal. Thus, <code class="inline">0.0 =:= -0.0</code> currently
│ │ │  returns <code class="inline">true</code>.</p><p>In Erlang/OTP 27, <code class="inline">0.0 =:= -0.0</code> will return <code class="inline">false</code>, and matching <code class="inline">0.0</code> against
│ │ │  <code class="inline">-0.0</code> will fail. When used as map keys, <code class="inline">0.0</code> and <code class="inline">-0.0</code> will be considered to
│ │ │  be distinct.</p><p>The <code class="inline">==</code> operator will continue to return <code class="inline">true</code> for <code class="inline">0.0 == -0.0</code>.</p><p>To help to find code that might need to be revised, in OTP 27 there will be a
│ │ │  new compiler warning when matching against <code class="inline">0.0</code> or comparing to that value
│ │ │  using the <code class="inline">=:=</code> operator. The warning can be suppressed by matching against
│ │ │  <code class="inline">+0.0</code> instead of <code class="inline">0.0</code>.</p><p>We plan to introduce the same warning in OTP 26.1, but by default it will be
│ │ │  disabled.</p><p><a href="" id="singleton_typevars"></a></p><h3 id="singleton-type-variables-will-become-a-compile-time-error" class="section-heading">
│ │ │    <a href="#singleton-type-variables-will-become-a-compile-time-error" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Singleton type variables will become a compile-time error</span>
│ │ │  </h3>
│ │ │ -<p>Before Erlang/OTP 26, the compiler would silenty accept the following spec:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="7296257337-1">(</span><span class="n">Opts</span><span class="p" data-group-id="7296257337-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="7296257337-2">(</span><span class="p" data-group-id="7296257337-2">)</span><span class="w"> </span><span class="k">when</span><span class="w">
│ │ │ -    </span><span class="n">Opts</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="7296257337-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="7296257337-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7296257337-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="7296257337-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">f</span><span class="p" data-group-id="7296257337-5">(</span><span class="p">_</span><span class="p" data-group-id="7296257337-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">.</span></code></pre><p>In OTP 26, the compiler emits a warning pointing out that the type variable
│ │ │ -<code class="inline">Unknown</code> is unbound:</p><pre><code class="makeup erlang" translate="no"><span class="ss">t</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">6</span><span class="p">:</span><span class="mi">18</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="ss">variable</span><span class="w"> </span><span class="ss">&#39;Unknown&#39;</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">only</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="nf">once</span><span class="w"> </span><span class="p" data-group-id="3253303492-1">(</span><span class="ss">is</span><span class="w"> </span><span class="ss">unbound</span><span class="p" data-group-id="3253303492-1">)</span><span class="w">
│ │ │ +<p>Before Erlang/OTP 26, the compiler would silenty accept the following spec:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">spec</span><span class="w"> </span><span class="nf">f</span><span class="p" data-group-id="8971658721-1">(</span><span class="n">Opts</span><span class="p" data-group-id="8971658721-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">term</span><span class="p" data-group-id="8971658721-2">(</span><span class="p" data-group-id="8971658721-2">)</span><span class="w"> </span><span class="k">when</span><span class="w">
│ │ │ +    </span><span class="n">Opts</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="p" data-group-id="8971658721-3">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="8971658721-3">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8971658721-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Unknown</span><span class="p" data-group-id="8971658721-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">f</span><span class="p" data-group-id="8971658721-5">(</span><span class="p">_</span><span class="p" data-group-id="8971658721-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">error</span><span class="p">.</span></code></pre><p>In OTP 26, the compiler emits a warning pointing out that the type variable
│ │ │ +<code class="inline">Unknown</code> is unbound:</p><pre><code class="makeup erlang" translate="no"><span class="ss">t</span><span class="p">.</span><span class="nc">erl</span><span class="p">:</span><span class="mi">6</span><span class="p">:</span><span class="mi">18</span><span class="p">:</span><span class="w"> </span><span class="n">Warning</span><span class="p">:</span><span class="w"> </span><span class="ss">type</span><span class="w"> </span><span class="ss">variable</span><span class="w"> </span><span class="ss">&#39;Unknown&#39;</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">only</span><span class="w"> </span><span class="ss">used</span><span class="w"> </span><span class="nf">once</span><span class="w"> </span><span class="p" data-group-id="3711634159-1">(</span><span class="ss">is</span><span class="w"> </span><span class="ss">unbound</span><span class="p" data-group-id="3711634159-1">)</span><span class="w">
│ │ │  </span><span class="c1">%    6|     Opts :: {ok, Unknown} | {error, Unknown}.</span><span class="w">
│ │ │  </span><span class="c1">%     |                  ^</span></code></pre><p>In OTP 27, that warning will become an error.</p><p><a href="" id="escripts_will_be_compiled"></a></p><h3 id="escripts-will-be-compiled-by-default" class="section-heading">
│ │ │    <a href="#escripts-will-be-compiled-by-default" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Escripts will be compiled by default</span>
│ │ │  </h3>
│ │ │  <p>Escripts will be compiled by default instead of interpreted. That means that the
│ │ │  <code class="inline">compiler</code> application must be available.</p><p>The old behavior of interpreting escripts can be restored by adding the
│ │ │ -following line to the script file:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">mode</span><span class="p" data-group-id="2624431938-1">(</span><span class="ss">interpret</span><span class="p" data-group-id="2624431938-1">)</span><span class="p">.</span></code></pre><p>In OTP 28, support for interpreting an escript will be removed.</p><h3 id="code_path_choice-will-default-to-strict" class="section-heading">
│ │ │ +following line to the script file:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">mode</span><span class="p" data-group-id="8259701917-1">(</span><span class="ss">interpret</span><span class="p" data-group-id="8259701917-1">)</span><span class="p">.</span></code></pre><p>In OTP 28, support for interpreting an escript will be removed.</p><h3 id="code_path_choice-will-default-to-strict" class="section-heading">
│ │ │    <a href="#code_path_choice-will-default-to-strict" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">-code_path_choice will default to strict</span>
│ │ │  </h3>
│ │ │  <p>This command line option controls if paths given in the command line, boot
│ │ │  scripts, and the code server should be interpreted as is strict or relaxed.</p><p>OTP 26 and earlier defaults to <code class="inline">relaxed</code>, which means <code class="inline">-pa myapp/ebin</code> would
│ │ │ @@ -231,18 +231,18 @@
│ │ │  &quot;
│ │ │  String Content
│ │ │  &quot;
│ │ │  %%
│ │ │  %% In OTP 27 it is instead interpreted as a
│ │ │  %% Triple-Quoted String equivalent to
│ │ │  &quot;String Content&quot;</code></pre><pre><code class="makeup erlang" translate="no"><span class="s">&quot;&quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │ -</span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="9409059992-1">(</span><span class="p" data-group-id="9409059992-1">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │ +</span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3209354884-1">(</span><span class="p" data-group-id="3209354884-1">)</span><span class="w"> </span><span class="o">++</span><span class="w">
│ │ │  </span><span class="s">&quot;&quot;</span><span class="s">&quot;&quot;</span><span class="w">
│ │ │  </span><span class="c1">%% Became</span><span class="w">
│ │ │ -</span><span class="s">&quot;&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="9409059992-2">(</span><span class="p" data-group-id="9409059992-2">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="w">
│ │ │ +</span><span class="s">&quot;&quot;</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="nf">foo</span><span class="p" data-group-id="3209354884-2">(</span><span class="p" data-group-id="3209354884-2">)</span><span class="w"> </span><span class="o">++</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="w">
│ │ │  </span><span class="c1">%%</span><span class="w">
│ │ │  </span><span class="c1">%% In OTP 27 it is instead interpreted as a</span><span class="w">
│ │ │  </span><span class="c1">%% Triple-Quoted String (triple-or-more) equivalent to</span><span class="w">
│ │ │  </span><span class="s">&quot;++ foo() ++&quot;</span></code></pre><p>From Erlang/OTP 26.1 up to 27.0 the compiler issues a warning for a sequence of
│ │ │  3 or more double-quote characters since that is almost certainly a mistake or
│ │ │  something like a result of bad automatic code generation. If a users gets that
│ │ │  warning, the code should be corrected for example by inserting appropriate
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/alt_dist.html
│ │ │ @@ -237,50 +237,50 @@
│ │ │  <code class="inline">uds_dist</code> example using a port driver written in C, <code class="inline">erl_uds_dist</code> is written
│ │ │  entirely in Erlang.</p><h3 id="exported-callback-functions" class="section-heading">
│ │ │    <a href="#exported-callback-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Exported Callback Functions</span>
│ │ │  </h3>
│ │ │ -<p>The following functions are mandatory:</p><ul><li><pre id="listen"><code class="makeup erlang" translate="no"><span class="nf">listen</span><span class="p" data-group-id="5312201518-1">(</span><span class="n">Name</span><span class="p" data-group-id="5312201518-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="5312201518-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5312201518-3">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="5312201518-3">}</span><span class="p" data-group-id="5312201518-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5312201518-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5312201518-4">}</span><span class="w">
│ │ │ -</span><span class="nf">listen</span><span class="p" data-group-id="5312201518-5">(</span><span class="n">Name</span><span class="p">,</span><span class="n">Host</span><span class="p" data-group-id="5312201518-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="5312201518-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5312201518-7">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="5312201518-7">}</span><span class="p" data-group-id="5312201518-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5312201518-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5312201518-8">}</span></code></pre><p><code class="inline">listen/2</code> is called once in order to listen for incoming connection requests.
│ │ │ +<p>The following functions are mandatory:</p><ul><li><pre id="listen"><code class="makeup erlang" translate="no"><span class="nf">listen</span><span class="p" data-group-id="8943649663-1">(</span><span class="n">Name</span><span class="p" data-group-id="8943649663-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="8943649663-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8943649663-3">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="8943649663-3">}</span><span class="p" data-group-id="8943649663-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8943649663-4">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="8943649663-4">}</span><span class="w">
│ │ │ +</span><span class="nf">listen</span><span class="p" data-group-id="8943649663-5">(</span><span class="n">Name</span><span class="p">,</span><span class="n">Host</span><span class="p" data-group-id="8943649663-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="8943649663-6">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8943649663-7">{</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Address</span><span class="p">,</span><span class="w"> </span><span class="n">Creation</span><span class="p" data-group-id="8943649663-7">}</span><span class="p" data-group-id="8943649663-6">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8943649663-8">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="8943649663-8">}</span></code></pre><p><code class="inline">listen/2</code> is called once in order to listen for incoming connection requests.
│ │ │  The call is made when the distribution is brought up. The argument <code class="inline">Name</code> is
│ │ │  the part of the node name before the <code class="inline">@</code> sign in the full node name. It can be
│ │ │  either an atom or a string. The argument <code class="inline">Host</code> is the part of the node name
│ │ │  after the <code class="inline">@</code> sign in the full node name. It is always a string.</p><p>The return value consists of a <code class="inline">Listen</code> handle (which is later passed to the
│ │ │  <a href="alt_dist.html#accept"><code class="inline">accept/1</code></a> callback), <code class="inline">Address</code> which is a
│ │ │  <code class="inline">#net_address{}</code> record with information about the address for the node (the
│ │ │  <code class="inline">#net_address{}</code> record is defined in <code class="inline">kernel/include/net_address.hrl</code>), and
│ │ │  <code class="inline">Creation</code> which (currently) is an integer <code class="inline">1</code>, <code class="inline">2</code>, or <code class="inline">3</code>.</p><p>If <a href="epmd_cmd.html"><code class="inline">epmd</code></a> is to be used for node discovery, you typically want
│ │ │  to use the <code class="inline">erl_epmd</code> module (part of the <code class="inline">kernel</code> application) in order to
│ │ │ -register the listen port with <code class="inline">epmd</code> and retrieve <code class="inline">Creation</code> to use.</p></li><li><pre id="address"><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="4800053943-1">(</span><span class="p" data-group-id="4800053943-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +register the listen port with <code class="inline">epmd</code> and retrieve <code class="inline">Creation</code> to use.</p></li><li><pre id="address"><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="3520957661-1">(</span><span class="p" data-group-id="3520957661-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">Address</span></code></pre><p><code class="inline">address/0</code> is called in order to get the <code class="inline">Address</code> part of the
│ │ │  <a href="alt_dist.html#listen"><code class="inline">listen/2</code></a> function without creating a listen socket.
│ │ │ -All fields except <code class="inline">address</code> have to be set in the returned record</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="6628089647-1">(</span><span class="p" data-group-id="6628089647-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="6628089647-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Host</span><span class="p" data-group-id="6628089647-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">inet</span><span class="p">:</span><span class="nf">gethostname</span><span class="p" data-group-id="6628089647-3">(</span><span class="p" data-group-id="6628089647-3">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="o">#</span><span class="ss">net_address</span><span class="p" data-group-id="6628089647-4">{</span><span class="w"> </span><span class="ss">host</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Host</span><span class="p">,</span><span class="w"> </span><span class="ss">protocol</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">tcp</span><span class="p">,</span><span class="w"> </span><span class="ss">family</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">inet6</span><span class="w"> </span><span class="p" data-group-id="6628089647-4">}</span><span class="p">.</span></code></pre></li><li><pre id="accept"><code class="makeup erlang" translate="no"><span class="nf">accept</span><span class="p" data-group-id="6956813659-1">(</span><span class="n">Listen</span><span class="p" data-group-id="6956813659-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +All fields except <code class="inline">address</code> have to be set in the returned record</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">address</span><span class="p" data-group-id="4695652163-1">(</span><span class="p" data-group-id="4695652163-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4695652163-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Host</span><span class="p" data-group-id="4695652163-2">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">inet</span><span class="p">:</span><span class="nf">gethostname</span><span class="p" data-group-id="4695652163-3">(</span><span class="p" data-group-id="4695652163-3">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="o">#</span><span class="ss">net_address</span><span class="p" data-group-id="4695652163-4">{</span><span class="w"> </span><span class="ss">host</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Host</span><span class="p">,</span><span class="w"> </span><span class="ss">protocol</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">tcp</span><span class="p">,</span><span class="w"> </span><span class="ss">family</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">inet6</span><span class="w"> </span><span class="p" data-group-id="4695652163-4">}</span><span class="p">.</span></code></pre></li><li><pre id="accept"><code class="makeup erlang" translate="no"><span class="nf">accept</span><span class="p" data-group-id="1850283179-1">(</span><span class="n">Listen</span><span class="p" data-group-id="1850283179-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">AcceptorPid</span></code></pre><p><code class="inline">accept/1</code> should spawn a process that accepts connections. This process
│ │ │  should preferably execute on <code class="inline">max</code> priority. The process identifier of this
│ │ │  process should be returned.</p><p>The <code class="inline">Listen</code> argument will be the same as the <code class="inline">Listen</code> handle part of the
│ │ │  return value of the <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback above.
│ │ │  <code class="inline">accept/1</code> is called only once when the distribution protocol is started.</p><p>The caller of this function is a representative for <code class="inline">net_kernel</code> (this may or
│ │ │  may not be the process registered as <code class="inline">net_kernel</code>) and is in this document
│ │ │  identified as <code class="inline">Kernel</code>. When a connection has been accepted by the acceptor
│ │ │  process, it needs to inform <code class="inline">Kernel</code> about the accepted connection. This is
│ │ │ -done by passing a message on the form:</p><pre><code class="makeup erlang" translate="no"><span class="n">Kernel</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1488084685-1">{</span><span class="ss">accept</span><span class="p">,</span><span class="w"> </span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistController</span><span class="p">,</span><span class="w"> </span><span class="n">Family</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p" data-group-id="1488084685-1">}</span></code></pre><p><code class="inline">DistController</code> is either the process or port identifier of the distribution
│ │ │ +done by passing a message on the form:</p><pre><code class="makeup erlang" translate="no"><span class="n">Kernel</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="9646239485-1">{</span><span class="ss">accept</span><span class="p">,</span><span class="w"> </span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistController</span><span class="p">,</span><span class="w"> </span><span class="n">Family</span><span class="p">,</span><span class="w"> </span><span class="n">Proto</span><span class="p" data-group-id="9646239485-1">}</span></code></pre><p><code class="inline">DistController</code> is either the process or port identifier of the distribution
│ │ │  controller for the connection. The distribution controller should be created
│ │ │  by the acceptor processes when a new connection is accepted. Its job is to
│ │ │  dispatch traffic on the connection.</p><p><code class="inline">Kernel</code> responds with one of the following messages:</p><ul><li><p><strong><code class="inline">{Kernel, controller, SupervisorPid}</code></strong> - The request was accepted and
│ │ │  <code class="inline">SupervisorPid</code> is the process identifier of the connection supervisor
│ │ │  process (which is created in the
│ │ │  <a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a> callback).</p></li><li><p><strong><code class="inline">{Kernel, unsupported_protocol}</code></strong> - The request was rejected. This is a
│ │ │  fatal error. The acceptor process should terminate.</p></li></ul><p>When an accept sequence has been completed the acceptor process is expected to
│ │ │ -continue accepting further requests.</p></li><li><pre id="accept_connection"><code class="makeup erlang" translate="no"><span class="nf">accept_connection</span><span class="p" data-group-id="9411386468-1">(</span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">Allowed</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="9411386468-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +continue accepting further requests.</p></li><li><pre id="accept_connection"><code class="makeup erlang" translate="no"><span class="nf">accept_connection</span><span class="p" data-group-id="5357981066-1">(</span><span class="n">AcceptorPid</span><span class="p">,</span><span class="w"> </span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">Allowed</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="5357981066-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">ConnectionSupervisorPid</span></code></pre><p><code class="inline">accept_connection/5</code> should spawn a process that will perform the Erlang
│ │ │  distribution handshake for the connection. If the handshake successfully
│ │ │  completes it should continue to function as a connection supervisor. This
│ │ │  process should preferably execute on <code class="inline">max</code> priority and should be linked to
│ │ │  the caller. The <code class="inline">dist_util:net_ticker_spawn_options()</code> function can be called
│ │ │  to get spawn options suitable for this process which can be passed directly to
│ │ │  <a href="erlang.html#spawn_opt/4"><code class="inline">erlang:spawn_opt/4</code></a>. <code class="inline">dist_util:net_ticker_spawn_options()</code> will by default
│ │ │ @@ -294,15 +294,15 @@
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code>.</p></li><li><p><strong><code class="inline">Allowed</code></strong> - To be passed along to
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code>.</p></li><li><p><strong><code class="inline">SetupTime</code></strong> - Time used for creating a setup timer by a call to
│ │ │  <code class="inline">dist_util:start_timer(SetupTime)</code>. The timer should be passed along to
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code>.</p></li></ul><p>The created process should provide callbacks and other information needed for
│ │ │  the handshake in a <a href="alt_dist.html#hs_data_record"><code class="inline">#hs_data{}</code></a> record and call
│ │ │  <code class="inline">dist_util:handshake_other_started(HsData)</code> with this record.</p><p><code class="inline">dist_util:handshake_other_started(HsData)</code> will perform the handshake and if
│ │ │  the handshake successfully completes this process will then continue in a
│ │ │ -connection supervisor loop as long as the connection is up.</p></li><li><pre id="setup"><code class="makeup erlang" translate="no"><span class="nf">setup</span><span class="p" data-group-id="2960100390-1">(</span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">LongOrShortNames</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="2960100390-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +connection supervisor loop as long as the connection is up.</p></li><li><pre id="setup"><code class="makeup erlang" translate="no"><span class="nf">setup</span><span class="p" data-group-id="0054567968-1">(</span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">MyNode</span><span class="p">,</span><span class="w"> </span><span class="n">LongOrShortNames</span><span class="p">,</span><span class="w"> </span><span class="n">SetupTime</span><span class="p" data-group-id="0054567968-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │  </span><span class="err"> </span><span class="err"> </span><span class="n">ConnectionSupervisorPid</span></code></pre><p><code class="inline">setup/5</code> should spawn a process that connects to <code class="inline">Node</code>. When connection has
│ │ │  been established it should perform the Erlang distribution handshake for the
│ │ │  connection. If the handshake successfully completes it should continue to
│ │ │  function as a connection supervisor. This process should preferably execute on
│ │ │  <code class="inline">max</code> priority and should be linked to the caller. The
│ │ │  <code class="inline">dist_util:net_ticker_spawn_options()</code> function can be called to get spawn
│ │ │  options suitable for this process which can be passed directly to
│ │ │ @@ -320,23 +320,23 @@
│ │ │  may not be the process registered as <code class="inline">net_kernel</code>) and is in this document
│ │ │  identified as <code class="inline">Kernel</code>.</p><p>This function should, besides spawning the connection supervisor, also create
│ │ │  a distribution controller. The distribution controller is either a process or
│ │ │  a port which is responsible for dispatching traffic.</p><p>The created process should provide callbacks and other information needed for
│ │ │  the handshake in a <a href="alt_dist.html#hs_data_record"><code class="inline">#hs_data{}</code></a> record and call
│ │ │  <code class="inline">dist_util:handshake_we_started(HsData)</code> with this record.</p><p><code class="inline">dist_util:handshake_we_started(HsData)</code> will perform the handshake and the
│ │ │  handshake successfully completes this process will then continue in a
│ │ │ -connection supervisor loop as long as the connection is up.</p></li><li><pre id="close"><code class="makeup erlang" translate="no"><span class="nf">close</span><span class="p" data-group-id="2709889941-1">(</span><span class="n">Listen</span><span class="p" data-group-id="2709889941-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="nf">void</span><span class="p" data-group-id="2709889941-2">(</span><span class="p" data-group-id="2709889941-2">)</span></code></pre><p>Called in order to close the <code class="inline">Listen</code> handle that originally was passed from
│ │ │ -the <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback.</p></li><li><pre id="select"><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="2265190388-1">(</span><span class="n">NodeName</span><span class="p" data-group-id="2265190388-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="nf">boolean</span><span class="p" data-group-id="2265190388-2">(</span><span class="p" data-group-id="2265190388-2">)</span></code></pre><p>Return <code class="inline">true</code> if the host name part of the <code class="inline">NodeName</code> is valid for use with
│ │ │ -this protocol; otherwise, <code class="inline">false</code>.</p></li></ul><p>There are also two optional functions that may be exported:</p><ul><li><pre id="setopts"><code class="makeup erlang" translate="no"><span class="nf">setopts</span><span class="p" data-group-id="4099528016-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="4099528016-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4099528016-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4099528016-2">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │ +connection supervisor loop as long as the connection is up.</p></li><li><pre id="close"><code class="makeup erlang" translate="no"><span class="nf">close</span><span class="p" data-group-id="8626828825-1">(</span><span class="n">Listen</span><span class="p" data-group-id="8626828825-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="nf">void</span><span class="p" data-group-id="8626828825-2">(</span><span class="p" data-group-id="8626828825-2">)</span></code></pre><p>Called in order to close the <code class="inline">Listen</code> handle that originally was passed from
│ │ │ +the <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback.</p></li><li><pre id="select"><code class="makeup erlang" translate="no"><span class="nf">select</span><span class="p" data-group-id="7848350278-1">(</span><span class="n">NodeName</span><span class="p" data-group-id="7848350278-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="nf">boolean</span><span class="p" data-group-id="7848350278-2">(</span><span class="p" data-group-id="7848350278-2">)</span></code></pre><p>Return <code class="inline">true</code> if the host name part of the <code class="inline">NodeName</code> is valid for use with
│ │ │ +this protocol; otherwise, <code class="inline">false</code>.</p></li></ul><p>There are also two optional functions that may be exported:</p><ul><li><pre id="setopts"><code class="makeup erlang" translate="no"><span class="nf">setopts</span><span class="p" data-group-id="9151656115-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="9151656115-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9151656115-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="9151656115-2">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │  <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback. The argument <code class="inline">Opts</code> is a list of
│ │ │ -options to set on future connections.</p></li><li><pre id="getopts"><code class="makeup erlang" translate="no"><span class="nf">getopts</span><span class="p" data-group-id="1424269796-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="1424269796-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="1424269796-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="1424269796-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="1424269796-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="1424269796-3">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │ +options to set on future connections.</p></li><li><pre id="getopts"><code class="makeup erlang" translate="no"><span class="nf">getopts</span><span class="p" data-group-id="7251036370-1">(</span><span class="n">Listen</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7251036370-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="err"> </span><span class="err"> </span><span class="p" data-group-id="7251036370-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="7251036370-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7251036370-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="7251036370-3">}</span></code></pre><p>The argument <code class="inline">Listen</code> is the handle originally passed from the
│ │ │  <a href="alt_dist.html#listen"><code class="inline">listen/1</code></a> callback. The argument <code class="inline">Opts</code> is a list of
│ │ │  options to read for future connections.</p></li></ul><p><a href="" id="hs_data_record"></a></p><h3 id="the-hs_data-record" class="section-heading">
│ │ │    <a href="#the-hs_data-record" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">The #hs_data{} Record</span>
│ │ │  </h3>
│ │ │ @@ -350,44 +350,44 @@
│ │ │  <a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_other_node">other_node</code></strong> - Name of the other node. This field
│ │ │  is only mandatory when this node initiates the connection. That is, when
│ │ │  connection is set up via <a href="alt_dist.html#setup"><code class="inline">setup/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_this_node">this_node</code></strong> - The node name of this node.</p></li><li><p><strong><code class="inline" id="hs_data_socket">socket</code></strong> - The identifier of the distribution
│ │ │  controller.</p></li><li><p><strong><code class="inline" id="hs_data_timer">timer</code></strong> - The timer created using
│ │ │  <code class="inline">dist_util:start_timer/1</code>.</p></li><li><p><strong><code class="inline" id="hs_data_allowed">allowed</code></strong> - Information passed as <code class="inline">Allowed</code> to
│ │ │  <code class="inline">accept_connection/5</code>. This field is only mandatory when the remote node
│ │ │  initiated the connection. That is, when the connection is set up via
│ │ │ -<a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_f_send">f_send</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9176982984-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="9176982984-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9176982984-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="9176982984-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Data</code>
│ │ │ -is io data to pass to the other side.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_recv">f_recv</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9773606129-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="9773606129-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9773606129-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Packet</span><span class="p" data-group-id="9773606129-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9773606129-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="9773606129-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. If
│ │ │ +<a href="alt_dist.html#accept_connection"><code class="inline">accept_connection/5</code></a>.</p></li><li><p><strong><code class="inline" id="hs_data_f_send">f_send</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4099970160-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="4099970160-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4099970160-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4099970160-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Data</code>
│ │ │ +is io data to pass to the other side.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_recv">f_recv</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="2280297961-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Length</span><span class="p" data-group-id="2280297961-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2280297961-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Packet</span><span class="p" data-group-id="2280297961-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="2280297961-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Reason</span><span class="p" data-group-id="2280297961-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. If
│ │ │  <code class="inline">Length</code> is <code class="inline">0</code>, all available bytes should be returned. If <code class="inline">Length &gt; 0</code>,
│ │ │  exactly <code class="inline">Length</code> bytes should be returned, or an error; possibly discarding
│ │ │  less than <code class="inline">Length</code> bytes of data when the connection is closed from the other
│ │ │  side. It is used for passive receive of data from the other end.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_setopts_pre_nodeup">f_setopts_pre_nodeup</code></strong> - A fun with the
│ │ │ -following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4069289713-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="4069289713-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4069289713-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4069289713-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │ +following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1753007891-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="1753007891-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="1753007891-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="1753007891-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │  just before the distribution channel is taken up for normal traffic.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_setopts_post_nodeup">f_setopts_post_nodeup</code></strong> - A fun with
│ │ │ -the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4392879957-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="4392879957-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="4392879957-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="4392879957-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │ -just after distribution channel has been taken up for normal traffic.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_getll">f_getll</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0539169947-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="0539169947-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">ID</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">ID</code> is
│ │ │ +the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9028178464-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="9028178464-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="9028178464-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="9028178464-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. Called
│ │ │ +just after distribution channel has been taken up for normal traffic.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_getll">f_getll</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1035365695-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="1035365695-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">ID</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">ID</code> is
│ │ │  the identifier of the low level entity that handles the connection (often
│ │ │ -<code class="inline">DistCtrlr</code> itself).</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_address">f_address</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5326999286-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="5326999286-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">NetAddress</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │ +<code class="inline">DistCtrlr</code> itself).</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_f_address">f_address</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="6713333890-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p" data-group-id="6713333890-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">NetAddress</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │  the node name of the node on the other end, and <code class="inline">NetAddress</code> is a
│ │ │  <code class="inline">#net_address{}</code> record with information about the address for the <code class="inline">Node</code> on
│ │ │  the other end of the connection. The <code class="inline">#net_address{}</code> record is defined in
│ │ │ -<code class="inline">kernel/include/net_address.hrl</code>.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_mf_tick">mf_tick</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="4118391374-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="4118391374-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="4118391374-2">(</span><span class="p" data-group-id="4118391374-2">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. This
│ │ │ +<code class="inline">kernel/include/net_address.hrl</code>.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_mf_tick">mf_tick</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8590159160-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="8590159160-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="8590159160-2">(</span><span class="p" data-group-id="8590159160-2">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller. This
│ │ │  function should send information over the connection that is not interpreted
│ │ │  by the other end while increasing the statistics of received packets on the
│ │ │  other end. This is usually implemented by sending an empty packet.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is of vital importance that this operation does not block the caller for
│ │ │ -a long time. This since it is called from the connection supervisor.</p></section><p>Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getstat">mf_getstat</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7743172881-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="7743172881-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7743172881-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Received</span><span class="p">,</span><span class="w"> </span><span class="n">Sent</span><span class="p">,</span><span class="w"> </span><span class="n">PendSend</span><span class="p" data-group-id="7743172881-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Received</code>
│ │ │ +a long time. This since it is called from the connection supervisor.</p></section><p>Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getstat">mf_getstat</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3484268960-1">(</span><span class="n">DistCtrlr</span><span class="p" data-group-id="3484268960-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3484268960-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Received</span><span class="p">,</span><span class="w"> </span><span class="n">Sent</span><span class="p">,</span><span class="w"> </span><span class="n">PendSend</span><span class="p" data-group-id="3484268960-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Received</code>
│ │ │  is received packets, <code class="inline">Sent</code> is sent packets, and <code class="inline">PendSend</code> is amount of data
│ │ │  in queue to be sent (typically in bytes, but <code class="inline">dist_util</code> only checks whether
│ │ │  the value is non-zero to know there is data in queue) or a <a href="erlang.html#t:boolean/0"><code class="inline">boolean/0</code></a>
│ │ │  indicating whether there are packets in queue to be sent.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>It is of vital importance that this operation does not block the caller for
│ │ │  a long time. This since it is called from the connection supervisor.</p></section><p>Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_request_type">request_type</code></strong> - The request <code class="inline">Type</code> as passed to
│ │ │  <a href="alt_dist.html#setup"><code class="inline">setup/5</code></a>. This is only mandatory when the connection has
│ │ │ -been initiated by this node. That is, the connection is set up via <code class="inline">setup/5</code>.</p></li><li><p><strong><code class="inline" id="hs_data_mf_setopts">mf_setopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="8629893505-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="8629893505-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="8629893505-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="8629893505-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │ -is a list of options to set on the connection.</p><p>This function is optional. Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getopts">mf_getopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="7349086889-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="7349086889-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7349086889-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="7349086889-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="7349086889-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="7349086889-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │ +been initiated by this node. That is, the connection is set up via <code class="inline">setup/5</code>.</p></li><li><p><strong><code class="inline" id="hs_data_mf_setopts">mf_setopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5616499000-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="5616499000-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="5616499000-2">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="5616499000-2">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │ +is a list of options to set on the connection.</p><p>This function is optional. Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_mf_getopts">mf_getopts</code></strong> - A fun with the following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="0522436761-1">(</span><span class="n">DistCtrl</span><span class="p">,</span><span class="w"> </span><span class="n">Opts</span><span class="p" data-group-id="0522436761-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0522436761-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">OptionValues</span><span class="p" data-group-id="0522436761-2">}</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p" data-group-id="0522436761-3">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">Error</span><span class="p" data-group-id="0522436761-3">}</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller and <code class="inline">Opts</code>
│ │ │  is a list of options to read for the connection.</p><p>This function is optional. Used when connection is up.</p></li><li><p><strong><code class="inline" id="hs_data_f_handshake_complete">f_handshake_complete</code></strong> - A fun with the
│ │ │ -following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="3032174760-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">DHandle</span><span class="p" data-group-id="3032174760-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="3032174760-2">(</span><span class="p" data-group-id="3032174760-2">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │ +following signature:</p><pre><code class="makeup erlang" translate="no"><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="9234167515-1">(</span><span class="n">DistCtrlr</span><span class="p">,</span><span class="w"> </span><span class="n">Node</span><span class="p">,</span><span class="w"> </span><span class="n">DHandle</span><span class="p" data-group-id="9234167515-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">void</span><span class="p" data-group-id="9234167515-2">(</span><span class="p" data-group-id="9234167515-2">)</span></code></pre><p>where <code class="inline">DistCtrlr</code> is the identifier of the distribution controller, <code class="inline">Node</code> is
│ │ │  the node name of the node connected at the other end, and <code class="inline">DHandle</code> is a
│ │ │  distribution handle needed by a distribution controller process when calling
│ │ │  the following BIFs:</p><ul><li><a href="erlang.html#dist_ctrl_get_data/1"><code class="inline">erlang:dist_ctrl_get_data/1</code></a></li><li><a href="erlang.html#dist_ctrl_get_data_notification/1"><code class="inline">erlang:dist_ctrl_get_data_notification/1</code></a></li><li><a href="erlang.html#dist_ctrl_input_handler/2"><code class="inline">erlang:dist_ctrl_input_handler/2</code></a></li><li><a href="erlang.html#dist_ctrl_put_data/2"><code class="inline">erlang:dist_ctrl_put_data/2</code></a></li></ul><p>This function is called when the handshake has completed and the distribution
│ │ │  channel is up. The distribution controller can begin dispatching traffic over
│ │ │  the channel. This function is optional.</p><p>Only used during handshake phase.</p></li><li><p><strong><code class="inline" id="hs_data_add_flags">add_flags</code></strong> -
│ │ │  <a href="erl_dist_protocol.html#dflags">Distribution flags</a> to add to the connection.
│ │ │  Currently all (non obsolete) flags will automatically be enabled.</p><p>This flag field is optional.</p></li><li><p><strong><code class="inline" id="hs_data_reject_flags">reject_flags</code></strong> -
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/automaticyieldingofccode.html
│ │ │ @@ -209,17 +209,17 @@
│ │ │  they have to follow certain restrictions. The convention for making
│ │ │  this clear is to have a comment above the function that explains that
│ │ │  the function is transformed by YCF (see <code class="inline">maps_values_1_helper</code> in
│ │ │  <code class="inline">erl_map.c</code> for an example). If only the transformed version of the
│ │ │  function is used, the convention is to &quot;comment out&quot; the source for the
│ │ │  function by surrounding it with the following <code class="inline">#ifdef</code> (this way, one
│ │ │  will not get warnings about unused functions):</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="ss">ifdef</span><span class="w"> </span><span class="n">INCLUDE_YCF_TRANSFORMED_ONLY_FUNCTIONS</span><span class="w">
│ │ │ -</span><span class="ss">void</span><span class="w"> </span><span class="nf">my_fun</span><span class="p" data-group-id="4726475488-1">(</span><span class="p" data-group-id="4726475488-1">)</span><span class="w"> </span><span class="p" data-group-id="4726475488-2">{</span><span class="w">
│ │ │ +</span><span class="ss">void</span><span class="w"> </span><span class="nf">my_fun</span><span class="p" data-group-id="8885424329-1">(</span><span class="p" data-group-id="8885424329-1">)</span><span class="w"> </span><span class="p" data-group-id="8885424329-2">{</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4726475488-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8885424329-2">}</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="ss">endif</span><span class="w"> </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">INCLUDE_YCF_TRANSFORMED_ONLY_FUNCTIONS</span><span class="w"> </span><span class="o">*</span><span class="o">/</span></code></pre><p>While editing the function one can define
│ │ │  <code class="inline">INCLUDE_YCF_TRANSFORMED_ONLY_FUNCTIONS</code> so that one can see errors
│ │ │  and warnings in the non-transformed source.</p><h3 id="where-to-place-ycf-transformed-functions" class="section-heading">
│ │ │    <a href="#where-to-place-ycf-transformed-functions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Where to Place YCF Transformed Functions</span>
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/beam_makeops.html
│ │ │ @@ -151,17 +151,17 @@
│ │ │  The loader translates generic instructions to specific instructions.
│ │ │  In general, for each generic instruction, there exists a family of
│ │ │  specific instructions.  The OTP 20 release has 389 specific
│ │ │  instructions.</p></li><li><p>The implementation of specific instructions for the traditional
│ │ │  BEAM interpreter. For the <a href="beamasm.html">BeamAsm JIT</a> introduced
│ │ │  in OTP 24, the implementation of instructions are defined in emitter
│ │ │  functions written in C++.</p></li></ul><p>Generic instructions have typed operands. Here are a few examples of
│ │ │ -operands for <code class="inline">move/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4781033029-1">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="4781033029-2">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">id</span><span class="p" data-group-id="4781033029-2">}</span><span class="p">,</span><span class="p" data-group-id="4781033029-3">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="4781033029-3">}</span><span class="p" data-group-id="4781033029-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4781033029-4">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="4781033029-5">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4781033029-5">}</span><span class="p">,</span><span class="p" data-group-id="4781033029-6">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="4781033029-6">}</span><span class="p" data-group-id="4781033029-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4781033029-7">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="4781033029-8">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="4781033029-8">}</span><span class="p">,</span><span class="p" data-group-id="4781033029-9">{</span><span class="ss">y</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="4781033029-9">}</span><span class="p" data-group-id="4781033029-7">}</span><span class="p">.</span></code></pre><p>When those instructions are loaded, the loader rewrites them
│ │ │ +operands for <code class="inline">move/2</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7157569188-1">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="7157569188-2">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">id</span><span class="p" data-group-id="7157569188-2">}</span><span class="p">,</span><span class="p" data-group-id="7157569188-3">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7157569188-3">}</span><span class="p" data-group-id="7157569188-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7157569188-4">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="7157569188-5">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7157569188-5">}</span><span class="p">,</span><span class="p" data-group-id="7157569188-6">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="7157569188-6">}</span><span class="p" data-group-id="7157569188-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7157569188-7">{</span><span class="ss">move</span><span class="p">,</span><span class="p" data-group-id="7157569188-8">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="7157569188-8">}</span><span class="p">,</span><span class="p" data-group-id="7157569188-9">{</span><span class="ss">y</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="7157569188-9">}</span><span class="p" data-group-id="7157569188-7">}</span><span class="p">.</span></code></pre><p>When those instructions are loaded, the loader rewrites them
│ │ │  to specific instructions:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move_cx</span><span class="w"> </span><span class="ss">id</span><span class="w"> </span><span class="mi">5</span><span class="w">
│ │ │  </span><span class="ss">move_xx</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="mi">0</span><span class="w">
│ │ │  </span><span class="ss">move_xy</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="mi">1</span></code></pre><p>Corresponding to each generic instruction, there is a family of
│ │ │  specific instructions.  The types that an instance of a specific
│ │ │  instruction can handle are encoded in the instruction names.  For
│ │ │  example, <code class="inline">move_xy</code> takes an X register number as the first operand and
│ │ │  a Y register number as the second operand.  <code class="inline">move_cx</code> takes a tagged
│ │ │ @@ -185,17 +185,17 @@
│ │ │  </span><span class="ss">move</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="ss">x</span></code></pre><p>Each specific instructions is defined by following the name of the
│ │ │  instruction with the types for each operand.  An operand type is a
│ │ │  single letter.  For example, <code class="inline">x</code> means an X register, <code class="inline">y</code>
│ │ │  means a Y register, and <code class="inline">c</code> is a &quot;constant&quot; (a tagged term such as
│ │ │  an integer, an atom, or a literal).</p><p>Now let's look at the implementation of the <code class="inline">move</code> instruction.  There
│ │ │  are multiple files containing implementations of instructions in the
│ │ │  <code class="inline">erts/emulator/beam/emu</code> directory.  The <code class="inline">move</code> instruction is defined
│ │ │ -in <code class="inline">instrs.tab</code>.  It looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="4253912778-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="4253912778-1">)</span><span class="w"> </span><span class="p" data-group-id="4253912778-2">{</span><span class="w">
│ │ │ +in <code class="inline">instrs.tab</code>.  It looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="3882333834-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3882333834-1">)</span><span class="w"> </span><span class="p" data-group-id="3882333834-2">{</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4253912778-2">}</span></code></pre><p>The implementation for an instruction largely follows the C syntax,
│ │ │ +</span><span class="p" data-group-id="3882333834-2">}</span></code></pre><p>The implementation for an instruction largely follows the C syntax,
│ │ │  except that the variables in the function head don't have any types.
│ │ │  The <code class="inline">$</code> before an identifier denotes a macro expansion.  Thus,
│ │ │  <code class="inline">$Src</code> will expand to the code to pick up the source operand for
│ │ │  the instruction and <code class="inline">$Dst</code> to the code for the destination register.</p><p>We will look at the code for each specific instruction in turn.  To
│ │ │  make the code easier to understand, let's first look at the memory
│ │ │  layout for the instruction <code class="inline">{move,{atom,id},{x,5}}</code>:</p><pre><code class="makeup erlang" translate="no"><span class="w">     </span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="w">
│ │ │  </span><span class="n">I</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p">|</span><span class="w">                 </span><span class="mi">40</span><span class="w"> </span><span class="p">|</span><span class="w">       </span><span class="p">&amp;&amp;</span><span class="ss">lb_move_cx</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ @@ -204,61 +204,61 @@
│ │ │       </span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span></code></pre><p>This example and all other examples in the document assumes a 64-bit
│ │ │  architecture, and furthermore that pointers to C code fit in 32 bits.</p><p><code class="inline">I</code> in the BEAM virtual machine is the instruction pointer.  When BEAM
│ │ │  executes an instruction, <code class="inline">I</code> points to the first word of the
│ │ │  instruction.</p><p><code class="inline">&amp;&amp;lb_move_cx</code> is the address to C code that implements <code class="inline">move_cx</code>.  It
│ │ │  is stored in the lower 32 bits of the word.  In the upper 32 bits is
│ │ │  the byte offset to the X register; the register number 5 has been
│ │ │  multiplied by the word size size 8.</p><p>In the next word the tagged atom <code class="inline">id</code> is stored.</p><p>With that background, we can look at the generated code for <code class="inline">move_cx</code>
│ │ │ -in <code class="inline">beam_hot.h</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="1320705906-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="1320705906-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1320705906-2">{</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="1320705906-3">(</span><span class="n">I</span><span class="p" data-group-id="1320705906-4">[</span><span class="mi">2</span><span class="p" data-group-id="1320705906-4">]</span><span class="p" data-group-id="1320705906-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="1320705906-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="1320705906-6">(</span><span class="n">I</span><span class="p" data-group-id="1320705906-7">[</span><span class="mi">0</span><span class="p" data-group-id="1320705906-7">]</span><span class="p" data-group-id="1320705906-6">)</span><span class="p" data-group-id="1320705906-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="1320705906-8">[</span><span class="mi">1</span><span class="p" data-group-id="1320705906-8">]</span><span class="p">;</span><span class="w">
│ │ │ +in <code class="inline">beam_hot.h</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="5778568261-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="5778568261-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5778568261-2">{</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="5778568261-3">(</span><span class="n">I</span><span class="p" data-group-id="5778568261-4">[</span><span class="mi">2</span><span class="p" data-group-id="5778568261-4">]</span><span class="p" data-group-id="5778568261-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="5778568261-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="5778568261-6">(</span><span class="n">I</span><span class="p" data-group-id="5778568261-7">[</span><span class="mi">0</span><span class="p" data-group-id="5778568261-7">]</span><span class="p" data-group-id="5778568261-6">)</span><span class="p" data-group-id="5778568261-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="5778568261-8">[</span><span class="mi">1</span><span class="p" data-group-id="5778568261-8">]</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="1320705906-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="1320705906-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="1320705906-10">)</span><span class="p" data-group-id="1320705906-9">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="1320705906-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="1320705906-11">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1320705906-2">}</span></code></pre><p>We will go through each line in turn.</p><ul><li><p><code class="inline">OpCase(move_cx):</code> defines a label for the instruction.  The
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="5778568261-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5778568261-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="5778568261-10">)</span><span class="p" data-group-id="5778568261-9">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="5778568261-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="5778568261-11">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5778568261-2">}</span></code></pre><p>We will go through each line in turn.</p><ul><li><p><code class="inline">OpCase(move_cx):</code> defines a label for the instruction.  The
│ │ │  <code class="inline">OpCase()</code> macro is defined in <code class="inline">beam_emu.c</code>.  It will expand this line
│ │ │  to <code class="inline">lb_move_cx:</code>.</p></li><li><p><code class="inline">BeamInstr next_pf = BeamCodeAddr(I[2]);</code> fetches the pointer to
│ │ │  code for the next instruction to be executed.  The <code class="inline">BeamCodeAddr()</code>
│ │ │  macro extracts the pointer from the lower 32 bits of the instruction
│ │ │  word.</p></li><li><p><code class="inline">xb(BeamExtraData(I[0])) = I[1];</code> is the expansion of <code class="inline">$Dst = $Src</code>.
│ │ │  <code class="inline">BeamExtraData()</code> is a macro that will extract the upper 32 bits from
│ │ │  the instruction word.  In this example, it will return 40 which is the
│ │ │  byte offset for X register 5.  The <code class="inline">xb()</code> macro will cast a byte
│ │ │  pointer to an <code class="inline">Eterm</code> pointer and dereference it.  The <code class="inline">I[1]</code> on
│ │ │  the right-hand side of the <code class="inline">=</code> fetches an Erlang term (the atom <code class="inline">id</code> in
│ │ │  this case).</p></li><li><p><code class="inline">I += 2</code> advances the instruction pointer to the next
│ │ │  instruction.</p></li><li><p>In a debug-compiled emulator, <code class="inline">ASSERT(VALID_INSTR(next_pf));</code> makes
│ │ │  sure that <code class="inline">next_pf</code> is a valid instruction (that is, that it points
│ │ │ -within the <code class="inline">process_main()</code> function in <code class="inline">beam_emu.c</code>).</p></li><li><p><code class="inline">GotoPF(next_pf);</code> transfers control to the next instruction.</p></li></ul><p>Now let's look at the implementation of <code class="inline">move_xx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="3210866338-1">(</span><span class="ss">move_xx</span><span class="p" data-group-id="3210866338-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3210866338-2">{</span><span class="w">
│ │ │ -  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="3210866338-3">(</span><span class="n">I</span><span class="p" data-group-id="3210866338-4">[</span><span class="mi">0</span><span class="p" data-group-id="3210866338-4">]</span><span class="p" data-group-id="3210866338-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="3210866338-5">(</span><span class="n">I</span><span class="p" data-group-id="3210866338-6">[</span><span class="mi">1</span><span class="p" data-group-id="3210866338-6">]</span><span class="p" data-group-id="3210866338-5">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="3210866338-7">(</span><span class="p" data-group-id="3210866338-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="3210866338-8">)</span><span class="p" data-group-id="3210866338-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="3210866338-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="3210866338-9">)</span><span class="p">;</span><span class="w">
│ │ │ +within the <code class="inline">process_main()</code> function in <code class="inline">beam_emu.c</code>).</p></li><li><p><code class="inline">GotoPF(next_pf);</code> transfers control to the next instruction.</p></li></ul><p>Now let's look at the implementation of <code class="inline">move_xx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="8262144695-1">(</span><span class="ss">move_xx</span><span class="p" data-group-id="8262144695-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8262144695-2">{</span><span class="w">
│ │ │ +  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="8262144695-3">(</span><span class="n">I</span><span class="p" data-group-id="8262144695-4">[</span><span class="mi">0</span><span class="p" data-group-id="8262144695-4">]</span><span class="p" data-group-id="8262144695-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="8262144695-5">(</span><span class="n">I</span><span class="p" data-group-id="8262144695-6">[</span><span class="mi">1</span><span class="p" data-group-id="8262144695-6">]</span><span class="p" data-group-id="8262144695-5">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="8262144695-7">(</span><span class="p" data-group-id="8262144695-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="8262144695-8">)</span><span class="p" data-group-id="8262144695-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="8262144695-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="8262144695-9">)</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="3210866338-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3210866338-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="3210866338-11">)</span><span class="p" data-group-id="3210866338-10">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="3210866338-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="3210866338-12">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3210866338-2">}</span></code></pre><p>We will go through the lines that are new or have changed compared to
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="8262144695-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="8262144695-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="8262144695-11">)</span><span class="p" data-group-id="8262144695-10">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="8262144695-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="8262144695-12">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8262144695-2">}</span></code></pre><p>We will go through the lines that are new or have changed compared to
│ │ │  <code class="inline">move_cx</code>.</p><ul><li><p><code class="inline">Eterm tmp_packed1 = BeamExtraData(I[0]);</code> picks up both X register
│ │ │  numbers packed into the upper 32 bits of the instruction word.</p></li><li><p><code class="inline">BeamInstr next_pf = BeamCodeAddr(I[1]);</code> pre-fetches the address of
│ │ │  the next instruction. Note that because both X registers operands fits
│ │ │  into the instruction word, the next instruction is in the very next
│ │ │  word.</p></li><li><p><code class="inline">xb((tmp_packed1&gt;&gt;BEAM_TIGHT_SHIFT)) = xb(tmp_packed1&amp;BEAM_TIGHT_MASK);</code>
│ │ │  copies the source to the destination.  (For a 64-bit architecture,
│ │ │  <code class="inline">BEAM_TIGHT_SHIFT</code> is 16 and <code class="inline">BEAM_TIGHT_MASK</code> is <code class="inline">0xFFFF</code>.)</p></li><li><p><code class="inline">I += 1;</code> advances the instruction pointer to the next instruction.</p></li></ul><p><code class="inline">move_xy</code> is almost identical to <code class="inline">move_xx</code>.  The only difference is
│ │ │  the use of the <code class="inline">yb()</code> macro instead of <code class="inline">xb()</code> to reference the
│ │ │ -destination register:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="6664517291-1">(</span><span class="ss">move_xy</span><span class="p" data-group-id="6664517291-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6664517291-2">{</span><span class="w">
│ │ │ -  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="6664517291-3">(</span><span class="n">I</span><span class="p" data-group-id="6664517291-4">[</span><span class="mi">0</span><span class="p" data-group-id="6664517291-4">]</span><span class="p" data-group-id="6664517291-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="6664517291-5">(</span><span class="n">I</span><span class="p" data-group-id="6664517291-6">[</span><span class="mi">1</span><span class="p" data-group-id="6664517291-6">]</span><span class="p" data-group-id="6664517291-5">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">yb</span><span class="p" data-group-id="6664517291-7">(</span><span class="p" data-group-id="6664517291-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="6664517291-8">)</span><span class="p" data-group-id="6664517291-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="6664517291-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="6664517291-9">)</span><span class="p">;</span><span class="w">
│ │ │ +destination register:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="3626235961-1">(</span><span class="ss">move_xy</span><span class="p" data-group-id="3626235961-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3626235961-2">{</span><span class="w">
│ │ │ +  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">tmp_packed1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamExtraData</span><span class="p" data-group-id="3626235961-3">(</span><span class="n">I</span><span class="p" data-group-id="3626235961-4">[</span><span class="mi">0</span><span class="p" data-group-id="3626235961-4">]</span><span class="p" data-group-id="3626235961-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="3626235961-5">(</span><span class="n">I</span><span class="p" data-group-id="3626235961-6">[</span><span class="mi">1</span><span class="p" data-group-id="3626235961-6">]</span><span class="p" data-group-id="3626235961-5">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">yb</span><span class="p" data-group-id="3626235961-7">(</span><span class="p" data-group-id="3626235961-8">(</span><span class="ss">tmp_packed1</span><span class="p">&gt;&gt;</span><span class="n">BEAM_TIGHT_SHIFT</span><span class="p" data-group-id="3626235961-8">)</span><span class="p" data-group-id="3626235961-7">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="3626235961-9">(</span><span class="ss">tmp_packed1</span><span class="err">&amp;</span><span class="n">BEAM_TIGHT_MASK</span><span class="p" data-group-id="3626235961-9">)</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="6664517291-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="6664517291-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="6664517291-11">)</span><span class="p" data-group-id="6664517291-10">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="6664517291-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="6664517291-12">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6664517291-2">}</span></code></pre><h3 id="transformation-rules" class="section-heading">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="3626235961-10">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3626235961-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="3626235961-11">)</span><span class="p" data-group-id="3626235961-10">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="3626235961-12">(</span><span class="ss">next_pf</span><span class="p" data-group-id="3626235961-12">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3626235961-2">}</span></code></pre><h3 id="transformation-rules" class="section-heading">
│ │ │    <a href="#transformation-rules" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Transformation rules</span>
│ │ │  </h3>
│ │ │  <p>Next let's look at how we can do some optimizations using transformation
│ │ │  rules.  For simple instructions such as <code class="inline">move/2</code>, the instruction dispatch
│ │ │ @@ -271,21 +271,21 @@
│ │ │  with an uppercase letter just as in Erlang.  A pattern variable may be
│ │ │  followed <code class="inline">=</code> and one or more type letters to constrain the match to
│ │ │  one of those types.  The variables that are bound on the left-hand side can
│ │ │  be used on the right-hand side.</p><p>We will also need to define a specific instruction and an implementation:</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">ops</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │  </span><span class="ss">move2</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">instrs</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │ -</span><span class="nf">move2</span><span class="p" data-group-id="5819868671-1">(</span><span class="n">S1</span><span class="p">,</span><span class="w"> </span><span class="n">D1</span><span class="p">,</span><span class="w"> </span><span class="n">S2</span><span class="p">,</span><span class="w"> </span><span class="n">D2</span><span class="p" data-group-id="5819868671-1">)</span><span class="w"> </span><span class="p" data-group-id="5819868671-2">{</span><span class="w">
│ │ │ +</span><span class="nf">move2</span><span class="p" data-group-id="4722559786-1">(</span><span class="n">S1</span><span class="p">,</span><span class="w"> </span><span class="n">D1</span><span class="p">,</span><span class="w"> </span><span class="n">S2</span><span class="p">,</span><span class="w"> </span><span class="n">D2</span><span class="p" data-group-id="4722559786-1">)</span><span class="w"> </span><span class="p" data-group-id="4722559786-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="n">V1</span><span class="p">,</span><span class="w"> </span><span class="n">V2</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">V1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">V2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="mi">1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">V1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="mi">2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">V2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5819868671-2">}</span></code></pre><p>When the loader has found a match and replaced the matched instructions,
│ │ │ +</span><span class="p" data-group-id="4722559786-2">}</span></code></pre><p>When the loader has found a match and replaced the matched instructions,
│ │ │  it will match the new instructions against the transformation rules.
│ │ │  Because of that, we can define the rule for a <code class="inline">move3/6</code> instruction
│ │ │  as follows:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move2</span><span class="w"> </span><span class="n">X1</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y1</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="n">X2</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y2</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">move</span><span class="w"> </span><span class="n">X3</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y3</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │        </span><span class="ss">move3</span><span class="w"> </span><span class="n">X1</span><span class="w"> </span><span class="n">Y1</span><span class="w"> </span><span class="n">X2</span><span class="w"> </span><span class="n">Y2</span><span class="w"> </span><span class="n">X3</span><span class="w"> </span><span class="n">Y3</span></code></pre><p>(For readability, a long transformation line can be broken after <code class="inline">|</code>
│ │ │  and <code class="inline">=&gt;</code> operators.)</p><p>It would also be possible to define it like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="n">X1</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y1</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">move</span><span class="w"> </span><span class="n">X2</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y2</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">move</span><span class="w"> </span><span class="n">X3</span><span class="o">=</span><span class="ss">x</span><span class="w"> </span><span class="n">Y3</span><span class="o">=</span><span class="ss">y</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │       </span><span class="ss">move3</span><span class="w"> </span><span class="n">X1</span><span class="w"> </span><span class="n">Y1</span><span class="w"> </span><span class="n">X2</span><span class="w"> </span><span class="n">Y2</span><span class="w"> </span><span class="n">X3</span><span class="w"> </span><span class="n">Y3</span></code></pre><p>but in that case it must be defined before the rule for <code class="inline">move2/4</code>
│ │ │  because the first matching rule will be applied.</p><p>One must be careful not to create infinite loops.  For example, if we
│ │ │ @@ -433,29 +433,29 @@
│ │ │  </span><span class="ss">i_bs_get_integer_32</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">f</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="c1">%endif</span></code></pre><p>The specific instruction <code class="inline">i_bs_get_integer_32</code> will only be defined
│ │ │  on a 64-bit machine.</p><p>The condition can be inverted by using <code class="inline">%unless</code> instead of <code class="inline">%if</code>:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%unless NO_FPE_SIGNALS</span><span class="w">
│ │ │  </span><span class="ss">fcheckerror</span><span class="w"> </span><span class="ss">p</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">i_fcheckerror</span><span class="w">
│ │ │  </span><span class="ss">i_fcheckerror</span><span class="w">
│ │ │  </span><span class="ss">fclearerror</span><span class="w">
│ │ │  </span><span class="c1">%endif</span></code></pre><p>It is also possible to add an <code class="inline">%else</code> clause:</p><pre><code class="makeup erlang" translate="no"><span class="c1">%if ARCH_64</span><span class="w">
│ │ │ -</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="3562735752-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3562735752-1">)</span><span class="w"> </span><span class="p" data-group-id="3562735752-2">{</span><span class="w">
│ │ │ -    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3562735752-3">(</span><span class="sc">$A</span><span class="p" data-group-id="3562735752-3">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="3562735752-4">(</span><span class="sc">$B</span><span class="p" data-group-id="3562735752-4">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3562735752-5">(</span><span class="ss">res</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="sc">$B</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="p" data-group-id="3562735752-5">)</span><span class="w"> </span><span class="p" data-group-id="3562735752-6">{</span><span class="w">
│ │ │ +</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="0657238778-1">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0657238778-1">)</span><span class="w"> </span><span class="p" data-group-id="0657238778-2">{</span><span class="w">
│ │ │ +    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0657238778-3">(</span><span class="sc">$A</span><span class="p" data-group-id="0657238778-3">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="0657238778-4">(</span><span class="sc">$B</span><span class="p" data-group-id="0657238778-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0657238778-5">(</span><span class="ss">res</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="sc">$B</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="p" data-group-id="0657238778-5">)</span><span class="w"> </span><span class="p" data-group-id="0657238778-6">{</span><span class="w">
│ │ │          </span><span class="sc">$F</span><span class="ss">ail</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3562735752-6">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0657238778-6">}</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3562735752-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0657238778-2">}</span><span class="w">
│ │ │  </span><span class="c1">%else</span><span class="w">
│ │ │ -</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="3562735752-7">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3562735752-7">)</span><span class="w"> </span><span class="p" data-group-id="3562735752-8">{</span><span class="w">
│ │ │ -    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3562735752-9">(</span><span class="n">Uint64</span><span class="p" data-group-id="3562735752-9">)</span><span class="p" data-group-id="3562735752-10">(</span><span class="sc">$A</span><span class="p" data-group-id="3562735752-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="3562735752-11">(</span><span class="n">Uint64</span><span class="p" data-group-id="3562735752-11">)</span><span class="p" data-group-id="3562735752-12">(</span><span class="sc">$B</span><span class="p" data-group-id="3562735752-12">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3562735752-13">(</span><span class="p" data-group-id="3562735752-14">(</span><span class="ss">res</span><span class="w"> </span><span class="p">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="3562735752-15">(</span><span class="mi">8</span><span class="o">*</span><span class="nf">sizeof</span><span class="p" data-group-id="3562735752-16">(</span><span class="n">Uint</span><span class="p" data-group-id="3562735752-16">)</span><span class="p" data-group-id="3562735752-15">)</span><span class="p" data-group-id="3562735752-14">)</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3562735752-13">)</span><span class="w"> </span><span class="p" data-group-id="3562735752-17">{</span><span class="w">
│ │ │ +</span><span class="n">BS_SAFE_MUL</span><span class="p" data-group-id="0657238778-7">(</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0657238778-7">)</span><span class="w"> </span><span class="p" data-group-id="0657238778-8">{</span><span class="w">
│ │ │ +    </span><span class="n">Uint64</span><span class="w"> </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0657238778-9">(</span><span class="n">Uint64</span><span class="p" data-group-id="0657238778-9">)</span><span class="p" data-group-id="0657238778-10">(</span><span class="sc">$A</span><span class="p" data-group-id="0657238778-10">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="0657238778-11">(</span><span class="n">Uint64</span><span class="p" data-group-id="0657238778-11">)</span><span class="p" data-group-id="0657238778-12">(</span><span class="sc">$B</span><span class="p" data-group-id="0657238778-12">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0657238778-13">(</span><span class="p" data-group-id="0657238778-14">(</span><span class="ss">res</span><span class="w"> </span><span class="p">&gt;&gt;</span><span class="w"> </span><span class="p" data-group-id="0657238778-15">(</span><span class="mi">8</span><span class="o">*</span><span class="nf">sizeof</span><span class="p" data-group-id="0657238778-16">(</span><span class="n">Uint</span><span class="p" data-group-id="0657238778-16">)</span><span class="p" data-group-id="0657238778-15">)</span><span class="p" data-group-id="0657238778-14">)</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="0657238778-13">)</span><span class="w"> </span><span class="p" data-group-id="0657238778-17">{</span><span class="w">
│ │ │          </span><span class="sc">$F</span><span class="ss">ail</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3562735752-17">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0657238778-17">}</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3562735752-8">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0657238778-8">}</span><span class="w">
│ │ │  </span><span class="c1">%endif</span></code></pre><h4>Symbols that are defined in directives</h4><p>The following symbols are always defined.</p><ul><li><code class="inline">ARCH_64</code> - is 1 for a 64-bit machine, and 0 otherwise.</li><li><code class="inline">ARCH_32</code> - is 1 for 32-bit machine, and 0 otherwise.</li></ul><p>The <code class="inline">Makefile</code> for building the emulator currently defines the
│ │ │  following symbols by using the <code class="inline">-D</code> option on the command line for
│ │ │  <strong>beam_makeops</strong>.</p><ul><li><code class="inline">USE_VM_PROBES</code> - 1 if the runtime system is compiled to use VM
│ │ │  probes (support for dtrace or systemtap), 0 otherwise.</li></ul><h3 id="defining-external-generic-instructions" class="section-heading">
│ │ │    <a href="#defining-external-generic-instructions" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -676,15 +676,15 @@
│ │ │  match both source and destination registers.  As an operand in a specific
│ │ │  instruction, it must only be used for a destination register.)</p></li><li><p><code class="inline">o</code> - Overflow.  An untagged integer that does not fit in a machine word.</p></li></ul><h4>Predicates</h4><p>If the constraints described so far is not enough, additional
│ │ │  constraints can be implemented in C and be called as a guard function
│ │ │  on the left-hand side of the transformation.  If the guard function returns
│ │ │  a non-zero value, the matching of the rule will continue, otherwise
│ │ │  the match will fail.  Such guard functions are hereafter called
│ │ │  <em>predicates</em>.</p><p>The most commonly used guard constraints is <code class="inline">equal()</code>. It can be used
│ │ │ -to remove a redundant <code class="inline">move</code> instructio like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="n">R1</span><span class="w"> </span><span class="n">R2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="8972172484-1">(</span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="8972172484-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>or remove a redundant <code class="inline">is_eq_exact</code> instruction like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">is_eq_exact</span><span class="w"> </span><span class="n">Lbl</span><span class="w"> </span><span class="n">Src1</span><span class="w"> </span><span class="n">Src2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="9752793306-1">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="9752793306-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>At the time of writing, all predicates are defined in files named
│ │ │ +to remove a redundant <code class="inline">move</code> instructio like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="n">R1</span><span class="w"> </span><span class="n">R2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="0713720917-1">(</span><span class="n">R1</span><span class="p">,</span><span class="w"> </span><span class="n">R2</span><span class="p" data-group-id="0713720917-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>or remove a redundant <code class="inline">is_eq_exact</code> instruction like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">is_eq_exact</span><span class="w"> </span><span class="n">Lbl</span><span class="w"> </span><span class="n">Src1</span><span class="w"> </span><span class="n">Src2</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="nf">equal</span><span class="p" data-group-id="2738550603-1">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="2738550603-1">)</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p">_</span></code></pre><p>At the time of writing, all predicates are defined in files named
│ │ │  <code class="inline">predicates.tab</code> in several directories.  In <code class="inline">predicates.tab</code> directly
│ │ │  in <code class="inline">$ERL_TOP/erts/emulator/beam</code>, predicates that are used by both the
│ │ │  traditinal emulator and the JIT implementations are contained.
│ │ │  Predicates only used by the emulator can be found in
│ │ │  <code class="inline">emu/predicates.tab</code>.</p><h3 id="a-very-brief-note-on-implementation-of-predicates" class="section-heading">
│ │ │    <a href="#a-very-brief-note-on-implementation-of-predicates" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -692,41 +692,41 @@
│ │ │    <span class="text">A very brief note on implementation of predicates</span>
│ │ │  </h3>
│ │ │  <p>It is outside the scope for this document to describe in detail how
│ │ │  predicates are implemented because it requires knowledge of the
│ │ │  internal loader data structures, but here is quick look at the
│ │ │  implementation of a simple predicate called <code class="inline">literal_is_map()</code>.</p><p>Here is first an example how it is used:</p><p>   is<em>map Fail Lit=q | literal_is_map(Lit) =&gt; </em></p><p>If the <code class="inline">Lit</code> operand is a literal, then the <code class="inline">literal_is_map()</code>
│ │ │  predicate is called to determine whether it is a map literal.
│ │ │ -If it is, the instruction is not needed and can be removed.</p><p><code class="inline">literal_is_map()</code> is implemented like this (in <code class="inline">emu/predicates.tab</code>):</p><pre><code class="makeup erlang" translate="no"><span class="ss">pred</span><span class="p">.</span><span class="nf">literal_is_map</span><span class="p" data-group-id="1844709818-1">(</span><span class="n">Lit</span><span class="p" data-group-id="1844709818-1">)</span><span class="w"> </span><span class="p" data-group-id="1844709818-2">{</span><span class="w">
│ │ │ +If it is, the instruction is not needed and can be removed.</p><p><code class="inline">literal_is_map()</code> is implemented like this (in <code class="inline">emu/predicates.tab</code>):</p><pre><code class="makeup erlang" translate="no"><span class="ss">pred</span><span class="p">.</span><span class="nf">literal_is_map</span><span class="p" data-group-id="7648045377-1">(</span><span class="n">Lit</span><span class="p" data-group-id="7648045377-1">)</span><span class="w"> </span><span class="p" data-group-id="7648045377-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="1844709818-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="1844709818-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">beamfile_get_literal</span><span class="p" data-group-id="1844709818-4">(</span><span class="err">&amp;</span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">beam</span><span class="p">,</span><span class="w"> </span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="1844709818-4">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="1844709818-5">(</span><span class="ss">term</span><span class="p" data-group-id="1844709818-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1844709818-2">}</span></code></pre><p>The <code class="inline">pred.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="7648045377-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="7648045377-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">beamfile_get_literal</span><span class="p" data-group-id="7648045377-4">(</span><span class="err">&amp;</span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">beam</span><span class="p">,</span><span class="w"> </span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="7648045377-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="7648045377-5">(</span><span class="ss">term</span><span class="p" data-group-id="7648045377-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7648045377-2">}</span></code></pre><p>The <code class="inline">pred.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │  predicate.  Without the prefix, it would have been interpreted as the
│ │ │  implementation of an instruction (described in <strong>Defining the
│ │ │  implementation</strong>).</p><p>Predicate functions have a magic variabled called <code class="inline">S</code>, which is a
│ │ │  pointer to a state struct. In the example,
│ │ │  <code class="inline">beamfile_get_literal(&amp;S-&gt;beam, Lit.val);</code> is used to retrieve the actual term
│ │ │  for the literal.</p><p>At the time of writing, the expanded C code generated by
│ │ │ -<strong>beam_makeops</strong> looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">static</span><span class="w"> </span><span class="ss">int</span><span class="w"> </span><span class="nf">literal_is_map</span><span class="p" data-group-id="2486144592-1">(</span><span class="n">LoaderState</span><span class="o">*</span><span class="w"> </span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="n">BeamOpArg</span><span class="w"> </span><span class="n">Lit</span><span class="p" data-group-id="2486144592-1">)</span><span class="w"> </span><span class="p" data-group-id="2486144592-2">{</span><span class="w">
│ │ │ +<strong>beam_makeops</strong> looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">static</span><span class="w"> </span><span class="ss">int</span><span class="w"> </span><span class="nf">literal_is_map</span><span class="p" data-group-id="1628591723-1">(</span><span class="n">LoaderState</span><span class="o">*</span><span class="w"> </span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="n">BeamOpArg</span><span class="w"> </span><span class="n">Lit</span><span class="p" data-group-id="1628591723-1">)</span><span class="w"> </span><span class="p" data-group-id="1628591723-2">{</span><span class="w">
│ │ │    </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="2486144592-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="2486144592-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">literals</span><span class="p" data-group-id="2486144592-4">[</span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="2486144592-4">]</span><span class="p">.</span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="2486144592-5">(</span><span class="ss">term</span><span class="p" data-group-id="2486144592-5">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2486144592-2">}</span></code></pre><h4>Handling instructions with variable number of operands</h4><p>Some instructions, such as <code class="inline">select_val/3</code>, essentially has a variable
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="1628591723-3">(</span><span class="n">Lit</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_q</span><span class="p" data-group-id="1628591723-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">S</span><span class="p">-&gt;</span><span class="ss">literals</span><span class="p" data-group-id="1628591723-4">[</span><span class="n">Lit</span><span class="p">.</span><span class="ss">val</span><span class="p" data-group-id="1628591723-4">]</span><span class="p">.</span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">return</span><span class="w"> </span><span class="nf">is_map</span><span class="p" data-group-id="1628591723-5">(</span><span class="ss">term</span><span class="p" data-group-id="1628591723-5">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1628591723-2">}</span></code></pre><h4>Handling instructions with variable number of operands</h4><p>Some instructions, such as <code class="inline">select_val/3</code>, essentially has a variable
│ │ │  number of operands.  Such instructions have a <code class="inline">{list,[...]}</code> operand
│ │ │ -as their last operand in the BEAM assembly code.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3753039456-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="3753039456-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="3753039456-2">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3753039456-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3753039456-3">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3753039456-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="3753039456-5">[</span><span class="p" data-group-id="3753039456-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3753039456-6">}</span><span class="p">,</span><span class="p" data-group-id="3753039456-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3753039456-7">}</span><span class="p">,</span><span class="p" data-group-id="3753039456-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3753039456-8">}</span><span class="p">,</span><span class="p" data-group-id="3753039456-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3753039456-9">}</span><span class="p" data-group-id="3753039456-5">]</span><span class="p" data-group-id="3753039456-4">}</span><span class="p" data-group-id="3753039456-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │ +as their last operand in the BEAM assembly code.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6133309167-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="6133309167-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="6133309167-2">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6133309167-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6133309167-3">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="6133309167-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="6133309167-5">[</span><span class="p" data-group-id="6133309167-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6133309167-6">}</span><span class="p">,</span><span class="p" data-group-id="6133309167-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6133309167-7">}</span><span class="p">,</span><span class="p" data-group-id="6133309167-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6133309167-8">}</span><span class="p">,</span><span class="p" data-group-id="6133309167-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6133309167-9">}</span><span class="p" data-group-id="6133309167-5">]</span><span class="p" data-group-id="6133309167-4">}</span><span class="p" data-group-id="6133309167-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │  value is the number of elements in the list, followed by each element in
│ │ │  the list.  The instruction above would be translated to the following
│ │ │ -generic instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0713225727-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="0713225727-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0713225727-2">}</span><span class="p">,</span><span class="p" data-group-id="0713225727-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0713225727-3">}</span><span class="p">,</span><span class="p" data-group-id="0713225727-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0713225727-4">}</span><span class="p">,</span><span class="p" data-group-id="0713225727-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="0713225727-5">}</span><span class="p">,</span><span class="p" data-group-id="0713225727-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0713225727-6">}</span><span class="p">,</span><span class="p" data-group-id="0713225727-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="0713225727-7">}</span><span class="p">,</span><span class="p" data-group-id="0713225727-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0713225727-8">}</span><span class="p" data-group-id="0713225727-1">}</span></code></pre><p>To match a variable number of arguments we need to use the special
│ │ │ +generic instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="1754270611-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="1754270611-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="1754270611-2">}</span><span class="p">,</span><span class="p" data-group-id="1754270611-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1754270611-3">}</span><span class="p">,</span><span class="p" data-group-id="1754270611-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1754270611-4">}</span><span class="p">,</span><span class="p" data-group-id="1754270611-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="1754270611-5">}</span><span class="p">,</span><span class="p" data-group-id="1754270611-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="1754270611-6">}</span><span class="p">,</span><span class="p" data-group-id="1754270611-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="1754270611-7">}</span><span class="p">,</span><span class="p" data-group-id="1754270611-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="1754270611-8">}</span><span class="p" data-group-id="1754270611-1">}</span></code></pre><p>To match a variable number of arguments we need to use the special
│ │ │  operand type <code class="inline">*</code> like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">select_val</span><span class="w"> </span><span class="n">Src</span><span class="o">=</span><span class="ss">aiq</span><span class="w"> </span><span class="n">Fail</span><span class="o">=</span><span class="ss">f</span><span class="w"> </span><span class="n">Size</span><span class="o">=</span><span class="ss">u</span><span class="w"> </span><span class="n">List</span><span class="o">=</span><span class="o">*</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │      </span><span class="ss">i_const_select_val</span><span class="w"> </span><span class="n">Src</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="n">Size</span><span class="w"> </span><span class="n">List</span></code></pre><p>This transformation renames a <code class="inline">select_val/3</code> instruction
│ │ │  with a constant source operand to <code class="inline">i_const_select_val/3</code>.</p><h4>Constructing new instructions on the right-hand side</h4><p>The most common operand on the right-hand side is a variable that was
│ │ │  bound while matching the pattern on the left-hand side.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">trim</span><span class="w"> </span><span class="n">N</span><span class="w"> </span><span class="n">Remaining</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">i_trim</span><span class="w"> </span><span class="n">N</span></code></pre><p>An operand can also be a type letter to construct an operand of that
│ │ │  type.  Each type has a default value.  For example, the type <code class="inline">x</code> has
│ │ │  the default value 1023, which is the highest X register.  That makes
│ │ │  <code class="inline">x</code> on the right-hand side a convenient shortcut for a temporary X
│ │ │ @@ -746,53 +746,53 @@
│ │ │  transformation rule.</p><ul><li><p><code class="inline">u</code> - Construct an untagged integer.  The default value is 0.</p></li><li><p><code class="inline">x</code> - X register.  The default value is 1023.  That makes <code class="inline">x</code> convenient to
│ │ │  use as a temporary X register.</p></li><li><p><code class="inline">y</code> - Y register.  The default value is 0.</p></li><li><p><code class="inline">l</code> - Floating point register number.  The default value is 0.</p></li><li><p><code class="inline">i</code> - Tagged literal integer.  The default value is 0.</p></li><li><p><code class="inline">a</code> - Tagged atom.  The default value is the empty atom (<code class="inline">am_Empty</code>).</p></li><li><p><code class="inline">p</code> - Zero failure label.</p></li><li><p><code class="inline">n</code> - NIL (<code class="inline">[]</code>, the empty list).</p></li></ul><h4>Function call on the right-hand side</h4><p>Transformations that are not possible to describe with the rule
│ │ │  language as described here can be implemented as a generator function
│ │ │  in C and called from the right-hand side of a transformation.  The left-hand
│ │ │  side of the transformation will perform the match and bind operands to
│ │ │  variables.  The variables can then be passed to a generator function
│ │ │  on the right-hand side.  For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">bif2</span><span class="w"> </span><span class="n">Fail</span><span class="o">=</span><span class="ss">j</span><span class="w"> </span><span class="ss">u</span><span class="sc">$b</span><span class="nc">if</span><span class="p">:</span><span class="nc">erlang</span><span class="p">:</span><span class="nb">element</span><span class="p">/</span><span class="mi">2</span><span class="w"> </span><span class="n">Index</span><span class="o">=</span><span class="ss">s</span><span class="w"> </span><span class="n">Tuple</span><span class="o">=</span><span class="ss">xy</span><span class="w"> </span><span class="n">Dst</span><span class="o">=</span><span class="ss">d</span><span class="w"> </span><span class="p">=&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">element</span><span class="p" data-group-id="2284940500-1">(</span><span class="n">Jump</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="2284940500-1">)</span></code></pre><p>This transformation rule matches a call to the BIF <a href="erlang.html#element/2"><code class="inline">element/2</code></a>.
│ │ │ +    </span><span class="nf">element</span><span class="p" data-group-id="0646923355-1">(</span><span class="n">Jump</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0646923355-1">)</span></code></pre><p>This transformation rule matches a call to the BIF <a href="erlang.html#element/2"><code class="inline">element/2</code></a>.
│ │ │  The operands will be captured and the generator function <code class="inline">element()</code> will
│ │ │  be called.</p><p>The <code class="inline">element()</code> generator will produce one of two instructions
│ │ │  depending on <code class="inline">Index</code>.  If <code class="inline">Index</code> is an integer in the range from 1 up
│ │ │  to the maximum tuple size, the instruction <code class="inline">i_fast_element/2</code> will be
│ │ │  produced, otherwise the instruction <code class="inline">i_element/4</code> will be produced.
│ │ │  The corresponding specific instructions are:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_fast_element</span><span class="w"> </span><span class="ss">xy</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_element</span><span class="w"> </span><span class="ss">xy</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The <code class="inline">i_fast_element/2</code> instruction is faster because the tuple is
│ │ │  already an untagged integer.  It also knows that the index is at least
│ │ │  1, so it does not have to test for that.  The <code class="inline">i_element/4</code>
│ │ │  instruction will have to fetch the index from a register, test that it
│ │ │  is an integer, and untag the integer.</p><p>At the time of writing, all generators functions were defined in files
│ │ │  named <code class="inline">generators.tab</code> in several directories (in the same directories
│ │ │  as the <code class="inline">predicates.tab</code> files).</p><p>It is outside the scope of this document to describe in detail how
│ │ │  generator functions are written, but here is the implementation of
│ │ │ -<code class="inline">element()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">gen</span><span class="p">.</span><span class="nf">element</span><span class="p" data-group-id="0267309217-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0267309217-1">)</span><span class="w"> </span><span class="p" data-group-id="0267309217-2">{</span><span class="w">
│ │ │ +<code class="inline">element()</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">gen</span><span class="p">.</span><span class="nf">element</span><span class="p" data-group-id="3028977102-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Index</span><span class="p">,</span><span class="w"> </span><span class="n">Tuple</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3028977102-1">)</span><span class="w"> </span><span class="p" data-group-id="3028977102-2">{</span><span class="w">
│ │ │      </span><span class="n">BeamOp</span><span class="o">*</span><span class="w"> </span><span class="ss">op</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="sc">$N</span><span class="nf">ewBeamOp</span><span class="p" data-group-id="0267309217-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="ss">op</span><span class="p" data-group-id="0267309217-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$N</span><span class="nf">ewBeamOp</span><span class="p" data-group-id="3028977102-3">(</span><span class="n">S</span><span class="p">,</span><span class="w"> </span><span class="ss">op</span><span class="p" data-group-id="3028977102-3">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0267309217-4">(</span><span class="n">Index</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_i</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3028977102-4">(</span><span class="n">Index</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_i</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w">
│ │ │          </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">ERTS_MAX_TUPLE_SIZE</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0267309217-5">(</span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_y</span><span class="p" data-group-id="0267309217-5">)</span><span class="p" data-group-id="0267309217-4">)</span><span class="w"> </span><span class="p" data-group-id="0267309217-6">{</span><span class="w">
│ │ │ -        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="0267309217-7">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_fast_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="0267309217-7">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-8">[</span><span class="mi">0</span><span class="p" data-group-id="0267309217-8">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-9">[</span><span class="mi">1</span><span class="p" data-group-id="0267309217-9">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-10">[</span><span class="mi">2</span><span class="p" data-group-id="0267309217-10">]</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TAG_u</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-11">[</span><span class="mi">2</span><span class="p" data-group-id="0267309217-11">]</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-12">[</span><span class="mi">3</span><span class="p" data-group-id="0267309217-12">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0267309217-6">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p" data-group-id="0267309217-13">{</span><span class="w">
│ │ │ -        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="0267309217-14">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="0267309217-14">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-15">[</span><span class="mi">0</span><span class="p" data-group-id="0267309217-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-16">[</span><span class="mi">1</span><span class="p" data-group-id="0267309217-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-17">[</span><span class="mi">2</span><span class="p" data-group-id="0267309217-17">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="0267309217-18">[</span><span class="mi">3</span><span class="p" data-group-id="0267309217-18">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0267309217-13">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="3028977102-5">(</span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_x</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">Tuple</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">TAG_y</span><span class="p" data-group-id="3028977102-5">)</span><span class="p" data-group-id="3028977102-4">)</span><span class="w"> </span><span class="p" data-group-id="3028977102-6">{</span><span class="w">
│ │ │ +        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="3028977102-7">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_fast_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3028977102-7">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-8">[</span><span class="mi">0</span><span class="p" data-group-id="3028977102-8">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-9">[</span><span class="mi">1</span><span class="p" data-group-id="3028977102-9">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-10">[</span><span class="mi">2</span><span class="p" data-group-id="3028977102-10">]</span><span class="p">.</span><span class="ss">type</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">TAG_u</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-11">[</span><span class="mi">2</span><span class="p" data-group-id="3028977102-11">]</span><span class="p">.</span><span class="ss">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">.</span><span class="ss">val</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-12">[</span><span class="mi">3</span><span class="p" data-group-id="3028977102-12">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3028977102-6">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p" data-group-id="3028977102-13">{</span><span class="w">
│ │ │ +        </span><span class="sc">$B</span><span class="nf">eamOpNameArity</span><span class="p" data-group-id="3028977102-14">(</span><span class="ss">op</span><span class="p">,</span><span class="w"> </span><span class="ss">i_element</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3028977102-14">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-15">[</span><span class="mi">0</span><span class="p" data-group-id="3028977102-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Tuple</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-16">[</span><span class="mi">1</span><span class="p" data-group-id="3028977102-16">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Fail</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-17">[</span><span class="mi">2</span><span class="p" data-group-id="3028977102-17">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Index</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="ss">op</span><span class="p">-&gt;</span><span class="ss">a</span><span class="p" data-group-id="3028977102-18">[</span><span class="mi">3</span><span class="p" data-group-id="3028977102-18">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dst</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="3028977102-13">}</span><span class="w">
│ │ │  
│ │ │      </span><span class="ss">return</span><span class="w"> </span><span class="ss">op</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0267309217-2">}</span></code></pre><p>The <code class="inline">gen.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │ +</span><span class="p" data-group-id="3028977102-2">}</span></code></pre><p>The <code class="inline">gen.</code> prefix tells <strong>beam_makeops</strong> that this function is a
│ │ │  generator.  Without the prefix, it would have been interpreted as the
│ │ │  implementation of an instruction (described in <strong>Defining the
│ │ │  implementation</strong>).</p><p>Generator functions have a magic variabled called <code class="inline">S</code>, which is a
│ │ │  pointer to a state struct.  In the example, <code class="inline">S</code> is used in the invocation
│ │ │  of the <code class="inline">NewBeamOp</code> macro.</p><h3 id="defining-the-implementation" class="section-heading">
│ │ │    <a href="#defining-the-implementation" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -814,473 +814,473 @@
│ │ │  </span><span class="ss">msg_instrs</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │  </span><span class="ss">select_instrs</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │  </span><span class="ss">trace_instrs</span><span class="p">.</span><span class="ss">tab</span></code></pre><p>There is also a file that only contains macro definitions:</p><pre><code class="makeup erlang" translate="no"><span class="ss">macros</span><span class="p">.</span><span class="ss">tab</span></code></pre><p>The syntax of each file is similar to C code.  In fact, most of
│ │ │  the contents <em>is</em> C code, interspersed with macro invocations.</p><p>To allow Emacs to auto-indent the code, each file starts with the
│ │ │  following line:</p><pre><code class="makeup erlang" translate="no"><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="o">-</span><span class="o">*</span><span class="o">-</span><span class="w"> </span><span class="ss">c</span><span class="w"> </span><span class="o">-</span><span class="o">*</span><span class="o">-</span></code></pre><p>To avoid messing up the indentation, all comments are written
│ │ │  as C++ style comments (<code class="inline">//</code>) instead of <code class="inline">#</code>.  Note that a comment
│ │ │  must start at the beginning of a line.</p><p>The meat of an instruction definition file are macro definitions.
│ │ │ -We have seen this macro definition before:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="4309105967-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="4309105967-1">)</span><span class="w"> </span><span class="p" data-group-id="4309105967-2">{</span><span class="w">
│ │ │ +We have seen this macro definition before:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="0953688872-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0953688872-1">)</span><span class="w"> </span><span class="p" data-group-id="0953688872-2">{</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4309105967-2">}</span></code></pre><p>A macro definitions must start at the beginning of the line (no spaces
│ │ │ +</span><span class="p" data-group-id="0953688872-2">}</span></code></pre><p>A macro definitions must start at the beginning of the line (no spaces
│ │ │  allowed), the opening curly bracket must be on the same line, and the
│ │ │  finishing curly bracket must be at the beginning of a line.  It is
│ │ │  recommended that the macro body is properly indented.</p><p>As a convention, the macro arguments in the head all start with an
│ │ │  uppercase letter.  In the body, the macro arguments can be expanded
│ │ │  by preceding them with <code class="inline">$</code>.</p><p>A macro definition whose name and arity matches a family of
│ │ │  specific instructions is assumed to be the implementation of that
│ │ │  instruction.</p><p>A macro can also be invoked from within another macro.  For example,
│ │ │  <code class="inline">move_deallocate_return/2</code> avoids repeating code by invoking
│ │ │ -<code class="inline">$deallocate_return()</code> as a macro:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move_deallocate_return</span><span class="p" data-group-id="0684139084-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Deallocate</span><span class="p" data-group-id="0684139084-1">)</span><span class="w"> </span><span class="p" data-group-id="0684139084-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">x</span><span class="p" data-group-id="0684139084-3">(</span><span class="mi">0</span><span class="p" data-group-id="0684139084-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="0684139084-4">(</span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="0684139084-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0684139084-2">}</span></code></pre><p>Here is the definition of <code class="inline">deallocate_return/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">deallocate_return</span><span class="p" data-group-id="5942968222-1">(</span><span class="n">Deallocate</span><span class="p" data-group-id="5942968222-1">)</span><span class="w"> </span><span class="p" data-group-id="5942968222-2">{</span><span class="w">
│ │ │ +<code class="inline">$deallocate_return()</code> as a macro:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move_deallocate_return</span><span class="p" data-group-id="0027850406-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Deallocate</span><span class="p" data-group-id="0027850406-1">)</span><span class="w"> </span><span class="p" data-group-id="0027850406-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">x</span><span class="p" data-group-id="0027850406-3">(</span><span class="mi">0</span><span class="p" data-group-id="0027850406-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="0027850406-4">(</span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="0027850406-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0027850406-2">}</span></code></pre><p>Here is the definition of <code class="inline">deallocate_return/1</code>:</p><pre><code class="makeup erlang" translate="no"><span class="nf">deallocate_return</span><span class="p" data-group-id="7012439899-1">(</span><span class="n">Deallocate</span><span class="p" data-group-id="7012439899-1">)</span><span class="w"> </span><span class="p" data-group-id="7012439899-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │      </span><span class="ss">int</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">SET_I</span><span class="p" data-group-id="5942968222-3">(</span><span class="p" data-group-id="5942968222-4">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="5942968222-4">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="5942968222-5">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="5942968222-5">)</span><span class="p" data-group-id="5942968222-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="5942968222-6">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="5942968222-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="5942968222-7">(</span><span class="nf">x</span><span class="p" data-group-id="5942968222-8">(</span><span class="mi">0</span><span class="p" data-group-id="5942968222-8">)</span><span class="p" data-group-id="5942968222-7">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">SET_I</span><span class="p" data-group-id="7012439899-3">(</span><span class="p" data-group-id="7012439899-4">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="7012439899-4">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="7012439899-5">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="7012439899-5">)</span><span class="p" data-group-id="7012439899-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="7012439899-6">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="7012439899-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="7012439899-7">(</span><span class="nf">x</span><span class="p" data-group-id="7012439899-8">(</span><span class="mi">0</span><span class="p" data-group-id="7012439899-8">)</span><span class="p" data-group-id="7012439899-7">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">DispatchReturn</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5942968222-2">}</span></code></pre><p>The expanded code for <code class="inline">move_deallocate_return</code> will look this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="1230753540-1">(</span><span class="ss">move_deallocate_return_cQ</span><span class="p" data-group-id="1230753540-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1230753540-2">{</span><span class="w">
│ │ │ -  </span><span class="nf">x</span><span class="p" data-group-id="1230753540-3">(</span><span class="mi">0</span><span class="p" data-group-id="1230753540-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="1230753540-4">[</span><span class="mi">1</span><span class="p" data-group-id="1230753540-4">]</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="1230753540-5">{</span><span class="w">
│ │ │ -    </span><span class="ss">int</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Qb</span><span class="p" data-group-id="1230753540-6">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="1230753540-7">(</span><span class="n">I</span><span class="p" data-group-id="1230753540-8">[</span><span class="mi">0</span><span class="p" data-group-id="1230753540-8">]</span><span class="p" data-group-id="1230753540-7">)</span><span class="p" data-group-id="1230753540-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">SET_I</span><span class="p" data-group-id="1230753540-9">(</span><span class="p" data-group-id="1230753540-10">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="1230753540-10">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="1230753540-11">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="1230753540-11">)</span><span class="p" data-group-id="1230753540-9">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="1230753540-12">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="1230753540-12">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="1230753540-13">(</span><span class="nf">x</span><span class="p" data-group-id="1230753540-14">(</span><span class="mi">0</span><span class="p" data-group-id="1230753540-14">)</span><span class="p" data-group-id="1230753540-13">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7012439899-2">}</span></code></pre><p>The expanded code for <code class="inline">move_deallocate_return</code> will look this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="0537234515-1">(</span><span class="ss">move_deallocate_return_cQ</span><span class="p" data-group-id="0537234515-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0537234515-2">{</span><span class="w">
│ │ │ +  </span><span class="nf">x</span><span class="p" data-group-id="0537234515-3">(</span><span class="mi">0</span><span class="p" data-group-id="0537234515-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="0537234515-4">[</span><span class="mi">1</span><span class="p" data-group-id="0537234515-4">]</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="0537234515-5">{</span><span class="w">
│ │ │ +    </span><span class="ss">int</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Qb</span><span class="p" data-group-id="0537234515-6">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="0537234515-7">(</span><span class="n">I</span><span class="p" data-group-id="0537234515-8">[</span><span class="mi">0</span><span class="p" data-group-id="0537234515-8">]</span><span class="p" data-group-id="0537234515-7">)</span><span class="p" data-group-id="0537234515-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">SET_I</span><span class="p" data-group-id="0537234515-9">(</span><span class="p" data-group-id="0537234515-10">(</span><span class="n">BeamInstr</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="0537234515-10">)</span><span class="w"> </span><span class="nf">cp_val</span><span class="p" data-group-id="0537234515-11">(</span><span class="o">*</span><span class="n">E</span><span class="p" data-group-id="0537234515-11">)</span><span class="p" data-group-id="0537234515-9">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ADD_BYTE_OFFSET</span><span class="p" data-group-id="0537234515-12">(</span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="ss">words_to_pop</span><span class="p" data-group-id="0537234515-12">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">CHECK_TERM</span><span class="p" data-group-id="0537234515-13">(</span><span class="nf">x</span><span class="p" data-group-id="0537234515-14">(</span><span class="mi">0</span><span class="p" data-group-id="0537234515-14">)</span><span class="p" data-group-id="0537234515-13">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">DispatchReturn</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="1230753540-5">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="1230753540-15">(</span><span class="mi">0</span><span class="p" data-group-id="1230753540-15">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1230753540-2">}</span></code></pre><p>When expanding macros, <strong>beam_makeops</strong> wraps the expansion in a
│ │ │ +  </span><span class="p" data-group-id="0537234515-5">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="0537234515-15">(</span><span class="mi">0</span><span class="p" data-group-id="0537234515-15">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0537234515-2">}</span></code></pre><p>When expanding macros, <strong>beam_makeops</strong> wraps the expansion in a
│ │ │  <code class="inline">do</code>/<code class="inline">while</code> wrapper unless <strong>beam_makeops</strong> can clearly see that no
│ │ │  wrapper is needed.  In this case, the wrapper is needed.</p><p>Note that arguments for macros cannot be complex expressions, because
│ │ │  the arguments are split on <code class="inline">,</code>.  For example, the following would
│ │ │  not work because <strong>beam_makeops</strong> would split the expression into
│ │ │ -two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="1420937050-1">(</span><span class="nf">get_deallocation</span><span class="p" data-group-id="1420937050-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="1420937050-2">)</span><span class="p" data-group-id="1420937050-1">)</span><span class="p">;</span></code></pre><h4>Code generation directives</h4><p>Within macro definitions, <code class="inline">//</code> comments are in general not treated
│ │ │ +two arguments:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$d</span><span class="nf">eallocate_return</span><span class="p" data-group-id="2790858048-1">(</span><span class="nf">get_deallocation</span><span class="p" data-group-id="2790858048-2">(</span><span class="ss">y</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="ss">eallocate</span><span class="p" data-group-id="2790858048-2">)</span><span class="p" data-group-id="2790858048-1">)</span><span class="p">;</span></code></pre><h4>Code generation directives</h4><p>Within macro definitions, <code class="inline">//</code> comments are in general not treated
│ │ │  specially.  They will be copied to the file with the generated code
│ │ │  along with the rest of code in the body.</p><p>However, there is an exception. Within a macro definition, a line that
│ │ │  starts with whitespace followed by <code class="inline">//|</code> is treated specially.  The
│ │ │  rest of the line is assumed to contain directives to control code
│ │ │  generation.</p><p>Currently, two code generation directives are recognized:</p><ul><li><code class="inline">-no_prefetch</code></li><li><code class="inline">-no_next</code></li></ul><h5>The -no_prefetch directive</h5><p>To see what <code class="inline">-no_prefetch</code> does, let's first look at the default code
│ │ │ -generation.  Here is the code generated for <code class="inline">move_cx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="7118850110-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="7118850110-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7118850110-2">{</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="7118850110-3">(</span><span class="n">I</span><span class="p" data-group-id="7118850110-4">[</span><span class="mi">2</span><span class="p" data-group-id="7118850110-4">]</span><span class="p" data-group-id="7118850110-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="7118850110-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7118850110-6">(</span><span class="n">I</span><span class="p" data-group-id="7118850110-7">[</span><span class="mi">0</span><span class="p" data-group-id="7118850110-7">]</span><span class="p" data-group-id="7118850110-6">)</span><span class="p" data-group-id="7118850110-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="7118850110-8">[</span><span class="mi">1</span><span class="p" data-group-id="7118850110-8">]</span><span class="p">;</span><span class="w">
│ │ │ +generation.  Here is the code generated for <code class="inline">move_cx</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="7354279877-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="7354279877-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7354279877-2">{</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="7354279877-3">(</span><span class="n">I</span><span class="p" data-group-id="7354279877-4">[</span><span class="mi">2</span><span class="p" data-group-id="7354279877-4">]</span><span class="p" data-group-id="7354279877-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="7354279877-5">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7354279877-6">(</span><span class="n">I</span><span class="p" data-group-id="7354279877-7">[</span><span class="mi">0</span><span class="p" data-group-id="7354279877-7">]</span><span class="p" data-group-id="7354279877-6">)</span><span class="p" data-group-id="7354279877-5">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="7354279877-8">[</span><span class="mi">1</span><span class="p" data-group-id="7354279877-8">]</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="7118850110-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7118850110-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="7118850110-10">)</span><span class="p" data-group-id="7118850110-9">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="7118850110-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="7118850110-11">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7118850110-2">}</span></code></pre><p>Note that the very first thing done is to fetch the address to the
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="7354279877-9">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7354279877-10">(</span><span class="ss">next_pf</span><span class="p" data-group-id="7354279877-10">)</span><span class="p" data-group-id="7354279877-9">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="7354279877-11">(</span><span class="ss">next_pf</span><span class="p" data-group-id="7354279877-11">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7354279877-2">}</span></code></pre><p>Note that the very first thing done is to fetch the address to the
│ │ │  next instruction.  The reason is that it usually improves performance.</p><p>Just as a demonstration, we can add a <code class="inline">-no_prefetch</code> directive to
│ │ │ -the <code class="inline">move/2</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="2883451003-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="2883451003-1">)</span><span class="w"> </span><span class="p" data-group-id="2883451003-2">{</span><span class="w">
│ │ │ +the <code class="inline">move/2</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">move</span><span class="p" data-group-id="3913829878-1">(</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="3913829878-1">)</span><span class="w"> </span><span class="p" data-group-id="3913829878-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_prefetch</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2883451003-2">}</span></code></pre><p>We can see that the prefetch is no longer done:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="1133102123-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="1133102123-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1133102123-2">{</span><span class="w">
│ │ │ -  </span><span class="nf">xb</span><span class="p" data-group-id="1133102123-3">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="1133102123-4">(</span><span class="n">I</span><span class="p" data-group-id="1133102123-5">[</span><span class="mi">0</span><span class="p" data-group-id="1133102123-5">]</span><span class="p" data-group-id="1133102123-4">)</span><span class="p" data-group-id="1133102123-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="1133102123-6">[</span><span class="mi">1</span><span class="p" data-group-id="1133102123-6">]</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3913829878-2">}</span></code></pre><p>We can see that the prefetch is no longer done:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="1667735348-1">(</span><span class="ss">move_cx</span><span class="p" data-group-id="1667735348-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1667735348-2">{</span><span class="w">
│ │ │ +  </span><span class="nf">xb</span><span class="p" data-group-id="1667735348-3">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="1667735348-4">(</span><span class="n">I</span><span class="p" data-group-id="1667735348-5">[</span><span class="mi">0</span><span class="p" data-group-id="1667735348-5">]</span><span class="p" data-group-id="1667735348-4">)</span><span class="p" data-group-id="1667735348-3">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="1667735348-6">[</span><span class="mi">1</span><span class="p" data-group-id="1667735348-6">]</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="1133102123-7">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="1133102123-8">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="1133102123-8">)</span><span class="p" data-group-id="1133102123-7">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="1133102123-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="1133102123-9">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1133102123-2">}</span></code></pre><p>When would we want to turn off the prefetch in practice?</p><p>In instructions that will not always execute the next instruction.
│ │ │ -For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_atom</span><span class="p" data-group-id="9930771855-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="9930771855-1">)</span><span class="w"> </span><span class="p" data-group-id="9930771855-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9930771855-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="9930771855-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="9930771855-4">)</span><span class="p" data-group-id="9930771855-3">)</span><span class="w"> </span><span class="p" data-group-id="9930771855-5">{</span><span class="w">
│ │ │ -        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="9930771855-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="9930771855-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="9930771855-5">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9930771855-2">}</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="1667735348-7">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="1667735348-8">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="1667735348-8">)</span><span class="p" data-group-id="1667735348-7">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="1667735348-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="1667735348-9">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1667735348-2">}</span></code></pre><p>When would we want to turn off the prefetch in practice?</p><p>In instructions that will not always execute the next instruction.
│ │ │ +For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_atom</span><span class="p" data-group-id="0891697665-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="0891697665-1">)</span><span class="w"> </span><span class="p" data-group-id="0891697665-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0891697665-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="0891697665-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="0891697665-4">)</span><span class="p" data-group-id="0891697665-3">)</span><span class="w"> </span><span class="p" data-group-id="0891697665-5">{</span><span class="w">
│ │ │ +        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="0891697665-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="0891697665-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0891697665-5">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0891697665-2">}</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">From</span><span class="w"> </span><span class="ss">macros</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │ -</span><span class="n">FAIL</span><span class="p" data-group-id="9930771855-7">(</span><span class="n">Fail</span><span class="p" data-group-id="9930771855-7">)</span><span class="w"> </span><span class="p" data-group-id="9930771855-8">{</span><span class="w">
│ │ │ +</span><span class="n">FAIL</span><span class="p" data-group-id="0891697665-7">(</span><span class="n">Fail</span><span class="p" data-group-id="0891697665-7">)</span><span class="w"> </span><span class="p" data-group-id="0891697665-8">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_prefetch</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="9930771855-9">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="9930771855-9">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="9930771855-10">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="9930771855-10">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9930771855-8">}</span></code></pre><p><code class="inline">is_atom/2</code> may either execute the next instruction (if the second
│ │ │ -operand is an atom) or branch to the failure label.</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="9346068330-1">(</span><span class="ss">is_atom_fx</span><span class="p" data-group-id="9346068330-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9346068330-2">{</span><span class="w">
│ │ │ -  </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9346068330-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="9346068330-4">(</span><span class="nf">xb</span><span class="p" data-group-id="9346068330-5">(</span><span class="n">I</span><span class="p" data-group-id="9346068330-6">[</span><span class="mi">1</span><span class="p" data-group-id="9346068330-6">]</span><span class="p" data-group-id="9346068330-5">)</span><span class="p" data-group-id="9346068330-4">)</span><span class="p" data-group-id="9346068330-3">)</span><span class="w"> </span><span class="p" data-group-id="9346068330-7">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="9346068330-8">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="9346068330-9">(</span><span class="o">*</span><span class="p" data-group-id="9346068330-10">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="9346068330-11">(</span><span class="nf">fb</span><span class="p" data-group-id="9346068330-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="9346068330-13">(</span><span class="n">I</span><span class="p" data-group-id="9346068330-14">[</span><span class="mi">0</span><span class="p" data-group-id="9346068330-14">]</span><span class="p" data-group-id="9346068330-13">)</span><span class="p" data-group-id="9346068330-12">)</span><span class="p" data-group-id="9346068330-11">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="9346068330-10">)</span><span class="p" data-group-id="9346068330-9">)</span><span class="p" data-group-id="9346068330-8">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="9346068330-15">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="9346068330-16">(</span><span class="n">I</span><span class="p" data-group-id="9346068330-17">[</span><span class="mi">0</span><span class="p" data-group-id="9346068330-17">]</span><span class="p" data-group-id="9346068330-16">)</span><span class="p" data-group-id="9346068330-15">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="9346068330-18">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="9346068330-18">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9346068330-7">}</span><span class="w">
│ │ │ +    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="0891697665-9">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="0891697665-9">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="0891697665-10">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="0891697665-10">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0891697665-8">}</span></code></pre><p><code class="inline">is_atom/2</code> may either execute the next instruction (if the second
│ │ │ +operand is an atom) or branch to the failure label.</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="3236967104-1">(</span><span class="ss">is_atom_fx</span><span class="p" data-group-id="3236967104-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3236967104-2">{</span><span class="w">
│ │ │ +  </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="3236967104-3">(</span><span class="nf">is_not_atom</span><span class="p" data-group-id="3236967104-4">(</span><span class="nf">xb</span><span class="p" data-group-id="3236967104-5">(</span><span class="n">I</span><span class="p" data-group-id="3236967104-6">[</span><span class="mi">1</span><span class="p" data-group-id="3236967104-6">]</span><span class="p" data-group-id="3236967104-5">)</span><span class="p" data-group-id="3236967104-4">)</span><span class="p" data-group-id="3236967104-3">)</span><span class="w"> </span><span class="p" data-group-id="3236967104-7">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="3236967104-8">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3236967104-9">(</span><span class="o">*</span><span class="p" data-group-id="3236967104-10">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="3236967104-11">(</span><span class="nf">fb</span><span class="p" data-group-id="3236967104-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="3236967104-13">(</span><span class="n">I</span><span class="p" data-group-id="3236967104-14">[</span><span class="mi">0</span><span class="p" data-group-id="3236967104-14">]</span><span class="p" data-group-id="3236967104-13">)</span><span class="p" data-group-id="3236967104-12">)</span><span class="p" data-group-id="3236967104-11">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3236967104-10">)</span><span class="p" data-group-id="3236967104-9">)</span><span class="p" data-group-id="3236967104-8">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="3236967104-15">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="3236967104-16">(</span><span class="n">I</span><span class="p" data-group-id="3236967104-17">[</span><span class="mi">0</span><span class="p" data-group-id="3236967104-17">]</span><span class="p" data-group-id="3236967104-16">)</span><span class="p" data-group-id="3236967104-15">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="3236967104-18">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3236967104-18">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3236967104-7">}</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="9346068330-19">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="9346068330-20">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="9346068330-20">)</span><span class="p" data-group-id="9346068330-19">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="9346068330-21">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="9346068330-21">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9346068330-2">}</span></code></pre><h5>The -no_next directive</h5><p>Next we will look at when the <code class="inline">-no_next</code> directive can be used.  Here
│ │ │ -is the <code class="inline">jump/1</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="2467810776-1">(</span><span class="n">Fail</span><span class="p" data-group-id="2467810776-1">)</span><span class="w"> </span><span class="p" data-group-id="2467810776-2">{</span><span class="w">
│ │ │ -    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="2467810776-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="2467810776-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2467810776-2">}</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="3236967104-19">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3236967104-20">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3236967104-20">)</span><span class="p" data-group-id="3236967104-19">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="3236967104-21">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3236967104-21">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3236967104-2">}</span></code></pre><h5>The -no_next directive</h5><p>Next we will look at when the <code class="inline">-no_next</code> directive can be used.  Here
│ │ │ +is the <code class="inline">jump/1</code> instruction:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="3092932497-1">(</span><span class="n">Fail</span><span class="p" data-group-id="3092932497-1">)</span><span class="w"> </span><span class="p" data-group-id="3092932497-2">{</span><span class="w">
│ │ │ +    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="3092932497-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="3092932497-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3092932497-2">}</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">From</span><span class="w"> </span><span class="ss">macros</span><span class="p">.</span><span class="ss">tab</span><span class="w">
│ │ │ -</span><span class="n">JUMP</span><span class="p" data-group-id="2467810776-4">(</span><span class="n">Fail</span><span class="p" data-group-id="2467810776-4">)</span><span class="w"> </span><span class="p" data-group-id="2467810776-5">{</span><span class="w">
│ │ │ +</span><span class="n">JUMP</span><span class="p" data-group-id="3092932497-4">(</span><span class="n">Fail</span><span class="p" data-group-id="3092932497-4">)</span><span class="w"> </span><span class="p" data-group-id="3092932497-5">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="2467810776-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="2467810776-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="2467810776-7">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="2467810776-7">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2467810776-5">}</span></code></pre><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="6197665072-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="6197665072-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6197665072-2">{</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="6197665072-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="6197665072-4">(</span><span class="o">*</span><span class="p" data-group-id="6197665072-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="6197665072-6">(</span><span class="nf">fb</span><span class="p" data-group-id="6197665072-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="6197665072-8">(</span><span class="n">I</span><span class="p" data-group-id="6197665072-9">[</span><span class="mi">0</span><span class="p" data-group-id="6197665072-9">]</span><span class="p" data-group-id="6197665072-8">)</span><span class="p" data-group-id="6197665072-7">)</span><span class="p" data-group-id="6197665072-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6197665072-5">)</span><span class="p" data-group-id="6197665072-4">)</span><span class="p" data-group-id="6197665072-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="6197665072-10">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="6197665072-11">(</span><span class="n">I</span><span class="p" data-group-id="6197665072-12">[</span><span class="mi">0</span><span class="p" data-group-id="6197665072-12">]</span><span class="p" data-group-id="6197665072-11">)</span><span class="p" data-group-id="6197665072-10">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="6197665072-13">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="6197665072-13">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6197665072-2">}</span></code></pre><p>If we remove the <code class="inline">-no_next</code> directive, the code would look like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="4578762586-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="4578762586-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4578762586-2">{</span><span class="w">
│ │ │ -  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="4578762586-3">(</span><span class="n">I</span><span class="p" data-group-id="4578762586-4">[</span><span class="mi">1</span><span class="p" data-group-id="4578762586-4">]</span><span class="p" data-group-id="4578762586-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="4578762586-5">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="4578762586-6">(</span><span class="o">*</span><span class="p" data-group-id="4578762586-7">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="4578762586-8">(</span><span class="nf">fb</span><span class="p" data-group-id="4578762586-9">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="4578762586-10">(</span><span class="n">I</span><span class="p" data-group-id="4578762586-11">[</span><span class="mi">0</span><span class="p" data-group-id="4578762586-11">]</span><span class="p" data-group-id="4578762586-10">)</span><span class="p" data-group-id="4578762586-9">)</span><span class="p" data-group-id="4578762586-8">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="4578762586-7">)</span><span class="p" data-group-id="4578762586-6">)</span><span class="p" data-group-id="4578762586-5">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="4578762586-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="4578762586-13">(</span><span class="n">I</span><span class="p" data-group-id="4578762586-14">[</span><span class="mi">0</span><span class="p" data-group-id="4578762586-14">]</span><span class="p" data-group-id="4578762586-13">)</span><span class="p" data-group-id="4578762586-12">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">Goto</span><span class="p" data-group-id="4578762586-15">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="4578762586-15">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="3092932497-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="3092932497-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="3092932497-7">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3092932497-7">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3092932497-5">}</span></code></pre><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="8878960401-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="8878960401-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8878960401-2">{</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="8878960401-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="8878960401-4">(</span><span class="o">*</span><span class="p" data-group-id="8878960401-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="8878960401-6">(</span><span class="nf">fb</span><span class="p" data-group-id="8878960401-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="8878960401-8">(</span><span class="n">I</span><span class="p" data-group-id="8878960401-9">[</span><span class="mi">0</span><span class="p" data-group-id="8878960401-9">]</span><span class="p" data-group-id="8878960401-8">)</span><span class="p" data-group-id="8878960401-7">)</span><span class="p" data-group-id="8878960401-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8878960401-5">)</span><span class="p" data-group-id="8878960401-4">)</span><span class="p" data-group-id="8878960401-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="8878960401-10">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="8878960401-11">(</span><span class="n">I</span><span class="p" data-group-id="8878960401-12">[</span><span class="mi">0</span><span class="p" data-group-id="8878960401-12">]</span><span class="p" data-group-id="8878960401-11">)</span><span class="p" data-group-id="8878960401-10">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="8878960401-13">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="8878960401-13">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8878960401-2">}</span></code></pre><p>If we remove the <code class="inline">-no_next</code> directive, the code would look like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="7239295875-1">(</span><span class="ss">jump_f</span><span class="p" data-group-id="7239295875-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7239295875-2">{</span><span class="w">
│ │ │ +  </span><span class="n">BeamInstr</span><span class="w"> </span><span class="ss">next_pf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">BeamCodeAddr</span><span class="p" data-group-id="7239295875-3">(</span><span class="n">I</span><span class="p" data-group-id="7239295875-4">[</span><span class="mi">1</span><span class="p" data-group-id="7239295875-4">]</span><span class="p" data-group-id="7239295875-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="7239295875-5">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7239295875-6">(</span><span class="o">*</span><span class="p" data-group-id="7239295875-7">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="7239295875-8">(</span><span class="nf">fb</span><span class="p" data-group-id="7239295875-9">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7239295875-10">(</span><span class="n">I</span><span class="p" data-group-id="7239295875-11">[</span><span class="mi">0</span><span class="p" data-group-id="7239295875-11">]</span><span class="p" data-group-id="7239295875-10">)</span><span class="p" data-group-id="7239295875-9">)</span><span class="p" data-group-id="7239295875-8">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7239295875-7">)</span><span class="p" data-group-id="7239295875-6">)</span><span class="p" data-group-id="7239295875-5">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="nf">fb</span><span class="p" data-group-id="7239295875-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="7239295875-13">(</span><span class="n">I</span><span class="p" data-group-id="7239295875-14">[</span><span class="mi">0</span><span class="p" data-group-id="7239295875-14">]</span><span class="p" data-group-id="7239295875-13">)</span><span class="p" data-group-id="7239295875-12">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">Goto</span><span class="p" data-group-id="7239295875-15">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="7239295875-15">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │    </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">ASSERT</span><span class="p" data-group-id="4578762586-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="4578762586-17">(</span><span class="ss">next_pf</span><span class="p" data-group-id="4578762586-17">)</span><span class="p" data-group-id="4578762586-16">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">GotoPF</span><span class="p" data-group-id="4578762586-18">(</span><span class="ss">next_pf</span><span class="p" data-group-id="4578762586-18">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4578762586-2">}</span></code></pre><p>In the end, the C compiler will probably optimize this code to the
│ │ │ +  </span><span class="n">ASSERT</span><span class="p" data-group-id="7239295875-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="7239295875-17">(</span><span class="ss">next_pf</span><span class="p" data-group-id="7239295875-17">)</span><span class="p" data-group-id="7239295875-16">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="n">GotoPF</span><span class="p" data-group-id="7239295875-18">(</span><span class="ss">next_pf</span><span class="p" data-group-id="7239295875-18">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7239295875-2">}</span></code></pre><p>In the end, the C compiler will probably optimize this code to the
│ │ │  same native code as the first version, but the first version is certainly
│ │ │  much easier to read for human readers.</p><h4>Macros in the macros.tab file</h4><p>The file <code class="inline">macros.tab</code> contains many useful macros.  When implementing
│ │ │  new instructions it is good practice to look through <code class="inline">macros.tab</code> to
│ │ │  see if any of existing macros can be used rather than re-inventing
│ │ │  the wheel.</p><p>We will describe a few of the most useful macros here.</p><p><a href="" id="the-GC_REGEXP-definition"></a></p><h5>The GC_REGEXP definition</h5><p>The following line defines a regular expression that will recognize
│ │ │  a call to a function that does a garbage collection:</p><pre><code class="makeup erlang" translate="no"><span class="w"> </span><span class="n">GC_REGEXP</span><span class="o">=</span><span class="ss">erts_garbage_collect</span><span class="p">|</span><span class="ss">erts_gc</span><span class="p">|</span><span class="n">GcBifFunction</span><span class="p">;</span></code></pre><p>The purpose is that <strong>beam_makeops</strong> can verify that an instruction
│ │ │  that does a garbage collection and has an <code class="inline">d</code> operand uses the
│ │ │  <code class="inline">$REFRESH_GEN_DEST()</code> macro.</p><p>If you need to define a new function that does garbage collection,
│ │ │  you should give it the prefix <code class="inline">erts_gc_</code>.  If that is not possible
│ │ │  you should update the regular expression so that it will match your
│ │ │ -new function.</p><h5>FAIL(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Will suppress prefetch (<code class="inline">-no_prefetch</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_nonempty_list</span><span class="p" data-group-id="0139593137-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="0139593137-1">)</span><span class="w"> </span><span class="p" data-group-id="0139593137-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0139593137-3">(</span><span class="nf">is_not_list</span><span class="p" data-group-id="0139593137-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="0139593137-4">)</span><span class="p" data-group-id="0139593137-3">)</span><span class="w"> </span><span class="p" data-group-id="0139593137-5">{</span><span class="w">
│ │ │ -        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="0139593137-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="0139593137-6">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="0139593137-5">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0139593137-2">}</span></code></pre><h5>JUMP(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Suppresses generation of dispatch of the next
│ │ │ -instruction (<code class="inline">-no_next</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="9648355575-1">(</span><span class="n">Fail</span><span class="p" data-group-id="9648355575-1">)</span><span class="w"> </span><span class="p" data-group-id="9648355575-2">{</span><span class="w">
│ │ │ -    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="9648355575-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="9648355575-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9648355575-2">}</span></code></pre><h5>GC_TEST(NeedStack, NeedHeap, Live)</h5><p><code class="inline">$GC_TEST(NeedStack, NeedHeap, Live)</code> tests that given amount of
│ │ │ +new function.</p><h5>FAIL(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Will suppress prefetch (<code class="inline">-no_prefetch</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">is_nonempty_list</span><span class="p" data-group-id="4998950092-1">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="4998950092-1">)</span><span class="w"> </span><span class="p" data-group-id="4998950092-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="4998950092-3">(</span><span class="nf">is_not_list</span><span class="p" data-group-id="4998950092-4">(</span><span class="sc">$S</span><span class="ss">rc</span><span class="p" data-group-id="4998950092-4">)</span><span class="p" data-group-id="4998950092-3">)</span><span class="w"> </span><span class="p" data-group-id="4998950092-5">{</span><span class="w">
│ │ │ +        </span><span class="sc">$F</span><span class="n">AIL</span><span class="p" data-group-id="4998950092-6">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4998950092-6">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="4998950092-5">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4998950092-2">}</span></code></pre><h5>JUMP(Fail)</h5><p>Branch to <code class="inline">$Fail</code>.  Suppresses generation of dispatch of the next
│ │ │ +instruction (<code class="inline">-no_next</code>).  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">jump</span><span class="p" data-group-id="7001966200-1">(</span><span class="n">Fail</span><span class="p" data-group-id="7001966200-1">)</span><span class="w"> </span><span class="p" data-group-id="7001966200-2">{</span><span class="w">
│ │ │ +    </span><span class="sc">$J</span><span class="n">UMP</span><span class="p" data-group-id="7001966200-3">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="7001966200-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7001966200-2">}</span></code></pre><h5>GC_TEST(NeedStack, NeedHeap, Live)</h5><p><code class="inline">$GC_TEST(NeedStack, NeedHeap, Live)</code> tests that given amount of
│ │ │  stack space and heap space is available.  If not it will do a
│ │ │ -garbage collection.  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">test_heap</span><span class="p" data-group-id="1637361853-1">(</span><span class="n">Nh</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p" data-group-id="1637361853-1">)</span><span class="w"> </span><span class="p" data-group-id="1637361853-2">{</span><span class="w">
│ │ │ -    </span><span class="sc">$G</span><span class="n">C_TEST</span><span class="p" data-group-id="1637361853-3">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="ss">h</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p" data-group-id="1637361853-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1637361853-2">}</span></code></pre><h5>AH(NeedStack, NeedHeap, Live)</h5><p><code class="inline">AH(NeedStack, NeedHeap, Live)</code> allocates a stack frame and
│ │ │ +garbage collection.  Typical use:</p><pre><code class="makeup erlang" translate="no"><span class="nf">test_heap</span><span class="p" data-group-id="5223958240-1">(</span><span class="n">Nh</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p" data-group-id="5223958240-1">)</span><span class="w"> </span><span class="p" data-group-id="5223958240-2">{</span><span class="w">
│ │ │ +    </span><span class="sc">$G</span><span class="n">C_TEST</span><span class="p" data-group-id="5223958240-3">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="ss">h</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p" data-group-id="5223958240-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5223958240-2">}</span></code></pre><h5>AH(NeedStack, NeedHeap, Live)</h5><p><code class="inline">AH(NeedStack, NeedHeap, Live)</code> allocates a stack frame and
│ │ │  optionally additional heap space.</p><h4>Pre-defined macros and variables</h4><p><strong>beam_makeops</strong> defines several built-in macros and pre-bound variables.</p><h5>The NEXT_INSTRUCTION pre-bound variable</h5><p>The NEXT_INSTRUCTION is a pre-bound variable that is available in
│ │ │ -all instructions.  It expands to the address of the next instruction.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_call</span><span class="p" data-group-id="5607483323-1">(</span><span class="n">CallDest</span><span class="p" data-group-id="5607483323-1">)</span><span class="w"> </span><span class="p" data-group-id="5607483323-2">{</span><span class="w">
│ │ │ +all instructions.  It expands to the address of the next instruction.</p><p>Here is an example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_call</span><span class="p" data-group-id="9875550085-1">(</span><span class="n">CallDest</span><span class="p" data-group-id="9875550085-1">)</span><span class="w"> </span><span class="p" data-group-id="9875550085-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">AVE_CONTINUATION_POINTER</span><span class="p" data-group-id="5607483323-3">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="5607483323-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$D</span><span class="n">ISPATCH_REL</span><span class="p" data-group-id="5607483323-4">(</span><span class="sc">$C</span><span class="ss">allDest</span><span class="p" data-group-id="5607483323-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5607483323-2">}</span></code></pre><p>When calling a function, the return address is first stored in <code class="inline">E[0]</code>
│ │ │ +    </span><span class="sc">$S</span><span class="n">AVE_CONTINUATION_POINTER</span><span class="p" data-group-id="9875550085-3">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="9875550085-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$D</span><span class="n">ISPATCH_REL</span><span class="p" data-group-id="9875550085-4">(</span><span class="sc">$C</span><span class="ss">allDest</span><span class="p" data-group-id="9875550085-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9875550085-2">}</span></code></pre><p>When calling a function, the return address is first stored in <code class="inline">E[0]</code>
│ │ │  (using the <code class="inline">$SAVE_CONTINUATION_POINTER()</code> macro), and then control is
│ │ │ -transferred to the callee.  Here is the generated code:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="5418525957-1">(</span><span class="ss">i_call_f</span><span class="p" data-group-id="5418525957-1">)</span><span class="p">:</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5418525957-2">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="5418525957-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5418525957-4">(</span><span class="o">*</span><span class="p" data-group-id="5418525957-5">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="5418525957-5">)</span><span class="p" data-group-id="5418525957-4">)</span><span class="p" data-group-id="5418525957-3">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="o">*</span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5418525957-6">(</span><span class="n">BeamInstr</span><span class="p" data-group-id="5418525957-6">)</span><span class="w"> </span><span class="p" data-group-id="5418525957-7">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="5418525957-7">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │ +transferred to the callee.  Here is the generated code:</p><pre><code class="makeup erlang" translate="no"><span class="n">OpCase</span><span class="p" data-group-id="2894748580-1">(</span><span class="ss">i_call_f</span><span class="p" data-group-id="2894748580-1">)</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2894748580-2">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="2894748580-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="2894748580-4">(</span><span class="o">*</span><span class="p" data-group-id="2894748580-5">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="2894748580-5">)</span><span class="p" data-group-id="2894748580-4">)</span><span class="p" data-group-id="2894748580-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="o">*</span><span class="n">E</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2894748580-6">(</span><span class="n">BeamInstr</span><span class="p" data-group-id="2894748580-6">)</span><span class="w"> </span><span class="p" data-group-id="2894748580-7">(</span><span class="n">I</span><span class="o">+</span><span class="mi">2</span><span class="p" data-group-id="2894748580-7">)</span><span class="p">;</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │      </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">dispatch</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">intentionally</span><span class="w"> </span><span class="ss">left</span><span class="w"> </span><span class="ss">out</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5418525957-2">}</span></code></pre><p>We can see that that <code class="inline">$NEXT_INSTRUCTION</code> has been expanded to <code class="inline">I+2</code>.
│ │ │ +</span><span class="p" data-group-id="2894748580-2">}</span></code></pre><p>We can see that that <code class="inline">$NEXT_INSTRUCTION</code> has been expanded to <code class="inline">I+2</code>.
│ │ │  That makes sense since the size of the <code class="inline">i_call_f/1</code> instruction is
│ │ │  two words.</p><h5>The IP_ADJUSTMENT pre-bound variable</h5><p><code class="inline">$IP_ADJUSTMENT</code> is usually 0.  In a few combined instructions
│ │ │  (described below) it can be non-zero.  It is used like this
│ │ │ -in <code class="inline">macros.tab</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">SET_I_REL</span><span class="p" data-group-id="1784970065-1">(</span><span class="n">Offset</span><span class="p" data-group-id="1784970065-1">)</span><span class="w"> </span><span class="p" data-group-id="1784970065-2">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="1784970065-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="1784970065-4">(</span><span class="o">*</span><span class="p" data-group-id="1784970065-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="1784970065-6">(</span><span class="sc">$O</span><span class="ss">ffset</span><span class="p" data-group-id="1784970065-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="p" data-group-id="1784970065-5">)</span><span class="p" data-group-id="1784970065-4">)</span><span class="p" data-group-id="1784970065-3">)</span><span class="p">;</span><span class="w">
│ │ │ +in <code class="inline">macros.tab</code>:</p><pre><code class="makeup erlang" translate="no"><span class="n">SET_I_REL</span><span class="p" data-group-id="0579312963-1">(</span><span class="n">Offset</span><span class="p" data-group-id="0579312963-1">)</span><span class="w"> </span><span class="p" data-group-id="0579312963-2">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="0579312963-3">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="0579312963-4">(</span><span class="o">*</span><span class="p" data-group-id="0579312963-5">(</span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="0579312963-6">(</span><span class="sc">$O</span><span class="ss">ffset</span><span class="p" data-group-id="0579312963-6">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="p" data-group-id="0579312963-5">)</span><span class="p" data-group-id="0579312963-4">)</span><span class="p" data-group-id="0579312963-3">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="sc">$O</span><span class="ss">ffset</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1784970065-2">}</span></code></pre><p>Avoid using <code class="inline">IP_ADJUSTMENT</code> directly.  Use <code class="inline">SET_I_REL()</code> or
│ │ │ +</span><span class="p" data-group-id="0579312963-2">}</span></code></pre><p>Avoid using <code class="inline">IP_ADJUSTMENT</code> directly.  Use <code class="inline">SET_I_REL()</code> or
│ │ │  one of the macros that invoke such as <code class="inline">FAIL()</code> or <code class="inline">JUMP()</code>
│ │ │  defined in <code class="inline">macros.tab</code>.</p><h4>Pre-defined macro functions</h4><h5>The IF() macro</h5><p><code class="inline">$IF(Expr, IfTrue, IfFalse)</code> evaluates <code class="inline">Expr</code>, which must be a valid
│ │ │  Perl expression (which for simple numeric expressions have the same
│ │ │  syntax as C).  If <code class="inline">Expr</code> evaluates to 0, the entire <code class="inline">IF()</code> expression will be
│ │ │  replaced with <code class="inline">IfFalse</code>, otherwise it will be replaced with <code class="inline">IfTrue</code>.</p><p>See the description of <code class="inline">OPERAND_POSITION()</code> for an example.</p><h5>The OPERAND_POSITION() macro</h5><p><code class="inline">$OPERAND_POSITION(Expr)</code> returns the position for <code class="inline">Expr</code>, if
│ │ │  <code class="inline">Expr</code> is an operand that is not packed.  The first operand is
│ │ │ -at position 1.</p><p>Returns 0 otherwise.</p><p>This macro could be used like this in order to share code:</p><pre><code class="makeup erlang" translate="no"><span class="n">FAIL</span><span class="p" data-group-id="4870242456-1">(</span><span class="n">Fail</span><span class="p" data-group-id="4870242456-1">)</span><span class="w"> </span><span class="p" data-group-id="4870242456-2">{</span><span class="w">
│ │ │ +at position 1.</p><p>Returns 0 otherwise.</p><p>This macro could be used like this in order to share code:</p><pre><code class="makeup erlang" translate="no"><span class="n">FAIL</span><span class="p" data-group-id="5517257763-1">(</span><span class="n">Fail</span><span class="p" data-group-id="5517257763-1">)</span><span class="w"> </span><span class="p" data-group-id="5517257763-2">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_prefetch</span><span class="w">
│ │ │ -    </span><span class="sc">$I</span><span class="n">F</span><span class="p" data-group-id="4870242456-3">(</span><span class="sc">$O</span><span class="n">PERAND_POSITION</span><span class="p" data-group-id="4870242456-4">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4870242456-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="sc">$I</span><span class="n">F</span><span class="p" data-group-id="5517257763-3">(</span><span class="sc">$O</span><span class="n">PERAND_POSITION</span><span class="p" data-group-id="5517257763-4">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="5517257763-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="p">&amp;&amp;</span><span class="w"> </span><span class="sc">$I</span><span class="n">P_ADJUSTMENT</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │          </span><span class="ss">goto</span><span class="w"> </span><span class="ss">common_jump</span><span class="p">,</span><span class="w">
│ │ │ -        </span><span class="sc">$D</span><span class="n">O_JUMP</span><span class="p" data-group-id="4870242456-5">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4870242456-5">)</span><span class="p" data-group-id="4870242456-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4870242456-2">}</span><span class="w">
│ │ │ +        </span><span class="sc">$D</span><span class="n">O_JUMP</span><span class="p" data-group-id="5517257763-5">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="5517257763-5">)</span><span class="p" data-group-id="5517257763-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5517257763-2">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">DO_JUMP</span><span class="p" data-group-id="4870242456-6">(</span><span class="n">Fail</span><span class="p" data-group-id="4870242456-6">)</span><span class="w"> </span><span class="p" data-group-id="4870242456-7">{</span><span class="w">
│ │ │ -    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="4870242456-8">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="4870242456-8">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">Goto</span><span class="p" data-group-id="4870242456-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="4870242456-9">)</span><span class="p">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4870242456-7">}</span><span class="w">
│ │ │ +</span><span class="n">DO_JUMP</span><span class="p" data-group-id="5517257763-6">(</span><span class="n">Fail</span><span class="p" data-group-id="5517257763-6">)</span><span class="w"> </span><span class="p" data-group-id="5517257763-7">{</span><span class="w">
│ │ │ +    </span><span class="sc">$S</span><span class="n">ET_I_REL</span><span class="p" data-group-id="5517257763-8">(</span><span class="sc">$F</span><span class="ss">ail</span><span class="p" data-group-id="5517257763-8">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Goto</span><span class="p" data-group-id="5517257763-9">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="5517257763-9">)</span><span class="p">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5517257763-7">}</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">beam_emu</span><span class="p">.</span><span class="nc">c</span><span class="p">:</span><span class="w">
│ │ │  </span><span class="nc">common_jump</span><span class="p">:</span><span class="w">
│ │ │ -   </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="4870242456-10">[</span><span class="mi">1</span><span class="p" data-group-id="4870242456-10">]</span><span class="p">;</span><span class="w">
│ │ │ -   </span><span class="n">Goto</span><span class="p" data-group-id="4870242456-11">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="4870242456-11">)</span><span class="p">)</span><span class="p">;</span></code></pre><h4>The $REFRESH_GEN_DEST() macro</h4><p>When a specific instruction has a <code class="inline">d</code> operand, early during execution
│ │ │ +   </span><span class="n">I</span><span class="w"> </span><span class="o">+</span><span class="o">=</span><span class="w"> </span><span class="n">I</span><span class="p" data-group-id="5517257763-10">[</span><span class="mi">1</span><span class="p" data-group-id="5517257763-10">]</span><span class="p">;</span><span class="w">
│ │ │ +   </span><span class="n">Goto</span><span class="p" data-group-id="5517257763-11">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="5517257763-11">)</span><span class="p">)</span><span class="p">;</span></code></pre><h4>The $REFRESH_GEN_DEST() macro</h4><p>When a specific instruction has a <code class="inline">d</code> operand, early during execution
│ │ │  of the instruction, a pointer will be initialized to point to the X or
│ │ │  Y register in question.</p><p>If there is a garbage collection before the result is stored,
│ │ │  the stack will move and if the <code class="inline">d</code> operand referred to a Y
│ │ │  register, the pointer will no longer be valid.  (Y registers are
│ │ │  stored on the stack.)</p><p>In those circumstances, <code class="inline">$REFRESH_GEN_DEST()</code> must be invoked
│ │ │  to set up the pointer again. <strong>beam_makeops</strong> will notice
│ │ │  if there is a call to a function that does a garbage collection and
│ │ │  <code class="inline">$REFRESH_GEN_DEST()</code> is not called.</p><p>Here is a complete example.  The <code class="inline">new_map</code> instruction is defined
│ │ │ -like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">new_map</span><span class="w"> </span><span class="ss">d</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="n">I</span></code></pre><p>It is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new_map</span><span class="p" data-group-id="6141292827-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="6141292827-1">)</span><span class="w"> </span><span class="p" data-group-id="6141292827-2">{</span><span class="w">
│ │ │ +like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">new_map</span><span class="w"> </span><span class="ss">d</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="n">I</span></code></pre><p>It is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">new_map</span><span class="p" data-group-id="1009928879-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p" data-group-id="1009928879-1">)</span><span class="w"> </span><span class="p" data-group-id="1009928879-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │      </span><span class="n">HEAVY_SWAPOUT</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_new_map</span><span class="p" data-group-id="6141292827-3">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="6141292827-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_new_map</span><span class="p" data-group-id="1009928879-3">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="p">,</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p" data-group-id="1009928879-3">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPIN</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="6141292827-4">(</span><span class="p" data-group-id="6141292827-4">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="1009928879-4">(</span><span class="p" data-group-id="1009928879-4">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">res</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="sc">$N</span><span class="n">EXT</span><span class="p" data-group-id="6141292827-5">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="o">+</span><span class="sc">$N</span><span class="p" data-group-id="6141292827-5">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6141292827-2">}</span></code></pre><p>If we have forgotten the <code class="inline">$REFRESH_GEN_DEST()</code> there would be a message
│ │ │ -similar to this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pointer</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">destination</span><span class="w"> </span><span class="nb">register</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">invalid</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">GC</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="ss">use</span><span class="w"> </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="1582507578-1">(</span><span class="p" data-group-id="1582507578-1">)</span><span class="w">
│ │ │ -</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">body</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="ss">new_map</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">beam</span><span class="o">/</span><span class="ss">map_instrs</span><span class="p">.</span><span class="nf">tab</span><span class="p" data-group-id="1582507578-2">(</span><span class="mi">30</span><span class="p" data-group-id="1582507578-2">)</span></code></pre><h4>Variable number of operands</h4><p>Here follows an example of how to handle an instruction with a variable number
│ │ │ +    </span><span class="sc">$N</span><span class="n">EXT</span><span class="p" data-group-id="1009928879-5">(</span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="o">+</span><span class="sc">$N</span><span class="p" data-group-id="1009928879-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1009928879-2">}</span></code></pre><p>If we have forgotten the <code class="inline">$REFRESH_GEN_DEST()</code> there would be a message
│ │ │ +similar to this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">pointer</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">destination</span><span class="w"> </span><span class="nb">register</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">invalid</span><span class="w"> </span><span class="k">after</span><span class="w"> </span><span class="n">GC</span><span class="w"> </span><span class="o">--</span><span class="w"> </span><span class="ss">use</span><span class="w"> </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="6967004667-1">(</span><span class="p" data-group-id="6967004667-1">)</span><span class="w">
│ │ │ +</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">body</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="ss">new_map</span><span class="w"> </span><span class="ss">at</span><span class="w"> </span><span class="ss">beam</span><span class="o">/</span><span class="ss">map_instrs</span><span class="p">.</span><span class="nf">tab</span><span class="p" data-group-id="6967004667-2">(</span><span class="mi">30</span><span class="p" data-group-id="6967004667-2">)</span></code></pre><h4>Variable number of operands</h4><p>Here follows an example of how to handle an instruction with a variable number
│ │ │  of operands for the interpreter.  Here is the instruction definition in <code class="inline">emu/ops.tab</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">put_tuple2</span><span class="w"> </span><span class="ss">xy</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">*</span></code></pre><p>For the interpreter, the <code class="inline">*</code> is optional, because it does not effect code generation
│ │ │  in any way. However, it is recommended to include it to make it clear for human readers
│ │ │  that there is a variable number of operands.</p><p>Use the <code class="inline">$NEXT_INSTRUCTION</code> macro to obtain a pointer to the first of the variable
│ │ │ -operands.</p><p>Here is the implementation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">put_tuple2</span><span class="p" data-group-id="3803361180-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="3803361180-1">)</span><span class="w"> </span><span class="p" data-group-id="3803361180-2">{</span><span class="w">
│ │ │ +operands.</p><p>Here is the implementation:</p><pre><code class="makeup erlang" translate="no"><span class="nf">put_tuple2</span><span class="p" data-group-id="5756561474-1">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Arity</span><span class="p" data-group-id="5756561474-1">)</span><span class="w"> </span><span class="p" data-group-id="5756561474-2">{</span><span class="w">
│ │ │  </span><span class="n">Eterm</span><span class="o">*</span><span class="w"> </span><span class="ss">hp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">HTOP</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">arity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="ss">rity</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">Eterm</span><span class="o">*</span><span class="w"> </span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="err">&amp;</span><span class="p" data-group-id="3803361180-3">(</span><span class="sc">$D</span><span class="ss">st</span><span class="p" data-group-id="3803361180-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="n">Eterm</span><span class="o">*</span><span class="w"> </span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="err">&amp;</span><span class="p" data-group-id="5756561474-3">(</span><span class="sc">$D</span><span class="ss">st</span><span class="p" data-group-id="5756561474-3">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">/</span><span class="p">|</span><span class="w"> </span><span class="o">-</span><span class="ss">no_next</span><span class="w">
│ │ │ -</span><span class="n">ASSERT</span><span class="p" data-group-id="3803361180-4">(</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3803361180-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_arityval</span><span class="p" data-group-id="3803361180-5">(</span><span class="ss">arity</span><span class="p" data-group-id="3803361180-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="n">ASSERT</span><span class="p" data-group-id="5756561474-4">(</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5756561474-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_arityval</span><span class="p" data-group-id="5756561474-5">(</span><span class="ss">arity</span><span class="p" data-group-id="5756561474-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="n">The</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="w"> </span><span class="ss">macro</span><span class="w"> </span><span class="ss">points</span><span class="w"> </span><span class="ss">just</span><span class="w"> </span><span class="ss">beyond</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">fixed</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="ss">operands</span><span class="p">.</span><span class="w"> </span><span class="n">In</span><span class="w"> </span><span class="ss">this</span><span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="ss">it</span><span class="w"> </span><span class="ss">points</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">descriptor</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">first</span><span class="w"> </span><span class="nb">element</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">be</span><span class="w"> </span><span class="nb">put</span><span class="w"> </span><span class="ss">into</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">tuple</span><span class="p">.</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │  </span><span class="n">I</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="n">EXT_INSTRUCTION</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="3803361180-6">{</span><span class="w">
│ │ │ +</span><span class="ss">do</span><span class="w"> </span><span class="p" data-group-id="5756561474-6">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">I</span><span class="o">++</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">switch</span><span class="w"> </span><span class="p" data-group-id="3803361180-7">(</span><span class="nf">loader_tag</span><span class="p" data-group-id="3803361180-8">(</span><span class="ss">term</span><span class="p" data-group-id="3803361180-8">)</span><span class="p" data-group-id="3803361180-7">)</span><span class="w"> </span><span class="p" data-group-id="3803361180-9">{</span><span class="w">
│ │ │ +    </span><span class="nf">switch</span><span class="w"> </span><span class="p" data-group-id="5756561474-7">(</span><span class="nf">loader_tag</span><span class="p" data-group-id="5756561474-8">(</span><span class="ss">term</span><span class="p" data-group-id="5756561474-8">)</span><span class="p" data-group-id="5756561474-7">)</span><span class="w"> </span><span class="p" data-group-id="5756561474-9">{</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">LOADER_X_REG</span><span class="p">:</span><span class="w">
│ │ │ -    </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">x</span><span class="p" data-group-id="3803361180-10">(</span><span class="nf">loader_x_reg_index</span><span class="p" data-group-id="3803361180-11">(</span><span class="ss">term</span><span class="p" data-group-id="3803361180-11">)</span><span class="p" data-group-id="3803361180-10">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">x</span><span class="p" data-group-id="5756561474-10">(</span><span class="nf">loader_x_reg_index</span><span class="p" data-group-id="5756561474-11">(</span><span class="ss">term</span><span class="p" data-group-id="5756561474-11">)</span><span class="p" data-group-id="5756561474-10">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">break</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="k">case</span><span class="w"> </span><span class="n">LOADER_Y_REG</span><span class="p">:</span><span class="w">
│ │ │ -    </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">y</span><span class="p" data-group-id="3803361180-12">(</span><span class="nf">loader_y_reg_index</span><span class="p" data-group-id="3803361180-13">(</span><span class="ss">term</span><span class="p" data-group-id="3803361180-13">)</span><span class="p" data-group-id="3803361180-12">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">y</span><span class="p" data-group-id="5756561474-12">(</span><span class="nf">loader_y_reg_index</span><span class="p" data-group-id="5756561474-13">(</span><span class="ss">term</span><span class="p" data-group-id="5756561474-13">)</span><span class="p" data-group-id="5756561474-12">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">break</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="nc">default</span><span class="p">:</span><span class="w">
│ │ │      </span><span class="o">*</span><span class="ss">hp</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">term</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">break</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3803361180-9">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3803361180-6">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="3803361180-14">(</span><span class="o">--</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3803361180-14">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="o">*</span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_tuple</span><span class="p" data-group-id="3803361180-15">(</span><span class="n">HTOP</span><span class="p" data-group-id="3803361180-15">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5756561474-9">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5756561474-6">}</span><span class="w"> </span><span class="nf">while</span><span class="w"> </span><span class="p" data-group-id="5756561474-14">(</span><span class="o">--</span><span class="ss">arity</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5756561474-14">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="o">*</span><span class="ss">dst_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_tuple</span><span class="p" data-group-id="5756561474-15">(</span><span class="n">HTOP</span><span class="p" data-group-id="5756561474-15">)</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="n">HTOP</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">hp</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">ASSERT</span><span class="p" data-group-id="3803361180-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="3803361180-17">(</span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="3803361180-18">(</span><span class="n">Eterm</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="3803361180-18">)</span><span class="n">I</span><span class="p" data-group-id="3803361180-17">)</span><span class="p" data-group-id="3803361180-16">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="n">Goto</span><span class="p" data-group-id="3803361180-19">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="3803361180-19">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3803361180-2">}</span></code></pre><h4>Combined instructions</h4><p><strong>Problem</strong>: For frequently executed instructions we want to use
│ │ │ +</span><span class="n">ASSERT</span><span class="p" data-group-id="5756561474-16">(</span><span class="n">VALID_INSTR</span><span class="p" data-group-id="5756561474-17">(</span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="5756561474-18">(</span><span class="n">Eterm</span><span class="w"> </span><span class="o">*</span><span class="p" data-group-id="5756561474-18">)</span><span class="n">I</span><span class="p" data-group-id="5756561474-17">)</span><span class="p" data-group-id="5756561474-16">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="n">Goto</span><span class="p" data-group-id="5756561474-19">(</span><span class="o">*</span><span class="n">I</span><span class="p" data-group-id="5756561474-19">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5756561474-2">}</span></code></pre><h4>Combined instructions</h4><p><strong>Problem</strong>: For frequently executed instructions we want to use
│ │ │  &quot;fast&quot; operands types such as <code class="inline">x</code> and <code class="inline">y</code>, as opposed to <code class="inline">s</code> or <code class="inline">S</code>.
│ │ │  To avoid an explosion in code size, we want to share most of the
│ │ │  implementation between the instructions.  Here are the specific
│ │ │  instructions for <code class="inline">i_increment/5</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_increment</span><span class="w"> </span><span class="ss">r</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_increment</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │ -</span><span class="ss">i_increment</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The <code class="inline">i_increment</code> instruction is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_increment</span><span class="p" data-group-id="5464461202-1">(</span><span class="n">Source</span><span class="p">,</span><span class="w"> </span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="5464461202-1">)</span><span class="w"> </span><span class="p" data-group-id="5464461202-2">{</span><span class="w">
│ │ │ +</span><span class="ss">i_increment</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The <code class="inline">i_increment</code> instruction is implemented like this:</p><pre><code class="makeup erlang" translate="no"><span class="nf">i_increment</span><span class="p" data-group-id="0906957250-1">(</span><span class="n">Source</span><span class="p">,</span><span class="w"> </span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="0906957250-1">)</span><span class="w"> </span><span class="p" data-group-id="0906957250-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_reg_source</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">ource</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$I</span><span class="ss">ncrementVal</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">live</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="5464461202-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="5464461202-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="5464461202-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="5464461202-5">)</span><span class="p" data-group-id="5464461202-4">)</span><span class="p" data-group-id="5464461202-3">)</span><span class="w"> </span><span class="p" data-group-id="5464461202-6">{</span><span class="w">
│ │ │ -        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="5464461202-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="5464461202-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="5464461202-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="5464461202-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="5464461202-10">(</span><span class="ss">i</span><span class="p" data-group-id="5464461202-10">)</span><span class="p" data-group-id="5464461202-9">)</span><span class="p" data-group-id="5464461202-8">)</span><span class="w"> </span><span class="p" data-group-id="5464461202-11">{</span><span class="w">
│ │ │ -            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="5464461202-12">(</span><span class="ss">i</span><span class="p" data-group-id="5464461202-12">)</span><span class="p">;</span><span class="w">
│ │ │ -            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="5464461202-13">(</span><span class="p" data-group-id="5464461202-13">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5464461202-11">}</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5464461202-6">}</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0906957250-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="0906957250-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="0906957250-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="0906957250-5">)</span><span class="p" data-group-id="0906957250-4">)</span><span class="p" data-group-id="0906957250-3">)</span><span class="w"> </span><span class="p" data-group-id="0906957250-6">{</span><span class="w">
│ │ │ +        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="0906957250-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="0906957250-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0906957250-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="0906957250-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="0906957250-10">(</span><span class="ss">i</span><span class="p" data-group-id="0906957250-10">)</span><span class="p" data-group-id="0906957250-9">)</span><span class="p" data-group-id="0906957250-8">)</span><span class="w"> </span><span class="p" data-group-id="0906957250-11">{</span><span class="w">
│ │ │ +            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="0906957250-12">(</span><span class="ss">i</span><span class="p" data-group-id="0906957250-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="0906957250-13">(</span><span class="p" data-group-id="0906957250-13">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0906957250-11">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0906957250-6">}</span><span class="w">
│ │ │      </span><span class="ss">live</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPOUT</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="5464461202-14">[</span><span class="ss">live</span><span class="p" data-group-id="5464461202-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="5464461202-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="5464461202-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="5464461202-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="5464461202-16">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="5464461202-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="5464461202-17">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="0906957250-14">[</span><span class="ss">live</span><span class="p" data-group-id="0906957250-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="0906957250-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="0906957250-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="0906957250-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="0906957250-16">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="0906957250-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="0906957250-17">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPIN</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="5464461202-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="5464461202-18">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="5464461202-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="5464461202-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="5464461202-21">(</span><span class="ss">result</span><span class="p" data-group-id="5464461202-21">)</span><span class="p" data-group-id="5464461202-20">)</span><span class="p" data-group-id="5464461202-19">)</span><span class="w"> </span><span class="p" data-group-id="5464461202-22">{</span><span class="w">
│ │ │ -        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="5464461202-23">(</span><span class="p" data-group-id="5464461202-23">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="0906957250-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="0906957250-18">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="0906957250-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="0906957250-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="0906957250-21">(</span><span class="ss">result</span><span class="p" data-group-id="0906957250-21">)</span><span class="p" data-group-id="0906957250-20">)</span><span class="p" data-group-id="0906957250-19">)</span><span class="w"> </span><span class="p" data-group-id="0906957250-22">{</span><span class="w">
│ │ │ +        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="0906957250-23">(</span><span class="p" data-group-id="0906957250-23">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="5464461202-24">(</span><span class="p" data-group-id="5464461202-24">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="5464461202-22">}</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="5464461202-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="5464461202-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="5464461202-26">)</span><span class="p" data-group-id="5464461202-25">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="0906957250-24">(</span><span class="p" data-group-id="0906957250-24">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="0906957250-22">}</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="0906957250-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="0906957250-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="0906957250-26">)</span><span class="p" data-group-id="0906957250-25">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">goto</span><span class="w"> </span><span class="ss">find_func_info</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5464461202-2">}</span></code></pre><p>There will be three almost identical copies of the code.  Given the
│ │ │ +</span><span class="p" data-group-id="0906957250-2">}</span></code></pre><p>There will be three almost identical copies of the code.  Given the
│ │ │  size of the code, that could be too high cost to pay.</p><p>To avoid the three copies of the code, we could use only one specific
│ │ │  instruction:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_increment</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>(The same implementation as above will work.)</p><p>That reduces the code size, but is slower because <code class="inline">S</code> means that
│ │ │  there will be extra code to test whether the operand refers to an X
│ │ │  register or a Y register.</p><p><strong>Solution</strong>: We can use &quot;combined instructions&quot;.  Combined
│ │ │  instructions are combined from instruction fragments.  The
│ │ │  bulk of the code can be shared.</p><p>Here we will show how <code class="inline">i_increment</code> can be implemented as a combined
│ │ │  instruction.  We will show each individual fragment first, and then
│ │ │  show how to connect them together.  First we will need a variable that
│ │ │ -we can store the value fetched from the register in:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="5465739929-1">(</span><span class="p" data-group-id="5465739929-1">)</span><span class="w"> </span><span class="p" data-group-id="5465739929-2">{</span><span class="w">
│ │ │ +we can store the value fetched from the register in:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="2036808272-1">(</span><span class="p" data-group-id="2036808272-1">)</span><span class="w"> </span><span class="p" data-group-id="2036808272-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5465739929-2">}</span></code></pre><p>The name <code class="inline">increment</code> is the name of the group that the fragment
│ │ │ +</span><span class="p" data-group-id="2036808272-2">}</span></code></pre><p>The name <code class="inline">increment</code> is the name of the group that the fragment
│ │ │  belongs to.  Note that it does not need to have the same
│ │ │  name as the instruction.  The group name is followed by <code class="inline">.</code> and
│ │ │  the name of the fragment.  The name <code class="inline">head</code> is pre-defined.
│ │ │  The code in it will be placed at the beginning of a block, so
│ │ │  that all fragments in the group can access it.</p><p>Next we define the fragment that will pick up the value from the
│ │ │ -register from the first operand:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="4298461466-1">(</span><span class="n">Src</span><span class="p" data-group-id="4298461466-1">)</span><span class="w"> </span><span class="p" data-group-id="4298461466-2">{</span><span class="w">
│ │ │ +register from the first operand:</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="1841534086-1">(</span><span class="n">Src</span><span class="p" data-group-id="1841534086-1">)</span><span class="w"> </span><span class="p" data-group-id="1841534086-2">{</span><span class="w">
│ │ │      </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4298461466-2">}</span></code></pre><p>We call this fragment <code class="inline">fetch</code>.  This fragment will be duplicated three
│ │ │ -times, one for each value of the first operand (<code class="inline">r</code>, <code class="inline">x</code>, and <code class="inline">y</code>).</p><p>Next we define the main part of the code that do the actual incrementing.</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="2103420600-1">(</span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="2103420600-1">)</span><span class="w"> </span><span class="p" data-group-id="2103420600-2">{</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1841534086-2">}</span></code></pre><p>We call this fragment <code class="inline">fetch</code>.  This fragment will be duplicated three
│ │ │ +times, one for each value of the first operand (<code class="inline">r</code>, <code class="inline">x</code>, and <code class="inline">y</code>).</p><p>Next we define the main part of the code that do the actual incrementing.</p><pre><code class="makeup erlang" translate="no"><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="9915008575-1">(</span><span class="n">IncrementVal</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="9915008575-1">)</span><span class="w"> </span><span class="p" data-group-id="9915008575-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$I</span><span class="ss">ncrementVal</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">live</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2103420600-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="2103420600-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="2103420600-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="2103420600-5">)</span><span class="p" data-group-id="2103420600-4">)</span><span class="p" data-group-id="2103420600-3">)</span><span class="w"> </span><span class="p" data-group-id="2103420600-6">{</span><span class="w">
│ │ │ -        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="2103420600-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="2103420600-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2103420600-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="2103420600-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="2103420600-10">(</span><span class="ss">i</span><span class="p" data-group-id="2103420600-10">)</span><span class="p" data-group-id="2103420600-9">)</span><span class="p" data-group-id="2103420600-8">)</span><span class="w"> </span><span class="p" data-group-id="2103420600-11">{</span><span class="w">
│ │ │ -            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="2103420600-12">(</span><span class="ss">i</span><span class="p" data-group-id="2103420600-12">)</span><span class="p">;</span><span class="w">
│ │ │ -            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="2103420600-13">(</span><span class="p" data-group-id="2103420600-13">)</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2103420600-11">}</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2103420600-6">}</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9915008575-3">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="9915008575-4">(</span><span class="nf">is_small</span><span class="p" data-group-id="9915008575-5">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="9915008575-5">)</span><span class="p" data-group-id="9915008575-4">)</span><span class="p" data-group-id="9915008575-3">)</span><span class="w"> </span><span class="p" data-group-id="9915008575-6">{</span><span class="w">
│ │ │ +        </span><span class="n">Sint</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">signed_val</span><span class="p" data-group-id="9915008575-7">(</span><span class="ss">increment_reg_val</span><span class="p" data-group-id="9915008575-7">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">increment_val</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9915008575-8">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="9915008575-9">(</span><span class="n">IS_SSMALL</span><span class="p" data-group-id="9915008575-10">(</span><span class="ss">i</span><span class="p" data-group-id="9915008575-10">)</span><span class="p" data-group-id="9915008575-9">)</span><span class="p" data-group-id="9915008575-8">)</span><span class="w"> </span><span class="p" data-group-id="9915008575-11">{</span><span class="w">
│ │ │ +            </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="9915008575-12">(</span><span class="ss">i</span><span class="p" data-group-id="9915008575-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="9915008575-13">(</span><span class="p" data-group-id="9915008575-13">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="9915008575-11">}</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9915008575-6">}</span><span class="w">
│ │ │      </span><span class="ss">live</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$L</span><span class="ss">ive</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPOUT</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="2103420600-14">[</span><span class="ss">live</span><span class="p" data-group-id="2103420600-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">reg</span><span class="p" data-group-id="2103420600-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="2103420600-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="2103420600-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="2103420600-16">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="2103420600-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="2103420600-17">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="9915008575-14">[</span><span class="ss">live</span><span class="p" data-group-id="9915008575-14">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">reg</span><span class="p" data-group-id="9915008575-15">[</span><span class="ss">live</span><span class="o">+</span><span class="mi">1</span><span class="p" data-group-id="9915008575-15">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_small</span><span class="p" data-group-id="9915008575-16">(</span><span class="ss">increment_val</span><span class="p" data-group-id="9915008575-16">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_gc_mixed_plus</span><span class="p" data-group-id="9915008575-17">(</span><span class="ss">c_p</span><span class="p">,</span><span class="w"> </span><span class="ss">reg</span><span class="p">,</span><span class="w"> </span><span class="ss">live</span><span class="p" data-group-id="9915008575-17">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">HEAVY_SWAPIN</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="2103420600-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="2103420600-18">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="2103420600-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="2103420600-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="2103420600-21">(</span><span class="ss">result</span><span class="p" data-group-id="2103420600-21">)</span><span class="p" data-group-id="2103420600-20">)</span><span class="p" data-group-id="2103420600-19">)</span><span class="w"> </span><span class="p" data-group-id="2103420600-22">{</span><span class="w">
│ │ │ -        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="2103420600-23">(</span><span class="p" data-group-id="2103420600-23">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ERTS_HOLE_CHECK</span><span class="p" data-group-id="9915008575-18">(</span><span class="ss">c_p</span><span class="p" data-group-id="9915008575-18">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">if</span><span class="w"> </span><span class="p" data-group-id="9915008575-19">(</span><span class="n">ERTS_LIKELY</span><span class="p" data-group-id="9915008575-20">(</span><span class="nf">is_value</span><span class="p" data-group-id="9915008575-21">(</span><span class="ss">result</span><span class="p" data-group-id="9915008575-21">)</span><span class="p" data-group-id="9915008575-20">)</span><span class="p" data-group-id="9915008575-19">)</span><span class="w"> </span><span class="p" data-group-id="9915008575-22">{</span><span class="w">
│ │ │ +        </span><span class="sc">$R</span><span class="n">EFRESH_GEN_DEST</span><span class="p" data-group-id="9915008575-23">(</span><span class="p" data-group-id="9915008575-23">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="sc">$D</span><span class="ss">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">result</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="2103420600-24">(</span><span class="p" data-group-id="2103420600-24">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2103420600-22">}</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="2103420600-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="2103420600-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="2103420600-26">)</span><span class="p" data-group-id="2103420600-25">)</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="sc">$N</span><span class="n">EXT0</span><span class="p" data-group-id="9915008575-24">(</span><span class="p" data-group-id="9915008575-24">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9915008575-22">}</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="9915008575-25">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">freason</span><span class="w"> </span><span class="o">!</span><span class="o">=</span><span class="w"> </span><span class="n">BADMATCH</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="nf">is_value</span><span class="p" data-group-id="9915008575-26">(</span><span class="ss">c_p</span><span class="p">-&gt;</span><span class="ss">fvalue</span><span class="p" data-group-id="9915008575-26">)</span><span class="p" data-group-id="9915008575-25">)</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">goto</span><span class="w"> </span><span class="ss">find_func_info</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2103420600-2">}</span></code></pre><p>We call this fragment <code class="inline">execute</code>.  It will handle the three remaining
│ │ │ +</span><span class="p" data-group-id="9915008575-2">}</span></code></pre><p>We call this fragment <code class="inline">execute</code>.  It will handle the three remaining
│ │ │  operands (<code class="inline">W t d</code>).  There will only be one copy of this fragment.</p><p>Now that we have defined the fragments, we need to inform
│ │ │  <strong>beam_makeops</strong> how they should be connected:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_increment</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">increment</span><span class="p">.</span><span class="ss">fetch</span><span class="p">.</span><span class="ss">execute</span><span class="p">;</span></code></pre><p>To the left of the <code class="inline">:=</code> is the name of the specific instruction that
│ │ │  should be implemented by the fragments, in this case <code class="inline">i_increment</code>.
│ │ │  To the right of <code class="inline">:=</code> is the name of the group with the fragments,
│ │ │  followed by a <code class="inline">.</code>.  Then the name of the fragments in the group are
│ │ │  listed in the order they should be executed.  Note that the <code class="inline">head</code>
│ │ │  fragment is not listed.</p><p>The line ends in <code class="inline">;</code> (to avoid messing up the indentation in Emacs).</p><p>(Note that in practice the <code class="inline">:=</code> line is usually placed before the
│ │ │ -fragments.)</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9198739449-1">{</span><span class="w">
│ │ │ +fragments.)</p><p>The generated code looks like this:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5460174925-1">{</span><span class="w">
│ │ │    </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">increment_reg_val</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="n">OpCase</span><span class="p" data-group-id="9198739449-2">(</span><span class="ss">i_increment_rWtd</span><span class="p" data-group-id="9198739449-2">)</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-3">{</span><span class="w">
│ │ │ -    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">r</span><span class="p" data-group-id="9198739449-4">(</span><span class="mi">0</span><span class="p" data-group-id="9198739449-4">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-3">}</span><span class="w">
│ │ │ +  </span><span class="n">OpCase</span><span class="p" data-group-id="5460174925-2">(</span><span class="ss">i_increment_rWtd</span><span class="p" data-group-id="5460174925-2">)</span><span class="p">:</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-3">{</span><span class="w">
│ │ │ +    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">r</span><span class="p" data-group-id="5460174925-4">(</span><span class="mi">0</span><span class="p" data-group-id="5460174925-4">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-3">}</span><span class="w">
│ │ │    </span><span class="ss">goto</span><span class="w"> </span><span class="ss">increment__execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -  </span><span class="n">OpCase</span><span class="p" data-group-id="9198739449-5">(</span><span class="ss">i_increment_xWtd</span><span class="p" data-group-id="9198739449-5">)</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-6">{</span><span class="w">
│ │ │ -    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="9198739449-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="9198739449-8">(</span><span class="n">I</span><span class="p" data-group-id="9198739449-9">[</span><span class="mi">0</span><span class="p" data-group-id="9198739449-9">]</span><span class="p" data-group-id="9198739449-8">)</span><span class="p" data-group-id="9198739449-7">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-6">}</span><span class="w">
│ │ │ +  </span><span class="n">OpCase</span><span class="p" data-group-id="5460174925-5">(</span><span class="ss">i_increment_xWtd</span><span class="p" data-group-id="5460174925-5">)</span><span class="p">:</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-6">{</span><span class="w">
│ │ │ +    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">xb</span><span class="p" data-group-id="5460174925-7">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="5460174925-8">(</span><span class="n">I</span><span class="p" data-group-id="5460174925-9">[</span><span class="mi">0</span><span class="p" data-group-id="5460174925-9">]</span><span class="p" data-group-id="5460174925-8">)</span><span class="p" data-group-id="5460174925-7">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-6">}</span><span class="w">
│ │ │    </span><span class="ss">goto</span><span class="w"> </span><span class="ss">increment__execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -  </span><span class="n">OpCase</span><span class="p" data-group-id="9198739449-10">(</span><span class="ss">i_increment_yWtd</span><span class="p" data-group-id="9198739449-10">)</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-11">{</span><span class="w">
│ │ │ -    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">yb</span><span class="p" data-group-id="9198739449-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="9198739449-13">(</span><span class="n">I</span><span class="p" data-group-id="9198739449-14">[</span><span class="mi">0</span><span class="p" data-group-id="9198739449-14">]</span><span class="p" data-group-id="9198739449-13">)</span><span class="p" data-group-id="9198739449-12">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-11">}</span><span class="w">
│ │ │ +  </span><span class="n">OpCase</span><span class="p" data-group-id="5460174925-10">(</span><span class="ss">i_increment_yWtd</span><span class="p" data-group-id="5460174925-10">)</span><span class="p">:</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-11">{</span><span class="w">
│ │ │ +    </span><span class="ss">increment_reg_val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">yb</span><span class="p" data-group-id="5460174925-12">(</span><span class="n">BeamExtraData</span><span class="p" data-group-id="5460174925-13">(</span><span class="n">I</span><span class="p" data-group-id="5460174925-14">[</span><span class="mi">0</span><span class="p" data-group-id="5460174925-14">]</span><span class="p" data-group-id="5460174925-13">)</span><span class="p" data-group-id="5460174925-12">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-11">}</span><span class="w">
│ │ │    </span><span class="ss">goto</span><span class="w"> </span><span class="ss">increment__execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │    </span><span class="nc">increment__execute</span><span class="p">:</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="9198739449-15">{</span><span class="w">
│ │ │ -    </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Here</span><span class="w"> </span><span class="ss">follows</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="9198739449-16">(</span><span class="p" data-group-id="9198739449-16">)</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="5460174925-15">{</span><span class="w">
│ │ │ +    </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Here</span><span class="w"> </span><span class="ss">follows</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">increment</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="5460174925-16">(</span><span class="p" data-group-id="5460174925-16">)</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9198739449-15">}</span></code></pre><h5>Some notes about combined instructions</h5><p>The operands that are different must be at
│ │ │ +</span><span class="p" data-group-id="5460174925-15">}</span></code></pre><h5>Some notes about combined instructions</h5><p>The operands that are different must be at
│ │ │  the beginning of the instruction.  All operands in the last
│ │ │  fragment must have the same operands in all variants of
│ │ │  the specific instruction.</p><p>As an example, the following specific instructions cannot be
│ │ │  implemented as a combined instruction:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_times</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>We would have to change the order of the operands so that the
│ │ │  two operands that are different are placed first:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_times</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">x</span><span class="w"> </span><span class="ss">y</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span><span class="w">
│ │ │  </span><span class="ss">i_times</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="w"> </span><span class="ss">d</span></code></pre><p>We can then define:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_times</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">times</span><span class="p">.</span><span class="ss">fetch</span><span class="p">.</span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">times</span><span class="p">.</span><span class="ss">head</span><span class="w"> </span><span class="p" data-group-id="8803072350-1">{</span><span class="w">
│ │ │ +</span><span class="ss">times</span><span class="p">.</span><span class="ss">head</span><span class="w"> </span><span class="p" data-group-id="1709021318-1">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">op1</span><span class="p">,</span><span class="w"> </span><span class="ss">op2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8803072350-1">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1709021318-1">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">times</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="8803072350-2">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="8803072350-2">)</span><span class="w"> </span><span class="p" data-group-id="8803072350-3">{</span><span class="w">
│ │ │ +</span><span class="ss">times</span><span class="p">.</span><span class="nf">fetch</span><span class="p" data-group-id="1709021318-2">(</span><span class="n">Src1</span><span class="p">,</span><span class="w"> </span><span class="n">Src2</span><span class="p" data-group-id="1709021318-2">)</span><span class="w"> </span><span class="p" data-group-id="1709021318-3">{</span><span class="w">
│ │ │      </span><span class="ss">op1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc1</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">op2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$S</span><span class="ss">rc2</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8803072350-3">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1709021318-3">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">times</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="8803072350-4">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="8803072350-4">)</span><span class="w"> </span><span class="p" data-group-id="8803072350-5">{</span><span class="w">
│ │ │ +</span><span class="ss">times</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="1709021318-4">(</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="1709021318-4">)</span><span class="w"> </span><span class="p" data-group-id="1709021318-5">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Multiply</span><span class="w"> </span><span class="ss">op1</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">op2</span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8803072350-5">}</span></code></pre><p>Several instructions can share a group.  As an example, the following
│ │ │ +</span><span class="p" data-group-id="1709021318-5">}</span></code></pre><p>Several instructions can share a group.  As an example, the following
│ │ │  instructions have different names, but in the end they all create a
│ │ │  binary.  The last two operands are common for all of them:</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_bs_init_fail</span><span class="w">       </span><span class="ss">xy</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_fail_heap</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="ss">j</span><span class="o">?</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init</span><span class="w">                </span><span class="n">W</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_heap</span><span class="w">         </span><span class="n">W</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="ss">t</span><span class="o">?</span><span class="w"> </span><span class="ss">x</span></code></pre><p>The instructions are defined like this (formatted with extra
│ │ │  spaces for clarity):</p><pre><code class="makeup erlang" translate="no"><span class="ss">i_bs_init_fail_heap</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">fail_heap</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">verify</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_fail</span><span class="w">      </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">fail</span><span class="w">      </span><span class="p">.</span><span class="w"> </span><span class="ss">verify</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init</span><span class="w">           </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w">           </span><span class="p">.</span><span class="w">  </span><span class="ss">plain</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="ss">i_bs_init_heap</span><span class="w">      </span><span class="p">:=</span><span class="w"> </span><span class="ss">bs_init</span><span class="w"> </span><span class="p">.</span><span class="w">               </span><span class="ss">heap</span><span class="w"> </span><span class="p">.</span><span class="w"> </span><span class="ss">execute</span><span class="p">;</span></code></pre><p>Note that the first two instruction have three fragments, while the
│ │ │ -other two only have two fragments.  Here are the fragments:</p><pre><code class="makeup erlang" translate="no"><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="4724023639-1">(</span><span class="p" data-group-id="4724023639-1">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-2">{</span><span class="w">
│ │ │ +other two only have two fragments.  Here are the fragments:</p><pre><code class="makeup erlang" translate="no"><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">head</span><span class="p" data-group-id="4039101804-1">(</span><span class="p" data-group-id="4039101804-1">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-2">{</span><span class="w">
│ │ │      </span><span class="n">Eterm</span><span class="w"> </span><span class="ss">num_bits_term</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">num_bits</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">Uint</span><span class="w"> </span><span class="ss">alloc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-2">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4039101804-2">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">plain</span><span class="p" data-group-id="4724023639-3">(</span><span class="n">NumBits</span><span class="p" data-group-id="4724023639-3">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-4">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">plain</span><span class="p" data-group-id="4039101804-3">(</span><span class="n">NumBits</span><span class="p" data-group-id="4039101804-3">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-4">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBits</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-4">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4039101804-4">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">heap</span><span class="p" data-group-id="4724023639-5">(</span><span class="n">NumBits</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="4724023639-5">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-6">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">heap</span><span class="p" data-group-id="4039101804-5">(</span><span class="n">NumBits</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="4039101804-5">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-6">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBits</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="ss">lloc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-6">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4039101804-6">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail</span><span class="p" data-group-id="4724023639-7">(</span><span class="n">NumBitsTerm</span><span class="p" data-group-id="4724023639-7">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-8">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail</span><span class="p" data-group-id="4039101804-7">(</span><span class="n">NumBitsTerm</span><span class="p" data-group-id="4039101804-7">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-8">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits_term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBitsTerm</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-8">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4039101804-8">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail_heap</span><span class="p" data-group-id="4724023639-9">(</span><span class="n">NumBitsTerm</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="4724023639-9">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-10">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">fail_heap</span><span class="p" data-group-id="4039101804-9">(</span><span class="n">NumBitsTerm</span><span class="p">,</span><span class="w"> </span><span class="n">Alloc</span><span class="p" data-group-id="4039101804-9">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-10">{</span><span class="w">
│ │ │      </span><span class="ss">num_bits_term</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$N</span><span class="ss">umBitsTerm</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">alloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">$A</span><span class="ss">lloc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-10">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4039101804-10">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">verify</span><span class="p" data-group-id="4724023639-11">(</span><span class="n">Fail</span><span class="p" data-group-id="4724023639-11">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-12">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">verify</span><span class="p" data-group-id="4039101804-11">(</span><span class="n">Fail</span><span class="p" data-group-id="4039101804-11">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-12">{</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Verify</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">num_bits_term</span><span class="p">,</span><span class="w"> </span><span class="ss">fail</span><span class="w"> </span><span class="ss">using</span><span class="w"> </span><span class="sc">$F</span><span class="n">AIL</span><span class="w">
│ │ │      </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="ss">there</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">problem</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-12">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4039101804-12">}</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="4724023639-13">(</span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="4724023639-13">)</span><span class="w"> </span><span class="p" data-group-id="4724023639-14">{</span><span class="w">
│ │ │ +</span><span class="ss">bs_init_bits</span><span class="p">.</span><span class="nf">execute</span><span class="p" data-group-id="4039101804-13">(</span><span class="n">Live</span><span class="p">,</span><span class="w"> </span><span class="n">Dst</span><span class="p" data-group-id="4039101804-13">)</span><span class="w"> </span><span class="p" data-group-id="4039101804-14">{</span><span class="w">
│ │ │     </span><span class="o">/</span><span class="o">/</span><span class="w"> </span><span class="n">Long</span><span class="w"> </span><span class="ss">complicated</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">create</span><span class="w"> </span><span class="ss">a</span><span class="w"> </span><span class="ss">binary</span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │     </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4724023639-14">}</span></code></pre><p>The full definitions of those instructions can be found in <code class="inline">bs_instrs.tab</code>.
│ │ │ +</span><span class="p" data-group-id="4039101804-14">}</span></code></pre><p>The full definitions of those instructions can be found in <code class="inline">bs_instrs.tab</code>.
│ │ │  The generated code can be found in <code class="inline">beam_warm.h</code>.</p><h3 id="code-generation-for-beamasm" class="section-heading">
│ │ │    <a href="#code-generation-for-beamasm" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Code generation for BeamAsm</span>
│ │ │  </h3>
│ │ │  <p>For the BeamAsm runtime system, the implementation of each instruction is defined
│ │ │  by emitter functions written in C++ that emit the assembly code for each instruction.
│ │ │  There is one emitter function for each family of specific instructions.</p><p>Take for example the <code class="inline">move</code> instruction. In <code class="inline">beam/asm/ops.tab</code> there is a
│ │ │ -single specific instruction for <code class="inline">move</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The implementation is found in <code class="inline">beam/asm/instr_common.cpp</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_move</span><span class="p" data-group-id="3870811921-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="3870811921-1">)</span><span class="w"> </span><span class="p" data-group-id="3870811921-2">{</span><span class="w">
│ │ │ -    </span><span class="nf">mov_arg</span><span class="p" data-group-id="3870811921-3">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="3870811921-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3870811921-2">}</span></code></pre><p>The <code class="inline">mov_arg()</code> helper function will handle all combinations of source and destination
│ │ │ -operands.  For example, the instruction <code class="inline">{move,{x,1},{y,1}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">rdi</span><span class="p">,</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="4866704022-1">[</span><span class="ss">rbx</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="4866704022-1">]</span><span class="w">
│ │ │ -</span><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="4866704022-2">[</span><span class="ss">rsp</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="4866704022-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">rdi</span></code></pre><p>while <code class="inline">{move,{integer,42},{x,0}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="3481673787-1">[</span><span class="ss">rbx</span><span class="p" data-group-id="3481673787-1">]</span><span class="p">,</span><span class="w"> </span><span class="mi">687</span></code></pre><p>It is possible to define more than one specific instruction, but there will still be
│ │ │ +single specific instruction for <code class="inline">move</code> defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">move</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">d</span></code></pre><p>The implementation is found in <code class="inline">beam/asm/instr_common.cpp</code>:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_move</span><span class="p" data-group-id="4273221146-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="4273221146-1">)</span><span class="w"> </span><span class="p" data-group-id="4273221146-2">{</span><span class="w">
│ │ │ +    </span><span class="nf">mov_arg</span><span class="p" data-group-id="4273221146-3">(</span><span class="n">Dst</span><span class="p">,</span><span class="w"> </span><span class="n">Src</span><span class="p" data-group-id="4273221146-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4273221146-2">}</span></code></pre><p>The <code class="inline">mov_arg()</code> helper function will handle all combinations of source and destination
│ │ │ +operands.  For example, the instruction <code class="inline">{move,{x,1},{y,1}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">rdi</span><span class="p">,</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="6994049772-1">[</span><span class="ss">rbx</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="6994049772-1">]</span><span class="w">
│ │ │ +</span><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="6994049772-2">[</span><span class="ss">rsp</span><span class="o">+</span><span class="mi">8</span><span class="p" data-group-id="6994049772-2">]</span><span class="p">,</span><span class="w"> </span><span class="ss">rdi</span></code></pre><p>while <code class="inline">{move,{integer,42},{x,0}}</code> will be translated like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">mov</span><span class="w"> </span><span class="ss">qword</span><span class="w"> </span><span class="p" data-group-id="8297016363-1">[</span><span class="ss">rbx</span><span class="p" data-group-id="8297016363-1">]</span><span class="p">,</span><span class="w"> </span><span class="mi">687</span></code></pre><p>It is possible to define more than one specific instruction, but there will still be
│ │ │  only one emitter function. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">fload</span><span class="w"> </span><span class="n">S</span><span class="w"> </span><span class="ss">l</span><span class="w">
│ │ │  </span><span class="ss">fload</span><span class="w"> </span><span class="ss">q</span><span class="w"> </span><span class="ss">l</span></code></pre><p>By defining <code class="inline">fload</code> like this, the source operand must be a X register, Y register, or
│ │ │  a literal.  If not, the loading will be aborted.  If the instruction instead had been
│ │ │  defined like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">fload</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">l</span></code></pre><p>attempting to load an invalid instruction such as <code class="inline">{fload,{atom,clearly_bad},{fr,0}}</code>
│ │ │  would cause a crash (either at load time or when the instruction was executed).</p><p>Regardless on how many specific instructions there are in the family,
│ │ │ -only a single <code class="inline">emit_fload()</code> function is allowed:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_fload</span><span class="p" data-group-id="2242227942-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="2242227942-1">)</span><span class="w"> </span><span class="p" data-group-id="2242227942-2">{</span><span class="w">
│ │ │ +only a single <code class="inline">emit_fload()</code> function is allowed:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_fload</span><span class="p" data-group-id="8338810973-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Dst</span><span class="p" data-group-id="8338810973-1">)</span><span class="w"> </span><span class="p" data-group-id="8338810973-2">{</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │      </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2242227942-2">}</span></code></pre><p><a href="" id="handling-a-variable-number-of-operands"></a></p><h4>Handling a variable number of operands</h4><p>Here follows an example of how an instruction with a variable number
│ │ │ +</span><span class="p" data-group-id="8338810973-2">}</span></code></pre><p><a href="" id="handling-a-variable-number-of-operands"></a></p><h4>Handling a variable number of operands</h4><p>Here follows an example of how an instruction with a variable number
│ │ │  of operands could be handled.  One such instructions is
│ │ │ -<code class="inline">select_val/3</code>. Here is an example how it can look like in BEAM code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="9721908789-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="9721908789-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="9721908789-2">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9721908789-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9721908789-3">}</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="9721908789-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="9721908789-5">[</span><span class="p" data-group-id="9721908789-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="9721908789-6">}</span><span class="p">,</span><span class="p" data-group-id="9721908789-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9721908789-7">}</span><span class="p">,</span><span class="p" data-group-id="9721908789-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="9721908789-8">}</span><span class="p">,</span><span class="p" data-group-id="9721908789-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9721908789-9">}</span><span class="p" data-group-id="9721908789-5">]</span><span class="p" data-group-id="9721908789-4">}</span><span class="p" data-group-id="9721908789-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │ +<code class="inline">select_val/3</code>. Here is an example how it can look like in BEAM code:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8016930613-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="8016930613-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="8016930613-2">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8016930613-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="8016930613-3">}</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="8016930613-4">{</span><span class="ss">list</span><span class="p">,</span><span class="p" data-group-id="8016930613-5">[</span><span class="p" data-group-id="8016930613-6">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="8016930613-6">}</span><span class="p">,</span><span class="p" data-group-id="8016930613-7">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="8016930613-7">}</span><span class="p">,</span><span class="p" data-group-id="8016930613-8">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="8016930613-8">}</span><span class="p">,</span><span class="p" data-group-id="8016930613-9">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8016930613-9">}</span><span class="p" data-group-id="8016930613-5">]</span><span class="p" data-group-id="8016930613-4">}</span><span class="p" data-group-id="8016930613-1">}</span><span class="p">.</span></code></pre><p>The loader will convert a <code class="inline">{list,[...]}</code> operand to an <code class="inline">u</code> operand whose
│ │ │  value is the number of elements in the list, followed by each element in
│ │ │  the list.  The instruction above would be translated to the following
│ │ │ -instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="6524999080-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="6524999080-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="6524999080-2">}</span><span class="p">,</span><span class="p" data-group-id="6524999080-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6524999080-3">}</span><span class="p">,</span><span class="p" data-group-id="6524999080-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6524999080-4">}</span><span class="p">,</span><span class="p" data-group-id="6524999080-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="6524999080-5">}</span><span class="p">,</span><span class="p" data-group-id="6524999080-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="6524999080-6">}</span><span class="p">,</span><span class="p" data-group-id="6524999080-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="6524999080-7">}</span><span class="p">,</span><span class="p" data-group-id="6524999080-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="6524999080-8">}</span><span class="p" data-group-id="6524999080-1">}</span></code></pre><p>A definition of a specific instruction for that instruction would look
│ │ │ +instruction:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="3612367381-1">{</span><span class="ss">select_val</span><span class="p">,</span><span class="p" data-group-id="3612367381-2">{</span><span class="ss">x</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="3612367381-2">}</span><span class="p">,</span><span class="p" data-group-id="3612367381-3">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="3612367381-3">}</span><span class="p">,</span><span class="p" data-group-id="3612367381-4">{</span><span class="ss">u</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3612367381-4">}</span><span class="p">,</span><span class="p" data-group-id="3612367381-5">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">b</span><span class="p" data-group-id="3612367381-5">}</span><span class="p">,</span><span class="p" data-group-id="3612367381-6">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="3612367381-6">}</span><span class="p">,</span><span class="p" data-group-id="3612367381-7">{</span><span class="ss">atom</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="3612367381-7">}</span><span class="p">,</span><span class="p" data-group-id="3612367381-8">{</span><span class="ss">f</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3612367381-8">}</span><span class="p" data-group-id="3612367381-1">}</span></code></pre><p>A definition of a specific instruction for that instruction would look
│ │ │  like this:</p><pre><code class="makeup erlang" translate="no"><span class="ss">select_val</span><span class="w"> </span><span class="ss">s</span><span class="w"> </span><span class="ss">f</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">*</span></code></pre><p>The <code class="inline">*</code> as the last operand will make sure that the variable operands
│ │ │  are passed in as a <code class="inline">Span</code> of <code class="inline">ArgVal</code> (will be <code class="inline">std::span</code> in C++20 onwards).
│ │ │ -Here is the emitter function:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_select_val</span><span class="p" data-group-id="3509555517-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w">
│ │ │ +Here is the emitter function:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_select_val</span><span class="p" data-group-id="7191528547-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p">,</span><span class="w">
│ │ │                                            </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Fail</span><span class="p">,</span><span class="w">
│ │ │                                            </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Size</span><span class="p">,</span><span class="w">
│ │ │ -                                          </span><span class="ss">const</span><span class="w"> </span><span class="n">Span</span><span class="o">&lt;</span><span class="n">ArgVal</span><span class="o">&gt;</span><span class="w"> </span><span class="err">&amp;</span><span class="ss">args</span><span class="p" data-group-id="3509555517-1">)</span><span class="w"> </span><span class="p" data-group-id="3509555517-2">{</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="3509555517-3">(</span><span class="n">Size</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="3509555517-4">(</span><span class="p" data-group-id="3509555517-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="ss">args</span><span class="p">.</span><span class="nf">size</span><span class="p" data-group-id="3509555517-5">(</span><span class="p" data-group-id="3509555517-5">)</span><span class="p" data-group-id="3509555517-3">)</span><span class="p">;</span><span class="w">
│ │ │ +                                          </span><span class="ss">const</span><span class="w"> </span><span class="n">Span</span><span class="o">&lt;</span><span class="n">ArgVal</span><span class="o">&gt;</span><span class="w"> </span><span class="err">&amp;</span><span class="ss">args</span><span class="p" data-group-id="7191528547-1">)</span><span class="w"> </span><span class="p" data-group-id="7191528547-2">{</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="7191528547-3">(</span><span class="n">Size</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="7191528547-4">(</span><span class="p" data-group-id="7191528547-4">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="ss">args</span><span class="p">.</span><span class="nf">size</span><span class="p" data-group-id="7191528547-5">(</span><span class="p" data-group-id="7191528547-5">)</span><span class="p" data-group-id="7191528547-3">)</span><span class="p">;</span><span class="w">
│ │ │         </span><span class="p">.</span><span class="w">
│ │ │         </span><span class="p">.</span><span class="w">
│ │ │         </span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3509555517-2">}</span></code></pre>
│ │ │ +</span><span class="p" data-group-id="7191528547-2">}</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="tracing.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/beamasm.html
│ │ │ @@ -145,26 +145,26 @@
│ │ │  </h2>
│ │ │  <p>The code is loaded very similarly to how it is loaded for the interpreter. Each beam
│ │ │  file is parsed and then optimized through the transformations described in
│ │ │  <a href="beam_makeops.html#defining-transformation-rules">beam_makeops</a>. The transformations
│ │ │  used in BeamAsm are much simpler than the interpreter's, as most of the
│ │ │  transformations for the interpreter are done only to eliminate the instruction
│ │ │  dispatch overhead.</p><p>Then each instruction is encoded using the C++ functions in the
│ │ │ -<code class="inline">jit/$ARCH/instr_*.cpp</code> files. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_is_nonempty_list</span><span class="p" data-group-id="8835496381-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p" data-group-id="8835496381-1">)</span><span class="w"> </span><span class="p" data-group-id="8835496381-2">{</span><span class="w">
│ │ │ -  </span><span class="ss">a</span><span class="p">.</span><span class="nf">test</span><span class="p" data-group-id="8835496381-3">(</span><span class="nf">getArgRef</span><span class="p" data-group-id="8835496381-4">(</span><span class="n">Src</span><span class="p" data-group-id="8835496381-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">imm</span><span class="p" data-group-id="8835496381-5">(</span><span class="p">_</span><span class="n">TAG_PRIMARY_MASK</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">TAG_PRIMARY_LIST</span><span class="p" data-group-id="8835496381-5">)</span><span class="p" data-group-id="8835496381-3">)</span><span class="p">;</span><span class="w">
│ │ │ -  </span><span class="ss">a</span><span class="p">.</span><span class="nf">jne</span><span class="p" data-group-id="8835496381-6">(</span><span class="ss">labels</span><span class="p" data-group-id="8835496381-7">[</span><span class="n">Fail</span><span class="p">.</span><span class="nf">getLabel</span><span class="p" data-group-id="8835496381-8">(</span><span class="p" data-group-id="8835496381-8">)</span><span class="p" data-group-id="8835496381-7">]</span><span class="p" data-group-id="8835496381-6">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8835496381-2">}</span></code></pre><p><a href="https://github.com/asmjit/asmjit">asmjit</a> provides a fairly straightforward
│ │ │ +<code class="inline">jit/$ARCH/instr_*.cpp</code> files. For example:</p><pre><code class="makeup erlang" translate="no"><span class="ss">void</span><span class="w"> </span><span class="n">BeamModuleAssembler</span><span class="p">:</span><span class="p">:</span><span class="nf">emit_is_nonempty_list</span><span class="p" data-group-id="6046162379-1">(</span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Fail</span><span class="p">,</span><span class="w"> </span><span class="ss">const</span><span class="w"> </span><span class="n">ArgVal</span><span class="w"> </span><span class="err">&amp;</span><span class="n">Src</span><span class="p" data-group-id="6046162379-1">)</span><span class="w"> </span><span class="p" data-group-id="6046162379-2">{</span><span class="w">
│ │ │ +  </span><span class="ss">a</span><span class="p">.</span><span class="nf">test</span><span class="p" data-group-id="6046162379-3">(</span><span class="nf">getArgRef</span><span class="p" data-group-id="6046162379-4">(</span><span class="n">Src</span><span class="p" data-group-id="6046162379-4">)</span><span class="p">,</span><span class="w"> </span><span class="nf">imm</span><span class="p" data-group-id="6046162379-5">(</span><span class="p">_</span><span class="n">TAG_PRIMARY_MASK</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">TAG_PRIMARY_LIST</span><span class="p" data-group-id="6046162379-5">)</span><span class="p" data-group-id="6046162379-3">)</span><span class="p">;</span><span class="w">
│ │ │ +  </span><span class="ss">a</span><span class="p">.</span><span class="nf">jne</span><span class="p" data-group-id="6046162379-6">(</span><span class="ss">labels</span><span class="p" data-group-id="6046162379-7">[</span><span class="n">Fail</span><span class="p">.</span><span class="nf">getLabel</span><span class="p" data-group-id="6046162379-8">(</span><span class="p" data-group-id="6046162379-8">)</span><span class="p" data-group-id="6046162379-7">]</span><span class="p" data-group-id="6046162379-6">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6046162379-2">}</span></code></pre><p><a href="https://github.com/asmjit/asmjit">asmjit</a> provides a fairly straightforward
│ │ │  mapping from a C++ function call to the x86 assembly instruction. The above
│ │ │  instruction tests if the value in the <code class="inline">Src</code> register is a non-empty list and if
│ │ │  it is not then it jumps to the fail label.</p><p>For comparison, the interpreter has 8 combinations and specializations of
│ │ │  this implementation to minimize the instruction dispatch overhead for
│ │ │  common patterns.</p><p>The original register allocation done by the Erlang compiler is used to manage the
│ │ │  liveness of values and the physical registers are statically allocated to keep
│ │ │  the necessary process state. At the moment this is the static register
│ │ │ -allocation on x86-64:</p><pre><code class="makeup erlang" translate="no"><span class="nc">rbx</span><span class="p">:</span><span class="w"> </span><span class="n">ErtsSchedulerRegisters</span><span class="w"> </span><span class="nf">struct</span><span class="w"> </span><span class="p" data-group-id="4598394322-1">(</span><span class="ss">contains</span><span class="w"> </span><span class="ss">x</span><span class="o">/</span><span class="nb">float</span><span class="w"> </span><span class="ss">registers</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">some</span><span class="w"> </span><span class="ss">metadata</span><span class="p" data-group-id="4598394322-1">)</span><span class="w">
│ │ │ +allocation on x86-64:</p><pre><code class="makeup erlang" translate="no"><span class="nc">rbx</span><span class="p">:</span><span class="w"> </span><span class="n">ErtsSchedulerRegisters</span><span class="w"> </span><span class="nf">struct</span><span class="w"> </span><span class="p" data-group-id="4519710154-1">(</span><span class="ss">contains</span><span class="w"> </span><span class="ss">x</span><span class="o">/</span><span class="nb">float</span><span class="w"> </span><span class="ss">registers</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">some</span><span class="w"> </span><span class="ss">metadata</span><span class="p" data-group-id="4519710154-1">)</span><span class="w">
│ │ │  </span><span class="nc">rbp</span><span class="p">:</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="ss">frame</span><span class="w"> </span><span class="ss">pointer</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="err">`</span><span class="ss">perf</span><span class="err">`</span><span class="w"> </span><span class="ss">support</span><span class="w"> </span><span class="ss">is</span><span class="w"> </span><span class="ss">enabled</span><span class="p">,</span><span class="w"> </span><span class="ss">otherwise</span><span class="w"> </span><span class="ss">this</span><span class="w">
│ │ │       </span><span class="ss">is</span><span class="w"> </span><span class="ss">an</span><span class="w"> </span><span class="ss">optional</span><span class="w"> </span><span class="ss">save</span><span class="w"> </span><span class="ss">slot</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="ss">stack</span><span class="w"> </span><span class="ss">pointer</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="ss">executing</span><span class="w"> </span><span class="n">C</span><span class="w">
│ │ │       </span><span class="ss">code</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="nc">r12</span><span class="p">:</span><span class="w"> </span><span class="n">Active</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">index</span><span class="w">
│ │ │  </span><span class="nc">r13</span><span class="p">:</span><span class="w"> </span><span class="n">Current</span><span class="w"> </span><span class="ss">running</span><span class="w"> </span><span class="ss">process</span><span class="w">
│ │ │  </span><span class="nc">r14</span><span class="p">:</span><span class="w"> </span><span class="n">Remaining</span><span class="w"> </span><span class="ss">reductions</span><span class="w">
│ │ │  </span><span class="nc">r15</span><span class="p">:</span><span class="w"> </span><span class="n">Erlang</span><span class="w"> </span><span class="ss">heap</span><span class="w"> </span><span class="ss">pointer</span></code></pre><p>Note that all of these are callee save registers under the System V and Windows
│ │ │ @@ -183,21 +183,21 @@
│ │ │  shared and only the arguments to the instructions vary. Using as little memory as
│ │ │  possible has many advantages; less memory is used, loading time decreases,
│ │ │  higher cache hit-rate.</p><p>In BeamAsm we need to achieve something similar since the load-time of a module
│ │ │  scales almost linearly with the amount of memory it uses. Early BeamAsm prototypes
│ │ │  used about double the amount of memory for code as the interpreter, while current
│ │ │  versions use about 10% more. How was this achieved?</p><p>In BeamAsm we heavily use shared code fragments to try to emit as much code as
│ │ │  possible as global shared fragments instead of duplicating the code unnecessarily.
│ │ │ -For instance, the return instruction looks something like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Label</span><span class="w"> </span><span class="ss">yield</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="nf">newLabel</span><span class="p" data-group-id="3933345777-1">(</span><span class="p" data-group-id="3933345777-1">)</span><span class="p">;</span><span class="w">
│ │ │ +For instance, the return instruction looks something like this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Label</span><span class="w"> </span><span class="ss">yield</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">a</span><span class="p">.</span><span class="nf">newLabel</span><span class="p" data-group-id="8231165983-1">(</span><span class="p" data-group-id="8231165983-1">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Decrement</span><span class="w"> </span><span class="ss">reduction</span><span class="w"> </span><span class="ss">counter</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">dec</span><span class="p" data-group-id="3933345777-2">(</span><span class="n">FCALLS</span><span class="p" data-group-id="3933345777-2">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">dec</span><span class="p" data-group-id="8231165983-2">(</span><span class="n">FCALLS</span><span class="p" data-group-id="8231165983-2">)</span><span class="p">;</span><span class="w">
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">If</span><span class="w"> </span><span class="n">FCALLS</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">jump</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">yield</span><span class="o">-</span><span class="ss">on</span><span class="o">-</span><span class="ss">return</span><span class="w"> </span><span class="ss">fragment</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">jl</span><span class="p" data-group-id="3933345777-3">(</span><span class="nf">resolve_fragment</span><span class="p" data-group-id="3933345777-4">(</span><span class="ss">ga</span><span class="p">-&gt;</span><span class="nf">get_dispatch_return</span><span class="p" data-group-id="3933345777-5">(</span><span class="p" data-group-id="3933345777-5">)</span><span class="p" data-group-id="3933345777-4">)</span><span class="p" data-group-id="3933345777-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">ret</span><span class="p" data-group-id="3933345777-6">(</span><span class="p" data-group-id="3933345777-6">)</span><span class="p">;</span></code></pre><p>The code above is not exactly what is emitted, but close enough. The thing to note
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">jl</span><span class="p" data-group-id="8231165983-3">(</span><span class="nf">resolve_fragment</span><span class="p" data-group-id="8231165983-4">(</span><span class="ss">ga</span><span class="p">-&gt;</span><span class="nf">get_dispatch_return</span><span class="p" data-group-id="8231165983-5">(</span><span class="p" data-group-id="8231165983-5">)</span><span class="p" data-group-id="8231165983-4">)</span><span class="p" data-group-id="8231165983-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">ret</span><span class="p" data-group-id="8231165983-6">(</span><span class="p" data-group-id="8231165983-6">)</span><span class="p">;</span></code></pre><p>The code above is not exactly what is emitted, but close enough. The thing to note
│ │ │  is that the code for doing the context switch is never emitted. Instead, we jump
│ │ │  to a global fragment that all return instructions share. This greatly reduces
│ │ │  the amount of code that has to be emitted for each module.</p><h2 id="running-erlang-code" class="section-heading">
│ │ │    <a href="#running-erlang-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running Erlang code</span>
│ │ │ @@ -239,43 +239,43 @@
│ │ │    <a href="#running-c-code" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Running C code</span>
│ │ │  </h2>
│ │ │  <p>As Erlang stacks can be very small, we have to switch over to a different stack
│ │ │  when we need to execute C code (which may expect a much larger stack). This is
│ │ │ -done through <code class="inline">emit_enter_runtime</code> and <code class="inline">emit_leave_runtime</code>, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mov_arg</span><span class="p" data-group-id="2738316979-1">(</span><span class="n">ARG4</span><span class="p">,</span><span class="w"> </span><span class="n">NumFree</span><span class="p" data-group-id="2738316979-1">)</span><span class="p">;</span><span class="w">
│ │ │ +done through <code class="inline">emit_enter_runtime</code> and <code class="inline">emit_leave_runtime</code>, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">mov_arg</span><span class="p" data-group-id="1087279589-1">(</span><span class="n">ARG4</span><span class="p">,</span><span class="w"> </span><span class="n">NumFree</span><span class="p" data-group-id="1087279589-1">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Move</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="ss">stack</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">swap</span><span class="w"> </span><span class="ss">out</span><span class="w"> </span><span class="ss">our</span><span class="w"> </span><span class="ss">current</span><span class="w"> </span><span class="ss">reductions</span><span class="p">,</span><span class="w"> </span><span class="ss">stack</span><span class="o">-</span><span class="p">,</span><span class="w"> </span><span class="ow">and</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="ss">heap</span><span class="w"> </span><span class="ss">pointer</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">process</span><span class="w"> </span><span class="ss">structure</span><span class="p">.</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">emit_enter_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="2738316979-2">(</span><span class="p" data-group-id="2738316979-2">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">emit_enter_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="1087279589-2">(</span><span class="p" data-group-id="1087279589-2">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="2738316979-3">(</span><span class="n">ARG1</span><span class="p">,</span><span class="w"> </span><span class="ss">c_p</span><span class="p" data-group-id="2738316979-3">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">load_x_reg_array</span><span class="p" data-group-id="2738316979-4">(</span><span class="n">ARG2</span><span class="p" data-group-id="2738316979-4">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">make_move_patch</span><span class="p" data-group-id="2738316979-5">(</span><span class="n">ARG3</span><span class="p">,</span><span class="w"> </span><span class="ss">lambdas</span><span class="p" data-group-id="2738316979-6">[</span><span class="n">Fun</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="2738316979-7">(</span><span class="p" data-group-id="2738316979-7">)</span><span class="p" data-group-id="2738316979-6">]</span><span class="p">.</span><span class="ss">patches</span><span class="p" data-group-id="2738316979-5">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="1087279589-3">(</span><span class="n">ARG1</span><span class="p">,</span><span class="w"> </span><span class="ss">c_p</span><span class="p" data-group-id="1087279589-3">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">load_x_reg_array</span><span class="p" data-group-id="1087279589-4">(</span><span class="n">ARG2</span><span class="p" data-group-id="1087279589-4">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="nf">make_move_patch</span><span class="p" data-group-id="1087279589-5">(</span><span class="n">ARG3</span><span class="p">,</span><span class="w"> </span><span class="ss">lambdas</span><span class="p" data-group-id="1087279589-6">[</span><span class="n">Fun</span><span class="p">.</span><span class="nf">getValue</span><span class="p" data-group-id="1087279589-7">(</span><span class="p" data-group-id="1087279589-7">)</span><span class="p" data-group-id="1087279589-6">]</span><span class="p">.</span><span class="ss">patches</span><span class="p" data-group-id="1087279589-5">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Call</span><span class="w"> </span><span class="err">`</span><span class="ss">new_fun</span><span class="err">`</span><span class="p">,</span><span class="w"> </span><span class="ss">asserting</span><span class="w"> </span><span class="ss">that</span><span class="w"> </span><span class="ss">we</span><span class="err">&#39;</span><span class="ss">re</span><span class="w"> </span><span class="ss">on</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="ss">stack</span><span class="p">.</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">runtime_call</span><span class="o">&lt;</span><span class="mi">4</span><span class="o">&gt;</span><span class="p" data-group-id="2738316979-8">(</span><span class="ss">new_fun</span><span class="p" data-group-id="2738316979-8">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">runtime_call</span><span class="o">&lt;</span><span class="mi">4</span><span class="o">&gt;</span><span class="p" data-group-id="1087279589-8">(</span><span class="ss">new_fun</span><span class="p" data-group-id="1087279589-8">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │  </span><span class="o">/</span><span class="o">*</span><span class="w"> </span><span class="n">Move</span><span class="w"> </span><span class="ss">back</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="ss">stack</span><span class="p">,</span><span class="w"> </span><span class="ow">and</span><span class="w"> </span><span class="ss">read</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">updated</span><span class="w"> </span><span class="ss">values</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">process</span><span class="w">
│ │ │   </span><span class="o">*</span><span class="w"> </span><span class="ss">structure</span><span class="w"> </span><span class="o">*</span><span class="o">/</span><span class="w">
│ │ │ -</span><span class="ss">emit_leave_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="2738316979-9">(</span><span class="p" data-group-id="2738316979-9">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="ss">emit_leave_runtime</span><span class="o">&lt;</span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eReductions</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eStack</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Update</span><span class="p">:</span><span class="p">:</span><span class="ss">eHeap</span><span class="o">&gt;</span><span class="p" data-group-id="1087279589-9">(</span><span class="p" data-group-id="1087279589-9">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="2738316979-10">(</span><span class="nf">getXRef</span><span class="p" data-group-id="2738316979-11">(</span><span class="mi">0</span><span class="p" data-group-id="2738316979-11">)</span><span class="p">,</span><span class="w"> </span><span class="n">RET</span><span class="p" data-group-id="2738316979-10">)</span><span class="p">;</span></code></pre><p>All combinations of the <code class="inline">Update</code> constants are legal, but the ones given to
│ │ │ +</span><span class="ss">a</span><span class="p">.</span><span class="nf">mov</span><span class="p" data-group-id="1087279589-10">(</span><span class="nf">getXRef</span><span class="p" data-group-id="1087279589-11">(</span><span class="mi">0</span><span class="p" data-group-id="1087279589-11">)</span><span class="p">,</span><span class="w"> </span><span class="n">RET</span><span class="p" data-group-id="1087279589-10">)</span><span class="p">;</span></code></pre><p>All combinations of the <code class="inline">Update</code> constants are legal, but the ones given to
│ │ │  <code class="inline">emit_leave_runtime</code> <em>must</em> be the same as those given to <code class="inline">emit_enter_runtime</code>.</p><h2 id="tracing-and-nif-loading" class="section-heading">
│ │ │    <a href="#tracing-and-nif-loading" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Tracing and NIF Loading</span>
│ │ │  </h2>
│ │ │  <p>To make tracing and NIF loading work there needs to be a way to intercept
│ │ │  any function call. In the interpreter, this is done by rewriting the loaded
│ │ │  BEAM code, but this is more complicated in BeamAsm as we want to have a fast
│ │ │  and compact way to do this. This is solved by emitting the code below at the
│ │ │ -start of each function (x86 variant below):</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="mi">0</span><span class="nc">x0</span><span class="p">:</span><span class="w"> </span><span class="ss">short</span><span class="w"> </span><span class="ss">jmp</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p" data-group-id="8385376915-1">(</span><span class="ss">address</span><span class="w"> </span><span class="mi">0</span><span class="ss">x8</span><span class="p" data-group-id="8385376915-1">)</span><span class="w">
│ │ │ +start of each function (x86 variant below):</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="mi">0</span><span class="nc">x0</span><span class="p">:</span><span class="w"> </span><span class="ss">short</span><span class="w"> </span><span class="ss">jmp</span><span class="w"> </span><span class="mi">6</span><span class="w"> </span><span class="p" data-group-id="9575717427-1">(</span><span class="ss">address</span><span class="w"> </span><span class="mi">0</span><span class="ss">x8</span><span class="p" data-group-id="9575717427-1">)</span><span class="w">
│ │ │    </span><span class="mi">0</span><span class="nc">x2</span><span class="p">:</span><span class="w"> </span><span class="ss">nop</span><span class="w">
│ │ │    </span><span class="mi">0</span><span class="nc">x3</span><span class="p">:</span><span class="w"> </span><span class="ss">relative</span><span class="w"> </span><span class="ss">near</span><span class="w"> </span><span class="ss">call</span><span class="w"> </span><span class="ss">to</span><span class="w"> </span><span class="ss">shared</span><span class="w"> </span><span class="ss">breakpoint</span><span class="w"> </span><span class="ss">fragment</span><span class="w">
│ │ │    </span><span class="mi">0</span><span class="nc">x8</span><span class="p">:</span><span class="w"> </span><span class="ss">actual</span><span class="w"> </span><span class="ss">code</span><span class="w"> </span><span class="ss">for</span><span class="w"> </span><span class="ss">function</span></code></pre><p>When code starts to execute it will simply see the <code class="inline">short jmp 6</code> instruction
│ │ │  which skips the prologue and starts to execute the code directly.</p><p>When we want to enable a certain breakpoint we set the jmp target to be 1,
│ │ │  which means it will land on the call to the shared breakpoint fragment. This
│ │ │  fragment checks the current <code class="inline">breakpoint_flag</code> stored in the ErtsCodeInfo of
│ │ │  this function, and then calls <code class="inline">erts_call_nif_early</code> and
│ │ │ @@ -289,31 +289,31 @@
│ │ │    <span class="text">Updating code</span>
│ │ │  </h3>
│ │ │  <p>Because many environments enforce <a href="https://en.wikipedia.org/wiki/W%5EX" title="">W^X</a> it's not always possible to write
│ │ │  directly to the code pages. Because of this we map code twice: once with an
│ │ │  executable page and once with a writable page. Since they're backed by the
│ │ │  same memory, writes to the writable page appear magically in the executable
│ │ │  one.</p><p>The <code class="inline">erts_writable_code_ptr</code> function can be used to get writable pointers
│ │ │ -given a module instance, provided that it has been unsealed first:</p><pre><code class="makeup erlang" translate="no"><span class="nf">for</span><span class="w"> </span><span class="p" data-group-id="4126676526-1">(</span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="ss">n</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="o">++</span><span class="p" data-group-id="4126676526-1">)</span><span class="w"> </span><span class="p" data-group-id="4126676526-2">{</span><span class="w">
│ │ │ +given a module instance, provided that it has been unsealed first:</p><pre><code class="makeup erlang" translate="no"><span class="nf">for</span><span class="w"> </span><span class="p" data-group-id="9792249579-1">(</span><span class="ss">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="ss">n</span><span class="p">;</span><span class="w"> </span><span class="ss">i</span><span class="o">++</span><span class="p" data-group-id="9792249579-1">)</span><span class="w"> </span><span class="p" data-group-id="9792249579-2">{</span><span class="w">
│ │ │      </span><span class="ss">const</span><span class="w"> </span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="w"> </span><span class="ss">ci_rw</span><span class="p">;</span><span class="w">
│ │ │      </span><span class="ss">void</span><span class="w"> </span><span class="o">*</span><span class="ss">w_ptr</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">erts_unseal_module</span><span class="p" data-group-id="4126676526-3">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="4126676526-3">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">erts_unseal_module</span><span class="p" data-group-id="9792249579-3">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="9792249579-3">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="ss">ci_exec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">code_hdr</span><span class="p">-&gt;</span><span class="ss">functions</span><span class="p" data-group-id="4126676526-4">[</span><span class="ss">i</span><span class="p" data-group-id="4126676526-4">]</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">w_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_writable_code_ptr</span><span class="p" data-group-id="4126676526-5">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="4126676526-5">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="ss">ci_rw</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4126676526-6">(</span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="p" data-group-id="4126676526-6">)</span><span class="ss">w_ptr</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">ci_exec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ss">code_hdr</span><span class="p">-&gt;</span><span class="ss">functions</span><span class="p" data-group-id="9792249579-4">[</span><span class="ss">i</span><span class="p" data-group-id="9792249579-4">]</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">w_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erts_writable_code_ptr</span><span class="p" data-group-id="9792249579-5">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="9792249579-5">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="ss">ci_rw</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9792249579-6">(</span><span class="n">ErtsCodeInfo</span><span class="o">*</span><span class="p" data-group-id="9792249579-6">)</span><span class="ss">w_ptr</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">uninstall_breakpoint</span><span class="p" data-group-id="4126676526-7">(</span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="4126676526-7">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="nf">consolidate_bp_data</span><span class="p" data-group-id="4126676526-8">(</span><span class="ss">modp</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="4126676526-8">)</span><span class="p">;</span><span class="w">
│ │ │ -    </span><span class="n">ASSERT</span><span class="p" data-group-id="4126676526-9">(</span><span class="ss">ci_rw</span><span class="p">-&gt;</span><span class="ss">gen_bp</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">NULL</span><span class="p" data-group-id="4126676526-9">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">uninstall_breakpoint</span><span class="p" data-group-id="9792249579-7">(</span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_exec</span><span class="p" data-group-id="9792249579-7">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="nf">consolidate_bp_data</span><span class="p" data-group-id="9792249579-8">(</span><span class="ss">modp</span><span class="p">,</span><span class="w"> </span><span class="ss">ci_rw</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9792249579-8">)</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">ASSERT</span><span class="p" data-group-id="9792249579-9">(</span><span class="ss">ci_rw</span><span class="p">-&gt;</span><span class="ss">gen_bp</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">NULL</span><span class="p" data-group-id="9792249579-9">)</span><span class="p">;</span><span class="w">
│ │ │  
│ │ │ -    </span><span class="nf">erts_seal_module</span><span class="p" data-group-id="4126676526-10">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="4126676526-10">)</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4126676526-2">}</span></code></pre><p>Without the module instance there's no reliable way to figure out the writable
│ │ │ +    </span><span class="nf">erts_seal_module</span><span class="p" data-group-id="9792249579-10">(</span><span class="err">&amp;</span><span class="ss">modp</span><span class="p">-&gt;</span><span class="ss">curr</span><span class="p" data-group-id="9792249579-10">)</span><span class="p">;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9792249579-2">}</span></code></pre><p>Without the module instance there's no reliable way to figure out the writable
│ │ │  address of a code page, and we rely on <em>address space layout randomization</em>
│ │ │  (ASLR) to make it difficult to guess. On some platforms, security is further
│ │ │  enhanced by protecting the writable area from writes until the module has been
│ │ │  unsealed by <code class="inline">erts_unseal_module</code>.</p><h3 id="export-tracing" class="section-heading">
│ │ │    <a href="#export-tracing" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │ @@ -393,15 +393,15 @@
│ │ │  </span><span class="ss">perf</span><span class="w"> </span><span class="ss">script</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">perf</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="ss">run</span><span class="w"> </span><span class="ss">stackcollapse</span><span class="w">
│ │ │  </span><span class="ss">stackcollapse</span><span class="o">-</span><span class="ss">perf</span><span class="p">.</span><span class="ss">pl</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">perf</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Create</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">svg</span><span class="w">
│ │ │  </span><span class="ss">flamegraph</span><span class="p">.</span><span class="ss">pl</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">svg</span></code></pre><p>We get a graph that would look something like this:</p><p><img src="assets/perf-beamasm.svg" alt="Linux Perf FlameGraph: dialyzer PLT build"/></p><p>You can view a larger version <a href="assets/perf-beamasm.svg">here</a>. It contains
│ │ │  the same information, but it is easier to share with others as it does
│ │ │  not need the symbols in the executable.</p><p>Using the same data we can also produce a graph where the scheduler profile data
│ │ │ -has been merged by using <code class="inline">sed</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Strip</span><span class="w"> </span><span class="p" data-group-id="7407418039-1">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="7407418039-1">]</span><span class="o">+</span><span class="p">_</span><span class="w"> </span><span class="ow">and</span><span class="o">/</span><span class="ow">or</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="7407418039-2">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="7407418039-2">]</span><span class="o">+</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">scheduler</span><span class="w"> </span><span class="ss">names</span><span class="w">
│ │ │ +has been merged by using <code class="inline">sed</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Strip</span><span class="w"> </span><span class="p" data-group-id="8981911038-1">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="8981911038-1">]</span><span class="o">+</span><span class="p">_</span><span class="w"> </span><span class="ow">and</span><span class="o">/</span><span class="ow">or</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8981911038-2">[</span><span class="mi">0</span><span class="o">-</span><span class="mi">9</span><span class="p" data-group-id="8981911038-2">]</span><span class="o">+</span><span class="w"> </span><span class="ss">from</span><span class="w"> </span><span class="ss">all</span><span class="w"> </span><span class="ss">scheduler</span><span class="w"> </span><span class="ss">names</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="ss">scheduler</span><span class="w"> </span><span class="ss">names</span><span class="w"> </span><span class="ss">changed</span><span class="w"> </span><span class="ss">in</span><span class="w"> </span><span class="n">OTP26</span><span class="p">,</span><span class="w"> </span><span class="ss">hence</span><span class="w"> </span><span class="ss">two</span><span class="w"> </span><span class="ss">expressions</span><span class="w">
│ │ │  </span><span class="ss">sed</span><span class="w"> </span><span class="o">-</span><span class="ss">e</span><span class="w"> </span><span class="ss">&#39;s/^[0-9]\+_//&#39;</span><span class="w"> </span><span class="o">-</span><span class="ss">e</span><span class="w"> </span><span class="ss">&#39;s/^erts_\([^_]\+\)_[0-9]\+/erts_\1/&#39;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded_sched</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="p">#</span><span class="w"> </span><span class="n">Create</span><span class="w"> </span><span class="ss">the</span><span class="w"> </span><span class="ss">svg</span><span class="w">
│ │ │  </span><span class="ss">flamegraph</span><span class="p">.</span><span class="ss">pl</span><span class="w"> </span><span class="ss">out</span><span class="p">.</span><span class="ss">folded_sched</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="ss">out_sched</span><span class="p">.</span><span class="ss">svg</span></code></pre><p><img src="assets/perf-beamasm-merged.svg" alt="Linux Perf FlameGraph: dialyzer PLT build"/></p><p>You can view a larger version <a href="assets/perf-beamasm-merged.svg">here</a>.
│ │ │  There are many different transformations that you can do to make the graph show
│ │ │  you what you want.</p><h3 id="annotate-perf-functions" class="section-heading">
│ │ │    <a href="#annotate-perf-functions" class="hover-link">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/codeloading.html
│ │ │ @@ -163,16 +163,16 @@
│ │ │  only be done by one loader process at a time. A second loader process
│ │ │  trying to enter finishing phase will be suspended until the first
│ │ │  loader is done. This will only block the process, the scheduler is
│ │ │  free to schedule other work while the second loader is waiting. (See
│ │ │  <code class="inline">erts_try_seize_code_load_permission</code> and
│ │ │  <code class="inline">erts_release_code_load_permission</code>).</p><p>The ability to prepare several modules in parallel is not currently
│ │ │  used as almost all code loading is serialized by the code_server
│ │ │ -process. The BIF interface is however prepared for this.</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">prepare_loading</span><span class="p" data-group-id="0318648543-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="0318648543-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">LoaderState</span><span class="w">
│ │ │ -  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">finish_loading</span><span class="p" data-group-id="0318648543-2">(</span><span class="p" data-group-id="0318648543-3">[</span><span class="n">LoaderState</span><span class="p" data-group-id="0318648543-3">]</span><span class="p" data-group-id="0318648543-2">)</span></code></pre><p>The idea is that <code class="inline">prepare_loading</code> could be called in parallel for
│ │ │ +process. The BIF interface is however prepared for this.</p><pre><code class="makeup erlang" translate="no"><span class="w">  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">prepare_loading</span><span class="p" data-group-id="3637122793-1">(</span><span class="n">Module</span><span class="p">,</span><span class="w"> </span><span class="n">Code</span><span class="p" data-group-id="3637122793-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">LoaderState</span><span class="w">
│ │ │ +  </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">finish_loading</span><span class="p" data-group-id="3637122793-2">(</span><span class="p" data-group-id="3637122793-3">[</span><span class="n">LoaderState</span><span class="p" data-group-id="3637122793-3">]</span><span class="p" data-group-id="3637122793-2">)</span></code></pre><p>The idea is that <code class="inline">prepare_loading</code> could be called in parallel for
│ │ │  different modules and returns a &quot;magic binary&quot; containing the internal
│ │ │  state of each prepared module. Function <code class="inline">finish_loading</code> could take a
│ │ │  list of such states and do the finishing of all of them in one go.</p><p>Currently we use the legacy BIF <code class="inline">erlang:load_module</code> which is now
│ │ │  implemented in Erlang by calling the above two functions in
│ │ │  sequence. Function <code class="inline">finish_loading</code> is limited to only accepts a list
│ │ │  with one module state as we do not yet use the multi module loading
│ │ │  feature.</p><h2 id="the-finishing-sequence" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/crash_dump.html
│ │ │ @@ -401,21 +401,21 @@
│ │ │  <a href="erlang.html#put/2"><code class="inline">put/2</code></a> and <a href="erlang.html#get/1"><code class="inline">get/1</code></a> thing) is non-empty.</p><p>The raw memory information can be decoded by the Crashdump Viewer tool. You can
│ │ │  then see the stack dump, the message queue (if any), and the dictionary (if
│ │ │  any).</p><p>The stack dump is a dump of the Erlang process stack. Most of the live data
│ │ │  (that is, variables currently in use) are placed on the stack; thus this can be
│ │ │  interesting. One has to &quot;guess&quot; what is what, but as the information is
│ │ │  symbolic, thorough reading of this information can be useful. As an example, we
│ │ │  can find the state variable of the Erlang primitive loader online <code class="inline">(5)</code> and
│ │ │ -<code class="inline">(6)</code> in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0651773224-1">(</span><span class="mi">1</span><span class="p" data-group-id="0651773224-1">)</span><span class="w">  </span><span class="mi">3</span><span class="ss">cac44</span><span class="w">   </span><span class="n">Return</span><span class="w"> </span><span class="ss">addr</span><span class="w"> </span><span class="mi">0</span><span class="nf">x13BF58</span><span class="w"> </span><span class="p" data-group-id="0651773224-2">(</span><span class="o">&lt;</span><span class="ss">terminate</span><span class="w"> </span><span class="ss">process</span><span class="w"> </span><span class="ss">normally</span><span class="o">&gt;</span><span class="p" data-group-id="0651773224-2">)</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0651773224-3">(</span><span class="mi">2</span><span class="p" data-group-id="0651773224-3">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="0651773224-4">(</span><span class="mi">0</span><span class="p" data-group-id="0651773224-4">)</span><span class="w">     </span><span class="p" data-group-id="0651773224-5">[</span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/kernel/ebin&quot;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0651773224-6">(</span><span class="mi">3</span><span class="p" data-group-id="0651773224-6">)</span><span class="w">            </span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/stdlib/ebin&quot;</span><span class="p" data-group-id="0651773224-5">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0651773224-7">(</span><span class="mi">4</span><span class="p" data-group-id="0651773224-7">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="0651773224-8">(</span><span class="mi">1</span><span class="p" data-group-id="0651773224-8">)</span><span class="w">     </span><span class="o">&lt;</span><span class="mf">0.1</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0651773224-9">(</span><span class="mi">5</span><span class="p" data-group-id="0651773224-9">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="0651773224-10">(</span><span class="mi">2</span><span class="p" data-group-id="0651773224-10">)</span><span class="w">     </span><span class="p" data-group-id="0651773224-11">{</span><span class="ss">state</span><span class="p">,</span><span class="p" data-group-id="0651773224-12">[</span><span class="p" data-group-id="0651773224-12">]</span><span class="p">,</span><span class="ss">none</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">6.7085890</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">undefined</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">7.9000327</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0651773224-13">(</span><span class="mi">6</span><span class="p" data-group-id="0651773224-13">)</span><span class="w">            </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">8.116480692</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.2</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">9.10708760</span><span class="o">&gt;</span><span class="p" data-group-id="0651773224-11">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0651773224-14">(</span><span class="mi">7</span><span class="p" data-group-id="0651773224-14">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="0651773224-15">(</span><span class="mi">3</span><span class="p" data-group-id="0651773224-15">)</span><span class="w">     </span><span class="ss">infinity</span></code></pre><p>When interpreting the data for a process, it is helpful to know that anonymous
│ │ │ +<code class="inline">(6)</code> in the following example:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8025282097-1">(</span><span class="mi">1</span><span class="p" data-group-id="8025282097-1">)</span><span class="w">  </span><span class="mi">3</span><span class="ss">cac44</span><span class="w">   </span><span class="n">Return</span><span class="w"> </span><span class="ss">addr</span><span class="w"> </span><span class="mi">0</span><span class="nf">x13BF58</span><span class="w"> </span><span class="p" data-group-id="8025282097-2">(</span><span class="o">&lt;</span><span class="ss">terminate</span><span class="w"> </span><span class="ss">process</span><span class="w"> </span><span class="ss">normally</span><span class="o">&gt;</span><span class="p" data-group-id="8025282097-2">)</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8025282097-3">(</span><span class="mi">2</span><span class="p" data-group-id="8025282097-3">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="8025282097-4">(</span><span class="mi">0</span><span class="p" data-group-id="8025282097-4">)</span><span class="w">     </span><span class="p" data-group-id="8025282097-5">[</span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/kernel/ebin&quot;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8025282097-6">(</span><span class="mi">3</span><span class="p" data-group-id="8025282097-6">)</span><span class="w">            </span><span class="s">&quot;/view/siri_r10_dev/clearcase/otp/erts/lib/stdlib/ebin&quot;</span><span class="p" data-group-id="8025282097-5">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8025282097-7">(</span><span class="mi">4</span><span class="p" data-group-id="8025282097-7">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="8025282097-8">(</span><span class="mi">1</span><span class="p" data-group-id="8025282097-8">)</span><span class="w">     </span><span class="o">&lt;</span><span class="mf">0.1</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8025282097-9">(</span><span class="mi">5</span><span class="p" data-group-id="8025282097-9">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="8025282097-10">(</span><span class="mi">2</span><span class="p" data-group-id="8025282097-10">)</span><span class="w">     </span><span class="p" data-group-id="8025282097-11">{</span><span class="ss">state</span><span class="p">,</span><span class="p" data-group-id="8025282097-12">[</span><span class="p" data-group-id="8025282097-12">]</span><span class="p">,</span><span class="ss">none</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">6.7085890</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">undefined</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">7.9000327</span><span class="o">&gt;</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8025282097-13">(</span><span class="mi">6</span><span class="p" data-group-id="8025282097-13">)</span><span class="w">            </span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">8.116480692</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.2</span><span class="o">&gt;</span><span class="p">,</span><span class="ss">infinity</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_prim_loader</span><span class="p">.</span><span class="mf">9.10708760</span><span class="o">&gt;</span><span class="p" data-group-id="8025282097-11">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8025282097-14">(</span><span class="mi">7</span><span class="p" data-group-id="8025282097-14">)</span><span class="w">  </span><span class="nf">y</span><span class="p" data-group-id="8025282097-15">(</span><span class="mi">3</span><span class="p" data-group-id="8025282097-15">)</span><span class="w">     </span><span class="ss">infinity</span></code></pre><p>When interpreting the data for a process, it is helpful to know that anonymous
│ │ │  function objects (funs) are given the following:</p><ul><li>A name constructed from the name of the function in which they are created</li><li>A number (starting with 0) indicating the number of that fun within that
│ │ │  function</li></ul><h2 id="atoms" class="section-heading">
│ │ │    <a href="#atoms" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Atoms</span>
│ │ │  </h2>
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/driver.html
│ │ │ @@ -364,41 +364,41 @@
│ │ │  <p>Before a driver can be called from Erlang, it must be loaded and opened. Loading
│ │ │  is done using the <a href="../../../lib/kernel-10.2.7.2/doc/html/erl_ddll.html"><code class="inline">erl_ddll</code></a> module (the <a href="../../../lib/kernel-10.2.7.2/doc/html/erl_ddll.html"><code class="inline">erl_ddll</code></a> driver that loads dynamic
│ │ │  driver is actually a driver itself). If loading is successful, the port can be
│ │ │  opened with <a href="erlang.html#open_port/2"><code class="inline">open_port/2</code></a>. The port name must match the name of
│ │ │  the shared library and the name in the driver entry structure.</p><p>When the port has been opened, the driver can be called. In the <code class="inline">pg_sync</code>
│ │ │  example, we do not have any data from the port, only the return value from the
│ │ │  <a href="erlang.html#port_control/3"><code class="inline">port_control/3</code></a>.</p><p>The following code is the Erlang part of the synchronous postgres driver,
│ │ │ -<code class="inline">pg_sync.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3178003239-1">(</span><span class="ss">pg_sync</span><span class="p" data-group-id="3178003239-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">pg_sync.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="2803253644-1">(</span><span class="ss">pg_sync</span><span class="p" data-group-id="2803253644-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3178003239-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3178003239-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3178003239-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3178003239-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3178003239-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3178003239-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2803253644-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2803253644-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2803253644-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2803253644-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="2803253644-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="2803253644-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3178003239-5">(</span><span class="p" data-group-id="3178003239-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3178003239-6">]</span><span class="p" data-group-id="3178003239-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="2803253644-5">(</span><span class="p" data-group-id="2803253644-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="2803253644-6">]</span><span class="p" data-group-id="2803253644-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">connect</span><span class="p" data-group-id="3178003239-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="3178003239-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="3178003239-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_sync&quot;</span><span class="p" data-group-id="3178003239-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">connect</span><span class="p" data-group-id="2803253644-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="2803253644-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="2803253644-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_sync&quot;</span><span class="p" data-group-id="2803253644-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3178003239-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="3178003239-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="3178003239-10">(</span><span class="p" data-group-id="3178003239-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="3178003239-11">}</span><span class="p" data-group-id="3178003239-10">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="2803253644-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="2803253644-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="2803253644-10">(</span><span class="p" data-group-id="2803253644-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p" data-group-id="2803253644-11">}</span><span class="p" data-group-id="2803253644-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="3178003239-12">(</span><span class="p" data-group-id="3178003239-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="3178003239-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3178003239-14">[</span><span class="p" data-group-id="3178003239-14">]</span><span class="p" data-group-id="3178003239-12">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3178003239-15">(</span><span class="nf">port_control</span><span class="p" data-group-id="3178003239-16">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="3178003239-16">)</span><span class="p" data-group-id="3178003239-15">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ -        </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3178003239-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="3178003239-17">}</span><span class="p">;</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="2803253644-12">(</span><span class="p" data-group-id="2803253644-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="2803253644-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2803253644-14">[</span><span class="p" data-group-id="2803253644-14">]</span><span class="p" data-group-id="2803253644-12">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2803253644-15">(</span><span class="nf">port_control</span><span class="p" data-group-id="2803253644-16">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="2803253644-16">)</span><span class="p" data-group-id="2803253644-15">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +        </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2803253644-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="2803253644-17">}</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">Error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Error</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">disconnect</span><span class="p" data-group-id="3178003239-18">(</span><span class="n">Port</span><span class="p" data-group-id="3178003239-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3178003239-19">(</span><span class="nf">port_control</span><span class="p" data-group-id="3178003239-20">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="3178003239-20">)</span><span class="p" data-group-id="3178003239-19">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_close</span><span class="p" data-group-id="3178003239-21">(</span><span class="n">Port</span><span class="p" data-group-id="3178003239-21">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">disconnect</span><span class="p" data-group-id="2803253644-18">(</span><span class="n">Port</span><span class="p" data-group-id="2803253644-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2803253644-19">(</span><span class="nf">port_control</span><span class="p" data-group-id="2803253644-20">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="2803253644-20">)</span><span class="p" data-group-id="2803253644-19">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_close</span><span class="p" data-group-id="2803253644-21">(</span><span class="n">Port</span><span class="p" data-group-id="2803253644-21">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">select</span><span class="p" data-group-id="3178003239-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="3178003239-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3178003239-23">(</span><span class="nf">port_control</span><span class="p" data-group-id="3178003239-24">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="3178003239-24">)</span><span class="p" data-group-id="3178003239-23">)</span><span class="p">.</span></code></pre><p>The API is simple:</p><ul><li><code class="inline">connect/1</code> loads the driver, opens it, and logs on to the database, returning
│ │ │ +</span><span class="nf">select</span><span class="p" data-group-id="2803253644-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="2803253644-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2803253644-23">(</span><span class="nf">port_control</span><span class="p" data-group-id="2803253644-24">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="2803253644-24">)</span><span class="p" data-group-id="2803253644-23">)</span><span class="p">.</span></code></pre><p>The API is simple:</p><ul><li><code class="inline">connect/1</code> loads the driver, opens it, and logs on to the database, returning
│ │ │  the Erlang port if successful.</li><li><code class="inline">select/2</code> sends a query to the driver and returns the result.</li><li><code class="inline">disconnect/1</code> closes the database connection and the driver. (However, it
│ │ │  does not unload it.)</li></ul><p>The connection string is to be a connection string for postgres.</p><p>The driver is loaded with <a href="../../../lib/kernel-10.2.7.2/doc/html/erl_ddll.html#load_driver/2"><code class="inline">erl_ddll:load_driver/2</code></a>. If this is successful, or if
│ │ │  it is already loaded, it is opened. This will call the <code class="inline">start</code> function in the
│ │ │  driver.</p><p>We use the <a href="erlang.html#port_control/3"><code class="inline">port_control/3</code></a> function for all calls into the
│ │ │  driver. The result from the driver is returned immediately and converted to
│ │ │  terms by calling <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. (We trust that the
│ │ │  terms returned from the driver are well-formed, otherwise the <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>
│ │ │ @@ -536,51 +536,51 @@
│ │ │  successful, or error if it is not. If the connection is not yet established, we
│ │ │  simply return; <code class="inline">ready_io</code> is called again.</p><p>If we have a result from a connect, indicated by having data in the <code class="inline">x</code> buffer,
│ │ │  we no longer need to select on output (<a href="../../../erts-15.2.7.2/doc/html/driver_entry.html#ready_output" title=""><code class="inline">ready_output</code></a>), so we remove this by
│ │ │  calling <a href="../../../erts-15.2.7.2/doc/html/erl_driver.html#driver_select" title=""><code class="inline">driver_select</code></a>.</p><p>If we are not connecting, we wait for results from a <code class="inline">PQsendQuery</code>, so we get
│ │ │  the result and return it. The encoding is done with the same functions as in the
│ │ │  earlier example.</p><p>Error handling is to be added here, for example, checking that the socket is
│ │ │  still open, but this is only a simple example.</p><p>The Erlang part of the asynchronous driver consists of the sample file
│ │ │ -<code class="inline">pg_async.erl</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3382559154-1">(</span><span class="ss">pg_async</span><span class="p" data-group-id="3382559154-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">pg_async.erl</code>.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="0855011600-1">(</span><span class="ss">pg_async</span><span class="p" data-group-id="0855011600-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3382559154-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$C</span><span class="p" data-group-id="3382559154-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3382559154-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="p" data-group-id="3382559154-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="3382559154-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$S</span><span class="p" data-group-id="3382559154-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0855011600-2">(</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$C</span><span class="p" data-group-id="0855011600-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0855011600-3">(</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$D</span><span class="p" data-group-id="0855011600-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">define</span><span class="p" data-group-id="0855011600-4">(</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="sc">$S</span><span class="p" data-group-id="0855011600-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3382559154-5">(</span><span class="p" data-group-id="3382559154-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="3382559154-6">]</span><span class="p" data-group-id="3382559154-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="0855011600-5">(</span><span class="p" data-group-id="0855011600-6">[</span><span class="ss">connect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">disconnect</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">select</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="0855011600-6">]</span><span class="p" data-group-id="0855011600-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">connect</span><span class="p" data-group-id="3382559154-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="3382559154-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="3382559154-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_async&quot;</span><span class="p" data-group-id="3382559154-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">connect</span><span class="p" data-group-id="0855011600-7">(</span><span class="n">ConnectStr</span><span class="p" data-group-id="0855011600-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="0855011600-8">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;pg_async&quot;</span><span class="p" data-group-id="0855011600-8">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3382559154-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="3382559154-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="3382559154-10">(</span><span class="p" data-group-id="3382559154-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="3382559154-11">}</span><span class="p" data-group-id="3382559154-10">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0855011600-9">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="0855011600-9">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +        </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0855011600-10">(</span><span class="p" data-group-id="0855011600-11">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">could_not_load_driver</span><span class="p" data-group-id="0855011600-11">}</span><span class="p" data-group-id="0855011600-10">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="3382559154-12">(</span><span class="p" data-group-id="3382559154-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="3382559154-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382559154-14">[</span><span class="ss">binary</span><span class="p" data-group-id="3382559154-14">]</span><span class="p" data-group-id="3382559154-12">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="3382559154-15">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="3382559154-15">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="3382559154-16">(</span><span class="n">Port</span><span class="p" data-group-id="3382559154-16">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +    </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="0855011600-12">(</span><span class="p" data-group-id="0855011600-13">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">MODULE</span><span class="p" data-group-id="0855011600-13">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0855011600-14">[</span><span class="ss">binary</span><span class="p" data-group-id="0855011600-14">]</span><span class="p" data-group-id="0855011600-12">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="0855011600-15">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_CONNECT</span><span class="p">,</span><span class="w"> </span><span class="n">ConnectStr</span><span class="p" data-group-id="0855011600-15">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="0855011600-16">(</span><span class="n">Port</span><span class="p" data-group-id="0855011600-16">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="p" data-group-id="3382559154-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="3382559154-17">}</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="p" data-group-id="0855011600-17">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="0855011600-17">}</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="n">Error</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Error</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">disconnect</span><span class="p" data-group-id="3382559154-18">(</span><span class="n">Port</span><span class="p" data-group-id="3382559154-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="3382559154-19">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="3382559154-19">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="3382559154-20">(</span><span class="n">Port</span><span class="p" data-group-id="3382559154-20">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_close</span><span class="p" data-group-id="3382559154-21">(</span><span class="n">Port</span><span class="p" data-group-id="3382559154-21">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">disconnect</span><span class="p" data-group-id="0855011600-18">(</span><span class="n">Port</span><span class="p" data-group-id="0855011600-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="0855011600-19">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_DISCONNECT</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;&quot;</span><span class="p" data-group-id="0855011600-19">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">R</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">return_port_data</span><span class="p" data-group-id="0855011600-20">(</span><span class="n">Port</span><span class="p" data-group-id="0855011600-20">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_close</span><span class="p" data-group-id="0855011600-21">(</span><span class="n">Port</span><span class="p" data-group-id="0855011600-21">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="n">R</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">select</span><span class="p" data-group-id="3382559154-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="3382559154-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="3382559154-23">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="3382559154-23">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">return_port_data</span><span class="p" data-group-id="3382559154-24">(</span><span class="n">Port</span><span class="p" data-group-id="3382559154-24">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">select</span><span class="p" data-group-id="0855011600-22">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="0855011600-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="0855011600-23">(</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="o">?</span><span class="n">DRV_SELECT</span><span class="p">,</span><span class="w"> </span><span class="n">Query</span><span class="p" data-group-id="0855011600-23">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">return_port_data</span><span class="p" data-group-id="0855011600-24">(</span><span class="n">Port</span><span class="p" data-group-id="0855011600-24">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">return_port_data</span><span class="p" data-group-id="3382559154-25">(</span><span class="n">Port</span><span class="p" data-group-id="3382559154-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">return_port_data</span><span class="p" data-group-id="0855011600-25">(</span><span class="n">Port</span><span class="p" data-group-id="0855011600-25">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3382559154-26">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3382559154-27">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="3382559154-27">}</span><span class="p" data-group-id="3382559154-26">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3382559154-28">(</span><span class="n">Data</span><span class="p" data-group-id="3382559154-28">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0855011600-26">{</span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0855011600-27">{</span><span class="ss">data</span><span class="p">,</span><span class="w"> </span><span class="n">Data</span><span class="p" data-group-id="0855011600-27">}</span><span class="p" data-group-id="0855011600-26">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">binary_to_term</span><span class="p" data-group-id="0855011600-28">(</span><span class="n">Data</span><span class="p" data-group-id="0855011600-28">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>The Erlang code is slightly different, as we do not return the result
│ │ │  synchronously from <a href="erlang.html#port_control/3"><code class="inline">port_control/3</code></a>, instead we get it from <a href="../../../erts-15.2.7.2/doc/html/erl_driver.html#driver_output" title=""><code class="inline">driver_output</code></a> as
│ │ │  data in the message queue. The function <code class="inline">return_port_data</code> above receives data
│ │ │  from the port. As the data is in binary format, we use
│ │ │  <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a> to convert it to an Erlang term. Notice
│ │ │  that the driver is opened in binary mode (<a href="erlang.html#open_port/2"><code class="inline">open_port/2</code></a> is
│ │ │  called with option <code class="inline">[binary]</code>). This means that data sent from the driver to the
│ │ │ @@ -677,59 +677,59 @@
│ │ │      *rp++ = ERL_DRV_LIST;
│ │ │      *rp++ = n+1;
│ │ │      driver_output_term(port, result, result_n);
│ │ │      delete[] result;
│ │ │      delete d;
│ │ │  }</code></pre><p>This driver is called like the others from Erlang. However, as we use
│ │ │  <a href="../../../erts-15.2.7.2/doc/html/erl_driver.html#driver_output_term" title=""><code class="inline">driver_output_term</code></a>, there is no need to call <a href="erlang.html#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>. The Erlang code
│ │ │ -is in the sample file <code class="inline">next_perm.erl</code>.</p><p>The input is changed into a list of integers and sent to the driver.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3865170906-1">(</span><span class="ss">next_perm</span><span class="p" data-group-id="3865170906-1">)</span><span class="p">.</span><span class="w">
│ │ │ +is in the sample file <code class="inline">next_perm.erl</code>.</p><p>The input is changed into a list of integers and sent to the driver.</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="9653965982-1">(</span><span class="ss">next_perm</span><span class="p" data-group-id="9653965982-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3865170906-2">(</span><span class="p" data-group-id="3865170906-3">[</span><span class="ss">next_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">prev_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">all_perm</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="3865170906-3">]</span><span class="p" data-group-id="3865170906-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="9653965982-2">(</span><span class="p" data-group-id="9653965982-3">[</span><span class="ss">next_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">prev_perm</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">all_perm</span><span class="p">/</span><span class="mi">1</span><span class="p" data-group-id="9653965982-3">]</span><span class="p" data-group-id="9653965982-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">load</span><span class="p" data-group-id="3865170906-4">(</span><span class="p" data-group-id="3865170906-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="3865170906-5">(</span><span class="ss">next_perm</span><span class="p" data-group-id="3865170906-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +</span><span class="nf">load</span><span class="p" data-group-id="9653965982-4">(</span><span class="p" data-group-id="9653965982-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="k">case</span><span class="w"> </span><span class="nf">whereis</span><span class="p" data-group-id="9653965982-5">(</span><span class="ss">next_perm</span><span class="p" data-group-id="9653965982-5">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │          </span><span class="ss">undefined</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="3865170906-6">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="3865170906-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │ +            </span><span class="k">case</span><span class="w"> </span><span class="nc">erl_ddll</span><span class="p">:</span><span class="nf">load_driver</span><span class="p" data-group-id="9653965982-6">(</span><span class="s">&quot;.&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="9653965982-6">)</span><span class="w"> </span><span class="k">of</span><span class="w">
│ │ │                  </span><span class="ss">ok</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -                </span><span class="p" data-group-id="3865170906-7">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="3865170906-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ -                </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="3865170906-8">(</span><span class="n">E</span><span class="p" data-group-id="3865170906-8">)</span><span class="w">
│ │ │ +                </span><span class="p" data-group-id="9653965982-7">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="ss">already_loaded</span><span class="p" data-group-id="9653965982-7">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="ss">ok</span><span class="p">;</span><span class="w">
│ │ │ +                </span><span class="n">E</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="9653965982-8">(</span><span class="n">E</span><span class="p" data-group-id="9653965982-8">)</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="3865170906-9">(</span><span class="p" data-group-id="3865170906-10">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="3865170906-10">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3865170906-11">[</span><span class="p" data-group-id="3865170906-11">]</span><span class="p" data-group-id="3865170906-9">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="nf">register</span><span class="p" data-group-id="3865170906-12">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="3865170906-12">)</span><span class="p">;</span><span class="w">
│ │ │ +            </span><span class="n">Port</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">open_port</span><span class="p" data-group-id="9653965982-9">(</span><span class="p" data-group-id="9653965982-10">{</span><span class="nb">spawn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;next_perm&quot;</span><span class="p" data-group-id="9653965982-10">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9653965982-11">[</span><span class="p" data-group-id="9653965982-11">]</span><span class="p" data-group-id="9653965982-9">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">register</span><span class="p" data-group-id="9653965982-12">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="9653965982-12">)</span><span class="p">;</span><span class="w">
│ │ │          </span><span class="p">_</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="ss">ok</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="3865170906-13">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3865170906-14">[</span><span class="p" data-group-id="3865170906-15">&lt;&lt;</span><span class="n">I</span><span class="p">:</span><span class="mi">32</span><span class="o">/</span><span class="ss">integer</span><span class="o">-</span><span class="ss">native</span><span class="p" data-group-id="3865170906-15">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="3865170906-14">]</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="9653965982-13">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="9653965982-14">[</span><span class="p" data-group-id="9653965982-15">&lt;&lt;</span><span class="n">I</span><span class="p">:</span><span class="mi">32</span><span class="o">/</span><span class="ss">integer</span><span class="o">-</span><span class="ss">native</span><span class="p" data-group-id="9653965982-15">&gt;&gt;</span><span class="w"> </span><span class="p">||</span><span class="w"> </span><span class="n">I</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="n">L</span><span class="p" data-group-id="9653965982-14">]</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">next_perm</span><span class="p" data-group-id="3865170906-16">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">next_perm</span><span class="p" data-group-id="3865170906-17">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="3865170906-17">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">next_perm</span><span class="p" data-group-id="9653965982-16">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-16">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">next_perm</span><span class="p" data-group-id="9653965982-17">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9653965982-17">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">prev_perm</span><span class="p" data-group-id="3865170906-18">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">next_perm</span><span class="p" data-group-id="3865170906-19">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="3865170906-19">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">prev_perm</span><span class="p" data-group-id="9653965982-18">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-18">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">next_perm</span><span class="p" data-group-id="9653965982-19">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="9653965982-19">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">next_perm</span><span class="p" data-group-id="3865170906-20">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p" data-group-id="3865170906-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nf">load</span><span class="p" data-group-id="3865170906-21">(</span><span class="p" data-group-id="3865170906-21">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="3865170906-22">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-22">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">port_control</span><span class="p" data-group-id="3865170906-23">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="3865170906-23">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">next_perm</span><span class="p" data-group-id="9653965982-20">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p" data-group-id="9653965982-20">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nf">load</span><span class="p" data-group-id="9653965982-21">(</span><span class="p" data-group-id="9653965982-21">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">list_to_integer_binaries</span><span class="p" data-group-id="9653965982-22">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-22">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">port_control</span><span class="p" data-group-id="9653965982-23">(</span><span class="ss">next_perm</span><span class="p">,</span><span class="w"> </span><span class="n">Nxt</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p" data-group-id="9653965982-23">)</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │          </span><span class="n">Result</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">all_perm</span><span class="p" data-group-id="3865170906-24">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="3865170906-25">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-25">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">all_perm</span><span class="p" data-group-id="3865170906-26">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3865170906-27">[</span><span class="n">New</span><span class="p" data-group-id="3865170906-27">]</span><span class="p" data-group-id="3865170906-26">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">all_perm</span><span class="p" data-group-id="9653965982-24">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-24">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="9653965982-25">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-25">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">all_perm</span><span class="p" data-group-id="9653965982-26">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9653965982-27">[</span><span class="n">New</span><span class="p" data-group-id="9653965982-27">]</span><span class="p" data-group-id="9653965982-26">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">all_perm</span><span class="p" data-group-id="3865170906-28">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3865170906-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">all_perm</span><span class="p" data-group-id="9653965982-28">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9653965982-28">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">all_perm</span><span class="p" data-group-id="3865170906-29">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3865170906-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="3865170906-30">(</span><span class="n">L</span><span class="p" data-group-id="3865170906-30">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">all_perm</span><span class="p" data-group-id="3865170906-31">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3865170906-32">[</span><span class="n">New</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="3865170906-32">]</span><span class="p" data-group-id="3865170906-31">)</span><span class="p">.</span></code></pre>
│ │ │ +</span><span class="nf">all_perm</span><span class="p" data-group-id="9653965982-29">(</span><span class="n">L</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9653965982-29">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">New</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">prev_perm</span><span class="p" data-group-id="9653965982-30">(</span><span class="n">L</span><span class="p" data-group-id="9653965982-30">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">all_perm</span><span class="p" data-group-id="9653965982-31">(</span><span class="n">New</span><span class="p">,</span><span class="w"> </span><span class="n">Orig</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9653965982-32">[</span><span class="n">New</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="9653965982-32">]</span><span class="p" data-group-id="9653965982-31">)</span><span class="p">.</span></code></pre>
│ │ │  </div>
│ │ │  
│ │ │  <div class="bottom-actions" id="bottom-actions">
│ │ │    <div class="bottom-actions-item">
│ │ │  
│ │ │        <a href="tty.html" class="bottom-actions-button" rel="prev">
│ │ │          <span class="subheader">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erl_cmd.html
│ │ │ @@ -149,26 +149,26 @@
│ │ │  runtime system, more specifically to the <code class="inline">init</code> system process, see <a href="init.html"><code class="inline">init</code></a>.</p><p>The <code class="inline">init</code> process itself interprets some of these flags, the <em>init flags</em>. It
│ │ │  also stores any remaining flags, the <em>user flags</em>. The latter can be retrieved
│ │ │  by calling <a href="init.html#get_argument/1"><code class="inline">init:get_argument/1</code></a>.</p><p>A small number of &quot;-&quot; flags exist, which now actually are emulator flags, see
│ │ │  the description below.</p></li><li><p>Plain arguments are not interpreted in any way. They are also stored by the
│ │ │  <code class="inline">init</code> process and can be retrieved by calling <a href="init.html#get_plain_arguments/0"><code class="inline">init:get_plain_arguments/0</code></a>.
│ │ │  Plain arguments can occur before the first flag, or after a <code class="inline">--</code> flag. Also,
│ │ │  the <code class="inline">-extra</code> flag causes everything that follows to become plain arguments.</p></li></ul><p><em>Examples:</em></p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl +W w -sname arnie +R 9 -s my_init -extra +bertie</span><span class="gp unselectable">
│ │ │ -(arnie@host)1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="3226510961-1">(</span><span class="ss">sname</span><span class="p" data-group-id="3226510961-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3226510961-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="3226510961-3">[</span><span class="p" data-group-id="3226510961-4">[</span><span class="s">&quot;arnie&quot;</span><span class="p" data-group-id="3226510961-4">]</span><span class="p" data-group-id="3226510961-3">]</span><span class="p" data-group-id="3226510961-2">}</span><span class="gp unselectable">
│ │ │ -(arnie@host)2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="3226510961-5">(</span><span class="p" data-group-id="3226510961-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3226510961-6">[</span><span class="s">&quot;+bertie&quot;</span><span class="p" data-group-id="3226510961-6">]</span></code></pre><p>Here <code class="inline">+W w</code> and <code class="inline">+R 9</code> are emulator flags. <code class="inline">-s my_init</code> is an init flag,
│ │ │ +(arnie@host)1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="0795558893-1">(</span><span class="ss">sname</span><span class="p" data-group-id="0795558893-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0795558893-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="0795558893-3">[</span><span class="p" data-group-id="0795558893-4">[</span><span class="s">&quot;arnie&quot;</span><span class="p" data-group-id="0795558893-4">]</span><span class="p" data-group-id="0795558893-3">]</span><span class="p" data-group-id="0795558893-2">}</span><span class="gp unselectable">
│ │ │ +(arnie@host)2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="0795558893-5">(</span><span class="p" data-group-id="0795558893-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0795558893-6">[</span><span class="s">&quot;+bertie&quot;</span><span class="p" data-group-id="0795558893-6">]</span></code></pre><p>Here <code class="inline">+W w</code> and <code class="inline">+R 9</code> are emulator flags. <code class="inline">-s my_init</code> is an init flag,
│ │ │  interpreted by <code class="inline">init</code>. <code class="inline">-sname arnie</code> is a user flag, stored by <code class="inline">init</code>. It is
│ │ │  read by Kernel and causes the Erlang runtime system to become distributed.
│ │ │  Finally, everything after <code class="inline">-extra</code> (that is, <code class="inline">+bertie</code>) is considered as plain
│ │ │  arguments.</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl -myflag 1</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="1556347086-1">(</span><span class="ss">myflag</span><span class="p" data-group-id="1556347086-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1556347086-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="1556347086-3">[</span><span class="p" data-group-id="1556347086-4">[</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="1556347086-4">]</span><span class="p" data-group-id="1556347086-3">]</span><span class="p" data-group-id="1556347086-2">}</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="1556347086-5">(</span><span class="p" data-group-id="1556347086-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1556347086-6">[</span><span class="p" data-group-id="1556347086-6">]</span></code></pre><p>Here the user flag <code class="inline">-myflag 1</code> is passed to and stored by the <code class="inline">init</code> process. It
│ │ │ +1&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_argument</span><span class="p" data-group-id="8949557483-1">(</span><span class="ss">myflag</span><span class="p" data-group-id="8949557483-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8949557483-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8949557483-3">[</span><span class="p" data-group-id="8949557483-4">[</span><span class="s">&quot;1&quot;</span><span class="p" data-group-id="8949557483-4">]</span><span class="p" data-group-id="8949557483-3">]</span><span class="p" data-group-id="8949557483-2">}</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nc">init</span><span class="p">:</span><span class="nf">get_plain_arguments</span><span class="p" data-group-id="8949557483-5">(</span><span class="p" data-group-id="8949557483-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8949557483-6">[</span><span class="p" data-group-id="8949557483-6">]</span></code></pre><p>Here the user flag <code class="inline">-myflag 1</code> is passed to and stored by the <code class="inline">init</code> process. It
│ │ │  is a user-defined flag, presumably used by some user-defined application.</p><h2 id="flags" class="section-heading">
│ │ │    <a href="#flags" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Flags</span>
│ │ │  </h2>
│ │ │  <p>In the following list, init flags are marked &quot;(init flag)&quot;. Unless otherwise
│ │ │ @@ -700,15 +700,15 @@
│ │ │  processes) into a smaller set of schedulers when schedulers frequently run
│ │ │  out of work. When disabled, the frequency with which schedulers run out of
│ │ │  work is not taken into account by the load balancing logic.</p><p><code class="inline">+scl false</code> is similar to <a href="#%2Bsub"><code class="inline">+sub true</code></a>, but <code class="inline">+sub true</code>
│ │ │  also balances scheduler utilization between schedulers.</p></li><li><p><strong><code class="inline" id="+sct">+sct CpuTopology</code></strong> - Sets a user-defined CPU topology.
│ │ │  The user-defined CPU topology overrides
│ │ │  any automatically detected CPU topology. The CPU topology is used when
│ │ │  <a href="#%2Bsbt">binding schedulers to logical processors</a>. This option must be before
│ │ │ -<a href="#%2Bsbt"><code class="inline">+sbt</code></a> on the command-line.</p><pre><code class="makeup erlang" translate="no"><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="2953433298-1">(</span><span class="p" data-group-id="2953433298-1">)</span><span class="p">;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">65535</span><span class="w">
│ │ │ +<a href="#%2Bsbt"><code class="inline">+sbt</code></a> on the command-line.</p><pre><code class="makeup erlang" translate="no"><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">integer</span><span class="p" data-group-id="9195720202-1">(</span><span class="p" data-group-id="9195720202-1">)</span><span class="p">;</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="mi">65535</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">IdRange</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="o">-</span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&lt;</span><span class="n">Id</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="o">&lt;</span><span class="n">IdRange</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="o">&lt;</span><span class="n">IdOrIdRange</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">LogicalIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">L</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">ThreadIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">T</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">t</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">CoreIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">C</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">c</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="n">ProcessorIds</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">P</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">p</span><span class="o">&lt;</span><span class="n">IdList</span><span class="o">&gt;</span><span class="w">
│ │ │ @@ -733,30 +733,30 @@
│ │ │  node.</li><li><code class="inline">&lt;LogicalIds&gt;&lt;ThreadIds&gt;&lt;CoreIds&gt;&lt;NodeIds&gt;&lt;ProcessorIds&gt;</code>, that is, thread
│ │ │  is part of a core that is part of a NUMA node, which is part of a
│ │ │  processor.</li></ul><p>A CPU topology can consist of both processor external, and processor
│ │ │  internal NUMA nodes as long as each logical processor belongs to only one
│ │ │  NUMA node. If <code class="inline">&lt;ProcessorIds&gt;</code> is omitted, its default position is before
│ │ │  <code class="inline">&lt;NodeIds&gt;</code>. That is, the default is processor external NUMA nodes.</p><p>If a list of identifiers is used in an <code class="inline">&lt;IdDefs&gt;</code>:</p><ul><li><code class="inline">&lt;LogicalIds&gt;</code> must be a list of identifiers.</li><li>At least one other identifier type besides <code class="inline">&lt;LogicalIds&gt;</code> must also have a
│ │ │  list of identifiers.</li><li>All lists of identifiers must produce the same number of identifiers.</li></ul><p>A simple example. A single quad core processor can be described as follows:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl +sct L0-3c0-3</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="1425771628-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="1425771628-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1425771628-2">[</span><span class="p" data-group-id="1425771628-3">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="1425771628-4">[</span><span class="p" data-group-id="1425771628-5">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="1425771628-6">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="1425771628-6">}</span><span class="p" data-group-id="1425771628-5">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="1425771628-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="1425771628-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1425771628-8">}</span><span class="p" data-group-id="1425771628-7">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="1425771628-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="1425771628-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1425771628-10">}</span><span class="p" data-group-id="1425771628-9">}</span><span class="p">,</span><span class="w">
│ │ │ -             </span><span class="p" data-group-id="1425771628-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="1425771628-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1425771628-12">}</span><span class="p" data-group-id="1425771628-11">}</span><span class="p" data-group-id="1425771628-4">]</span><span class="p" data-group-id="1425771628-3">}</span><span class="p" data-group-id="1425771628-2">]</span></code></pre><p>A more complicated example with two quad core processors, each processor in
│ │ │ +1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="9310784391-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="9310784391-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9310784391-2">[</span><span class="p" data-group-id="9310784391-3">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="9310784391-4">[</span><span class="p" data-group-id="9310784391-5">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9310784391-6">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="9310784391-6">}</span><span class="p" data-group-id="9310784391-5">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9310784391-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9310784391-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9310784391-8">}</span><span class="p" data-group-id="9310784391-7">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9310784391-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9310784391-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9310784391-10">}</span><span class="p" data-group-id="9310784391-9">}</span><span class="p">,</span><span class="w">
│ │ │ +             </span><span class="p" data-group-id="9310784391-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9310784391-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9310784391-12">}</span><span class="p" data-group-id="9310784391-11">}</span><span class="p" data-group-id="9310784391-4">]</span><span class="p" data-group-id="9310784391-3">}</span><span class="p" data-group-id="9310784391-2">]</span></code></pre><p>A more complicated example with two quad core processors, each processor in
│ │ │  its own NUMA node. The ordering of logical processors is a bit weird. This
│ │ │  to give a better example of identifier lists:</p><pre><code class="makeup erlang" translate="no"><span class="c1">% erl +sct L0-1,3-2c0-3p0N0:L7,4,6-5c0-3p1N1</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="9202280435-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="9202280435-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9202280435-2">[</span><span class="p" data-group-id="9202280435-3">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="9202280435-4">[</span><span class="p" data-group-id="9202280435-5">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="9202280435-6">[</span><span class="p" data-group-id="9202280435-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="9202280435-8">}</span><span class="p" data-group-id="9202280435-7">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9202280435-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="9202280435-10">}</span><span class="p" data-group-id="9202280435-9">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9202280435-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="9202280435-12">}</span><span class="p" data-group-id="9202280435-11">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9202280435-13">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-14">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="9202280435-14">}</span><span class="p" data-group-id="9202280435-13">}</span><span class="p" data-group-id="9202280435-6">]</span><span class="p" data-group-id="9202280435-5">}</span><span class="p" data-group-id="9202280435-4">]</span><span class="p" data-group-id="9202280435-3">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="9202280435-15">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="9202280435-16">[</span><span class="p" data-group-id="9202280435-17">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="9202280435-18">[</span><span class="p" data-group-id="9202280435-19">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-20">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="9202280435-20">}</span><span class="p" data-group-id="9202280435-19">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9202280435-21">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-22">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="9202280435-22">}</span><span class="p" data-group-id="9202280435-21">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9202280435-23">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-24">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="9202280435-24">}</span><span class="p" data-group-id="9202280435-23">}</span><span class="p">,</span><span class="w">
│ │ │ -                    </span><span class="p" data-group-id="9202280435-25">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="9202280435-26">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="9202280435-26">}</span><span class="p" data-group-id="9202280435-25">}</span><span class="p" data-group-id="9202280435-18">]</span><span class="p" data-group-id="9202280435-17">}</span><span class="p" data-group-id="9202280435-16">]</span><span class="p" data-group-id="9202280435-15">}</span><span class="p" data-group-id="9202280435-2">]</span></code></pre><p>As long as real identifiers are correct, it is OK to pass a CPU topology
│ │ │ +1&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="0010850264-1">(</span><span class="ss">cpu_topology</span><span class="p" data-group-id="0010850264-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0010850264-2">[</span><span class="p" data-group-id="0010850264-3">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="0010850264-4">[</span><span class="p" data-group-id="0010850264-5">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="0010850264-6">[</span><span class="p" data-group-id="0010850264-7">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-8">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="0010850264-8">}</span><span class="p" data-group-id="0010850264-7">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0010850264-9">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-10">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="0010850264-10">}</span><span class="p" data-group-id="0010850264-9">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0010850264-11">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-12">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0010850264-12">}</span><span class="p" data-group-id="0010850264-11">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0010850264-13">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-14">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="0010850264-14">}</span><span class="p" data-group-id="0010850264-13">}</span><span class="p" data-group-id="0010850264-6">]</span><span class="p" data-group-id="0010850264-5">}</span><span class="p" data-group-id="0010850264-4">]</span><span class="p" data-group-id="0010850264-3">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="0010850264-15">{</span><span class="nb">node</span><span class="p">,</span><span class="p" data-group-id="0010850264-16">[</span><span class="p" data-group-id="0010850264-17">{</span><span class="ss">processor</span><span class="p">,</span><span class="p" data-group-id="0010850264-18">[</span><span class="p" data-group-id="0010850264-19">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-20">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">7</span><span class="p" data-group-id="0010850264-20">}</span><span class="p" data-group-id="0010850264-19">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0010850264-21">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-22">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0010850264-22">}</span><span class="p" data-group-id="0010850264-21">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0010850264-23">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-24">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="0010850264-24">}</span><span class="p" data-group-id="0010850264-23">}</span><span class="p">,</span><span class="w">
│ │ │ +                    </span><span class="p" data-group-id="0010850264-25">{</span><span class="ss">core</span><span class="p">,</span><span class="p" data-group-id="0010850264-26">{</span><span class="ss">logical</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0010850264-26">}</span><span class="p" data-group-id="0010850264-25">}</span><span class="p" data-group-id="0010850264-18">]</span><span class="p" data-group-id="0010850264-17">}</span><span class="p" data-group-id="0010850264-16">]</span><span class="p" data-group-id="0010850264-15">}</span><span class="p" data-group-id="0010850264-2">]</span></code></pre><p>As long as real identifiers are correct, it is OK to pass a CPU topology
│ │ │  that is not a correct description of the CPU topology. When used with care
│ │ │  this can be very useful. This to trick the emulator to bind its schedulers
│ │ │  as you want. For example, if you want to run multiple Erlang runtime systems
│ │ │  on the same machine, you want to reduce the number of schedulers used and
│ │ │  manipulate the CPU topology so that they bind to different logical CPUs. An
│ │ │  example, with two Erlang runtime systems on a quad core machine:</p><pre><code class="text">% erl +sct L0-3c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname one
│ │ │  % erl +sct L3-0c0-3 +sbt db +S3:2 -detached -noinput -noshell -sname two</code></pre><p>In this example, each runtime system have two schedulers each online, and
│ │ │ @@ -923,18 +923,18 @@
│ │ │  </h2>
│ │ │  <p>The standard Erlang/OTP system can be reconfigured to change the default
│ │ │  behavior on startup.</p><ul><li><p><strong>The <code class="inline">.erlang</code> startup file</strong> - When Erlang/OTP is started, the system
│ │ │  searches for a file named <code class="inline">.erlang</code> in the
│ │ │  <a href="init.html#home">user's home directory</a> and then
│ │ │  <a href="../../../lib/stdlib-6.2.2.2/doc/html/filename.html#user_config"><code class="inline">filename:basedir(user_config, &quot;erlang&quot;)</code></a>.</p><p>If an <code class="inline">.erlang</code> file is found, it is assumed to contain valid Erlang
│ │ │  expressions. These expressions are evaluated as if they were input to the
│ │ │ -shell.</p><p>A typical <code class="inline">.erlang</code> file contains a set of search paths, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6097663926-1">(</span><span class="s">&quot;executing user profile in $HOME/.erlang\n&quot;</span><span class="p">,</span><span class="p" data-group-id="6097663926-2">[</span><span class="p" data-group-id="6097663926-2">]</span><span class="p" data-group-id="6097663926-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="6097663926-3">(</span><span class="s">&quot;/home/calvin/test/ebin&quot;</span><span class="p" data-group-id="6097663926-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="6097663926-4">(</span><span class="s">&quot;/home/hobbes/bigappl-1.2/ebin&quot;</span><span class="p" data-group-id="6097663926-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6097663926-5">(</span><span class="s">&quot;.erlang rc finished\n&quot;</span><span class="p">,</span><span class="p" data-group-id="6097663926-6">[</span><span class="p" data-group-id="6097663926-6">]</span><span class="p" data-group-id="6097663926-5">)</span><span class="p">.</span></code></pre></li><li><p><strong>user_default</strong> and <strong>shell_default</strong> - Functions in the shell that are not
│ │ │ +shell.</p><p>A typical <code class="inline">.erlang</code> file contains a set of search paths, for example:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0184516912-1">(</span><span class="s">&quot;executing user profile in $HOME/.erlang\n&quot;</span><span class="p">,</span><span class="p" data-group-id="0184516912-2">[</span><span class="p" data-group-id="0184516912-2">]</span><span class="p" data-group-id="0184516912-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="0184516912-3">(</span><span class="s">&quot;/home/calvin/test/ebin&quot;</span><span class="p" data-group-id="0184516912-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nc">code</span><span class="p">:</span><span class="nf">add_path</span><span class="p" data-group-id="0184516912-4">(</span><span class="s">&quot;/home/hobbes/bigappl-1.2/ebin&quot;</span><span class="p" data-group-id="0184516912-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0184516912-5">(</span><span class="s">&quot;.erlang rc finished\n&quot;</span><span class="p">,</span><span class="p" data-group-id="0184516912-6">[</span><span class="p" data-group-id="0184516912-6">]</span><span class="p" data-group-id="0184516912-5">)</span><span class="p">.</span></code></pre></li><li><p><strong>user_default</strong> and <strong>shell_default</strong> - Functions in the shell that are not
│ │ │  prefixed by a module name are assumed to be functional objects (funs),
│ │ │  built-in functions (BIFs), or belong to the module <code class="inline">user_default</code> or
│ │ │  <code class="inline">shell_default</code>.</p><p>To include private shell commands, define them in a module <code class="inline">user_default</code> and
│ │ │  add the following argument as the first line in the <code class="inline">.erlang</code> file:</p><pre><code class="text">code:load_abs(&quot;..../user_default&quot;).</code></pre></li><li><p><strong>erl</strong> - If the contents of <code class="inline">.erlang</code> are changed and a private version of
│ │ │  <code class="inline">user_default</code> is defined, the Erlang/OTP environment can be customized. More
│ │ │  powerful changes can be made by supplying command-line arguments in the
│ │ │  startup script <code class="inline">erl</code>. For more information, see <a href="init.html"><code class="inline">init</code></a>.</p></li></ul><h2 id="see-also" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erl_dist_protocol.html
│ │ │ @@ -252,32 +252,32 @@
│ │ │  ---
│ │ │  sequenceDiagram
│ │ │      participant client as Client (or Node)
│ │ │      participant EPMD
│ │ │      
│ │ │      client -&gt;&gt; EPMD: NAMES_REQ
│ │ │      EPMD --&gt;&gt; client: NAMES_RESP</code></pre><table><thead><tr><th style="text-align: left;">1</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">110</code></td></tr></tbody></table><p><em>Table: NAMES_REQ (110)</em></p><p>The response for a <code class="inline">NAMES_REQ</code> is as follows:</p><table><thead><tr><th style="text-align: left;">4</th><th style="text-align: left;"></th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">EPMDPortNo</code></td><td style="text-align: left;"><code class="inline">NodeInfo*</code></td></tr></tbody></table><p><em>Table: NAMES_RESP</em></p><p><code class="inline">NodeInfo</code> is a string written for each active node. When all <code class="inline">NodeInfo</code> has
│ │ │ -been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="2404364875-1">(</span><span class="s">&quot;name ~ts at port </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2404364875-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="2404364875-2">]</span><span class="p" data-group-id="2404364875-1">)</span><span class="p">.</span></code></pre><h3 id="dump-all-data-from-epmd" class="section-heading">
│ │ │ +been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="6667201544-1">(</span><span class="s">&quot;name ~ts at port </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6667201544-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p" data-group-id="6667201544-2">]</span><span class="p" data-group-id="6667201544-1">)</span><span class="p">.</span></code></pre><h3 id="dump-all-data-from-epmd" class="section-heading">
│ │ │    <a href="#dump-all-data-from-epmd" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Dump All Data from EPMD</span>
│ │ │  </h3>
│ │ │  <p>This request is not really used, it is to be regarded as a debug feature.</p><pre><code class="mermaid">---
│ │ │  title: Dump All Data from EPMD
│ │ │  ---
│ │ │  sequenceDiagram
│ │ │      participant client as Client (or Node)
│ │ │      participant EPMD
│ │ │      
│ │ │      client -&gt;&gt; EPMD: DUMP_REQ
│ │ │      EPMD --&gt;&gt; client: DUMP_RESP</code></pre><table><thead><tr><th style="text-align: left;">1</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">100</code></td></tr></tbody></table><p><em>Table: DUMP_REQ</em></p><p>The response for a <code class="inline">DUMP_REQ</code> is as follows:</p><table><thead><tr><th style="text-align: left;">4</th><th style="text-align: left;"></th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">EPMDPortNo</code></td><td style="text-align: left;"><code class="inline">NodeInfo*</code></td></tr></tbody></table><p><em>Table: DUMP_RESP</em></p><p><code class="inline">NodeInfo</code> is a string written for each node kept in the EPMD. When all
│ │ │ -<code class="inline">NodeInfo</code> has been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5566024283-1">(</span><span class="s">&quot;active name     ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="5566024283-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="5566024283-2">]</span><span class="p" data-group-id="5566024283-1">)</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="8581483594-1">(</span><span class="s">&quot;old/unused name ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ -          </span><span class="p" data-group-id="8581483594-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="8581483594-2">]</span><span class="p" data-group-id="8581483594-1">)</span><span class="p">.</span></code></pre><h3 id="kill-epmd" class="section-heading">
│ │ │ +<code class="inline">NodeInfo</code> has been written the connection is closed by the EPMD.</p><p><code class="inline">NodeInfo</code> is, as expressed in Erlang:</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="1683999103-1">(</span><span class="s">&quot;active name     ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="1683999103-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="1683999103-2">]</span><span class="p" data-group-id="1683999103-1">)</span><span class="p">.</span></code></pre><p>or</p><pre><code class="makeup erlang" translate="no"><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="3116609736-1">(</span><span class="s">&quot;old/unused name ~ts at port </span><span class="si">~p</span><span class="s">, fd = </span><span class="si">~p</span><span class="s"> </span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w">
│ │ │ +          </span><span class="p" data-group-id="3116609736-2">[</span><span class="n">NodeName</span><span class="p">,</span><span class="w"> </span><span class="n">Port</span><span class="p">,</span><span class="w"> </span><span class="n">Fd</span><span class="p" data-group-id="3116609736-2">]</span><span class="p" data-group-id="3116609736-1">)</span><span class="p">.</span></code></pre><h3 id="kill-epmd" class="section-heading">
│ │ │    <a href="#kill-epmd" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Kill EPMD</span>
│ │ │  </h3>
│ │ │  <p>This request kills the running EPMD. It is almost never used.</p><pre><code class="mermaid">---
│ │ │  title: Kill EPMD
│ │ │ @@ -407,54 +407,54 @@
│ │ │  received from <code class="inline">A</code> is correct and generates a digest from the challenge
│ │ │  received from <code class="inline">A</code>. The digest is then sent to <code class="inline">A</code>. The message is as follows:</p><table><thead><tr><th style="text-align: left;">1</th><th style="text-align: left;">16</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">'a'</code></td><td style="text-align: left;"><code class="inline">Digest</code></td></tr></tbody></table><p><em>Table: The challenge_ack message</em></p><p><code class="inline">Digest</code> is the digest calculated by <code class="inline">B</code> for <code class="inline">A</code>'s challenge.</p></li><li><p><strong>7) check</strong> - <code class="inline">A</code> checks the digest from <code class="inline">B</code> and the connection is up.</p></li></ul><h3 id="semigraphic-view" class="section-heading">
│ │ │    <a href="#semigraphic-view" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">Semigraphic View</span>
│ │ │  </h3>
│ │ │ -<pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="p" data-group-id="0220738191-1">(</span><span class="ss">initiator</span><span class="p" data-group-id="0220738191-1">)</span><span class="w">                                      </span><span class="n">B</span><span class="w"> </span><span class="p" data-group-id="0220738191-2">(</span><span class="ss">acceptor</span><span class="p" data-group-id="0220738191-2">)</span><span class="w">
│ │ │ +<pre><code class="makeup erlang" translate="no"><span class="n">A</span><span class="w"> </span><span class="p" data-group-id="5284579835-1">(</span><span class="ss">initiator</span><span class="p" data-group-id="5284579835-1">)</span><span class="w">                                      </span><span class="n">B</span><span class="w"> </span><span class="p" data-group-id="5284579835-2">(</span><span class="ss">acceptor</span><span class="p" data-group-id="5284579835-2">)</span><span class="w">
│ │ │  
│ │ │  </span><span class="n">TCP</span><span class="w"> </span><span class="ss">connect</span><span class="w"> </span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">&gt;</span><span class="w">
│ │ │                                                     </span><span class="n">TCP</span><span class="w"> </span><span class="ss">accept</span><span class="w">
│ │ │  
│ │ │  </span><span class="ss">send_name</span><span class="w"> </span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">&gt;</span><span class="w">
│ │ │                                                     </span><span class="ss">recv_name</span><span class="w">
│ │ │  
│ │ │    </span><span class="o">&lt;-</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">-</span><span class="w"> </span><span class="ss">send_status</span><span class="w">
│ │ │  </span><span class="nf">recv_status</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0220738191-3">(</span><span class="k">if</span><span class="w"> </span><span class="ss">status</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="ss">&#39;alive&#39;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5284579835-3">(</span><span class="k">if</span><span class="w"> </span><span class="ss">status</span><span class="w"> </span><span class="ss">was</span><span class="w"> </span><span class="ss">&#39;alive&#39;</span><span class="w">
│ │ │   </span><span class="ss">send_status</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                                   </span><span class="ss">recv_status</span><span class="p" data-group-id="0220738191-3">)</span><span class="w">
│ │ │ +                                                   </span><span class="ss">recv_status</span><span class="p" data-group-id="5284579835-3">)</span><span class="w">
│ │ │  
│ │ │ -                          </span><span class="p" data-group-id="0220738191-4">(</span><span class="n">ChB</span><span class="p" data-group-id="0220738191-4">)</span><span class="w">                      </span><span class="n">ChB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="0220738191-5">(</span><span class="p" data-group-id="0220738191-5">)</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="5284579835-4">(</span><span class="n">ChB</span><span class="p" data-group-id="5284579835-4">)</span><span class="w">                      </span><span class="n">ChB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="5284579835-5">(</span><span class="p" data-group-id="5284579835-5">)</span><span class="w">
│ │ │    </span><span class="o">&lt;-</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">-</span><span class="w"> </span><span class="ss">send_challenge</span><span class="w">
│ │ │  </span><span class="nf">recv_challenge</span><span class="w">
│ │ │  
│ │ │ -</span><span class="p" data-group-id="0220738191-6">(</span><span class="k">if</span><span class="w"> </span><span class="ss">old</span><span class="w"> </span><span class="ss">send_name</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5284579835-6">(</span><span class="k">if</span><span class="w"> </span><span class="ss">old</span><span class="w"> </span><span class="ss">send_name</span><span class="w">
│ │ │   </span><span class="ss">send_complement</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                                   </span><span class="ss">recv_complement</span><span class="p" data-group-id="0220738191-6">)</span><span class="w">
│ │ │ +                                                   </span><span class="ss">recv_complement</span><span class="p" data-group-id="5284579835-6">)</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">ChA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="0220738191-7">(</span><span class="p" data-group-id="0220738191-7">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">OCA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="0220738191-8">(</span><span class="n">B</span><span class="p" data-group-id="0220738191-8">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">DiA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="0220738191-9">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">OCA</span><span class="p" data-group-id="0220738191-9">)</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="0220738191-10">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">DiA</span><span class="p" data-group-id="0220738191-10">)</span><span class="w">
│ │ │ +</span><span class="n">ChA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_challenge</span><span class="p" data-group-id="5284579835-7">(</span><span class="p" data-group-id="5284579835-7">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">OCA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="5284579835-8">(</span><span class="n">B</span><span class="p" data-group-id="5284579835-8">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">DiA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="5284579835-9">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">OCA</span><span class="p" data-group-id="5284579835-9">)</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="5284579835-10">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">DiA</span><span class="p" data-group-id="5284579835-10">)</span><span class="w">
│ │ │  </span><span class="ss">send_challenge_reply</span><span class="w"> </span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="p">-&gt;</span><span class="w">
│ │ │                                                     </span><span class="ss">recv_challenge_reply</span><span class="w">
│ │ │ -                                                   </span><span class="n">ICB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="0220738191-11">(</span><span class="n">A</span><span class="p" data-group-id="0220738191-11">)</span><span class="p">,</span><span class="w">
│ │ │ +                                                   </span><span class="n">ICB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="5284579835-11">(</span><span class="n">A</span><span class="p" data-group-id="5284579835-11">)</span><span class="p">,</span><span class="w">
│ │ │                                                     </span><span class="nc">check</span><span class="p">:</span><span class="w">
│ │ │ -                                                   </span><span class="n">DiA</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="0220738191-12">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">ICB</span><span class="p" data-group-id="0220738191-12">)</span><span class="o">?</span><span class="w">
│ │ │ +                                                   </span><span class="n">DiA</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="5284579835-12">(</span><span class="n">ChB</span><span class="p">,</span><span class="w"> </span><span class="n">ICB</span><span class="p" data-group-id="5284579835-12">)</span><span class="o">?</span><span class="w">
│ │ │  </span><span class="w">                                                   </span><span class="p">-</span><span class="w"> </span><span class="na">if</span><span class="w"> </span><span class="n">OK</span><span class="p">:</span><span class="w">
│ │ │ -                                                    </span><span class="n">OCB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="0220738191-13">(</span><span class="n">A</span><span class="p" data-group-id="0220738191-13">)</span><span class="p">,</span><span class="w">
│ │ │ -                                                    </span><span class="n">DiB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="0220738191-14">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">OCB</span><span class="p" data-group-id="0220738191-14">)</span><span class="w">
│ │ │ -                          </span><span class="p" data-group-id="0220738191-15">(</span><span class="n">DiB</span><span class="p" data-group-id="0220738191-15">)</span><span class="w">
│ │ │ +                                                    </span><span class="n">OCB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">out_cookie</span><span class="p" data-group-id="5284579835-13">(</span><span class="n">A</span><span class="p" data-group-id="5284579835-13">)</span><span class="p">,</span><span class="w">
│ │ │ +                                                    </span><span class="n">DiB</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">gen_digest</span><span class="w"> </span><span class="p" data-group-id="5284579835-14">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">OCB</span><span class="p" data-group-id="5284579835-14">)</span><span class="w">
│ │ │ +                          </span><span class="p" data-group-id="5284579835-15">(</span><span class="n">DiB</span><span class="p" data-group-id="5284579835-15">)</span><span class="w">
│ │ │    </span><span class="o">&lt;-</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="w"> </span><span class="ss">send_challenge_ack</span><span class="w">
│ │ │  </span><span class="ss">recv_challenge_ack</span><span class="w">                                  </span><span class="n">DONE</span><span class="w">
│ │ │ -</span><span class="n">ICA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="0220738191-16">(</span><span class="n">B</span><span class="p" data-group-id="0220738191-16">)</span><span class="p">,</span><span class="w">                                </span><span class="o">-</span><span class="w"> </span><span class="nc">else</span><span class="p">:</span><span class="w">
│ │ │ +</span><span class="n">ICA</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">in_cookie</span><span class="p" data-group-id="5284579835-16">(</span><span class="n">B</span><span class="p" data-group-id="5284579835-16">)</span><span class="p">,</span><span class="w">                                </span><span class="o">-</span><span class="w"> </span><span class="nc">else</span><span class="p">:</span><span class="w">
│ │ │  </span><span class="nc">check</span><span class="p">:</span><span class="w">                                              </span><span class="n">CLOSE</span><span class="w">
│ │ │ -</span><span class="n">DiB</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="0220738191-17">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">ICA</span><span class="p" data-group-id="0220738191-17">)</span><span class="o">?</span><span class="w">
│ │ │ +</span><span class="n">DiB</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nf">gen_digest</span><span class="p" data-group-id="5284579835-17">(</span><span class="n">ChA</span><span class="p">,</span><span class="w"> </span><span class="n">ICA</span><span class="p" data-group-id="5284579835-17">)</span><span class="o">?</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="w"> </span><span class="na">if</span><span class="w"> </span><span class="n">OK</span><span class="p">:</span><span class="w">
│ │ │   </span><span class="n">DONE</span><span class="w">
│ │ │  </span><span class="p">-</span><span class="w"> </span><span class="na">else</span><span class="p">:</span><span class="w">
│ │ │   </span><span class="n">CLOSE</span></code></pre><p><a href="" id="dflags"></a></p><h3 id="distribution-flags" class="section-heading">
│ │ │    <a href="#distribution-flags" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erl_ext_dist.html
│ │ │ @@ -436,15 +436,15 @@
│ │ │    </a>
│ │ │    <span class="text">SMALL_BIG_EXT</span>
│ │ │  </h2>
│ │ │  <table><thead><tr><th style="text-align: left;">1</th><th style="text-align: left;">1</th><th style="text-align: left;">1</th><th style="text-align: left;">n</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">110</code></td><td style="text-align: left;"><code class="inline">n</code></td><td style="text-align: left;"><code class="inline">Sign</code></td><td style="text-align: left;"><code class="inline">d(0)</code> ... <code class="inline">d(n-1)</code></td></tr></tbody></table><p>Bignums are stored in unary form with a <code class="inline">Sign</code> byte, that is, 0 if the bignum is
│ │ │  positive and 1 if it is negative. The digits are stored with the least
│ │ │  significant byte stored first. To calculate the integer, the following formula
│ │ │  can be used:</p><pre><code class="makeup erlang" translate="no"><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">256</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7268064663-1">(</span><span class="ss">d0</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">0</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d1</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d2</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">2</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="nf">d</span><span class="p" data-group-id="7268064663-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="7268064663-2">)</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="p" data-group-id="7268064663-3">(</span><span class="ss">n</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="7268064663-3">)</span><span class="p" data-group-id="7268064663-1">)</span></code></pre><h2 id="large_big_ext" class="section-heading">
│ │ │ +</span><span class="p" data-group-id="9206414447-1">(</span><span class="ss">d0</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">0</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d1</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="ss">d2</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="mi">2</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="w"> </span><span class="nf">d</span><span class="p" data-group-id="9206414447-2">(</span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9206414447-2">)</span><span class="o">*</span><span class="n">B</span><span class="err">^</span><span class="p" data-group-id="9206414447-3">(</span><span class="ss">n</span><span class="o">-</span><span class="mi">1</span><span class="p" data-group-id="9206414447-3">)</span><span class="p" data-group-id="9206414447-1">)</span></code></pre><h2 id="large_big_ext" class="section-heading">
│ │ │    <a href="#large_big_ext" class="hover-link">
│ │ │      <i class="ri-link-m" aria-hidden="true"></i>
│ │ │    </a>
│ │ │    <span class="text">LARGE_BIG_EXT</span>
│ │ │  </h2>
│ │ │  <table><thead><tr><th style="text-align: left;">1</th><th style="text-align: left;">4</th><th style="text-align: left;">1</th><th style="text-align: left;">n</th></tr></thead><tbody><tr><td style="text-align: left;"><code class="inline">111</code></td><td style="text-align: left;"><code class="inline">n</code></td><td style="text-align: left;"><code class="inline">Sign</code></td><td style="text-align: left;"><code class="inline">d(0)</code> ... <code class="inline">d(n-1)</code></td></tr></tbody></table><p>Same as <a href="erl_ext_dist.html#small_big_ext"><code class="inline">SMALL_BIG_EXT</code></a> except that the length
│ │ │  field is an unsigned 4 byte integer.</p><h2 id="reference_ext-deprecated" class="section-heading">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erl_nif.html
│ │ │ @@ -161,27 +161,27 @@
│ │ │  }
│ │ │  
│ │ │  static ErlNifFunc nif_funcs[] =
│ │ │  {
│ │ │      {&quot;hello&quot;, 0, hello}
│ │ │  };
│ │ │  
│ │ │ -ERL_NIF_INIT(niftest,nif_funcs,NULL,NULL,NULL,NULL)</code></pre><p>The Erlang module can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6745355820-1">(</span><span class="ss">niftest</span><span class="p" data-group-id="6745355820-1">)</span><span class="p">.</span><span class="w">
│ │ │ +ERL_NIF_INIT(niftest,nif_funcs,NULL,NULL,NULL,NULL)</code></pre><p>The Erlang module can look as follows:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8610123767-1">(</span><span class="ss">niftest</span><span class="p" data-group-id="8610123767-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6745355820-2">(</span><span class="p" data-group-id="6745355820-3">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6745355820-3">]</span><span class="p" data-group-id="6745355820-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8610123767-2">(</span><span class="p" data-group-id="8610123767-3">[</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8610123767-3">]</span><span class="p" data-group-id="8610123767-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="6745355820-4">(</span><span class="p" data-group-id="6745355820-5">[</span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6745355820-5">]</span><span class="p" data-group-id="6745355820-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">nifs</span><span class="p" data-group-id="8610123767-4">(</span><span class="p" data-group-id="8610123767-5">[</span><span class="ss">hello</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8610123767-5">]</span><span class="p" data-group-id="8610123767-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="6745355820-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="6745355820-6">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">on_load</span><span class="p" data-group-id="8610123767-6">(</span><span class="ss">init</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8610123767-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">init</span><span class="p" data-group-id="6745355820-7">(</span><span class="p" data-group-id="6745355820-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="6745355820-8">(</span><span class="s">&quot;./niftest&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="6745355820-8">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">init</span><span class="p" data-group-id="8610123767-7">(</span><span class="p" data-group-id="8610123767-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="8610123767-8">(</span><span class="s">&quot;./niftest&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8610123767-8">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">hello</span><span class="p" data-group-id="6745355820-9">(</span><span class="p" data-group-id="6745355820-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="6745355820-10">(</span><span class="s">&quot;NIF library not loaded&quot;</span><span class="p" data-group-id="6745355820-10">)</span><span class="p">.</span></code></pre><p>Compile and test can look as follows (on Linux):</p><pre><code class="text">$&gt; gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
│ │ │ +</span><span class="nf">hello</span><span class="p" data-group-id="8610123767-9">(</span><span class="p" data-group-id="8610123767-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +      </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">nif_error</span><span class="p" data-group-id="8610123767-10">(</span><span class="s">&quot;NIF library not loaded&quot;</span><span class="p" data-group-id="8610123767-10">)</span><span class="p">.</span></code></pre><p>Compile and test can look as follows (on Linux):</p><pre><code class="text">$&gt; gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
│ │ │  $&gt; erl
│ │ │  
│ │ │  1&gt; c(niftest).
│ │ │  {ok,niftest}
│ │ │  2&gt; niftest:hello().
│ │ │  &quot;Hello world!&quot;</code></pre><p>In the example above the <a href="../../../doc/system/code_loading.html#on_load"><em><code class="inline">on_load</code></em></a>
│ │ │  directive is used get function <code class="inline">init</code> called automatically when the module is
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erl_prim_loader.html
│ │ │ @@ -398,15 +398,15 @@
│ │ │                          when Filename :: <a href="erlang.html#t:string/0">string</a>(), FileInfo :: <a href="../../../lib/kernel-10.2.7.2/doc/html/file.html#t:file_info/0">file:file_info</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Retrieves information about a file.</p><p>Returns <code class="inline">{ok, FileInfo}</code> if successful, otherwise <code class="inline">error</code>. <code class="inline">FileInfo</code> is a
│ │ │  record <a href="../../../lib/kernel-10.2.7.2/doc/html/file.html#t:file_info/0"><code class="inline">file_info</code></a>, defined in the Kernel include file
│ │ │   <code class="inline">file.hrl</code>. Include the following directive in the module from which the
│ │ │ -function is called:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="6543132606-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="6543132606-1">)</span><span class="p">.</span></code></pre><p>For more information about the record see <a href="../../../lib/kernel-10.2.7.2/doc/html/file.html#read_file_info/2"><code class="inline">file:read_file_info/2</code></a>.</p><p><code class="inline">Filename</code> can also be a file in an archive, for example,
│ │ │ +function is called:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">include_lib</span><span class="p" data-group-id="7483432998-1">(</span><span class="s">&quot;kernel/include/file.hrl&quot;</span><span class="p" data-group-id="7483432998-1">)</span><span class="p">.</span></code></pre><p>For more information about the record see <a href="../../../lib/kernel-10.2.7.2/doc/html/file.html#read_file_info/2"><code class="inline">file:read_file_info/2</code></a>.</p><p><code class="inline">Filename</code> can also be a file in an archive, for example,
│ │ │  <code class="inline">$OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin/mnesia</code>. For information
│ │ │  about archive files, see <a href="../../../lib/kernel-10.2.7.2/doc/html/code.html"><code class="inline">code</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="read_link_info/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erl_tracer.html
│ │ │ @@ -145,44 +145,44 @@
│ │ │    <span class="text">Erl Tracer Module Example</span>
│ │ │  </h2>
│ │ │  <p>In this example, a tracer module with a NIF back end sends a message for each
│ │ │  <code class="inline">send</code> trace tag containing only the sender and receiver. Using this tracer
│ │ │  module, a much more lightweight message tracer is used, which only records who
│ │ │  sent messages to who.</p><p>The following is an example session using it on Linux:</p><pre><code class="makeup erlang" translate="no"><span class="sc">$ </span><span class="ss">gcc</span><span class="w"> </span><span class="o">-</span><span class="n">I</span><span class="w"> </span><span class="ss">erts</span><span class="o">-</span><span class="mf">8.0</span><span class="o">/</span><span class="ss">include</span><span class="o">/</span><span class="w"> </span><span class="o">-</span><span class="ss">fPIC</span><span class="w"> </span><span class="o">-</span><span class="ss">shared</span><span class="w"> </span><span class="o">-</span><span class="ss">o</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">.</span><span class="ss">so</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">.</span><span class="ss">c</span><span class="w">
│ │ │  </span><span class="sc">$ </span><span class="ss">erl</span><span class="w">
│ │ │ -</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">19</span><span class="w"> </span><span class="p" data-group-id="0583921911-1">[</span><span class="n">DEVELOPMENT</span><span class="p" data-group-id="0583921911-1">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-2">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">8.0</span><span class="p" data-group-id="0583921911-2">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-3">[</span><span class="ss">source</span><span class="o">-</span><span class="ss">ed2b56b</span><span class="p" data-group-id="0583921911-3">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-4">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="0583921911-4">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-5">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="0583921911-5">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="0583921911-6">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="0583921911-7">]</span><span class="w"> </span><span class="p" data-group-id="0583921911-8">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="0583921911-8">]</span><span class="w">
│ │ │ +</span><span class="n">Erlang</span><span class="o">/</span><span class="n">OTP</span><span class="w"> </span><span class="mi">19</span><span class="w"> </span><span class="p" data-group-id="5222434504-1">[</span><span class="n">DEVELOPMENT</span><span class="p" data-group-id="5222434504-1">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-2">[</span><span class="ss">erts</span><span class="o">-</span><span class="mf">8.0</span><span class="p" data-group-id="5222434504-2">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-3">[</span><span class="ss">source</span><span class="o">-</span><span class="ss">ed2b56b</span><span class="p" data-group-id="5222434504-3">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-4">[</span><span class="mi">64</span><span class="o">-</span><span class="ss">bit</span><span class="p" data-group-id="5222434504-4">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-5">[</span><span class="nc">smp</span><span class="p">:</span><span class="mi">8</span><span class="p">:</span><span class="mi">8</span><span class="p" data-group-id="5222434504-5">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-6">[</span><span class="ss">async</span><span class="o">-</span><span class="nc">threads</span><span class="p">:</span><span class="mi">10</span><span class="p" data-group-id="5222434504-6">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-7">[</span><span class="ss">hipe</span><span class="p" data-group-id="5222434504-7">]</span><span class="w"> </span><span class="p" data-group-id="5222434504-8">[</span><span class="ss">kernel</span><span class="o">-</span><span class="nc">poll</span><span class="p">:</span><span class="ss">false</span><span class="p" data-group-id="5222434504-8">]</span><span class="w">
│ │ │  
│ │ │ -</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V8</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="0583921911-9">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="0583921911-9">)</span><span class="gp unselectable">
│ │ │ -1&gt; </span><span class="nf">c</span><span class="p" data-group-id="0583921911-10">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="0583921911-10">)</span><span class="p">,</span><span class="w"> </span><span class="nc">erl_msg_tracer</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="0583921911-11">(</span><span class="p" data-group-id="0583921911-11">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="n">Eshell</span><span class="w"> </span><span class="n">V8</span><span class="p">.</span><span class="mi">0</span><span class="w">  </span><span class="p" data-group-id="5222434504-9">(</span><span class="ss">abort</span><span class="w"> </span><span class="ss">with</span><span class="w"> </span><span class="err">^</span><span class="n">G</span><span class="p" data-group-id="5222434504-9">)</span><span class="gp unselectable">
│ │ │ +1&gt; </span><span class="nf">c</span><span class="p" data-group-id="5222434504-10">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="5222434504-10">)</span><span class="p">,</span><span class="w"> </span><span class="nc">erl_msg_tracer</span><span class="p">:</span><span class="nf">load</span><span class="p" data-group-id="5222434504-11">(</span><span class="p" data-group-id="5222434504-11">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="n">Tracer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="0583921911-12">(</span><span class="k">fun</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0583921911-13">(</span><span class="p" data-group-id="0583921911-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="0583921911-14">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="0583921911-15">[</span><span class="n">M</span><span class="p" data-group-id="0583921911-15">]</span><span class="p" data-group-id="0583921911-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="0583921911-16">(</span><span class="p" data-group-id="0583921911-16">)</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="0583921911-12">)</span><span class="p">.</span><span class="w">
│ │ │ +2&gt; </span><span class="n">Tracer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">spawn</span><span class="p" data-group-id="5222434504-12">(</span><span class="k">fun</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="5222434504-13">(</span><span class="p" data-group-id="5222434504-13">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">receive</span><span class="w"> </span><span class="n">M</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="5222434504-14">(</span><span class="s">&quot;</span><span class="si">~p</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="p" data-group-id="5222434504-15">[</span><span class="n">M</span><span class="p" data-group-id="5222434504-15">]</span><span class="p" data-group-id="5222434504-14">)</span><span class="p">,</span><span class="w"> </span><span class="n">F</span><span class="p" data-group-id="5222434504-16">(</span><span class="p" data-group-id="5222434504-16">)</span><span class="w"> </span><span class="k">end</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="5222434504-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.37</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="gp unselectable">
│ │ │ -3&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="0583921911-17">(</span><span class="ss">new</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0583921911-18">[</span><span class="nb">send</span><span class="p">,</span><span class="p" data-group-id="0583921911-19">{</span><span class="ss">tracer</span><span class="p">,</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">,</span><span class="w"> </span><span class="n">Tracer</span><span class="p" data-group-id="0583921911-19">}</span><span class="p" data-group-id="0583921911-18">]</span><span class="p" data-group-id="0583921911-17">)</span><span class="p">.</span><span class="w">
│ │ │ +3&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">trace</span><span class="p" data-group-id="5222434504-17">(</span><span class="ss">new</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5222434504-18">[</span><span class="nb">send</span><span class="p">,</span><span class="p" data-group-id="5222434504-19">{</span><span class="ss">tracer</span><span class="p">,</span><span class="w"> </span><span class="ss">erl_msg_tracer</span><span class="p">,</span><span class="w"> </span><span class="n">Tracer</span><span class="p" data-group-id="5222434504-19">}</span><span class="p" data-group-id="5222434504-18">]</span><span class="p" data-group-id="5222434504-17">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">0</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-20">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-20">}</span><span class="gp unselectable">
│ │ │ -4&gt; </span><span class="p" data-group-id="0583921911-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="0583921911-21">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="0583921911-22">(</span><span class="s">&quot;/tmp/tmp.data&quot;</span><span class="p">,</span><span class="p" data-group-id="0583921911-23">[</span><span class="ss">write</span><span class="p" data-group-id="0583921911-23">]</span><span class="p" data-group-id="0583921911-22">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-24">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.486</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-24">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-25">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.21</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-25">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-26">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.487</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-26">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-27">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.488</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-27">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-28">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.489</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-28">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-29">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.490</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-29">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-30">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-30">}</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0583921911-31">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.41</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="0583921911-31">}</span><span class="w">
│ │ │ -</span><span class="mi">5</span><span class="o">&gt;</span></code></pre><p><code class="inline">erl_msg_tracer.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="8734364917-1">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="8734364917-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-20">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.39</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-20">}</span><span class="gp unselectable">
│ │ │ +4&gt; </span><span class="p" data-group-id="5222434504-21">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">D</span><span class="p" data-group-id="5222434504-21">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">file</span><span class="p">:</span><span class="nf">open</span><span class="p" data-group-id="5222434504-22">(</span><span class="s">&quot;/tmp/tmp.data&quot;</span><span class="p">,</span><span class="p" data-group-id="5222434504-23">[</span><span class="ss">write</span><span class="p" data-group-id="5222434504-23">]</span><span class="p" data-group-id="5222434504-22">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-24">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.486</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-24">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-25">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.21</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-25">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-26">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.487</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-26">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-27">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.488</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-27">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-28">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.489</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-28">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-29">{</span><span class="nb">trace</span><span class="p">,</span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.490</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-29">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-30">{</span><span class="ss">ok</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.40</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-30">}</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5222434504-31">{</span><span class="nb">trace</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.41</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.27</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5222434504-31">}</span><span class="w">
│ │ │ +</span><span class="mi">5</span><span class="o">&gt;</span></code></pre><p><code class="inline">erl_msg_tracer.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3963874165-1">(</span><span class="ss">erl_msg_tracer</span><span class="p" data-group-id="3963874165-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="8734364917-2">(</span><span class="p" data-group-id="8734364917-3">[</span><span class="ss">enabled</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nb">trace</span><span class="p">/</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="8734364917-3">]</span><span class="p" data-group-id="8734364917-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3963874165-2">(</span><span class="p" data-group-id="3963874165-3">[</span><span class="ss">enabled</span><span class="p">/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="nb">trace</span><span class="p">/</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="ss">load</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3963874165-3">]</span><span class="p" data-group-id="3963874165-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">load</span><span class="p" data-group-id="8734364917-4">(</span><span class="p" data-group-id="8734364917-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="8734364917-5">(</span><span class="s">&quot;erl_msg_tracer&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8734364917-6">[</span><span class="p" data-group-id="8734364917-6">]</span><span class="p" data-group-id="8734364917-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">load</span><span class="p" data-group-id="3963874165-4">(</span><span class="p" data-group-id="3963874165-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">load_nif</span><span class="p" data-group-id="3963874165-5">(</span><span class="s">&quot;erl_msg_tracer&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3963874165-6">[</span><span class="p" data-group-id="3963874165-6">]</span><span class="p" data-group-id="3963874165-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">enabled</span><span class="p" data-group-id="8734364917-7">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8734364917-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">enabled</span><span class="p" data-group-id="3963874165-7">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3963874165-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">error</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">trace</span><span class="p" data-group-id="8734364917-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8734364917-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">trace</span><span class="p" data-group-id="3963874165-8">(</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3963874165-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="ss">error</span><span class="p">.</span></code></pre><p><code class="inline">erl_msg_tracer.c</code>:</p><pre><code class="c">#include &lt;erl_nif.h&gt;
│ │ │  
│ │ │  /* NIF interface declarations */
│ │ │  static int load(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info);
│ │ │  static int upgrade(ErlNifEnv* env, void** priv_data, void** old_priv_data, ERL_NIF_TERM load_info);
│ │ │  static void unload(ErlNifEnv* env, void* priv_data);
│ │ ├── ./usr/share/doc/erlang-doc/html/erts-15.2.7.2/doc/html/erlang.html
│ │ │ @@ -6846,16 +6846,16 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> adler32(OldAdler, Data) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when OldAdler :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(), Data :: <a href="#t:iodata/0">iodata</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Continues computing the adler32 checksum by combining the previous checksum,
│ │ │ -<code class="inline">OldAdler</code>, with the checksum of <code class="inline">Data</code>.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9112759474-1">(</span><span class="n">Data1</span><span class="p" data-group-id="9112759474-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="9112759474-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="9112759474-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Y</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="8385200831-1">(</span><span class="p" data-group-id="8385200831-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="8385200831-2">]</span><span class="p" data-group-id="8385200831-1">)</span><span class="p">.</span></code></pre>
│ │ │ +<code class="inline">OldAdler</code>, with the checksum of <code class="inline">Data</code>.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="2355941942-1">(</span><span class="n">Data1</span><span class="p" data-group-id="2355941942-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="2355941942-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="2355941942-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Y</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="3140537588-1">(</span><span class="p" data-group-id="3140537588-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="3140537588-2">]</span><span class="p" data-group-id="3140537588-1">)</span><span class="p">.</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="adler32_combine/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#adler32_combine/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -6878,18 +6878,18 @@
│ │ │                               FirstAdler :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                               SecondAdler :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                               SecondSize :: <a href="#t:non_neg_integer/0">non_neg_integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Combines two previously computed adler32 checksums.</p><p>This computation requires the size of the data object for the second checksum
│ │ │ -to be known.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="8528015120-1">(</span><span class="n">Data1</span><span class="p" data-group-id="8528015120-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="8528015120-2">(</span><span class="n">Y</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="8528015120-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Z</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="6157419769-1">(</span><span class="n">Data1</span><span class="p" data-group-id="6157419769-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="6157419769-2">(</span><span class="n">Data2</span><span class="p" data-group-id="6157419769-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32_combine</span><span class="p" data-group-id="6157419769-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="6157419769-4">(</span><span class="n">Data2</span><span class="p" data-group-id="6157419769-4">)</span><span class="p" data-group-id="6157419769-3">)</span><span class="p">.</span></code></pre>
│ │ │ +to be known.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="5222727567-1">(</span><span class="n">Data1</span><span class="p" data-group-id="5222727567-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="5222727567-2">(</span><span class="n">Y</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="5222727567-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Z</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="4243106583-1">(</span><span class="n">Data1</span><span class="p" data-group-id="4243106583-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32</span><span class="p" data-group-id="4243106583-2">(</span><span class="n">Data2</span><span class="p" data-group-id="4243106583-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">adler32_combine</span><span class="p" data-group-id="4243106583-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="4243106583-4">(</span><span class="n">Data2</span><span class="p" data-group-id="4243106583-4">)</span><span class="p" data-group-id="4243106583-3">)</span><span class="p">.</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="crc32/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#crc32/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -6934,16 +6934,16 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> crc32(OldCrc, Data) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when OldCrc :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(), Data :: <a href="#t:iodata/0">iodata</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Continues computing the crc32 checksum by combining the previous checksum,
│ │ │ -<code class="inline">OldCrc</code>, with the checksum of <code class="inline">Data</code>.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="4947739106-1">(</span><span class="n">Data1</span><span class="p" data-group-id="4947739106-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="4947739106-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="4947739106-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Y</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0610342089-1">(</span><span class="p" data-group-id="0610342089-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="0610342089-2">]</span><span class="p" data-group-id="0610342089-1">)</span><span class="p">.</span></code></pre>
│ │ │ +<code class="inline">OldCrc</code>, with the checksum of <code class="inline">Data</code>.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0727076894-1">(</span><span class="n">Data1</span><span class="p" data-group-id="0727076894-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0727076894-2">(</span><span class="n">X</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="0727076894-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Y</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="7732843815-1">(</span><span class="p" data-group-id="7732843815-2">[</span><span class="n">Data1</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="7732843815-2">]</span><span class="p" data-group-id="7732843815-1">)</span><span class="p">.</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="crc32_combine/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#crc32_combine/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -6966,18 +6966,18 @@
│ │ │                             FirstCrc :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                             SecondCrc :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                             SecondSize :: <a href="#t:non_neg_integer/0">non_neg_integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Combines two previously computed crc32 checksums.</p><p>This computation requires the size of the data object for the second checksum
│ │ │ -to be known.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="2110727905-1">(</span><span class="n">Data1</span><span class="p" data-group-id="2110727905-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="2110727905-2">(</span><span class="n">Y</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="2110727905-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Z</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0073290246-1">(</span><span class="n">Data1</span><span class="p" data-group-id="0073290246-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0073290246-2">(</span><span class="n">Data2</span><span class="p" data-group-id="0073290246-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32_combine</span><span class="p" data-group-id="0073290246-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="0073290246-4">(</span><span class="n">Data2</span><span class="p" data-group-id="0073290246-4">)</span><span class="p" data-group-id="0073290246-3">)</span><span class="p">.</span></code></pre>
│ │ │ +to be known.</p><p>The following code:</p><pre><code class="makeup erlang" translate="no"><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0303442123-1">(</span><span class="n">Data1</span><span class="p" data-group-id="0303442123-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="0303442123-2">(</span><span class="n">Y</span><span class="p">,</span><span class="n">Data2</span><span class="p" data-group-id="0303442123-2">)</span><span class="p">.</span></code></pre><p>assigns the same value to <code class="inline">Z</code> as this:</p><pre><code class="makeup erlang" translate="no"><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="3493798666-1">(</span><span class="n">Data1</span><span class="p" data-group-id="3493798666-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32</span><span class="p" data-group-id="3493798666-2">(</span><span class="n">Data2</span><span class="p" data-group-id="3493798666-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">crc32_combine</span><span class="p" data-group-id="3493798666-3">(</span><span class="n">X</span><span class="p">,</span><span class="n">Y</span><span class="p">,</span><span class="nf">iolist_size</span><span class="p" data-group-id="3493798666-4">(</span><span class="n">Data2</span><span class="p" data-group-id="3493798666-4">)</span><span class="p" data-group-id="3493798666-3">)</span><span class="p">.</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="md5/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#md5/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8129,19 +8129,19 @@
│ │ │  the <code class="inline">Info</code> map in the returned result will contain the key <code class="inline">node_type</code>
│ │ │  associated with the value <code class="inline">NodeTypeInfo</code>. Currently the following node types
│ │ │  exist:</p><ul><li><p><strong><code class="inline">visible</code></strong> - The node is connected to the node of the calling process
│ │ │  through an ordinary visible connection. That is, the node name would appear
│ │ │  in the result returned by <a href="#nodes/0"><code class="inline">nodes/0</code></a>.</p></li><li><p><strong><code class="inline">hidden</code></strong> - The node is connected to the node of the calling process
│ │ │  through a hidden connection. That is, the node name would <em>not</em> appear in
│ │ │  the result returned by <a href="#nodes/0"><code class="inline">nodes/0</code></a>.</p></li><li><p><strong><code class="inline">this</code></strong> - This is the node of the calling process.</p></li><li><p><strong><code class="inline">known</code></strong> - The node is not connected but known to the node of the calling
│ │ │ -process.</p></li></ul></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(a@localhost)1&gt; </span><span class="nf">nodes</span><span class="p" data-group-id="6732578417-1">(</span><span class="p" data-group-id="6732578417-2">[</span><span class="ss">this</span><span class="p">,</span><span class="w"> </span><span class="ss">connected</span><span class="p" data-group-id="6732578417-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6732578417-3">#{</span><span class="ss">connection_id</span><span class="p">=&gt;</span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="ss">node_type</span><span class="p">=&gt;</span><span class="ss">true</span><span class="p" data-group-id="6732578417-3">}</span><span class="p" data-group-id="6732578417-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6732578417-4">[</span><span class="p" data-group-id="6732578417-5">{</span><span class="ss">c@localhost</span><span class="p">,</span><span class="p" data-group-id="6732578417-6">#{</span><span class="ss">connection_id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">13892108</span><span class="p">,</span><span class="ss">node_type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">hidden</span><span class="p" data-group-id="6732578417-6">}</span><span class="p" data-group-id="6732578417-5">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6732578417-7">{</span><span class="ss">b@localhost</span><span class="p">,</span><span class="p" data-group-id="6732578417-8">#{</span><span class="ss">connection_id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3067553</span><span class="p">,</span><span class="ss">node_type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">visible</span><span class="p" data-group-id="6732578417-8">}</span><span class="p" data-group-id="6732578417-7">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="6732578417-9">{</span><span class="ss">a@localhost</span><span class="p">,</span><span class="p" data-group-id="6732578417-10">#{</span><span class="ss">connection_id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">undefined</span><span class="p">,</span><span class="ss">node_type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">this</span><span class="p" data-group-id="6732578417-10">}</span><span class="p" data-group-id="6732578417-9">}</span><span class="p" data-group-id="6732578417-4">]</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6732578417-11">(</span><span class="ss">a@localhost</span><span class="p" data-group-id="6732578417-11">)</span><span class="mi">2</span><span class="o">&gt;</span></code></pre>
│ │ │ +process.</p></li></ul></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">(a@localhost)1&gt; </span><span class="nf">nodes</span><span class="p" data-group-id="4012152336-1">(</span><span class="p" data-group-id="4012152336-2">[</span><span class="ss">this</span><span class="p">,</span><span class="w"> </span><span class="ss">connected</span><span class="p" data-group-id="4012152336-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4012152336-3">#{</span><span class="ss">connection_id</span><span class="p">=&gt;</span><span class="ss">true</span><span class="p">,</span><span class="w"> </span><span class="ss">node_type</span><span class="p">=&gt;</span><span class="ss">true</span><span class="p" data-group-id="4012152336-3">}</span><span class="p" data-group-id="4012152336-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4012152336-4">[</span><span class="p" data-group-id="4012152336-5">{</span><span class="ss">c@localhost</span><span class="p">,</span><span class="p" data-group-id="4012152336-6">#{</span><span class="ss">connection_id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">13892108</span><span class="p">,</span><span class="ss">node_type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">hidden</span><span class="p" data-group-id="4012152336-6">}</span><span class="p" data-group-id="4012152336-5">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4012152336-7">{</span><span class="ss">b@localhost</span><span class="p">,</span><span class="p" data-group-id="4012152336-8">#{</span><span class="ss">connection_id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">3067553</span><span class="p">,</span><span class="ss">node_type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">visible</span><span class="p" data-group-id="4012152336-8">}</span><span class="p" data-group-id="4012152336-7">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="4012152336-9">{</span><span class="ss">a@localhost</span><span class="p">,</span><span class="p" data-group-id="4012152336-10">#{</span><span class="ss">connection_id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">undefined</span><span class="p">,</span><span class="ss">node_type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">this</span><span class="p" data-group-id="4012152336-10">}</span><span class="p" data-group-id="4012152336-9">}</span><span class="p" data-group-id="4012152336-4">]</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4012152336-11">(</span><span class="ss">a@localhost</span><span class="p" data-group-id="4012152336-11">)</span><span class="mi">2</span><span class="o">&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="set_cookie/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#set_cookie/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8237,17 +8237,17 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> abs(Float) -> <a href="#t:float/0">float</a>() when Float :: <a href="#t:float/0">float</a>();
│ │ │           (Int) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Int :: <a href="#t:integer/0">integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns an integer or float that is the arithmetical absolute value of <code class="inline">Float</code>
│ │ │ -or <code class="inline">Int</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">abs</span><span class="p" data-group-id="9092344444-1">(</span><span class="o">-</span><span class="mf">3.33</span><span class="p" data-group-id="9092344444-1">)</span><span class="p">.</span><span class="w">
│ │ │ +or <code class="inline">Int</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">abs</span><span class="p" data-group-id="8671460895-1">(</span><span class="o">-</span><span class="mf">3.33</span><span class="p" data-group-id="8671460895-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">3.33</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">abs</span><span class="p" data-group-id="9092344444-2">(</span><span class="o">-</span><span class="mi">3</span><span class="p" data-group-id="9092344444-2">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">abs</span><span class="p" data-group-id="8671460895-2">(</span><span class="o">-</span><span class="mi">3</span><span class="p" data-group-id="8671460895-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="append_element/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#append_element/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8269,16 +8269,16 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> append_element(Tuple1, Term) -> Tuple2 when Tuple1 :: <a href="#t:tuple/0">tuple</a>(), Tuple2 :: <a href="#t:tuple/0">tuple</a>(), Term :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a new tuple that has one element more than <code class="inline">Tuple1</code>, and contains the
│ │ │  elements in <code class="inline">Tuple1</code> followed by <code class="inline">Term</code> as the last element.</p><p>Semantically equivalent to
│ │ │  <a href="#list_to_tuple/1"><code class="inline">list_to_tuple(tuple_to_list(Tuple1) ++ [Term])</code></a>, but much
│ │ │ -faster.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">append_element</span><span class="p" data-group-id="4151287024-1">(</span><span class="p" data-group-id="4151287024-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p" data-group-id="4151287024-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="4151287024-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4151287024-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">two</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="4151287024-3">}</span></code></pre>
│ │ │ +faster.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">append_element</span><span class="p" data-group-id="6759283083-1">(</span><span class="p" data-group-id="6759283083-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p" data-group-id="6759283083-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="6759283083-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6759283083-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">two</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="6759283083-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="atom_to_binary/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#atom_to_binary/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8333,16 +8333,16 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a binary corresponding to the text representation of <code class="inline">Atom</code>.</p><p>If <code class="inline">Encoding</code> is <code class="inline">latin1</code>, one byte exists for each character in the text
│ │ │  representation. If <code class="inline">Encoding</code> is <code class="inline">utf8</code> or <code class="inline">unicode</code>, the characters are encoded
│ │ │  using UTF-8 where characters may require multiple bytes.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>As from Erlang/OTP 20, atoms can contain any Unicode character and
│ │ │  <a href="#atom_to_binary/2"><code class="inline">atom_to_binary(Atom, latin1)</code></a> may fail if the text
│ │ │ -representation for <code class="inline">Atom</code> contains a Unicode character &gt; 255.</p></section><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="1544848324-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="1544848324-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1544848324-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="1544848324-2">&gt;&gt;</span></code></pre>
│ │ │ +representation for <code class="inline">Atom</code> contains a Unicode character &gt; 255.</p></section><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">atom_to_binary</span><span class="p" data-group-id="6570827790-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="6570827790-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6570827790-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6570827790-2">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="atom_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#atom_to_list/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8363,17 +8363,17 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> atom_to_list(Atom) -> <a href="#t:string/0">string</a>() when Atom :: <a href="#t:atom/0">atom</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a list of unicode code points corresponding to the text representation
│ │ │ -of <code class="inline">Atom</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="3283492448-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="3283492448-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="s">&quot;Erlang&quot;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="8615789503-1">(</span><span class="ss">&#39;你好&#39;</span><span class="p" data-group-id="8615789503-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8615789503-2">[</span><span class="mi">20320</span><span class="p">,</span><span class="mi">22909</span><span class="p" data-group-id="8615789503-2">]</span></code></pre><p>See <a href="../../../lib/stdlib-6.2.2.2/doc/html/unicode.html"><code class="inline">unicode</code></a> for how to convert the resulting list to different formats.</p>
│ │ │ +of <code class="inline">Atom</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="4543567518-1">(</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="4543567518-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="s">&quot;Erlang&quot;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">atom_to_list</span><span class="p" data-group-id="0589565654-1">(</span><span class="ss">&#39;你好&#39;</span><span class="p" data-group-id="0589565654-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0589565654-2">[</span><span class="mi">20320</span><span class="p">,</span><span class="mi">22909</span><span class="p" data-group-id="0589565654-2">]</span></code></pre><p>See <a href="../../../lib/stdlib-6.2.2.2/doc/html/unicode.html"><code class="inline">unicode</code></a> for how to convert the resulting list to different formats.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_part/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_part/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8400,19 +8400,19 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> binary_part(Subject, PosLen) -> <a href="#t:binary/0">binary</a>()
│ │ │                       when
│ │ │                           Subject :: <a href="#t:binary/0">binary</a>(),
│ │ │                           PosLen :: {Start :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(), Length :: <a href="#t:integer/0">integer</a>()}.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Extracts the part of the binary described by <code class="inline">PosLen</code>.</p><p>Negative length can be used to extract bytes at the end of a binary. </p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9872142717-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="9872142717-1">&gt;&gt;</span><span class="p">.</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="9872142717-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="p" data-group-id="9872142717-3">{</span><span class="nf">byte_size</span><span class="p" data-group-id="9872142717-4">(</span><span class="n">Bin</span><span class="p" data-group-id="9872142717-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">5</span><span class="p" data-group-id="9872142717-3">}</span><span class="p" data-group-id="9872142717-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9872142717-5">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="9872142717-5">&gt;&gt;</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">PosLen</code> in any way references outside the binary.</p><p><code class="inline">Start</code> is zero-based, that is:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5302141748-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5302141748-1">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -2&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="5302141748-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="p" data-group-id="5302141748-3">{</span><span class="mi">0</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5302141748-3">}</span><span class="p" data-group-id="5302141748-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5302141748-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="5302141748-4">&gt;&gt;</span></code></pre><p>For details about the <code class="inline">PosLen</code> semantics, see <a href="../../../lib/stdlib-6.2.2.2/doc/html/binary.html"><code class="inline">binary</code></a>.</p>
│ │ │ +<p>Extracts the part of the binary described by <code class="inline">PosLen</code>.</p><p>Negative length can be used to extract bytes at the end of a binary. </p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8593917984-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="8593917984-1">&gt;&gt;</span><span class="p">.</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="8593917984-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="p" data-group-id="8593917984-3">{</span><span class="nf">byte_size</span><span class="p" data-group-id="8593917984-4">(</span><span class="n">Bin</span><span class="p" data-group-id="8593917984-4">)</span><span class="p">,</span><span class="w"> </span><span class="o">-</span><span class="mi">5</span><span class="p" data-group-id="8593917984-3">}</span><span class="p" data-group-id="8593917984-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8593917984-5">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p" data-group-id="8593917984-5">&gt;&gt;</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">PosLen</code> in any way references outside the binary.</p><p><code class="inline">Start</code> is zero-based, that is:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">1&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3048087081-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3048087081-1">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +2&gt; </span><span class="nf">binary_part</span><span class="p" data-group-id="3048087081-2">(</span><span class="n">Bin</span><span class="p">,</span><span class="p" data-group-id="3048087081-3">{</span><span class="mi">0</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3048087081-3">}</span><span class="p" data-group-id="3048087081-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3048087081-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="3048087081-4">&gt;&gt;</span></code></pre><p>For details about the <code class="inline">PosLen</code> semantics, see <a href="../../../lib/stdlib-6.2.2.2/doc/html/binary.html"><code class="inline">binary</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_part/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_part/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8505,16 +8505,16 @@
│ │ │  capable of decoding any Unicode character. Earlier versions would fail if the
│ │ │  binary contained Unicode characters &gt; 255.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The number of characters that are permitted in an atom name is limited. The
│ │ │  default limits can be found in the
│ │ │  <a href="../../../doc/system/system_limits.html">Efficiency Guide (section System Limits)</a>.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>There is configurable limit on how many atoms that can exist and atoms are not
│ │ │  garbage collected. Therefore, it is recommended to consider whether
│ │ │  <a href="#binary_to_existing_atom/2"><code class="inline">binary_to_existing_atom/2</code></a> is a better option
│ │ │  than <a href="#binary_to_atom/2"><code class="inline">binary_to_atom/2</code></a>. The default limits can be found
│ │ │ -in <a href="../../../doc/system/system_limits.html#atoms">Efficiency Guide (section System Limits)</a>.</p></section><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="0967762097-1">(</span><span class="p" data-group-id="0967762097-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="0967762097-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="0967762097-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">&#39;Erlang&#39;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="5894084089-1">(</span><span class="p" data-group-id="5894084089-2">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="5894084089-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="5894084089-1">)</span><span class="p">.</span><span class="w">
│ │ │ +in <a href="../../../doc/system/system_limits.html#atoms">Efficiency Guide (section System Limits)</a>.</p></section><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="2417870201-1">(</span><span class="p" data-group-id="2417870201-2">&lt;&lt;</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="2417870201-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">latin1</span><span class="p" data-group-id="2417870201-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="ss">&#39;Erlang&#39;</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_atom</span><span class="p" data-group-id="2632778395-1">(</span><span class="p" data-group-id="2632778395-2">&lt;&lt;</span><span class="mi">1024</span><span class="o">/</span><span class="ss">utf8</span><span class="p" data-group-id="2632778395-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="ss">utf8</span><span class="p" data-group-id="2632778395-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">&#39;Ѐ&#39;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_existing_atom/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#binary_to_existing_atom/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8613,15 +8613,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> binary_to_float(Binary) -> <a href="#t:float/0">float</a>() when Binary :: <a href="#t:binary/0">binary</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the float whose text representation is <code class="inline">Binary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="8039218634-1">(</span><span class="p" data-group-id="8039218634-2">&lt;&lt;</span><span class="s">&quot;2.2017764e+0&quot;</span><span class="p" data-group-id="8039218634-2">&gt;&gt;</span><span class="p" data-group-id="8039218634-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the float whose text representation is <code class="inline">Binary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_float</span><span class="p" data-group-id="3399119562-1">(</span><span class="p" data-group-id="3399119562-2">&lt;&lt;</span><span class="s">&quot;2.2017764e+0&quot;</span><span class="p" data-group-id="3399119562-2">&gt;&gt;</span><span class="p" data-group-id="3399119562-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">2.2017764</span></code></pre><p>The float string format is the same as the format for
│ │ │  <a href="../../../doc/system/data_types.html">Erlang float literals</a> except for that underscores
│ │ │  are not permitted.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">Binary</code> contains a bad representation of a float.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_integer/1">
│ │ │  
│ │ │ @@ -8646,15 +8646,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> binary_to_integer(Binary) -> <a href="#t:integer/0">integer</a>() when Binary :: <a href="#t:binary/0">binary</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer whose text representation is <code class="inline">Binary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="3241448566-1">(</span><span class="p" data-group-id="3241448566-2">&lt;&lt;</span><span class="s">&quot;123&quot;</span><span class="p" data-group-id="3241448566-2">&gt;&gt;</span><span class="p" data-group-id="3241448566-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer whose text representation is <code class="inline">Binary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="0171501925-1">(</span><span class="p" data-group-id="0171501925-2">&lt;&lt;</span><span class="s">&quot;123&quot;</span><span class="p" data-group-id="0171501925-2">&gt;&gt;</span><span class="p" data-group-id="0171501925-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">123</span></code></pre><p><a href="#binary_to_integer/1"><code class="inline">binary_to_integer/1</code></a> accepts the same string formats
│ │ │  as <a href="#list_to_integer/1"><code class="inline">list_to_integer/1</code></a>.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">Binary</code> contains a bad representation of an integer.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_integer/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -8678,15 +8678,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> binary_to_integer(Binary, Base) -> <a href="#t:integer/0">integer</a>() when Binary :: <a href="#t:binary/0">binary</a>(), Base :: 2..36.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer whose text representation in base <code class="inline">Base</code> is <code class="inline">Binary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="3401065335-1">(</span><span class="p" data-group-id="3401065335-2">&lt;&lt;</span><span class="s">&quot;3FF&quot;</span><span class="p" data-group-id="3401065335-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="3401065335-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer whose text representation in base <code class="inline">Base</code> is <code class="inline">Binary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_integer</span><span class="p" data-group-id="0964713973-1">(</span><span class="p" data-group-id="0964713973-2">&lt;&lt;</span><span class="s">&quot;3FF&quot;</span><span class="p" data-group-id="0964713973-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="0964713973-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">1023</span></code></pre><p><a href="#binary_to_integer/2"><code class="inline">binary_to_integer/2</code></a> accepts the same string formats
│ │ │  as <a href="#list_to_integer/2"><code class="inline">list_to_integer/2</code></a>.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">Binary</code> contains a bad representation of an integer.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="binary_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -8771,17 +8771,17 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> binary_to_term(Binary) -> <a href="#t:term/0">term</a>() when Binary :: <a href="#t:ext_binary/0">ext_binary</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns an Erlang term that is the result of decoding binary object <code class="inline">Binary</code>,
│ │ │  which must be encoded according to the
│ │ │ -<a href="erl_ext_dist.html">Erlang external term format</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="9715404467-1">(</span><span class="ss">hello</span><span class="p" data-group-id="9715404467-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9715404467-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="9715404467-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="ss">hello</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="9715404467-3">(</span><span class="n">Bin</span><span class="p" data-group-id="9715404467-3">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="erl_ext_dist.html">Erlang external term format</a>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="1518239857-1">(</span><span class="ss">hello</span><span class="p" data-group-id="1518239857-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1518239857-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="1518239857-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="ss">hello</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1518239857-3">(</span><span class="n">Bin</span><span class="p" data-group-id="1518239857-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>When decoding binaries from untrusted sources, the untrusted source may submit
│ │ │  data in a way to create resources, such as atoms and remote references, that
│ │ │  cannot be garbage collected and lead to Denial of Service attack. In such
│ │ │  cases, consider using <a href="#binary_to_term/2"><code class="inline">binary_to_term/2</code></a> with the <code class="inline">safe</code>
│ │ │  option.</p></section><p>See also <a href="#term_to_binary/1"><code class="inline">term_to_binary/1</code></a> and <a href="#binary_to_term/2"><code class="inline">binary_to_term/2</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │ @@ -8820,30 +8820,30 @@
│ │ │  <p>Equivalent to <a href="#binary_to_term/1"><code class="inline">binary_to_term(Binary)</code></a>, but can be configured to
│ │ │  fit special purposes.</p><p>The allowed options are:</p><ul><li><p><strong><code class="inline">safe</code></strong> - Use this option when receiving binaries from an untrusted source.</p><p>When enabled, it prevents decoding data that can be used to attack the Erlang
│ │ │  runtime. In the event of receiving unsafe data, decoding fails with a <code class="inline">badarg</code>
│ │ │  error.</p><p>This prevents creation of new atoms directly, creation of new atoms indirectly
│ │ │  (as they are embedded in certain structures, such as process identifiers,
│ │ │  refs, and funs), and creation of new external function references. None of
│ │ │  those resources are garbage collected, so unchecked creation of them can
│ │ │ -exhaust available memory.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1202934567-1">(</span><span class="p" data-group-id="1202934567-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1202934567-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1202934567-3">[</span><span class="ss">safe</span><span class="p" data-group-id="1202934567-3">]</span><span class="p" data-group-id="1202934567-1">)</span><span class="p">.</span><span class="w">
│ │ │ +exhaust available memory.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3458264156-1">(</span><span class="p" data-group-id="3458264156-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3458264156-2">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3458264156-3">[</span><span class="ss">safe</span><span class="p" data-group-id="3458264156-3">]</span><span class="p" data-group-id="3458264156-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: bad argument</span><span class="gp unselectable">
│ │ │  &gt; </span><span class="ss">hello</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="1202934567-4">(</span><span class="p" data-group-id="1202934567-5">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="1202934567-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1202934567-6">[</span><span class="ss">safe</span><span class="p" data-group-id="1202934567-6">]</span><span class="p" data-group-id="1202934567-4">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3458264156-4">(</span><span class="p" data-group-id="3458264156-5">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;hello&quot;</span><span class="p" data-group-id="3458264156-5">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3458264156-6">[</span><span class="ss">safe</span><span class="p" data-group-id="3458264156-6">]</span><span class="p" data-group-id="3458264156-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>The <code class="inline">safe</code> option ensures the data is safely processed by the Erlang runtime
│ │ │  but it does not guarantee the data is safe to your application. You must
│ │ │  always validate data from untrusted sources. If the binary is stored or
│ │ │  transits through untrusted sources, you should also consider
│ │ │  cryptographically signing it.</p></section></li><li><p><strong><code class="inline">used</code></strong> - Changes the return value to <code class="inline">{Term, Used}</code> where <code class="inline">Used</code> is the
│ │ │ -number of bytes actually read from <code class="inline">Binary</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Input</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6979257892-1">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="6979257892-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6979257892-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">114</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">100</span><span class="p" data-group-id="6979257892-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="p" data-group-id="6979257892-3">{</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="6979257892-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="6979257892-4">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6979257892-5">[</span><span class="ss">used</span><span class="p" data-group-id="6979257892-5">]</span><span class="p" data-group-id="6979257892-4">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6979257892-6">{</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="6979257892-6">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">split_binary</span><span class="p" data-group-id="6979257892-7">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="6979257892-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6979257892-8">{</span><span class="p" data-group-id="6979257892-9">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="6979257892-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6979257892-10">&lt;&lt;</span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="6979257892-10">&gt;&gt;</span><span class="p" data-group-id="6979257892-8">}</span></code></pre></li></ul><p>Failure: <code class="inline">badarg</code> if <code class="inline">safe</code> is specified and unsafe data is decoded.</p><p>See also <a href="#term_to_binary/1"><code class="inline">term_to_binary/1</code></a>, <a href="#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>, and <a href="#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a>.</p>
│ │ │ +number of bytes actually read from <code class="inline">Binary</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Input</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="2932538884-1">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;hello&quot;</span><span class="p">,</span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="2932538884-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2932538884-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">119</span><span class="p">,</span><span class="mi">111</span><span class="p">,</span><span class="mi">114</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">100</span><span class="p" data-group-id="2932538884-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="p" data-group-id="2932538884-3">{</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="2932538884-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2932538884-4">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2932538884-5">[</span><span class="ss">used</span><span class="p" data-group-id="2932538884-5">]</span><span class="p" data-group-id="2932538884-4">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2932538884-6">{</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p" data-group-id="2932538884-6">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">split_binary</span><span class="p" data-group-id="2932538884-7">(</span><span class="n">Input</span><span class="p">,</span><span class="w"> </span><span class="n">Used</span><span class="p" data-group-id="2932538884-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2932538884-8">{</span><span class="p" data-group-id="2932538884-9">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="2932538884-9">&gt;&gt;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2932538884-10">&lt;&lt;</span><span class="s">&quot;world&quot;</span><span class="p" data-group-id="2932538884-10">&gt;&gt;</span><span class="p" data-group-id="2932538884-8">}</span></code></pre></li></ul><p>Failure: <code class="inline">badarg</code> if <code class="inline">safe</code> is specified and unsafe data is decoded.</p><p>See also <a href="#term_to_binary/1"><code class="inline">term_to_binary/1</code></a>, <a href="#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>, and <a href="#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="bit_size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#bit_size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8865,17 +8865,17 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> bit_size(Bitstring) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Bitstring :: <a href="#t:bitstring/0">bitstring</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer that is the size in bits of <code class="inline">Bitstring</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="8910691608-1">(</span><span class="p" data-group-id="8910691608-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="8910691608-2">&gt;&gt;</span><span class="p" data-group-id="8910691608-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer that is the size in bits of <code class="inline">Bitstring</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="8084072611-1">(</span><span class="p" data-group-id="8084072611-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="8084072611-2">&gt;&gt;</span><span class="p" data-group-id="8084072611-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">19</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="8910691608-3">(</span><span class="p" data-group-id="8910691608-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8910691608-4">&gt;&gt;</span><span class="p" data-group-id="8910691608-3">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">bit_size</span><span class="p" data-group-id="8084072611-3">(</span><span class="p" data-group-id="8084072611-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8084072611-4">&gt;&gt;</span><span class="p" data-group-id="8084072611-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">24</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="bitstring_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#bitstring_to_list/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8897,17 +8897,17 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> bitstring_to_list(Bitstring) -> [<a href="#t:byte/0">byte</a>() | <a href="#t:bitstring/0">bitstring</a>()] when Bitstring :: <a href="#t:bitstring/0">bitstring</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a list of integers corresponding to the bytes of <code class="inline">Bitstring</code>.</p><p>If the number of bits in the binary is not divisible by 8, the last element of
│ │ │ -the list is a bitstring containing the remaining 1-7 bits.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="1124272542-1">(</span><span class="p" data-group-id="1124272542-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="1124272542-2">&gt;&gt;</span><span class="p" data-group-id="1124272542-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1124272542-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p" data-group-id="1124272542-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="2620740756-1">(</span><span class="p" data-group-id="2620740756-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="2620740756-2">&gt;&gt;</span><span class="p" data-group-id="2620740756-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2620740756-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p">,</span><span class="p" data-group-id="2620740756-4">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="2620740756-4">&gt;&gt;</span><span class="p" data-group-id="2620740756-3">]</span></code></pre>
│ │ │ +the list is a bitstring containing the remaining 1-7 bits.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="6444474523-1">(</span><span class="p" data-group-id="6444474523-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p" data-group-id="6444474523-2">&gt;&gt;</span><span class="p" data-group-id="6444474523-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6444474523-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p" data-group-id="6444474523-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">bitstring_to_list</span><span class="p" data-group-id="3325784960-1">(</span><span class="p" data-group-id="3325784960-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="3325784960-2">&gt;&gt;</span><span class="p" data-group-id="3325784960-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3325784960-3">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">177</span><span class="p">,</span><span class="p" data-group-id="3325784960-4">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="3325784960-4">&gt;&gt;</span><span class="p" data-group-id="3325784960-3">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="byte_size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#byte_size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -8931,17 +8931,17 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> byte_size(Bitstring) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Bitstring :: <a href="#t:bitstring/0">bitstring</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns an integer that is the number of bytes needed to contain <code class="inline">Bitstring</code>.
│ │ │  That is, if the number of bits in <code class="inline">Bitstring</code> is not divisible by 8, the
│ │ │ -resulting number of bytes is rounded <em>up</em>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="4465196146-1">(</span><span class="p" data-group-id="4465196146-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="4465196146-2">&gt;&gt;</span><span class="p" data-group-id="4465196146-1">)</span><span class="p">.</span><span class="w">
│ │ │ +resulting number of bytes is rounded <em>up</em>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="3419403763-1">(</span><span class="p" data-group-id="3419403763-2">&lt;&lt;</span><span class="mi">433</span><span class="p">:</span><span class="mi">16</span><span class="p">,</span><span class="mi">3</span><span class="p">:</span><span class="mi">3</span><span class="p" data-group-id="3419403763-2">&gt;&gt;</span><span class="p" data-group-id="3419403763-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="4465196146-3">(</span><span class="p" data-group-id="4465196146-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="4465196146-4">&gt;&gt;</span><span class="p" data-group-id="4465196146-3">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="3419403763-3">(</span><span class="p" data-group-id="3419403763-4">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3419403763-4">&gt;&gt;</span><span class="p" data-group-id="3419403763-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="ceil/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#ceil/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -8966,15 +8966,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> ceil(Number) -> <a href="#t:integer/0">integer</a>() when Number :: <a href="#t:number/0">number</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the smallest integer not less than <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="7931057197-1">(</span><span class="mf">5.5</span><span class="p" data-group-id="7931057197-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the smallest integer not less than <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">ceil</span><span class="p" data-group-id="3458359322-1">(</span><span class="mf">5.5</span><span class="p" data-group-id="3458359322-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">6</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="decode_packet/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#decode_packet/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9074,18 +9074,18 @@
│ │ │  <a href="https://www.ietf.org/rfc/rfc2732.txt">RFC2732 </a>.</p></li></ul><p>Options:</p><ul><li><p><strong><code class="inline">{packet_size, integer() &gt;= 0}</code></strong> - Sets the maximum allowed size of the
│ │ │  packet body. If the packet header indicates that the length of the packet is
│ │ │  longer than the maximum allowed length, the packet is considered invalid.
│ │ │  Defaults to 0, which means no size limit.</p></li><li><p><strong><code class="inline">{line_length, integer() &gt;= 0}</code></strong> - For packet type <code class="inline">line</code>, lines longer
│ │ │  than the indicated length are truncated.</p><p>Option <code class="inline">line_length</code> also applies to <code class="inline">http*</code> packet types as an alias for
│ │ │  option <code class="inline">packet_size</code> if <code class="inline">packet_size</code> itself is not set. This use is only
│ │ │  intended for backward compatibility.</p></li><li><p><strong><code class="inline">{line_delimiter, 0 =&lt; byte() =&lt; 255}</code></strong> - For packet type <code class="inline">line</code>, sets the
│ │ │ -delimiting byte. Default is the latin-1 character <code class="inline">$\n</code>.</p></li></ul><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="2610138657-1">(</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="2610138657-2">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="2610138657-2">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="2610138657-3">[</span><span class="p" data-group-id="2610138657-3">]</span><span class="p" data-group-id="2610138657-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2610138657-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="2610138657-5">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="2610138657-5">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="2610138657-6">&lt;&lt;</span><span class="s">&quot;d&quot;</span><span class="p" data-group-id="2610138657-6">&gt;&gt;</span><span class="p" data-group-id="2610138657-4">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="2610138657-7">(</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="2610138657-8">&lt;&lt;</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="2610138657-8">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="2610138657-9">[</span><span class="p" data-group-id="2610138657-9">]</span><span class="p" data-group-id="2610138657-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2610138657-10">{</span><span class="ss">more</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="2610138657-10">}</span></code></pre>
│ │ │ +delimiting byte. Default is the latin-1 character <code class="inline">$\n</code>.</p></li></ul><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="8957492484-1">(</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8957492484-2">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="8957492484-2">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="8957492484-3">[</span><span class="p" data-group-id="8957492484-3">]</span><span class="p" data-group-id="8957492484-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8957492484-4">{</span><span class="ss">ok</span><span class="p">,</span><span class="p" data-group-id="8957492484-5">&lt;&lt;</span><span class="s">&quot;abc&quot;</span><span class="p" data-group-id="8957492484-5">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="8957492484-6">&lt;&lt;</span><span class="s">&quot;d&quot;</span><span class="p" data-group-id="8957492484-6">&gt;&gt;</span><span class="p" data-group-id="8957492484-4">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">decode_packet</span><span class="p" data-group-id="8957492484-7">(</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8957492484-8">&lt;&lt;</span><span class="mi">5</span><span class="p">,</span><span class="s">&quot;abcd&quot;</span><span class="p" data-group-id="8957492484-8">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="8957492484-9">[</span><span class="p" data-group-id="8957492484-9">]</span><span class="p" data-group-id="8957492484-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8957492484-10">{</span><span class="ss">more</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8957492484-10">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="delete_element/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#delete_element/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9106,16 +9106,16 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> delete_element(Index, Tuple1) -> Tuple2
│ │ │                          when Index :: <a href="#t:pos_integer/0">pos_integer</a>(), Tuple1 :: <a href="#t:tuple/0">tuple</a>(), Tuple2 :: <a href="#t:tuple/0">tuple</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a new tuple with element at <code class="inline">Index</code> removed from tuple <code class="inline">Tuple1</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">delete_element</span><span class="p" data-group-id="6307770333-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6307770333-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="6307770333-2">}</span><span class="p" data-group-id="6307770333-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6307770333-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="6307770333-3">}</span></code></pre>
│ │ │ +<p>Returns a new tuple with element at <code class="inline">Index</code> removed from tuple <code class="inline">Tuple1</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">delete_element</span><span class="p" data-group-id="8760928108-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8760928108-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="8760928108-2">}</span><span class="p" data-group-id="8760928108-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8760928108-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="8760928108-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="display/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#display/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9165,15 +9165,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> element(N, Tuple) -> <a href="#t:term/0">term</a>() when N :: <a href="#t:pos_integer/0">pos_integer</a>(), Tuple :: <a href="#t:tuple/0">tuple</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the <code class="inline">N</code>th element (numbering from 1) of <code class="inline">Tuple</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">element</span><span class="p" data-group-id="1840765827-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1840765827-2">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="1840765827-2">}</span><span class="p" data-group-id="1840765827-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the <code class="inline">N</code>th element (numbering from 1) of <code class="inline">Tuple</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">element</span><span class="p" data-group-id="1064454820-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1064454820-2">{</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="1064454820-2">}</span><span class="p" data-group-id="1064454820-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">b</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="external_size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#external_size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9195,18 +9195,18 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> external_size(Term) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Term :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Calculates, without doing the encoding, the maximum byte size for a term encoded
│ │ │ -in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="0691192094-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="0691192094-2">(</span><span class="n">Term</span><span class="p" data-group-id="0691192094-2">)</span><span class="p" data-group-id="0691192094-1">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Size2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="0691192094-3">(</span><span class="n">Term</span><span class="p" data-group-id="0691192094-3">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │ +in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="1462845376-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="1462845376-2">(</span><span class="n">Term</span><span class="p" data-group-id="1462845376-2">)</span><span class="p" data-group-id="1462845376-1">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Size2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="1462845376-3">(</span><span class="n">Term</span><span class="p" data-group-id="1462845376-3">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │  &gt; </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Size1</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">Size2</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="ss">true</span></code></pre><p>This is equivalent to a call to:</p><pre><code class="makeup erlang" translate="no"><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="5455392314-1">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5455392314-2">[</span><span class="p" data-group-id="5455392314-2">]</span><span class="p" data-group-id="5455392314-1">)</span></code></pre>
│ │ │ +</span><span class="ss">true</span></code></pre><p>This is equivalent to a call to:</p><pre><code class="makeup erlang" translate="no"><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="6465453635-1">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6465453635-2">[</span><span class="p" data-group-id="6465453635-2">]</span><span class="p" data-group-id="6465453635-1">)</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="external_size/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#external_size/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9235,16 +9235,16 @@
│ │ │                                  deterministic |
│ │ │                                  {minor_version, Version :: 0..2} |
│ │ │                                  local].</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Calculates, without doing the encoding, the maximum byte size for a term encoded
│ │ │ -in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="8282126922-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="8282126922-2">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="8282126922-2">)</span><span class="p" data-group-id="8282126922-1">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Size2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="8282126922-3">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="8282126922-3">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │ +in the Erlang external term format.</p><p>The following condition applies always:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Size1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">byte_size</span><span class="p" data-group-id="0949912563-1">(</span><span class="nf">term_to_binary</span><span class="p" data-group-id="0949912563-2">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="0949912563-2">)</span><span class="p" data-group-id="0949912563-1">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Size2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">external_size</span><span class="p" data-group-id="0949912563-3">(</span><span class="n">Term</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="p" data-group-id="0949912563-3">)</span><span class="p">,</span><span class="gp unselectable">
│ │ │  &gt; </span><span class="ss">true</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Size1</span><span class="w"> </span><span class="o">=&lt;</span><span class="w"> </span><span class="n">Size2</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><p>Option <code class="inline">{minor_version, Version}</code> specifies how floats are encoded. For a
│ │ │  detailed description, see <a href="#term_to_binary/2"><code class="inline">term_to_binary/2</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="float/1">
│ │ │  
│ │ │ @@ -9269,15 +9269,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> float(Number) -> <a href="#t:float/0">float</a>() when Number :: <a href="#t:number/0">number</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a float by converting <code class="inline">Number</code> to a float.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">float</span><span class="p" data-group-id="9317239574-1">(</span><span class="mi">55</span><span class="p" data-group-id="9317239574-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns a float by converting <code class="inline">Number</code> to a float.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">float</span><span class="p" data-group-id="7344838236-1">(</span><span class="mi">55</span><span class="p" data-group-id="7344838236-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">55.0</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If used on the top level in a guard, it tests whether the argument is a
│ │ │  floating point number; for clarity, use <a href="#is_float/1"><code class="inline">is_float/1</code></a> instead.</p><p>When <a href="#float/1"><code class="inline">float/1</code></a> is used in an expression in a guard, such as
│ │ │  '<code class="inline">float(A) == 4.0</code>', it converts a number as described earlier.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="float_to_binary/1">
│ │ │  
│ │ │ @@ -9340,26 +9340,26 @@
│ │ │                                   {decimals, Decimals :: 0..253} |
│ │ │                                   {scientific, Decimals :: 0..249} |
│ │ │                                   compact | short.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a binary corresponding to the text representation of <code class="inline">Float</code> using fixed
│ │ │ -decimal point formatting.</p><p><code class="inline">Options</code> behaves in the same way as <a href="#float_to_list/2"><code class="inline">float_to_list/2</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="6602868115-1">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602868115-2">[</span><span class="p" data-group-id="6602868115-3">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="6602868115-3">}</span><span class="p" data-group-id="6602868115-2">]</span><span class="p" data-group-id="6602868115-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6602868115-4">&lt;&lt;</span><span class="s">&quot;7.1200&quot;</span><span class="p" data-group-id="6602868115-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="6602868115-5">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602868115-6">[</span><span class="p" data-group-id="6602868115-7">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="6602868115-7">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compact</span><span class="p" data-group-id="6602868115-6">]</span><span class="p" data-group-id="6602868115-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6602868115-8">&lt;&lt;</span><span class="s">&quot;7.12&quot;</span><span class="p" data-group-id="6602868115-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="6602868115-9">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602868115-10">[</span><span class="p" data-group-id="6602868115-11">{</span><span class="ss">scientific</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6602868115-11">}</span><span class="p" data-group-id="6602868115-10">]</span><span class="p" data-group-id="6602868115-9">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6602868115-12">&lt;&lt;</span><span class="s">&quot;7.120e+00&quot;</span><span class="p" data-group-id="6602868115-12">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="6602868115-13">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602868115-14">[</span><span class="ss">short</span><span class="p" data-group-id="6602868115-14">]</span><span class="p" data-group-id="6602868115-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6602868115-15">&lt;&lt;</span><span class="s">&quot;7.12&quot;</span><span class="p" data-group-id="6602868115-15">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="6602868115-16">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6602868115-17">[</span><span class="ss">short</span><span class="p" data-group-id="6602868115-17">]</span><span class="p" data-group-id="6602868115-16">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6602868115-18">&lt;&lt;</span><span class="s">&quot;0.30000000000000004&quot;</span><span class="p" data-group-id="6602868115-18">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="6602868115-19">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p" data-group-id="6602868115-19">)</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6602868115-20">&lt;&lt;</span><span class="s">&quot;3.00000000000000044409e-01&quot;</span><span class="p" data-group-id="6602868115-20">&gt;&gt;</span></code></pre>
│ │ │ +decimal point formatting.</p><p><code class="inline">Options</code> behaves in the same way as <a href="#float_to_list/2"><code class="inline">float_to_list/2</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3381538475-1">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3381538475-2">[</span><span class="p" data-group-id="3381538475-3">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3381538475-3">}</span><span class="p" data-group-id="3381538475-2">]</span><span class="p" data-group-id="3381538475-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3381538475-4">&lt;&lt;</span><span class="s">&quot;7.1200&quot;</span><span class="p" data-group-id="3381538475-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3381538475-5">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3381538475-6">[</span><span class="p" data-group-id="3381538475-7">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="3381538475-7">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compact</span><span class="p" data-group-id="3381538475-6">]</span><span class="p" data-group-id="3381538475-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3381538475-8">&lt;&lt;</span><span class="s">&quot;7.12&quot;</span><span class="p" data-group-id="3381538475-8">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3381538475-9">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3381538475-10">[</span><span class="p" data-group-id="3381538475-11">{</span><span class="ss">scientific</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="3381538475-11">}</span><span class="p" data-group-id="3381538475-10">]</span><span class="p" data-group-id="3381538475-9">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3381538475-12">&lt;&lt;</span><span class="s">&quot;7.120e+00&quot;</span><span class="p" data-group-id="3381538475-12">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3381538475-13">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3381538475-14">[</span><span class="ss">short</span><span class="p" data-group-id="3381538475-14">]</span><span class="p" data-group-id="3381538475-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3381538475-15">&lt;&lt;</span><span class="s">&quot;7.12&quot;</span><span class="p" data-group-id="3381538475-15">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3381538475-16">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3381538475-17">[</span><span class="ss">short</span><span class="p" data-group-id="3381538475-17">]</span><span class="p" data-group-id="3381538475-16">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3381538475-18">&lt;&lt;</span><span class="s">&quot;0.30000000000000004&quot;</span><span class="p" data-group-id="3381538475-18">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">float_to_binary</span><span class="p" data-group-id="3381538475-19">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p" data-group-id="3381538475-19">)</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3381538475-20">&lt;&lt;</span><span class="s">&quot;3.00000000000000044409e-01&quot;</span><span class="p" data-group-id="3381538475-20">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="float_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#float_to_list/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9427,25 +9427,25 @@
│ │ │  are truncated. This option is only meaningful together with option <code class="inline">decimals</code>.</li><li>If option <code class="inline">scientific</code> is specified, the float is formatted using scientific
│ │ │  notation with <code class="inline">Decimals</code> digits of precision.</li><li>If option <code class="inline">short</code> is specified, the float is formatted with the smallest
│ │ │  number of digits that still guarantees that
│ │ │  <code class="inline">F =:= list_to_float(float_to_list(F, [short]))</code>. When the float is inside the
│ │ │  range (-2⁵³, 2⁵³), the notation that yields the smallest number of characters
│ │ │  is used (scientific notation or normal decimal notation). Floats outside the
│ │ │  range (-2⁵³, 2⁵³) are always formatted using scientific notation to avoid
│ │ │ -confusing results when doing arithmetic operations.</li><li>If <code class="inline">Options</code> is <code class="inline">[]</code>, the function behaves as <a href="#float_to_list/1"><code class="inline">float_to_list/1</code></a>.</li></ul><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1706143543-1">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1706143543-2">[</span><span class="p" data-group-id="1706143543-3">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="1706143543-3">}</span><span class="p" data-group-id="1706143543-2">]</span><span class="p" data-group-id="1706143543-1">)</span><span class="p">.</span><span class="w">
│ │ │ +confusing results when doing arithmetic operations.</li><li>If <code class="inline">Options</code> is <code class="inline">[]</code>, the function behaves as <a href="#float_to_list/1"><code class="inline">float_to_list/1</code></a>.</li></ul><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7377031920-1">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7377031920-2">[</span><span class="p" data-group-id="7377031920-3">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="7377031920-3">}</span><span class="p" data-group-id="7377031920-2">]</span><span class="p" data-group-id="7377031920-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;7.1200&quot;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1706143543-4">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1706143543-5">[</span><span class="p" data-group-id="1706143543-6">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="1706143543-6">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compact</span><span class="p" data-group-id="1706143543-5">]</span><span class="p" data-group-id="1706143543-4">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7377031920-4">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7377031920-5">[</span><span class="p" data-group-id="7377031920-6">{</span><span class="ss">decimals</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p" data-group-id="7377031920-6">}</span><span class="p">,</span><span class="w"> </span><span class="ss">compact</span><span class="p" data-group-id="7377031920-5">]</span><span class="p" data-group-id="7377031920-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;7.12&quot;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1706143543-7">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1706143543-8">[</span><span class="p" data-group-id="1706143543-9">{</span><span class="ss">scientific</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1706143543-9">}</span><span class="p" data-group-id="1706143543-8">]</span><span class="p" data-group-id="1706143543-7">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7377031920-7">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7377031920-8">[</span><span class="p" data-group-id="7377031920-9">{</span><span class="ss">scientific</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="7377031920-9">}</span><span class="p" data-group-id="7377031920-8">]</span><span class="p" data-group-id="7377031920-7">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;7.120e+00&quot;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1706143543-10">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1706143543-11">[</span><span class="ss">short</span><span class="p" data-group-id="1706143543-11">]</span><span class="p" data-group-id="1706143543-10">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7377031920-10">(</span><span class="mf">7.12</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7377031920-11">[</span><span class="ss">short</span><span class="p" data-group-id="7377031920-11">]</span><span class="p" data-group-id="7377031920-10">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;7.12&quot;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1706143543-12">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1706143543-13">[</span><span class="ss">short</span><span class="p" data-group-id="1706143543-13">]</span><span class="p" data-group-id="1706143543-12">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7377031920-12">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7377031920-13">[</span><span class="ss">short</span><span class="p" data-group-id="7377031920-13">]</span><span class="p" data-group-id="7377031920-12">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;0.30000000000000004&quot;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="1706143543-14">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p" data-group-id="1706143543-14">)</span><span class="w">
│ │ │ +&gt; </span><span class="nf">float_to_list</span><span class="p" data-group-id="7377031920-14">(</span><span class="mf">0.1</span><span class="o">+</span><span class="mf">0.2</span><span class="p" data-group-id="7377031920-14">)</span><span class="w">
│ │ │  </span><span class="s">&quot;3.00000000000000044409e-01&quot;</span></code></pre><p>In the last example, <a href="#float_to_list/1"><code class="inline">float_to_list(0.1+0.2)</code></a> evaluates to
│ │ │  <code class="inline">&quot;3.00000000000000044409e-01&quot;</code>. The reason for this is explained in
│ │ │  <a href="../../../doc/system/data_types.html#float_representation_problem">Representation of Floating Point Numbers</a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="floor/1">
│ │ │  
│ │ │ @@ -9472,15 +9472,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> floor(Number) -> <a href="#t:integer/0">integer</a>() when Number :: <a href="#t:number/0">number</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the largest integer not greater than <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">floor</span><span class="p" data-group-id="4358753207-1">(</span><span class="o">-</span><span class="mf">10.5</span><span class="p" data-group-id="4358753207-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the largest integer not greater than <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">floor</span><span class="p" data-group-id="0941874265-1">(</span><span class="o">-</span><span class="mf">10.5</span><span class="p" data-group-id="0941874265-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">-</span><span class="mi">11</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="fun_info/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#fun_info/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9600,25 +9600,25 @@
│ │ │  named <code class="inline">module</code>, <code class="inline">index</code> and <code class="inline">uniq</code> in the result of
│ │ │  <a href="#fun_info/1"><code class="inline">erlang:fun_info(Fun)</code></a>.</p></li><li><p><strong>uncompiled code</strong> - All funs created from fun expressions in uncompiled code
│ │ │  with the same arity are mapped to the same list by
│ │ │  <a href="#fun_to_list/1"><code class="inline">fun_to_list/1</code></a>.</p></li></ul><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Generally, one can not use <a href="#fun_to_list/1"><code class="inline">fun_to_list/1</code></a> to check if two
│ │ │  funs are equal as <a href="#fun_to_list/1"><code class="inline">fun_to_list/1</code></a> does not take the fun's
│ │ │  environment into account. See <a href="#fun_info/1"><code class="inline">erlang:fun_info/1</code></a> for how to
│ │ │  get the environment of a fun.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>The output of <a href="#fun_to_list/1"><code class="inline">fun_to_list/1</code></a> can differ between Erlang
│ │ │ -implementations and may change in future versions.</p></section><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="3758137691-1">(</span><span class="ss">test</span><span class="p" data-group-id="3758137691-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="3758137691-2">(</span><span class="p" data-group-id="3758137691-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">add2</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">fun_tuple</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="3758137691-3">]</span><span class="p" data-group-id="3758137691-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add</span><span class="p" data-group-id="3758137691-4">(</span><span class="n">A</span><span class="p" data-group-id="3758137691-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3758137691-5">(</span><span class="n">B</span><span class="p" data-group-id="3758137691-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">add2</span><span class="p" data-group-id="3758137691-6">(</span><span class="p" data-group-id="3758137691-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="nf">fun_tuple</span><span class="p" data-group-id="3758137691-7">(</span><span class="p" data-group-id="3758137691-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3758137691-8">{</span><span class="nf">fun</span><span class="p" data-group-id="3758137691-9">(</span><span class="p" data-group-id="3758137691-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="3758137691-10">(</span><span class="p" data-group-id="3758137691-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="3758137691-8">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="6954039023-1">{</span><span class="k">fun</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="nf">add2</span><span class="p" data-group-id="6954039023-2">(</span><span class="p" data-group-id="6954039023-2">)</span><span class="p" data-group-id="6954039023-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6954039023-3">{</span><span class="k">fun</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">1.107738983</span><span class="o">&gt;</span><span class="p" data-group-id="6954039023-3">}</span></code></pre><p>Explanation: <code class="inline">fun test:add/1</code> is upgradable but <code class="inline">test:add2()</code> is not upgradable.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="9885532602-1">{</span><span class="nc">test</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9885532602-2">(</span><span class="mi">1</span><span class="p" data-group-id="9885532602-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="9885532602-3">(</span><span class="mi">42</span><span class="p" data-group-id="9885532602-3">)</span><span class="p" data-group-id="9885532602-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9885532602-4">{</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">0.107738983</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">0.107738983</span><span class="o">&gt;</span><span class="p" data-group-id="9885532602-4">}</span></code></pre><p>Explanation: <code class="inline">test:add(1)</code> and <code class="inline">test:add(42)</code> has the same string representation
│ │ │ -as the environment is not taken into account.</p><pre><code class="makeup erlang" translate="no"><span class="o">&gt;</span><span class="nc">test</span><span class="p">:</span><span class="nf">fun_tuple</span><span class="p" data-group-id="3738936831-1">(</span><span class="p" data-group-id="3738936831-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3738936831-2">{</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">2.107738983</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">3.107738983</span><span class="o">&gt;</span><span class="p" data-group-id="3738936831-2">}</span></code></pre><p>Explanation: The string representations differ because the funs come from
│ │ │ -different fun expressions.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="8384599669-1">{</span><span class="nf">fun</span><span class="p" data-group-id="8384599669-2">(</span><span class="p" data-group-id="8384599669-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="8384599669-3">(</span><span class="p" data-group-id="8384599669-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="8384599669-1">}</span><span class="p">.</span><span class="w"> </span><span class="o">&gt;</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8384599669-4">{</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">45.97283095</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">45.97283095</span><span class="o">&gt;</span><span class="p" data-group-id="8384599669-4">}</span></code></pre><p>Explanation: All funs created from fun expressions of this form in uncompiled
│ │ │ +implementations and may change in future versions.</p></section><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="1382680491-1">(</span><span class="ss">test</span><span class="p" data-group-id="1382680491-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="1382680491-2">(</span><span class="p" data-group-id="1382680491-3">[</span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">add2</span><span class="p">/</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="ss">fun_tuple</span><span class="p">/</span><span class="mi">0</span><span class="p" data-group-id="1382680491-3">]</span><span class="p" data-group-id="1382680491-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add</span><span class="p" data-group-id="1382680491-4">(</span><span class="n">A</span><span class="p" data-group-id="1382680491-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1382680491-5">(</span><span class="n">B</span><span class="p" data-group-id="1382680491-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="k">end</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">add2</span><span class="p" data-group-id="1382680491-6">(</span><span class="p" data-group-id="1382680491-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">fun_tuple</span><span class="p" data-group-id="1382680491-7">(</span><span class="p" data-group-id="1382680491-7">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1382680491-8">{</span><span class="nf">fun</span><span class="p" data-group-id="1382680491-9">(</span><span class="p" data-group-id="1382680491-9">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="1382680491-10">(</span><span class="p" data-group-id="1382680491-10">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="1382680491-8">}</span><span class="p">.</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7428666624-1">{</span><span class="k">fun</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="nf">add2</span><span class="p" data-group-id="7428666624-2">(</span><span class="p" data-group-id="7428666624-2">)</span><span class="p" data-group-id="7428666624-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7428666624-3">{</span><span class="k">fun</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="ss">add</span><span class="p">/</span><span class="mi">1</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">1.107738983</span><span class="o">&gt;</span><span class="p" data-group-id="7428666624-3">}</span></code></pre><p>Explanation: <code class="inline">fun test:add/1</code> is upgradable but <code class="inline">test:add2()</code> is not upgradable.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="6310796004-1">{</span><span class="nc">test</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="6310796004-2">(</span><span class="mi">1</span><span class="p" data-group-id="6310796004-2">)</span><span class="p">,</span><span class="w"> </span><span class="nc">test</span><span class="p">:</span><span class="nf">add</span><span class="p" data-group-id="6310796004-3">(</span><span class="mi">42</span><span class="p" data-group-id="6310796004-3">)</span><span class="p" data-group-id="6310796004-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6310796004-4">{</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">0.107738983</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">0.107738983</span><span class="o">&gt;</span><span class="p" data-group-id="6310796004-4">}</span></code></pre><p>Explanation: <code class="inline">test:add(1)</code> and <code class="inline">test:add(42)</code> has the same string representation
│ │ │ +as the environment is not taken into account.</p><pre><code class="makeup erlang" translate="no"><span class="o">&gt;</span><span class="nc">test</span><span class="p">:</span><span class="nf">fun_tuple</span><span class="p" data-group-id="6054513839-1">(</span><span class="p" data-group-id="6054513839-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6054513839-2">{</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">2.107738983</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">test</span><span class="p">.</span><span class="mf">3.107738983</span><span class="o">&gt;</span><span class="p" data-group-id="6054513839-2">}</span></code></pre><p>Explanation: The string representations differ because the funs come from
│ │ │ +different fun expressions.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="4262233999-1">{</span><span class="nf">fun</span><span class="p" data-group-id="4262233999-2">(</span><span class="p" data-group-id="4262233999-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nf">fun</span><span class="p" data-group-id="4262233999-3">(</span><span class="p" data-group-id="4262233999-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">end</span><span class="p" data-group-id="4262233999-1">}</span><span class="p">.</span><span class="w"> </span><span class="o">&gt;</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4262233999-4">{</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">45.97283095</span><span class="o">&gt;</span><span class="p">,</span><span class="p">#</span><span class="n">Fun</span><span class="o">&lt;</span><span class="ss">erl_eval</span><span class="p">.</span><span class="mf">45.97283095</span><span class="o">&gt;</span><span class="p" data-group-id="4262233999-4">}</span></code></pre><p>Explanation: All funs created from fun expressions of this form in uncompiled
│ │ │  code with the same arity are mapped to the same list by
│ │ │  <a href="#fun_to_list/1"><code class="inline">fun_to_list/1</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="hd/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -9642,16 +9642,16 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> hd(List) -> Head when List :: <a href="#t:nonempty_maybe_improper_list/0">nonempty_maybe_improper_list</a>(), Head :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the head of <code class="inline">List</code>, that is, the first element.</p><p>It works with improper lists.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="2033725979-1">(</span><span class="p" data-group-id="2033725979-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2033725979-2">]</span><span class="p" data-group-id="2033725979-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="8931164932-1">(</span><span class="p" data-group-id="8931164932-2">[</span><span class="ss">first</span><span class="p">,</span><span class="w"> </span><span class="ss">second</span><span class="p">,</span><span class="w"> </span><span class="ss">third</span><span class="p">,</span><span class="w"> </span><span class="ss">so_on</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="8931164932-2">]</span><span class="p" data-group-id="8931164932-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the head of <code class="inline">List</code>, that is, the first element.</p><p>It works with improper lists.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="2259829500-1">(</span><span class="p" data-group-id="2259829500-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="2259829500-2">]</span><span class="p" data-group-id="2259829500-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">hd</span><span class="p" data-group-id="7015945800-1">(</span><span class="p" data-group-id="7015945800-2">[</span><span class="ss">first</span><span class="p">,</span><span class="w"> </span><span class="ss">second</span><span class="p">,</span><span class="w"> </span><span class="ss">third</span><span class="p">,</span><span class="w"> </span><span class="ss">so_on</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="7015945800-2">]</span><span class="p" data-group-id="7015945800-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">first</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">List</code> is an empty list <code class="inline">[]</code>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="insert_element/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#insert_element/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9676,16 +9676,16 @@
│ │ │                          when
│ │ │                              Index :: <a href="#t:pos_integer/0">pos_integer</a>(), Tuple1 :: <a href="#t:tuple/0">tuple</a>(), Tuple2 :: <a href="#t:tuple/0">tuple</a>(), Term :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a new tuple with element <code class="inline">Term</code> inserted at position <code class="inline">Index</code> in tuple
│ │ │  <code class="inline">Tuple1</code>. All elements from position <code class="inline">Index</code> and upwards are pushed one step
│ │ │ -higher in the new tuple <code class="inline">Tuple2</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">insert_element</span><span class="p" data-group-id="1114881401-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1114881401-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="1114881401-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">new</span><span class="p" data-group-id="1114881401-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1114881401-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">new</span><span class="p">,</span><span class="ss">two</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="1114881401-3">}</span></code></pre>
│ │ │ +higher in the new tuple <code class="inline">Tuple2</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">insert_element</span><span class="p" data-group-id="3581101098-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3581101098-2">{</span><span class="ss">one</span><span class="p">,</span><span class="w"> </span><span class="ss">two</span><span class="p">,</span><span class="w"> </span><span class="ss">three</span><span class="p" data-group-id="3581101098-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">new</span><span class="p" data-group-id="3581101098-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3581101098-3">{</span><span class="ss">one</span><span class="p">,</span><span class="ss">new</span><span class="p">,</span><span class="ss">two</span><span class="p">,</span><span class="ss">three</span><span class="p" data-group-id="3581101098-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="integer_to_binary/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#integer_to_binary/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9707,16 +9707,16 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> integer_to_binary(Integer) -> <a href="#t:binary/0">binary</a>() when Integer :: <a href="#t:integer/0">integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a binary corresponding to the text representation of <code class="inline">Integer</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="7759694404-1">(</span><span class="mi">77</span><span class="p" data-group-id="7759694404-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7759694404-2">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="7759694404-2">&gt;&gt;</span></code></pre>
│ │ │ +<p>Returns a binary corresponding to the text representation of <code class="inline">Integer</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="7253888369-1">(</span><span class="mi">77</span><span class="p" data-group-id="7253888369-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7253888369-2">&lt;&lt;</span><span class="s">&quot;77&quot;</span><span class="p" data-group-id="7253888369-2">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="integer_to_binary/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#integer_to_binary/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9739,16 +9739,16 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> integer_to_binary(Integer, Base) -> <a href="#t:binary/0">binary</a>() when Integer :: <a href="#t:integer/0">integer</a>(), Base :: 2..36.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a binary corresponding to the text representation of <code class="inline">Integer</code> in base
│ │ │ -<code class="inline">Base</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="4409982267-1">(</span><span class="mi">1023</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="4409982267-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4409982267-2">&lt;&lt;</span><span class="s">&quot;3FF&quot;</span><span class="p" data-group-id="4409982267-2">&gt;&gt;</span></code></pre>
│ │ │ +<code class="inline">Base</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_binary</span><span class="p" data-group-id="9846440139-1">(</span><span class="mi">1023</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="9846440139-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9846440139-2">&lt;&lt;</span><span class="s">&quot;3FF&quot;</span><span class="p" data-group-id="9846440139-2">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="integer_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#integer_to_list/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9768,15 +9768,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> integer_to_list(Integer) -> <a href="#t:string/0">string</a>() when Integer :: <a href="#t:integer/0">integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a string corresponding to the text representation of <code class="inline">Integer</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="4985290916-1">(</span><span class="mi">77</span><span class="p" data-group-id="4985290916-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns a string corresponding to the text representation of <code class="inline">Integer</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="9950112072-1">(</span><span class="mi">77</span><span class="p" data-group-id="9950112072-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;77&quot;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="integer_to_list/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#integer_to_list/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9798,15 +9798,15 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> integer_to_list(Integer, Base) -> <a href="#t:string/0">string</a>() when Integer :: <a href="#t:integer/0">integer</a>(), Base :: 2..36.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a string corresponding to the text representation of <code class="inline">Integer</code> in base
│ │ │ -<code class="inline">Base</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="1062353817-1">(</span><span class="mi">1023</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="1062353817-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">Base</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">integer_to_list</span><span class="p" data-group-id="8326223563-1">(</span><span class="mi">1023</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="8326223563-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;3FF&quot;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="iolist_size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#iolist_size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9828,15 +9828,15 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> iolist_size(Item) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Item :: <a href="#t:iolist/0">iolist</a>() | <a href="#t:binary/0">binary</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns an integer, that is the size in bytes, of the binary that would be the
│ │ │ -result of <a href="#iolist_to_binary/1"><code class="inline">iolist_to_binary(Item)</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">iolist_size</span><span class="p" data-group-id="0342691824-1">(</span><span class="p" data-group-id="0342691824-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="0342691824-3">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="0342691824-3">&gt;&gt;</span><span class="p" data-group-id="0342691824-2">]</span><span class="p" data-group-id="0342691824-1">)</span><span class="p">.</span><span class="w">
│ │ │ +result of <a href="#iolist_to_binary/1"><code class="inline">iolist_to_binary(Item)</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">iolist_size</span><span class="p" data-group-id="5786391217-1">(</span><span class="p" data-group-id="5786391217-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">|</span><span class="p" data-group-id="5786391217-3">&lt;&lt;</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p" data-group-id="5786391217-3">&gt;&gt;</span><span class="p" data-group-id="5786391217-2">]</span><span class="p" data-group-id="5786391217-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">4</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="iolist_to_binary/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#iolist_to_binary/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -9858,22 +9858,22 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> iolist_to_binary(IoListOrBinary) -> <a href="#t:binary/0">binary</a>() when IoListOrBinary :: <a href="#t:iolist/0">iolist</a>() | <a href="#t:binary/0">binary</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a binary that is made from the integers and binaries in
│ │ │ -<code class="inline">IoListOrBinary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8135575947-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8135575947-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8135575947-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8135575947-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8135575947-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8135575947-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8135575947-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8135575947-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8135575947-5">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8135575947-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8135575947-6">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8135575947-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">iolist_to_binary</span><span class="p" data-group-id="8135575947-7">(</span><span class="p" data-group-id="8135575947-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8135575947-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="8135575947-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="8135575947-8">]</span><span class="p" data-group-id="8135575947-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8135575947-10">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8135575947-10">&gt;&gt;</span></code></pre>
│ │ │ +<code class="inline">IoListOrBinary</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8208756089-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8208756089-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8208756089-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8208756089-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8208756089-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8208756089-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8208756089-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8208756089-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8208756089-5">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8208756089-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8208756089-6">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8208756089-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">iolist_to_binary</span><span class="p" data-group-id="8208756089-7">(</span><span class="p" data-group-id="8208756089-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8208756089-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="8208756089-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="8208756089-8">]</span><span class="p" data-group-id="8208756089-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8208756089-10">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8208756089-10">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="iolist_to_iovec/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#iolist_to_iovec/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -9899,31 +9899,31 @@
│ │ │  
│ │ │  <p>Returns an <a href="#t:iovec/0">iovec</a> that is made from the integers and binaries in
│ │ │  <code class="inline">IoListOrBinary</code>. This function is useful when you want to flatten an iolist but
│ │ │  you do not need a single binary. This can be useful for passing the data to nif
│ │ │  functions such as <a href="erl_nif.html#enif_inspect_iovec"><code class="inline">enif_inspect_iovec</code></a> or do
│ │ │  more efficient message passing. The advantage of using this function over
│ │ │  <a href="#iolist_to_binary/1"><code class="inline">iolist_to_binary/1</code></a> is that it does not have to copy
│ │ │ -<a href="../../../doc/system/binaryhandling.html#refc_binary">off-heap binaries</a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8548704664-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8548704664-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8548704664-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8548704664-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8548704664-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8548704664-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8548704664-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8548704664-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8548704664-5">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8548704664-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8548704664-6">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8548704664-6">&gt;&gt;</span><span class="w">
│ │ │ +<a href="../../../doc/system/binaryhandling.html#refc_binary">off-heap binaries</a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7205562287-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7205562287-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7205562287-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7205562287-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7205562287-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7205562287-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7205562287-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7205562287-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7205562287-5">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="7205562287-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7205562287-6">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="7205562287-6">&gt;&gt;</span><span class="w">
│ │ │  </span><span class="c1">%% If you pass small binaries and integers it works as iolist_to_binary</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">iolist_to_iovec</span><span class="p" data-group-id="8548704664-7">(</span><span class="p" data-group-id="8548704664-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8548704664-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="8548704664-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="8548704664-8">]</span><span class="p" data-group-id="8548704664-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8548704664-10">[</span><span class="p" data-group-id="8548704664-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8548704664-11">&gt;&gt;</span><span class="p" data-group-id="8548704664-10">]</span><span class="w">
│ │ │ +&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">iolist_to_iovec</span><span class="p" data-group-id="7205562287-7">(</span><span class="p" data-group-id="7205562287-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="7205562287-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="7205562287-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="7205562287-8">]</span><span class="p" data-group-id="7205562287-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7205562287-10">[</span><span class="p" data-group-id="7205562287-11">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="7205562287-11">&gt;&gt;</span><span class="p" data-group-id="7205562287-10">]</span><span class="w">
│ │ │  </span><span class="c1">%% If you pass larger binaries, they are split and returned in a form</span><span class="w">
│ │ │  </span><span class="c1">%% optimized for calling the C function writev.</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">iolist_to_iovec</span><span class="p" data-group-id="8548704664-12">(</span><span class="p" data-group-id="8548704664-13">[</span><span class="p" data-group-id="8548704664-14">&lt;&lt;</span><span class="mi">1</span><span class="p" data-group-id="8548704664-14">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="8548704664-15">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">8096</span><span class="p" data-group-id="8548704664-15">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="8548704664-16">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">8096</span><span class="p" data-group-id="8548704664-16">&gt;&gt;</span><span class="p" data-group-id="8548704664-13">]</span><span class="p" data-group-id="8548704664-12">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8548704664-17">[</span><span class="p" data-group-id="8548704664-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="mi">0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8548704664-18">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8548704664-19">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8548704664-19">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="8548704664-20">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="8548704664-20">&gt;&gt;</span><span class="p" data-group-id="8548704664-17">]</span></code></pre>
│ │ │ +&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">iolist_to_iovec</span><span class="p" data-group-id="7205562287-12">(</span><span class="p" data-group-id="7205562287-13">[</span><span class="p" data-group-id="7205562287-14">&lt;&lt;</span><span class="mi">1</span><span class="p" data-group-id="7205562287-14">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="7205562287-15">&lt;&lt;</span><span class="mi">2</span><span class="p">:</span><span class="mi">8096</span><span class="p" data-group-id="7205562287-15">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="7205562287-16">&lt;&lt;</span><span class="mi">3</span><span class="p">:</span><span class="mi">8096</span><span class="p" data-group-id="7205562287-16">&gt;&gt;</span><span class="p" data-group-id="7205562287-13">]</span><span class="p" data-group-id="7205562287-12">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7205562287-17">[</span><span class="p" data-group-id="7205562287-18">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="mi">0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7205562287-18">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7205562287-19">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="w">
│ │ │ +   </span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7205562287-19">&gt;&gt;</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7205562287-20">&lt;&lt;</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="7205562287-20">&gt;&gt;</span><span class="p" data-group-id="7205562287-17">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="is_atom/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#is_atom/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -10253,19 +10253,19 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> is_map_key(Key, Map) -> <a href="#t:boolean/0">boolean</a>() when Key :: <a href="#t:term/0">term</a>(), Map :: <a href="#t:map/0">map</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns <code class="inline">true</code> if map <code class="inline">Map</code> contains <code class="inline">Key</code> and returns <code class="inline">false</code> if it does not
│ │ │ -contain the <code class="inline">Key</code>.</p><p>The call fails with a <code class="inline">{badmap,Map}</code> exception if <code class="inline">Map</code> is not a map.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="6642611404-1">#{</span><span class="s">&quot;42&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="6642611404-1">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6642611404-2">#{</span><span class="s">&quot;42&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="6642611404-2">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">is_map_key</span><span class="p" data-group-id="6642611404-3">(</span><span class="s">&quot;42&quot;</span><span class="p">,</span><span class="n">Map</span><span class="p" data-group-id="6642611404-3">)</span><span class="p">.</span><span class="w">
│ │ │ +contain the <code class="inline">Key</code>.</p><p>The call fails with a <code class="inline">{badmap,Map}</code> exception if <code class="inline">Map</code> is not a map.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="4526366373-1">#{</span><span class="s">&quot;42&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="4526366373-1">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4526366373-2">#{</span><span class="s">&quot;42&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value</span><span class="p" data-group-id="4526366373-2">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">is_map_key</span><span class="p" data-group-id="4526366373-3">(</span><span class="s">&quot;42&quot;</span><span class="p">,</span><span class="n">Map</span><span class="p" data-group-id="4526366373-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">is_map_key</span><span class="p" data-group-id="6642611404-4">(</span><span class="ss">value</span><span class="p">,</span><span class="n">Map</span><span class="p" data-group-id="6642611404-4">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">is_map_key</span><span class="p" data-group-id="4526366373-4">(</span><span class="ss">value</span><span class="p">,</span><span class="n">Map</span><span class="p" data-group-id="4526366373-4">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="is_number/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#is_number/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -10508,15 +10508,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> length(List) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when List :: [<a href="#t:term/0">term</a>()].</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the length of <code class="inline">List</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">length</span><span class="p" data-group-id="5890068756-1">(</span><span class="p" data-group-id="5890068756-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="5890068756-2">]</span><span class="p" data-group-id="5890068756-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the length of <code class="inline">List</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">length</span><span class="p" data-group-id="7815320260-1">(</span><span class="p" data-group-id="7815320260-2">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p" data-group-id="7815320260-2">]</span><span class="p" data-group-id="7815320260-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">9</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_atom/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#list_to_atom/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -10546,15 +10546,15 @@
│ │ │  Unicode characters above 255.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The number of characters that are permitted in an atom name is limited. The
│ │ │  default limits can be found in the
│ │ │  <a href="../../../doc/system/system_limits.html">efficiency guide (section System Limits)</a>.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>There is a <a href="../../../doc/system/system_limits.html#atoms">configurable limit</a>
│ │ │  on how many atoms that can exist and atoms are not
│ │ │  garbage collected. Therefore, it is recommended to consider if
│ │ │  <a href="#list_to_existing_atom/1"><code class="inline">list_to_existing_atom/1</code></a> is a better option than
│ │ │  <a href="#list_to_atom/1"><code class="inline">list_to_atom/1</code></a>. The default limits can be found in the
│ │ │ -<a href="../../../doc/system/system_limits.html">Efficiency Guide (section System Limits)</a>.</p></section><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="6901818083-1">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="6901818083-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="../../../doc/system/system_limits.html">Efficiency Guide (section System Limits)</a>.</p></section><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_atom</span><span class="p" data-group-id="4589887404-1">(</span><span class="s">&quot;Erlang&quot;</span><span class="p" data-group-id="4589887404-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">&#39;Erlang&#39;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_binary/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#list_to_binary/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -10575,22 +10575,22 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_binary(IoList) -> <a href="#t:binary/0">binary</a>() when IoList :: <a href="#t:iolist/0">iolist</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a binary that is made from the integers and binaries in <code class="inline">IoList</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3727814435-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3727814435-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3727814435-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="3727814435-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3727814435-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3727814435-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3727814435-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="3727814435-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="3727814435-5">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="3727814435-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3727814435-6">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="3727814435-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="3727814435-7">(</span><span class="p" data-group-id="3727814435-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="3727814435-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="3727814435-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="3727814435-8">]</span><span class="p" data-group-id="3727814435-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3727814435-10">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="3727814435-10">&gt;&gt;</span></code></pre>
│ │ │ +<p>Returns a binary that is made from the integers and binaries in <code class="inline">IoList</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8921520905-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8921520905-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8921520905-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8921520905-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8921520905-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8921520905-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8921520905-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="8921520905-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="8921520905-5">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8921520905-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8921520905-6">&lt;&lt;</span><span class="mi">6</span><span class="p" data-group-id="8921520905-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">list_to_binary</span><span class="p" data-group-id="8921520905-7">(</span><span class="p" data-group-id="8921520905-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="8921520905-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="8921520905-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="8921520905-8">]</span><span class="p" data-group-id="8921520905-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8921520905-10">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p" data-group-id="8921520905-10">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_bitstring/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#list_to_bitstring/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -10612,22 +10612,22 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_bitstring(BitstringList) -> <a href="#t:bitstring/0">bitstring</a>() when BitstringList :: <a href="#t:bitstring_list/0">bitstring_list</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a bitstring that is made from the integers and bitstrings in
│ │ │  <code class="inline">BitstringList</code>. (The last tail in <code class="inline">BitstringList</code> is allowed to be a
│ │ │ -bitstring.)</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0979991547-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0979991547-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0979991547-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="0979991547-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0979991547-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0979991547-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0979991547-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="0979991547-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="0979991547-5">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="0979991547-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0979991547-6">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="0979991547-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">list_to_bitstring</span><span class="p" data-group-id="0979991547-7">(</span><span class="p" data-group-id="0979991547-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="0979991547-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="0979991547-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="0979991547-8">]</span><span class="p" data-group-id="0979991547-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0979991547-10">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="0979991547-10">&gt;&gt;</span></code></pre>
│ │ │ +bitstring.)</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7240590357-1">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7240590357-1">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7240590357-2">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="7240590357-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7240590357-3">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7240590357-3">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7240590357-4">&lt;&lt;</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p" data-group-id="7240590357-4">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="n">Bin3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="7240590357-5">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7240590357-5">&gt;&gt;</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7240590357-6">&lt;&lt;</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7240590357-6">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">list_to_bitstring</span><span class="p" data-group-id="7240590357-7">(</span><span class="p" data-group-id="7240590357-8">[</span><span class="n">Bin1</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="p" data-group-id="7240590357-9">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">Bin2</span><span class="p" data-group-id="7240590357-9">]</span><span class="p">,</span><span class="mi">4</span><span class="p">|</span><span class="n">Bin3</span><span class="p" data-group-id="7240590357-8">]</span><span class="p" data-group-id="7240590357-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7240590357-10">&lt;&lt;</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">:</span><span class="mi">4</span><span class="p" data-group-id="7240590357-10">&gt;&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_existing_atom/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#list_to_existing_atom/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -10683,15 +10683,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_float(String) -> <a href="#t:float/0">float</a>() when String :: <a href="#t:string/0">string</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the float whose text representation is <code class="inline">String</code>. </p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="1522179311-1">(</span><span class="s">&quot;2.2017764e+0&quot;</span><span class="p" data-group-id="1522179311-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the float whose text representation is <code class="inline">String</code>. </p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_float</span><span class="p" data-group-id="5389451746-1">(</span><span class="s">&quot;2.2017764e+0&quot;</span><span class="p" data-group-id="5389451746-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">2.2017764</span></code></pre><p>The float string format is the same as the format for
│ │ │  <a href="../../../doc/system/data_types.html">Erlang float literals</a> except for that underscores
│ │ │  are not permitted.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">String</code> contains a bad representation of a float.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_integer/1">
│ │ │  
│ │ │ @@ -10714,17 +10714,17 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_integer(String) -> <a href="#t:integer/0">integer</a>() when String :: <a href="#t:string/0">string</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer whose text representation is <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1634034183-1">(</span><span class="s">&quot;123&quot;</span><span class="p" data-group-id="1634034183-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">123</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="0411277807-1">(</span><span class="s">&quot;-123&quot;</span><span class="p" data-group-id="0411277807-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">-</span><span class="mi">123</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1057351710-1">(</span><span class="s">&quot;+123234982304982309482093833234234&quot;</span><span class="p" data-group-id="1057351710-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer whose text representation is <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="4806097015-1">(</span><span class="s">&quot;123&quot;</span><span class="p" data-group-id="4806097015-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">123</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="9383290331-1">(</span><span class="s">&quot;-123&quot;</span><span class="p" data-group-id="9383290331-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">-</span><span class="mi">123</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="9304940301-1">(</span><span class="s">&quot;+123234982304982309482093833234234&quot;</span><span class="p" data-group-id="9304940301-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">123234982304982309482093833234234</span></code></pre><p><code class="inline">String</code> must contain at least one digit character and can have an optional
│ │ │  prefix consisting of a single &quot;<code class="inline">+</code>&quot; or &quot;<code class="inline">-</code>&quot; character (that is, <code class="inline">String</code> must
│ │ │  match the regular expression <code class="inline">&quot;^[+-]?[0-9]+$&quot;</code>).</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">String</code> contains a bad representation of an integer.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_integer/2">
│ │ │  
│ │ │ @@ -10747,19 +10747,19 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_integer(String, Base) -> <a href="#t:integer/0">integer</a>() when String :: <a href="#t:string/0">string</a>(), Base :: 2..36.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer whose text representation in base <code class="inline">Base</code> is <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1833080825-1">(</span><span class="s">&quot;3FF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="1833080825-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1772090843-1">(</span><span class="s">&quot;+3FF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="1772090843-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="8280049050-1">(</span><span class="s">&quot;3ff&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="8280049050-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="7068895429-1">(</span><span class="s">&quot;3fF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="7068895429-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="6096916563-1">(</span><span class="s">&quot;-3FF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="6096916563-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer whose text representation in base <code class="inline">Base</code> is <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="8877316375-1">(</span><span class="s">&quot;3FF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="8877316375-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="1088231839-1">(</span><span class="s">&quot;+3FF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="1088231839-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="8618436148-1">(</span><span class="s">&quot;3ff&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="8618436148-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="6337594931-1">(</span><span class="s">&quot;3fF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="6337594931-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1023</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_integer</span><span class="p" data-group-id="6835174985-1">(</span><span class="s">&quot;-3FF&quot;</span><span class="p">,</span><span class="w"> </span><span class="mi">16</span><span class="p" data-group-id="6835174985-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">-</span><span class="mi">1023</span></code></pre><p>For example, when <code class="inline">Base</code> is 16, <code class="inline">String</code> must match the regular expression
│ │ │  <code class="inline">&quot;^[+-]?([0-9]|[A-F]|[a-f])+$&quot;</code>.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">String</code> contains a bad representation of an integer.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_pid/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -10781,15 +10781,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_pid(String) -> <a href="#t:pid/0">pid</a>() when String :: <a href="#t:string/0">string</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a process identifier whose text representation is a <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_pid</span><span class="p" data-group-id="4455986032-1">(</span><span class="s">&quot;&lt;0.4.1&gt;&quot;</span><span class="p" data-group-id="4455986032-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns a process identifier whose text representation is a <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_pid</span><span class="p" data-group-id="7621270847-1">(</span><span class="s">&quot;&lt;0.4.1&gt;&quot;</span><span class="p" data-group-id="7621270847-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">1</span><span class="o">&gt;</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">String</code> contains a bad representation of a process
│ │ │  identifier.</p><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>This BIF is intended for debugging and is not to be used in application
│ │ │  programs.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_port/1">
│ │ │  
│ │ │ @@ -10814,15 +10814,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_port(String) -> <a href="#t:port/0">port</a>() when String :: <a href="#t:string/0">string</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a port identifier whose text representation is a <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_port</span><span class="p" data-group-id="9734633767-1">(</span><span class="s">&quot;#Port&lt;0.4&gt;&quot;</span><span class="p" data-group-id="9734633767-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns a port identifier whose text representation is a <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_port</span><span class="p" data-group-id="2141038614-1">(</span><span class="s">&quot;#Port&lt;0.4&gt;&quot;</span><span class="p" data-group-id="2141038614-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Port</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="o">&gt;</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">String</code> contains a bad representation of a port
│ │ │  identifier.</p><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>This BIF is intended for debugging and is not to be used in application
│ │ │  programs.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_ref/1">
│ │ │  
│ │ │ @@ -10847,15 +10847,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_ref(String) -> <a href="#t:reference/0">reference</a>() when String :: <a href="#t:string/0">string</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a reference whose text representation is a <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_ref</span><span class="p" data-group-id="0743196483-1">(</span><span class="s">&quot;#Ref&lt;0.4192537678.4073193475.71181&gt;&quot;</span><span class="p" data-group-id="0743196483-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns a reference whose text representation is a <code class="inline">String</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_ref</span><span class="p" data-group-id="6675330421-1">(</span><span class="s">&quot;#Ref&lt;0.4192537678.4073193475.71181&gt;&quot;</span><span class="p" data-group-id="6675330421-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="p">#</span><span class="n">Ref</span><span class="o">&lt;</span><span class="mf">0.4192537678</span><span class="p">.</span><span class="mf">4073193475.71181</span><span class="o">&gt;</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">String</code> contains a bad representation of a reference.</p><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>This BIF is intended for debugging and is not to be used in application
│ │ │  programs.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="list_to_tuple/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -10877,16 +10877,16 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> list_to_tuple(List) -> <a href="#t:tuple/0">tuple</a>() when List :: [<a href="#t:term/0">term</a>()].</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a tuple corresponding to <code class="inline">List</code>, for example</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="4329315107-1">(</span><span class="p" data-group-id="4329315107-2">[</span><span class="ss">share</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4329315107-3">[</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="w"> </span><span class="mi">163</span><span class="p" data-group-id="4329315107-3">]</span><span class="p" data-group-id="4329315107-2">]</span><span class="p" data-group-id="4329315107-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4329315107-4">{</span><span class="ss">share</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4329315107-5">[</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="w"> </span><span class="mi">163</span><span class="p" data-group-id="4329315107-5">]</span><span class="p" data-group-id="4329315107-4">}</span></code></pre><p><code class="inline">List</code> can contain any Erlang terms.</p>
│ │ │ +<p>Returns a tuple corresponding to <code class="inline">List</code>, for example</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">list_to_tuple</span><span class="p" data-group-id="6406269808-1">(</span><span class="p" data-group-id="6406269808-2">[</span><span class="ss">share</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6406269808-3">[</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="w"> </span><span class="mi">163</span><span class="p" data-group-id="6406269808-3">]</span><span class="p" data-group-id="6406269808-2">]</span><span class="p" data-group-id="6406269808-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6406269808-4">{</span><span class="ss">share</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6406269808-5">[</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="w"> </span><span class="mi">163</span><span class="p" data-group-id="6406269808-5">]</span><span class="p" data-group-id="6406269808-4">}</span></code></pre><p><code class="inline">List</code> can contain any Erlang terms.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="make_ref/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#make_ref/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -10936,16 +10936,16 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> make_tuple(Arity, InitialValue) -> <a href="#t:tuple/0">tuple</a>() when Arity :: <a href="#t:arity/0">arity</a>(), InitialValue :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Creates a new tuple of the specified <code class="inline">Arity</code>, where all elements are
│ │ │ -<code class="inline">InitialValue</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">make_tuple</span><span class="p" data-group-id="0824527783-1">(</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0824527783-2">[</span><span class="p" data-group-id="0824527783-2">]</span><span class="p" data-group-id="0824527783-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0824527783-3">{</span><span class="p" data-group-id="0824527783-4">[</span><span class="p" data-group-id="0824527783-4">]</span><span class="p">,</span><span class="p" data-group-id="0824527783-5">[</span><span class="p" data-group-id="0824527783-5">]</span><span class="p">,</span><span class="p" data-group-id="0824527783-6">[</span><span class="p" data-group-id="0824527783-6">]</span><span class="p">,</span><span class="p" data-group-id="0824527783-7">[</span><span class="p" data-group-id="0824527783-7">]</span><span class="p" data-group-id="0824527783-3">}</span></code></pre>
│ │ │ +<code class="inline">InitialValue</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">make_tuple</span><span class="p" data-group-id="5773605726-1">(</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5773605726-2">[</span><span class="p" data-group-id="5773605726-2">]</span><span class="p" data-group-id="5773605726-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5773605726-3">{</span><span class="p" data-group-id="5773605726-4">[</span><span class="p" data-group-id="5773605726-4">]</span><span class="p">,</span><span class="p" data-group-id="5773605726-5">[</span><span class="p" data-group-id="5773605726-5">]</span><span class="p">,</span><span class="p" data-group-id="5773605726-6">[</span><span class="p" data-group-id="5773605726-6">]</span><span class="p">,</span><span class="p" data-group-id="5773605726-7">[</span><span class="p" data-group-id="5773605726-7">]</span><span class="p" data-group-id="5773605726-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="make_tuple/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#make_tuple/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -10971,16 +10971,16 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Creates a tuple of size <code class="inline">Arity</code>, where each element has value <code class="inline">DefaultValue</code>,
│ │ │  and then fills in values from <code class="inline">InitList</code>.</p><p>Each list element in <code class="inline">InitList</code> must be a two-tuple, where the first element is
│ │ │  a position in the newly created tuple and the second element is any term. If a
│ │ │  position occurs more than once in the list, the term corresponding to the last
│ │ │ -occurrence is used.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">make_tuple</span><span class="p" data-group-id="5130762410-1">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5130762410-2">[</span><span class="p" data-group-id="5130762410-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5130762410-3">[</span><span class="p" data-group-id="5130762410-4">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">ignored</span><span class="p" data-group-id="5130762410-4">}</span><span class="p">,</span><span class="p" data-group-id="5130762410-5">{</span><span class="mi">5</span><span class="p">,</span><span class="ss">zz</span><span class="p" data-group-id="5130762410-5">}</span><span class="p">,</span><span class="p" data-group-id="5130762410-6">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">aa</span><span class="p" data-group-id="5130762410-6">}</span><span class="p" data-group-id="5130762410-3">]</span><span class="p" data-group-id="5130762410-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5130762410-7">{</span><span class="p" data-group-id="5130762410-8">[</span><span class="p" data-group-id="5130762410-8">]</span><span class="p">,</span><span class="ss">aa</span><span class="p">,</span><span class="p" data-group-id="5130762410-9">[</span><span class="p" data-group-id="5130762410-9">]</span><span class="p">,</span><span class="p" data-group-id="5130762410-10">[</span><span class="p" data-group-id="5130762410-10">]</span><span class="p">,</span><span class="ss">zz</span><span class="p" data-group-id="5130762410-7">}</span></code></pre>
│ │ │ +occurrence is used.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">make_tuple</span><span class="p" data-group-id="3909936178-1">(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3909936178-2">[</span><span class="p" data-group-id="3909936178-2">]</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3909936178-3">[</span><span class="p" data-group-id="3909936178-4">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">ignored</span><span class="p" data-group-id="3909936178-4">}</span><span class="p">,</span><span class="p" data-group-id="3909936178-5">{</span><span class="mi">5</span><span class="p">,</span><span class="ss">zz</span><span class="p" data-group-id="3909936178-5">}</span><span class="p">,</span><span class="p" data-group-id="3909936178-6">{</span><span class="mi">2</span><span class="p">,</span><span class="ss">aa</span><span class="p" data-group-id="3909936178-6">}</span><span class="p" data-group-id="3909936178-3">]</span><span class="p" data-group-id="3909936178-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3909936178-7">{</span><span class="p" data-group-id="3909936178-8">[</span><span class="p" data-group-id="3909936178-8">]</span><span class="p">,</span><span class="ss">aa</span><span class="p">,</span><span class="p" data-group-id="3909936178-9">[</span><span class="p" data-group-id="3909936178-9">]</span><span class="p">,</span><span class="p" data-group-id="3909936178-10">[</span><span class="p" data-group-id="3909936178-10">]</span><span class="p">,</span><span class="ss">zz</span><span class="p" data-group-id="3909936178-7">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="map_get/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#map_get/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -11006,16 +11006,16 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> map_get(Key, Map) -> Value when Map :: <a href="#t:map/0">map</a>(), Key :: <a href="#t:any/0">any</a>(), Value :: <a href="#t:any/0">any</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns value <code class="inline">Value</code> associated with <code class="inline">Key</code> if <code class="inline">Map</code> contains <code class="inline">Key</code>.</p><p>The call fails with a <code class="inline">{badmap,Map}</code> exception if <code class="inline">Map</code> is not a map, or with a
│ │ │  <code class="inline">{badkey,Key}</code> exception if no value is associated with <code class="inline">Key</code>.</p><p><em>Example:</em></p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Key</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1337</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9285321719-1">#{</span><span class="mi">42</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value_two</span><span class="p">,</span><span class="mi">1337</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;value one&quot;</span><span class="p">,</span><span class="s">&quot;a&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9285321719-1">}</span><span class="p">,</span><span class="w">
│ │ │ -  </span><span class="nf">map_get</span><span class="p" data-group-id="9285321719-2">(</span><span class="n">Key</span><span class="p">,</span><span class="n">Map</span><span class="p" data-group-id="9285321719-2">)</span><span class="p">.</span><span class="w">
│ │ │ +  </span><span class="n">Map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5971398889-1">#{</span><span class="mi">42</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">value_two</span><span class="p">,</span><span class="mi">1337</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="s">&quot;value one&quot;</span><span class="p">,</span><span class="s">&quot;a&quot;</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="5971398889-1">}</span><span class="p">,</span><span class="w">
│ │ │ +  </span><span class="nf">map_get</span><span class="p" data-group-id="5971398889-2">(</span><span class="n">Key</span><span class="p">,</span><span class="n">Map</span><span class="p" data-group-id="5971398889-2">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;value one&quot;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="map_size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#map_size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11040,15 +11040,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> map_size(Map) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Map :: <a href="#t:map/0">map</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer, which is the number of key-value pairs in <code class="inline">Map</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="9255857583-1">(</span><span class="p" data-group-id="9255857583-2">#{</span><span class="ss">a</span><span class="p">=&gt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">=&gt;</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p">=&gt;</span><span class="mi">3</span><span class="p" data-group-id="9255857583-2">}</span><span class="p" data-group-id="9255857583-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer, which is the number of key-value pairs in <code class="inline">Map</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">map_size</span><span class="p" data-group-id="2649006820-1">(</span><span class="p" data-group-id="2649006820-2">#{</span><span class="ss">a</span><span class="p">=&gt;</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">=&gt;</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p">=&gt;</span><span class="mi">3</span><span class="p" data-group-id="2649006820-2">}</span><span class="p" data-group-id="2649006820-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="match_spec_test/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#match_spec_test/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11119,18 +11119,18 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> max(Term1, Term2) -> Maximum when Term1 :: <a href="#t:term/0">term</a>(), Term2 :: <a href="#t:term/0">term</a>(), Maximum :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the largest of <code class="inline">Term1</code> and <code class="inline">Term2</code>. If the terms compare equal with the
│ │ │  <code class="inline">==</code> operator, <code class="inline">Term1</code> is returned.</p><p>The <a href="../../../doc/system/expressions.html#term-comparisons">Expressions section</a> contains
│ │ │ -descriptions of the <code class="inline">==</code> operator and how terms are ordered.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="5403010115-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="5403010115-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">2</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="1468237854-1">(</span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="1468237854-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mf">1.0</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="2451140061-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="2451140061-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="1457724646-1">(</span><span class="s">&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;b&quot;</span><span class="p" data-group-id="1457724646-1">)</span><span class="p">.</span><span class="w">
│ │ │ +descriptions of the <code class="inline">==</code> operator and how terms are ordered.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="2464399479-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2464399479-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">2</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="2665082277-1">(</span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2665082277-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mf">1.0</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="6812508443-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="6812508443-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">max</span><span class="p" data-group-id="1639391712-1">(</span><span class="s">&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;b&quot;</span><span class="p" data-group-id="1639391712-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;b&quot;</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Allowed in guards tests from Erlang/OTP 26.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="min/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#min/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11155,18 +11155,18 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> min(Term1, Term2) -> Minimum when Term1 :: <a href="#t:term/0">term</a>(), Term2 :: <a href="#t:term/0">term</a>(), Minimum :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the smallest of <code class="inline">Term1</code> and <code class="inline">Term2</code>. If the terms compare equal with the
│ │ │  <code class="inline">==</code> operator, <code class="inline">Term1</code> is returned.</p><p>The <a href="../../../doc/system/expressions.html#term-comparisons">Expressions section</a> contains
│ │ │ -descriptions of the <code class="inline">==</code> operator and how terms are ordered.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="2003385931-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="2003385931-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="0815689517-1">(</span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="0815689517-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mf">1.0</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="4801321940-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="4801321940-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="2768852295-1">(</span><span class="s">&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;b&quot;</span><span class="p" data-group-id="2768852295-1">)</span><span class="p">.</span><span class="w">
│ │ │ +descriptions of the <code class="inline">==</code> operator and how terms are ordered.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="8207969851-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="8207969851-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="2538392771-1">(</span><span class="mf">1.0</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="2538392771-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mf">1.0</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="8750085794-1">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="p" data-group-id="8750085794-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">1</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">min</span><span class="p" data-group-id="3669839955-1">(</span><span class="s">&quot;abc&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;b&quot;</span><span class="p" data-group-id="3669839955-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;abc&quot;</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Allowed in guards tests from Erlang/OTP 26.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="node/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#node/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11276,15 +11276,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> pid_to_list(Pid) -> <a href="#t:string/0">string</a>() when Pid :: <a href="#t:pid/0">pid</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a string corresponding to the text representation of <code class="inline">Pid</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">pid_to_list</span><span class="p" data-group-id="7090633064-1">(</span><span class="nf">self</span><span class="p" data-group-id="7090633064-2">(</span><span class="p" data-group-id="7090633064-2">)</span><span class="p" data-group-id="7090633064-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns a string corresponding to the text representation of <code class="inline">Pid</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">pid_to_list</span><span class="p" data-group-id="4781976668-1">(</span><span class="nf">self</span><span class="p" data-group-id="4781976668-2">(</span><span class="p" data-group-id="4781976668-2">)</span><span class="p" data-group-id="4781976668-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;&lt;0.85.0&gt;&quot;</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The <a href="erl_dist_protocol.html">creation</a> for the node is not included in the list
│ │ │  representation of <code class="inline">Pid</code>. This means that processes in different incarnations
│ │ │  of a node with a specific name can get the same list representation.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="port_to_list/1">
│ │ │  
│ │ │ @@ -11367,18 +11367,18 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> round(Number) -> <a href="#t:integer/0">integer</a>() when Number :: <a href="#t:number/0">number</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer by rounding <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="5018019011-1">(</span><span class="mf">42.1</span><span class="p" data-group-id="5018019011-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">42</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="8134387916-1">(</span><span class="mf">5.5</span><span class="p" data-group-id="8134387916-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">6</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="6518468566-1">(</span><span class="o">-</span><span class="mf">5.5</span><span class="p" data-group-id="6518468566-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">-</span><span class="mi">6</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="9702078776-1">(</span><span class="mf">36028797018963969.0</span><span class="p" data-group-id="9702078776-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer by rounding <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="2210779524-1">(</span><span class="mf">42.1</span><span class="p" data-group-id="2210779524-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">42</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="6314937289-1">(</span><span class="mf">5.5</span><span class="p" data-group-id="6314937289-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">6</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="3786686953-1">(</span><span class="o">-</span><span class="mf">5.5</span><span class="p" data-group-id="3786686953-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">-</span><span class="mi">6</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="nf">round</span><span class="p" data-group-id="6050143268-1">(</span><span class="mf">36028797018963969.0</span><span class="p" data-group-id="6050143268-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">36028797018963968</span></code></pre><p>In the last example, <a href="#round/1"><code class="inline">round(36028797018963969.0)</code></a> evaluates to
│ │ │  <code class="inline">36028797018963968</code>. The reason for this is that the number
│ │ │  <code class="inline">36028797018963969.0</code> cannot be represented exactly as a float value. Instead,
│ │ │  the float literal is represented as <code class="inline">36028797018963968.0</code>, which is the closest
│ │ │  number that can be represented exactly as a float value. See
│ │ │  <a href="../../../doc/system/data_types.html#float_representation_problem">Representation of Floating Point Numbers</a>
│ │ │  for additional information.</p>
│ │ │ @@ -11408,16 +11408,16 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> setelement(Index, Tuple1, Value) -> Tuple2
│ │ │                      when Index :: <a href="#t:pos_integer/0">pos_integer</a>(), Tuple1 :: <a href="#t:tuple/0">tuple</a>(), Tuple2 :: <a href="#t:tuple/0">tuple</a>(), Value :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a tuple that is a copy of argument <code class="inline">Tuple1</code> with the element specified
│ │ │  by integer argument <code class="inline">Index</code> (the first element is the element with index 1)
│ │ │ -replaced by argument <code class="inline">Value</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">setelement</span><span class="p" data-group-id="3415736874-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3415736874-2">{</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="p">,</span><span class="w"> </span><span class="ss">bottles</span><span class="p" data-group-id="3415736874-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">red</span><span class="p" data-group-id="3415736874-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3415736874-3">{</span><span class="mi">10</span><span class="p">,</span><span class="ss">red</span><span class="p">,</span><span class="ss">bottles</span><span class="p" data-group-id="3415736874-3">}</span></code></pre>
│ │ │ +replaced by argument <code class="inline">Value</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">setelement</span><span class="p" data-group-id="0608913973-1">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0608913973-2">{</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="ss">green</span><span class="p">,</span><span class="w"> </span><span class="ss">bottles</span><span class="p" data-group-id="0608913973-2">}</span><span class="p">,</span><span class="w"> </span><span class="ss">red</span><span class="p" data-group-id="0608913973-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0608913973-3">{</span><span class="mi">10</span><span class="p">,</span><span class="ss">red</span><span class="p">,</span><span class="ss">bottles</span><span class="p" data-group-id="0608913973-3">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="size/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#size/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -11440,17 +11440,17 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> size(Item) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Item :: <a href="#t:tuple/0">tuple</a>() | <a href="#t:binary/0">binary</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the number of elements in a tuple or the number of bytes in a binary or
│ │ │ -bitstring.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">size</span><span class="p" data-group-id="5663777042-1">(</span><span class="p" data-group-id="5663777042-2">{</span><span class="ss">morni</span><span class="p">,</span><span class="w"> </span><span class="ss">mulle</span><span class="p">,</span><span class="w"> </span><span class="ss">bwange</span><span class="p" data-group-id="5663777042-2">}</span><span class="p" data-group-id="5663777042-1">)</span><span class="p">.</span><span class="w">
│ │ │ +bitstring.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">size</span><span class="p" data-group-id="1142128828-1">(</span><span class="p" data-group-id="1142128828-2">{</span><span class="ss">morni</span><span class="p">,</span><span class="w"> </span><span class="ss">mulle</span><span class="p">,</span><span class="w"> </span><span class="ss">bwange</span><span class="p" data-group-id="1142128828-2">}</span><span class="p" data-group-id="1142128828-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">size</span><span class="p" data-group-id="5663777042-3">(</span><span class="p" data-group-id="5663777042-4">&lt;&lt;</span><span class="mi">11</span><span class="p">,</span><span class="w"> </span><span class="mi">22</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="5663777042-4">&gt;&gt;</span><span class="p" data-group-id="5663777042-3">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">size</span><span class="p" data-group-id="1142128828-3">(</span><span class="p" data-group-id="1142128828-4">&lt;&lt;</span><span class="mi">11</span><span class="p">,</span><span class="w"> </span><span class="mi">22</span><span class="p">,</span><span class="w"> </span><span class="mi">33</span><span class="p" data-group-id="1142128828-4">&gt;&gt;</span><span class="p" data-group-id="1142128828-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre><p>For bitstrings, the number of whole bytes is returned. That is, if the number of
│ │ │  bits in the bitstring is not divisible by 8, the resulting number of bytes is
│ │ │  rounded <em>down</em>.</p><p>See also <a href="#tuple_size/1"><code class="inline">tuple_size/1</code></a>, <a href="#byte_size/1"><code class="inline">byte_size/1</code></a>, and <a href="#bit_size/1"><code class="inline">bit_size/1</code></a>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="split_binary/2">
│ │ │  
│ │ │ @@ -11474,23 +11474,23 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> split_binary(Bin, Pos) -> {<a href="#t:binary/0">binary</a>(), <a href="#t:binary/0">binary</a>()} when Bin :: <a href="#t:binary/0">binary</a>(), Pos :: <a href="#t:non_neg_integer/0">non_neg_integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a tuple containing the binaries that are the result of splitting <code class="inline">Bin</code>
│ │ │ -into two parts at position <code class="inline">Pos</code>.</p><p>This is not a destructive operation. After the operation, there are three binaries altogether.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">list_to_binary</span><span class="p" data-group-id="1063645599-1">(</span><span class="s">&quot;0123456789&quot;</span><span class="p" data-group-id="1063645599-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1063645599-2">&lt;&lt;</span><span class="s">&quot;0123456789&quot;</span><span class="p" data-group-id="1063645599-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="1063645599-3">(</span><span class="n">B</span><span class="p" data-group-id="1063645599-3">)</span><span class="p">.</span><span class="w">
│ │ │ +into two parts at position <code class="inline">Pos</code>.</p><p>This is not a destructive operation. After the operation, there are three binaries altogether.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">list_to_binary</span><span class="p" data-group-id="5983122569-1">(</span><span class="s">&quot;0123456789&quot;</span><span class="p" data-group-id="5983122569-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5983122569-2">&lt;&lt;</span><span class="s">&quot;0123456789&quot;</span><span class="p" data-group-id="5983122569-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="5983122569-3">(</span><span class="n">B</span><span class="p" data-group-id="5983122569-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">10</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="p" data-group-id="1063645599-4">{</span><span class="n">B1</span><span class="p">,</span><span class="w"> </span><span class="n">B2</span><span class="p" data-group-id="1063645599-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">split_binary</span><span class="p" data-group-id="1063645599-5">(</span><span class="n">B</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1063645599-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1063645599-6">{</span><span class="p" data-group-id="1063645599-7">&lt;&lt;</span><span class="s">&quot;012&quot;</span><span class="p" data-group-id="1063645599-7">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="1063645599-8">&lt;&lt;</span><span class="s">&quot;3456789&quot;</span><span class="p" data-group-id="1063645599-8">&gt;&gt;</span><span class="p" data-group-id="1063645599-6">}</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="1063645599-9">(</span><span class="n">B1</span><span class="p" data-group-id="1063645599-9">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="p" data-group-id="5983122569-4">{</span><span class="n">B1</span><span class="p">,</span><span class="w"> </span><span class="n">B2</span><span class="p" data-group-id="5983122569-4">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">split_binary</span><span class="p" data-group-id="5983122569-5">(</span><span class="n">B</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="5983122569-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5983122569-6">{</span><span class="p" data-group-id="5983122569-7">&lt;&lt;</span><span class="s">&quot;012&quot;</span><span class="p" data-group-id="5983122569-7">&gt;&gt;</span><span class="p">,</span><span class="p" data-group-id="5983122569-8">&lt;&lt;</span><span class="s">&quot;3456789&quot;</span><span class="p" data-group-id="5983122569-8">&gt;&gt;</span><span class="p" data-group-id="5983122569-6">}</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="5983122569-9">(</span><span class="n">B1</span><span class="p" data-group-id="5983122569-9">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="1063645599-10">(</span><span class="n">B2</span><span class="p" data-group-id="1063645599-10">)</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="nf">byte_size</span><span class="p" data-group-id="5983122569-10">(</span><span class="n">B2</span><span class="p" data-group-id="5983122569-10">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">7</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="term_to_binary/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#term_to_binary/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11514,17 +11514,17 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> term_to_binary(Term) -> <a href="#t:ext_binary/0">ext_binary</a>() when Term :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a binary data object that is the result of encoding <code class="inline">Term</code> according to
│ │ │  the <a href="erl_ext_dist.html">Erlang external term format.</a></p><p>This can be used for various purposes, for example, writing a term to a file in
│ │ │  an efficient way, or sending an Erlang term to some type of communications
│ │ │ -channel not supported by distributed Erlang.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="3347400895-1">(</span><span class="ss">hello</span><span class="p" data-group-id="3347400895-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3347400895-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="3347400895-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="ss">hello</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="3347400895-3">(</span><span class="n">Bin</span><span class="p" data-group-id="3347400895-3">)</span><span class="p">.</span><span class="w">
│ │ │ +channel not supported by distributed Erlang.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Bin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">term_to_binary</span><span class="p" data-group-id="2040926281-1">(</span><span class="ss">hello</span><span class="p" data-group-id="2040926281-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2040926281-2">&lt;&lt;</span><span class="mi">131</span><span class="p">,</span><span class="mi">100</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">104</span><span class="p">,</span><span class="mi">101</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">108</span><span class="p">,</span><span class="mi">111</span><span class="p" data-group-id="2040926281-2">&gt;&gt;</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="ss">hello</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">binary_to_term</span><span class="p" data-group-id="2040926281-3">(</span><span class="n">Bin</span><span class="p" data-group-id="2040926281-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">hello</span></code></pre><p>See also <a href="#binary_to_term/1"><code class="inline">binary_to_term/1</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>There is no guarantee that this function will return the same encoded
│ │ │  representation for the same term.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="term_to_binary/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -11741,18 +11741,18 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> tl(List) -> Tail when List :: <a href="#t:nonempty_maybe_improper_list/0">nonempty_maybe_improper_list</a>(), Tail :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the tail of <code class="inline">List</code>, that is, the list minus the first element</p><p>It works with improper lists.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="2454860754-1">(</span><span class="p" data-group-id="2454860754-2">[</span><span class="ss">geesties</span><span class="p">,</span><span class="w"> </span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="p" data-group-id="2454860754-2">]</span><span class="p" data-group-id="2454860754-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2454860754-3">[</span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="p" data-group-id="2454860754-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="0663128761-1">(</span><span class="p" data-group-id="0663128761-2">[</span><span class="ss">geesties</span><span class="p" data-group-id="0663128761-2">]</span><span class="p" data-group-id="0663128761-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="0663128761-3">[</span><span class="p" data-group-id="0663128761-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="2299055980-1">(</span><span class="p" data-group-id="2299055980-2">[</span><span class="ss">geesties</span><span class="p">,</span><span class="w"> </span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="2299055980-2">]</span><span class="p" data-group-id="2299055980-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2299055980-3">[</span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="2299055980-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="8996163816-1">(</span><span class="p" data-group-id="8996163816-2">[</span><span class="ss">geesties</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="8996163816-2">]</span><span class="p" data-group-id="8996163816-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the tail of <code class="inline">List</code>, that is, the list minus the first element</p><p>It works with improper lists.</p><p>Examples:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="1369984801-1">(</span><span class="p" data-group-id="1369984801-2">[</span><span class="ss">geesties</span><span class="p">,</span><span class="w"> </span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="p" data-group-id="1369984801-2">]</span><span class="p" data-group-id="1369984801-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1369984801-3">[</span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="p" data-group-id="1369984801-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="2234490712-1">(</span><span class="p" data-group-id="2234490712-2">[</span><span class="ss">geesties</span><span class="p" data-group-id="2234490712-2">]</span><span class="p" data-group-id="2234490712-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2234490712-3">[</span><span class="p" data-group-id="2234490712-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="9502235144-1">(</span><span class="p" data-group-id="9502235144-2">[</span><span class="ss">geesties</span><span class="p">,</span><span class="w"> </span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="9502235144-2">]</span><span class="p" data-group-id="9502235144-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9502235144-3">[</span><span class="ss">guilies</span><span class="p">,</span><span class="w"> </span><span class="ss">beasties</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="9502235144-3">]</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tl</span><span class="p" data-group-id="2788915782-1">(</span><span class="p" data-group-id="2788915782-2">[</span><span class="ss">geesties</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="ss">improper_end</span><span class="p" data-group-id="2788915782-2">]</span><span class="p" data-group-id="2788915782-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">improper_end</span></code></pre><p>Failure: <code class="inline">badarg</code> if <code class="inline">List</code> is an empty list <code class="inline">[]</code>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="trunc/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#trunc/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11775,18 +11775,18 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> trunc(Number) -> <a href="#t:integer/0">integer</a>() when Number :: <a href="#t:number/0">number</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Truncates the decimals of <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="1705924888-1">(</span><span class="mf">5.7</span><span class="p" data-group-id="1705924888-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">5</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="4588753641-1">(</span><span class="o">-</span><span class="mf">5.7</span><span class="p" data-group-id="4588753641-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="o">-</span><span class="mi">5</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="6405922413-1">(</span><span class="mi">5</span><span class="p" data-group-id="6405922413-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="mi">5</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="3948693479-1">(</span><span class="mf">36028797018963969.0</span><span class="p" data-group-id="3948693479-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Truncates the decimals of <code class="inline">Number</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="0922627760-1">(</span><span class="mf">5.7</span><span class="p" data-group-id="0922627760-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">5</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="3569367859-1">(</span><span class="o">-</span><span class="mf">5.7</span><span class="p" data-group-id="3569367859-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="o">-</span><span class="mi">5</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="3835773175-1">(</span><span class="mi">5</span><span class="p" data-group-id="3835773175-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="mi">5</span></code></pre><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">trunc</span><span class="p" data-group-id="8057810562-1">(</span><span class="mf">36028797018963969.0</span><span class="p" data-group-id="8057810562-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">36028797018963968</span></code></pre><p>In the last example, <a href="#trunc/1"><code class="inline">trunc(36028797018963969.0)</code></a> evaluates to
│ │ │  <code class="inline">36028797018963968</code>. The reason for this is that the number
│ │ │  <code class="inline">36028797018963969.0</code> cannot be represented exactly as a float value. Instead,
│ │ │  the float literal is represented as <code class="inline">36028797018963968.0</code>, which is the closest
│ │ │  number that can be represented exactly as a float value. See
│ │ │  <a href="../../../doc/system/data_types.html#float_representation_problem">Representation of Floating Point Numbers</a>
│ │ │  for additional information.</p>
│ │ │ @@ -11815,15 +11815,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> tuple_size(Tuple) -> <a href="#t:non_neg_integer/0">non_neg_integer</a>() when Tuple :: <a href="#t:tuple/0">tuple</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns an integer that is the number of elements in <code class="inline">Tuple</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="0967984359-1">(</span><span class="p" data-group-id="0967984359-2">{</span><span class="ss">morni</span><span class="p">,</span><span class="w"> </span><span class="ss">mulle</span><span class="p">,</span><span class="w"> </span><span class="ss">bwange</span><span class="p" data-group-id="0967984359-2">}</span><span class="p" data-group-id="0967984359-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns an integer that is the number of elements in <code class="inline">Tuple</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tuple_size</span><span class="p" data-group-id="0070353059-1">(</span><span class="p" data-group-id="0070353059-2">{</span><span class="ss">morni</span><span class="p">,</span><span class="w"> </span><span class="ss">mulle</span><span class="p">,</span><span class="w"> </span><span class="ss">bwange</span><span class="p" data-group-id="0070353059-2">}</span><span class="p" data-group-id="0070353059-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mi">3</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="tuple_to_list/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#tuple_to_list/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -11845,16 +11845,16 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> tuple_to_list(Tuple) -> [<a href="#t:term/0">term</a>()] when Tuple :: <a href="#t:tuple/0">tuple</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a list corresponding to <code class="inline">Tuple</code>. <code class="inline">Tuple</code> can contain any Erlang terms.
│ │ │ -Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="6747458313-1">(</span><span class="p" data-group-id="6747458313-2">{</span><span class="ss">share</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6747458313-3">{</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="w"> </span><span class="mi">163</span><span class="p" data-group-id="6747458313-3">}</span><span class="p" data-group-id="6747458313-2">}</span><span class="p" data-group-id="6747458313-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6747458313-4">[</span><span class="ss">share</span><span class="p">,</span><span class="p" data-group-id="6747458313-5">{</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="mi">163</span><span class="p" data-group-id="6747458313-5">}</span><span class="p" data-group-id="6747458313-4">]</span></code></pre>
│ │ │ +Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">tuple_to_list</span><span class="p" data-group-id="3343392066-1">(</span><span class="p" data-group-id="3343392066-2">{</span><span class="ss">share</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3343392066-3">{</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="w"> </span><span class="mi">163</span><span class="p" data-group-id="3343392066-3">}</span><span class="p" data-group-id="3343392066-2">}</span><span class="p" data-group-id="3343392066-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3343392066-4">[</span><span class="ss">share</span><span class="p">,</span><span class="p" data-group-id="3343392066-5">{</span><span class="ss">&#39;Ericsson_B&#39;</span><span class="p">,</span><span class="mi">163</span><span class="p" data-group-id="3343392066-5">}</span><span class="p" data-group-id="3343392066-4">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="unique_integer/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#unique_integer/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12009,35 +12009,35 @@
│ │ │  
│ │ │  <p>Create an alias which can be used when sending messages to the process that
│ │ │  created the alias. When the alias has been deactivated, messages sent using the
│ │ │  alias will be dropped. An alias can be deactivated using <a href="#unalias/1"><code class="inline">unalias/1</code></a>.</p><p>Currently available options for <a href="#alias/1"><code class="inline">alias/1</code></a>:</p><ul><li><p><strong><code class="inline">explicit_unalias</code></strong> - The alias can only be deactivated via a call to
│ │ │  <a href="#unalias/1"><code class="inline">unalias/1</code></a>. This is also the default behaviour if no options
│ │ │  are passed or if <a href="#alias/0"><code class="inline">alias/0</code></a> is called.</p></li><li><p><strong><code class="inline">reply</code></strong> - The alias will be automatically deactivated when a reply message
│ │ │  sent via the alias is received. The alias can also still be deactivated via a
│ │ │ -call to <a href="#unalias/1"><code class="inline">unalias/1</code></a>.</p></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="0363302753-1">(</span><span class="p" data-group-id="0363302753-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +call to <a href="#unalias/1"><code class="inline">unalias/1</code></a>.</p></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="0025481123-1">(</span><span class="p" data-group-id="0025481123-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0363302753-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0363302753-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="0363302753-3">(</span><span class="n">Request</span><span class="p" data-group-id="0363302753-3">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0363302753-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0363302753-4">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0025481123-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0025481123-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="0025481123-3">(</span><span class="n">Request</span><span class="p" data-group-id="0025481123-3">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0025481123-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0025481123-4">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="0363302753-5">(</span><span class="p" data-group-id="0363302753-5">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="0025481123-5">(</span><span class="p" data-group-id="0025481123-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="0363302753-6">(</span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0363302753-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alias</span><span class="p" data-group-id="0363302753-7">(</span><span class="p" data-group-id="0363302753-8">[</span><span class="ss">reply</span><span class="p" data-group-id="0363302753-8">]</span><span class="p" data-group-id="0363302753-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0363302753-9">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0363302753-9">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="0025481123-6">(</span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0025481123-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">alias</span><span class="p" data-group-id="0025481123-7">(</span><span class="p" data-group-id="0025481123-8">[</span><span class="ss">reply</span><span class="p" data-group-id="0025481123-8">]</span><span class="p" data-group-id="0025481123-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0025481123-9">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0025481123-9">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% Alias will be automatically deactivated if we receive a reply</span><span class="w">
│ │ │      </span><span class="c1">%% since we used the &#39;reply&#39; option...</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="0363302753-10">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0363302753-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0025481123-10">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0025481123-10">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │      </span><span class="k">after</span><span class="w"> </span><span class="mi">5000</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">unalias</span><span class="p" data-group-id="0363302753-11">(</span><span class="n">AliasReqId</span><span class="p" data-group-id="0363302753-11">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="nf">unalias</span><span class="p" data-group-id="0025481123-11">(</span><span class="n">AliasReqId</span><span class="p" data-group-id="0025481123-11">)</span><span class="p">,</span><span class="w">
│ │ │              </span><span class="c1">%% Flush message queue in case the reply arrived</span><span class="w">
│ │ │              </span><span class="c1">%% just before the alias was deactivated...</span><span class="w">
│ │ │ -            </span><span class="k">receive</span><span class="w"> </span><span class="p" data-group-id="0363302753-12">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0363302753-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │ -            </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0363302753-13">(</span><span class="ss">timeout</span><span class="p" data-group-id="0363302753-13">)</span><span class="w">
│ │ │ +            </span><span class="k">receive</span><span class="w"> </span><span class="p" data-group-id="0025481123-12">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0025481123-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="n">Result</span><span class="w">
│ │ │ +            </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0025481123-13">(</span><span class="ss">timeout</span><span class="p" data-group-id="0025481123-13">)</span><span class="w">
│ │ │              </span><span class="k">end</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Note that both the server and the client in this example must be executing on at
│ │ │  least OTP 24 systems in order for this to work.</p><p>For more information on process aliases see the
│ │ │  <a href="../../../doc/system/ref_man_processes.html#process-aliases"><em>Process Aliases</em></a> section of
│ │ │  the <em>Erlang Reference Manual</em>.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │ @@ -12096,17 +12096,17 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> apply(Module, Function, Args) -> <a href="#t:term/0">term</a>()
│ │ │                 when Module :: <a href="#t:module/0">module</a>(), Function :: <a href="#t:atom/0">atom</a>(), Args :: [<a href="#t:term/0">term</a>()].</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the result of applying <code class="inline">Function</code> in <code class="inline">Module</code> to <code class="inline">Args</code>. The applied
│ │ │  function must be exported from <code class="inline">Module</code>. The arity of the function is the length
│ │ │ -of <code class="inline">Args</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">apply</span><span class="p" data-group-id="8547206598-1">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="ss">reverse</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8547206598-2">[</span><span class="p" data-group-id="8547206598-3">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="8547206598-3">]</span><span class="p" data-group-id="8547206598-2">]</span><span class="p" data-group-id="8547206598-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8547206598-4">[</span><span class="ss">c</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="8547206598-4">]</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nf">apply</span><span class="p" data-group-id="8547206598-5">(</span><span class="ss">erlang</span><span class="p">,</span><span class="w"> </span><span class="nb">atom_to_list</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8547206598-6">[</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="8547206598-6">]</span><span class="p" data-group-id="8547206598-5">)</span><span class="p">.</span><span class="w">
│ │ │ +of <code class="inline">Args</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">apply</span><span class="p" data-group-id="7763750266-1">(</span><span class="ss">lists</span><span class="p">,</span><span class="w"> </span><span class="ss">reverse</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7763750266-2">[</span><span class="p" data-group-id="7763750266-3">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="7763750266-3">]</span><span class="p" data-group-id="7763750266-2">]</span><span class="p" data-group-id="7763750266-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7763750266-4">[</span><span class="ss">c</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">a</span><span class="p" data-group-id="7763750266-4">]</span><span class="gp unselectable">
│ │ │ +&gt; </span><span class="nf">apply</span><span class="p" data-group-id="7763750266-5">(</span><span class="ss">erlang</span><span class="p">,</span><span class="w"> </span><span class="nb">atom_to_list</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7763750266-6">[</span><span class="ss">&#39;Erlang&#39;</span><span class="p" data-group-id="7763750266-6">]</span><span class="p" data-group-id="7763750266-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="s">&quot;Erlang&quot;</span></code></pre><p>If the number of arguments are known at compile time, the call is better written
│ │ │  as <code class="inline">Module:Function(Arg1, Arg2, ..., ArgN)</code>.</p><p>Failure: <a href="../../../lib/kernel-10.2.7.2/doc/html/error_handler.html#undefined_function/3"><code class="inline">error_handler:undefined_function/3</code></a> is called if the applied function
│ │ │  is not exported. The error handler can be redefined (see <a href="#process_flag/2"><code class="inline">process_flag/2</code></a>). If
│ │ │  <code class="inline">error_handler</code> is undefined, or if the user has redefined the default
│ │ │  <code class="inline">error_handler</code> so the replacement module is undefined, an error with reason
│ │ │  <code class="inline">undef</code> is generated.</p>
│ │ │    </section>
│ │ │ @@ -12213,17 +12213,17 @@
│ │ │                     when MonitorRef :: <a href="#t:reference/0">reference</a>(), OptionList :: [Option], Option :: flush | info.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>The returned value is <code class="inline">true</code> unless <code class="inline">info</code> is part of <code class="inline">OptionList</code>.</p><p><a href="#demonitor/2"><code class="inline">demonitor(MonitorRef, [])</code></a> is equivalent to
│ │ │  <a href="#demonitor/1"><code class="inline">demonitor(MonitorRef)</code></a>.</p><p><code class="inline">Option</code>s:</p><ul><li><p><strong><code class="inline">flush</code></strong> - Removes (one) <code class="inline">{_, MonitorRef, _, _, _}</code> message, if there is
│ │ │  one, from the caller message queue after monitoring has been stopped.</p><p>Calling <a href="#demonitor/2"><code class="inline">demonitor(MonitorRef, [flush])</code></a> is equivalent to the
│ │ │ -following, but more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">demonitor</span><span class="p" data-group-id="3801237471-1">(</span><span class="n">MonitorRef</span><span class="p" data-group-id="3801237471-1">)</span><span class="p">,</span><span class="w">
│ │ │ +following, but more efficient:</p><pre><code class="makeup erlang" translate="no"><span class="nf">demonitor</span><span class="p" data-group-id="8924628877-1">(</span><span class="n">MonitorRef</span><span class="p" data-group-id="8924628877-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="3801237471-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="3801237471-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="8924628877-2">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="8924628877-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre></li><li><p><strong><code class="inline">info</code></strong> - The returned value is one of the following:</p><ul><li><p><strong><code class="inline">true</code></strong> - The monitor was found and removed. In this case, no <code class="inline">'DOWN'</code>
│ │ │  message corresponding to this monitor has been delivered and will not be
│ │ │  delivered.</p></li><li><p><strong><code class="inline">false</code></strong> - The monitor was not found and could not be removed. This
│ │ │  probably because someone already has placed a <code class="inline">'DOWN'</code> message corresponding
│ │ │ @@ -12252,18 +12252,18 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> erase() -> [{Key, Val}] when Key :: <a href="#t:term/0">term</a>(), Val :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the process dictionary and deletes it.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="8712750979-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712750979-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="8712750979-2">}</span><span class="p" data-group-id="8712750979-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="8712750979-3">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8712750979-4">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="8712750979-4">]</span><span class="p" data-group-id="8712750979-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">erase</span><span class="p" data-group-id="8712750979-5">(</span><span class="p" data-group-id="8712750979-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8712750979-6">[</span><span class="p" data-group-id="8712750979-7">{</span><span class="ss">key1</span><span class="p">,</span><span class="p" data-group-id="8712750979-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="8712750979-8">}</span><span class="p" data-group-id="8712750979-7">}</span><span class="p">,</span><span class="p" data-group-id="8712750979-9">{</span><span class="ss">key2</span><span class="p">,</span><span class="p" data-group-id="8712750979-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="8712750979-10">]</span><span class="p" data-group-id="8712750979-9">}</span><span class="p" data-group-id="8712750979-6">]</span></code></pre>
│ │ │ +<p>Returns the process dictionary and deletes it.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="6462236148-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6462236148-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="6462236148-2">}</span><span class="p" data-group-id="6462236148-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="6462236148-3">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6462236148-4">[</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="ss">b</span><span class="p">,</span><span class="w"> </span><span class="ss">c</span><span class="p" data-group-id="6462236148-4">]</span><span class="p" data-group-id="6462236148-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">erase</span><span class="p" data-group-id="6462236148-5">(</span><span class="p" data-group-id="6462236148-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6462236148-6">[</span><span class="p" data-group-id="6462236148-7">{</span><span class="ss">key1</span><span class="p">,</span><span class="p" data-group-id="6462236148-8">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6462236148-8">}</span><span class="p" data-group-id="6462236148-7">}</span><span class="p">,</span><span class="p" data-group-id="6462236148-9">{</span><span class="ss">key2</span><span class="p">,</span><span class="p" data-group-id="6462236148-10">[</span><span class="ss">a</span><span class="p">,</span><span class="ss">b</span><span class="p">,</span><span class="ss">c</span><span class="p" data-group-id="6462236148-10">]</span><span class="p" data-group-id="6462236148-9">}</span><span class="p" data-group-id="6462236148-6">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="erase/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#erase/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12286,18 +12286,18 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> erase(Key) -> Val | undefined when Key :: <a href="#t:term/0">term</a>(), Val :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the value <code class="inline">Val</code> associated with <code class="inline">Key</code> and deletes it from the process
│ │ │  dictionary. Returns <code class="inline">undefined</code> if no value is associated with <code class="inline">Key</code>.</p><p>The average time complexity for the current implementation of this function is
│ │ │  O(<code class="inline">1</code>) and the worst case time complexity is O(<code class="inline">N</code>), where <code class="inline">N</code> is the number of
│ │ │ -items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="7592475353-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7592475353-2">{</span><span class="ss">merry</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p">,</span><span class="w"> </span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="7592475353-2">}</span><span class="p" data-group-id="7592475353-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erase</span><span class="p" data-group-id="7592475353-3">(</span><span class="ss">key1</span><span class="p" data-group-id="7592475353-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7592475353-4">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">erase</span><span class="p" data-group-id="7592475353-5">(</span><span class="ss">key1</span><span class="p" data-group-id="7592475353-5">)</span><span class="p" data-group-id="7592475353-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7592475353-6">{</span><span class="p" data-group-id="7592475353-7">{</span><span class="ss">merry</span><span class="p">,</span><span class="ss">lambs</span><span class="p">,</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="7592475353-7">}</span><span class="p">,</span><span class="ss">undefined</span><span class="p" data-group-id="7592475353-6">}</span></code></pre>
│ │ │ +items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="6174129348-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6174129348-2">{</span><span class="ss">merry</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p">,</span><span class="w"> </span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="6174129348-2">}</span><span class="p" data-group-id="6174129348-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">erase</span><span class="p" data-group-id="6174129348-3">(</span><span class="ss">key1</span><span class="p" data-group-id="6174129348-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6174129348-4">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="nf">erase</span><span class="p" data-group-id="6174129348-5">(</span><span class="ss">key1</span><span class="p" data-group-id="6174129348-5">)</span><span class="p" data-group-id="6174129348-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6174129348-6">{</span><span class="p" data-group-id="6174129348-7">{</span><span class="ss">merry</span><span class="p">,</span><span class="ss">lambs</span><span class="p">,</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="6174129348-7">}</span><span class="p">,</span><span class="ss">undefined</span><span class="p" data-group-id="6174129348-6">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="error/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#error/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12321,22 +12321,22 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Raises an exception of class <code class="inline">error</code> with the reason <code class="inline">Reason</code>.</p><p>As evaluating this function causes an exception to be thrown, it has no return value.</p><p>The intent of the exception class <code class="inline">error</code> is to signal that an unexpected error
│ │ │  has happened (for example, a function is called with a parameter that has an
│ │ │  incorrect type). See the guide about
│ │ │  <a href="../../../doc/system/errors.html">errors and error handling</a> for additional information.
│ │ │ -Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="9683587235-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="9683587235-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9683587235-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="9683587235-3">{</span><span class="ss">foobar</span><span class="p">,</span><span class="p" data-group-id="9683587235-4">[</span><span class="p" data-group-id="9683587235-5">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ -                        </span><span class="p" data-group-id="9683587235-6">[</span><span class="p" data-group-id="9683587235-7">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9683587235-7">}</span><span class="p">,</span><span class="p" data-group-id="9683587235-8">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">906</span><span class="p" data-group-id="9683587235-8">}</span><span class="p" data-group-id="9683587235-6">]</span><span class="p" data-group-id="9683587235-5">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="9683587235-9">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="9683587235-10">[</span><span class="p" data-group-id="9683587235-11">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="9683587235-11">}</span><span class="p">,</span><span class="p" data-group-id="9683587235-12">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="9683587235-12">}</span><span class="p" data-group-id="9683587235-10">]</span><span class="p" data-group-id="9683587235-9">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="9683587235-13">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">expr</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="p" data-group-id="9683587235-14">[</span><span class="p" data-group-id="9683587235-15">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="9683587235-15">}</span><span class="p">,</span><span class="p" data-group-id="9683587235-16">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">430</span><span class="p" data-group-id="9683587235-16">}</span><span class="p" data-group-id="9683587235-14">]</span><span class="p" data-group-id="9683587235-13">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="9683587235-17">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="9683587235-18">[</span><span class="p" data-group-id="9683587235-19">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9683587235-19">}</span><span class="p">,</span><span class="p" data-group-id="9683587235-20">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="9683587235-20">}</span><span class="p" data-group-id="9683587235-18">]</span><span class="p" data-group-id="9683587235-17">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="9683587235-21">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="9683587235-22">[</span><span class="p" data-group-id="9683587235-23">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9683587235-23">}</span><span class="p">,</span><span class="p" data-group-id="9683587235-24">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="9683587235-24">}</span><span class="p" data-group-id="9683587235-22">]</span><span class="p" data-group-id="9683587235-21">}</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="p" data-group-id="9683587235-25">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="9683587235-26">[</span><span class="p" data-group-id="9683587235-27">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="9683587235-27">}</span><span class="p">,</span><span class="p" data-group-id="9683587235-28">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="9683587235-28">}</span><span class="p" data-group-id="9683587235-26">]</span><span class="p" data-group-id="9683587235-25">}</span><span class="p" data-group-id="9683587235-4">]</span><span class="p" data-group-id="9683587235-3">}</span><span class="p" data-group-id="9683587235-2">}</span></code></pre>
│ │ │ +Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">error</span><span class="p" data-group-id="5025544142-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="5025544142-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5025544142-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="p" data-group-id="5025544142-3">{</span><span class="ss">foobar</span><span class="p">,</span><span class="p" data-group-id="5025544142-4">[</span><span class="p" data-group-id="5025544142-5">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">apply_fun</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="w">
│ │ │ +                        </span><span class="p" data-group-id="5025544142-6">[</span><span class="p" data-group-id="5025544142-7">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5025544142-7">}</span><span class="p">,</span><span class="p" data-group-id="5025544142-8">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">906</span><span class="p" data-group-id="5025544142-8">}</span><span class="p" data-group-id="5025544142-6">]</span><span class="p" data-group-id="5025544142-5">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="5025544142-9">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">do_apply</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="p" data-group-id="5025544142-10">[</span><span class="p" data-group-id="5025544142-11">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="5025544142-11">}</span><span class="p">,</span><span class="p" data-group-id="5025544142-12">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">677</span><span class="p" data-group-id="5025544142-12">}</span><span class="p" data-group-id="5025544142-10">]</span><span class="p" data-group-id="5025544142-9">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="5025544142-13">{</span><span class="ss">erl_eval</span><span class="p">,</span><span class="ss">expr</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="p" data-group-id="5025544142-14">[</span><span class="p" data-group-id="5025544142-15">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;erl_eval.erl&quot;</span><span class="p" data-group-id="5025544142-15">}</span><span class="p">,</span><span class="p" data-group-id="5025544142-16">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">430</span><span class="p" data-group-id="5025544142-16">}</span><span class="p" data-group-id="5025544142-14">]</span><span class="p" data-group-id="5025544142-13">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="5025544142-17">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="5025544142-18">[</span><span class="p" data-group-id="5025544142-19">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5025544142-19">}</span><span class="p">,</span><span class="p" data-group-id="5025544142-20">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">687</span><span class="p" data-group-id="5025544142-20">}</span><span class="p" data-group-id="5025544142-18">]</span><span class="p" data-group-id="5025544142-17">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="5025544142-21">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_exprs</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="p" data-group-id="5025544142-22">[</span><span class="p" data-group-id="5025544142-23">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5025544142-23">}</span><span class="p">,</span><span class="p" data-group-id="5025544142-24">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">642</span><span class="p" data-group-id="5025544142-24">}</span><span class="p" data-group-id="5025544142-22">]</span><span class="p" data-group-id="5025544142-21">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="p" data-group-id="5025544142-25">{</span><span class="ss">shell</span><span class="p">,</span><span class="ss">eval_loop</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="p" data-group-id="5025544142-26">[</span><span class="p" data-group-id="5025544142-27">{</span><span class="ss">file</span><span class="p">,</span><span class="s">&quot;shell.erl&quot;</span><span class="p" data-group-id="5025544142-27">}</span><span class="p">,</span><span class="p" data-group-id="5025544142-28">{</span><span class="ss">line</span><span class="p">,</span><span class="mi">627</span><span class="p" data-group-id="5025544142-28">}</span><span class="p" data-group-id="5025544142-26">]</span><span class="p" data-group-id="5025544142-25">}</span><span class="p" data-group-id="5025544142-4">]</span><span class="p" data-group-id="5025544142-3">}</span><span class="p" data-group-id="5025544142-2">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="error/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#error/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12365,21 +12365,21 @@
│ │ │  <code class="inline">none</code>.</p><p>If <code class="inline">Args</code> is a list, it is used to provide the arguments for the current
│ │ │  function in the stack back-trace. If it is <code class="inline">none</code>, the arity of the calling
│ │ │  function is used in the stacktrace. As evaluating this function causes an
│ │ │  exception to be raised, it has no return value.</p><p>The intent of the exception class <code class="inline">error</code> is to signal that an unexpected error
│ │ │  has happened (for example, a function is called with a parameter that has an
│ │ │  incorrect type). See the guide about
│ │ │  <a href="../../../doc/system/errors.html">errors and error handling</a> for additional information.
│ │ │ -Example:</p><p><code class="inline">test.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="6243375990-1">(</span><span class="ss">test</span><span class="p" data-group-id="6243375990-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="6243375990-2">(</span><span class="p" data-group-id="6243375990-3">[</span><span class="ss">example_fun</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="6243375990-3">]</span><span class="p" data-group-id="6243375990-2">)</span><span class="p">.</span><span class="w">
│ │ │ +Example:</p><p><code class="inline">test.erl</code>:</p><pre><code class="makeup erlang" translate="no"><span class="p">-</span><span class="na">module</span><span class="p" data-group-id="7719078772-1">(</span><span class="ss">test</span><span class="p" data-group-id="7719078772-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p">-</span><span class="na">export</span><span class="p" data-group-id="7719078772-2">(</span><span class="p" data-group-id="7719078772-3">[</span><span class="ss">example_fun</span><span class="p">/</span><span class="mi">2</span><span class="p" data-group-id="7719078772-3">]</span><span class="p" data-group-id="7719078772-2">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">example_fun</span><span class="p" data-group-id="6243375990-4">(</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="6243375990-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">error</span><span class="p" data-group-id="6243375990-5">(</span><span class="ss">my_error</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6243375990-6">[</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="6243375990-6">]</span><span class="p" data-group-id="6243375990-5">)</span><span class="p">.</span></code></pre><p>Erlang shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nf">c</span><span class="p" data-group-id="5436420340-1">(</span><span class="ss">test</span><span class="p" data-group-id="5436420340-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="5436420340-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">test</span><span class="p" data-group-id="5436420340-2">}</span><span class="gp unselectable">
│ │ │ -7&gt; </span><span class="nc">test</span><span class="p">:</span><span class="nf">example_fun</span><span class="p" data-group-id="5436420340-3">(</span><span class="ss">arg1</span><span class="p">,</span><span class="s">&quot;this is the second argument&quot;</span><span class="p" data-group-id="5436420340-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="nf">example_fun</span><span class="p" data-group-id="7719078772-4">(</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="7719078772-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">error</span><span class="p" data-group-id="7719078772-5">(</span><span class="ss">my_error</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7719078772-6">[</span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">A2</span><span class="p" data-group-id="7719078772-6">]</span><span class="p" data-group-id="7719078772-5">)</span><span class="p">.</span></code></pre><p>Erlang shell:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">6&gt; </span><span class="nf">c</span><span class="p" data-group-id="4309655437-1">(</span><span class="ss">test</span><span class="p" data-group-id="4309655437-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="4309655437-2">{</span><span class="ss">ok</span><span class="p">,</span><span class="ss">test</span><span class="p" data-group-id="4309655437-2">}</span><span class="gp unselectable">
│ │ │ +7&gt; </span><span class="nc">test</span><span class="p">:</span><span class="nf">example_fun</span><span class="p" data-group-id="4309655437-3">(</span><span class="ss">arg1</span><span class="p">,</span><span class="s">&quot;this is the second argument&quot;</span><span class="p" data-group-id="4309655437-3">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception error: my_error
│ │ │       in function  test:example_fun/2
│ │ │           called as test:example_fun(arg1,&quot;this is the second argument&quot;)</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="error/3">
│ │ │  
│ │ │ @@ -12456,18 +12456,18 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Raises an exception of class <code class="inline">exit</code> with exit reason <code class="inline">Reason</code>.</p><p>As evaluating this function causes an exception to be raised, it has no return value.</p><p>The intent of the exception class <code class="inline">exit</code> is that the current process should be
│ │ │  stopped (for example when a message telling a process to stop is received).</p><p>This function differ from <a href="#error/1"><code class="inline">error/1,2,3</code></a> by causing an exception of
│ │ │  a different class and by having a reason that does not include the list of
│ │ │  functions from the call stack.</p><p>See the guide about <a href="../../../doc/system/errors.html">errors and error handling</a> for
│ │ │ -additional information.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">exit</span><span class="p" data-group-id="7144234124-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="7144234124-1">)</span><span class="p">.</span><span class="w">
│ │ │ +additional information.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">exit</span><span class="p" data-group-id="0597686238-1">(</span><span class="ss">foobar</span><span class="p" data-group-id="0597686238-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="gt">** exception exit: foobar</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="7144234124-2">(</span><span class="ss">foobar</span><span class="p" data-group-id="7144234124-2">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="7144234124-3">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="ss">foobar</span><span class="p" data-group-id="7144234124-3">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If a process calls <a href="#exit/1"><code class="inline">exit(kill)</code></a> and does not catch the exception,
│ │ │ +&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">exit</span><span class="p" data-group-id="0597686238-2">(</span><span class="ss">foobar</span><span class="p" data-group-id="0597686238-2">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0597686238-3">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="ss">foobar</span><span class="p" data-group-id="0597686238-3">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If a process calls <a href="#exit/1"><code class="inline">exit(kill)</code></a> and does not catch the exception,
│ │ │  it will terminate with exit reason <code class="inline">kill</code> and also emit exit signals with exit
│ │ │  reason <code class="inline">kill</code> (not <code class="inline">killed</code>) to all linked processes. Such exit signals with
│ │ │  exit reason <code class="inline">kill</code> can be trapped by the linked processes. Note that this
│ │ │  means that signals with exit reason <code class="inline">kill</code> behave differently depending on how
│ │ │  they are sent because the signal will be untrappable if a process sends such a
│ │ │  signal to another process with <a href="#exit/2"><code class="inline">erlang:exit/2</code></a>.</p></section>
│ │ │    </section>
│ │ │ @@ -12660,19 +12660,19 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> get() -> [{Key, Val}] when Key :: <a href="#t:term/0">term</a>(), Val :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the process dictionary as a list of <code class="inline">{Key, Val}</code> tuples. The items in
│ │ │ -the returned list can be in any order.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="9213792914-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="ss">merry</span><span class="p" data-group-id="9213792914-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="9213792914-2">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p" data-group-id="9213792914-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="9213792914-3">(</span><span class="ss">key3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9213792914-4">{</span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="9213792914-4">}</span><span class="p" data-group-id="9213792914-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">get</span><span class="p" data-group-id="9213792914-5">(</span><span class="p" data-group-id="9213792914-5">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9213792914-6">[</span><span class="p" data-group-id="9213792914-7">{</span><span class="ss">key1</span><span class="p">,</span><span class="ss">merry</span><span class="p" data-group-id="9213792914-7">}</span><span class="p">,</span><span class="p" data-group-id="9213792914-8">{</span><span class="ss">key2</span><span class="p">,</span><span class="ss">lambs</span><span class="p" data-group-id="9213792914-8">}</span><span class="p">,</span><span class="p" data-group-id="9213792914-9">{</span><span class="ss">key3</span><span class="p">,</span><span class="p" data-group-id="9213792914-10">{</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="9213792914-10">}</span><span class="p" data-group-id="9213792914-9">}</span><span class="p" data-group-id="9213792914-6">]</span></code></pre>
│ │ │ +the returned list can be in any order.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="3565352662-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="ss">merry</span><span class="p" data-group-id="3565352662-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="3565352662-2">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p" data-group-id="3565352662-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="3565352662-3">(</span><span class="ss">key3</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3565352662-4">{</span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="3565352662-4">}</span><span class="p" data-group-id="3565352662-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">get</span><span class="p" data-group-id="3565352662-5">(</span><span class="p" data-group-id="3565352662-5">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="3565352662-6">[</span><span class="p" data-group-id="3565352662-7">{</span><span class="ss">key1</span><span class="p">,</span><span class="ss">merry</span><span class="p" data-group-id="3565352662-7">}</span><span class="p">,</span><span class="p" data-group-id="3565352662-8">{</span><span class="ss">key2</span><span class="p">,</span><span class="ss">lambs</span><span class="p" data-group-id="3565352662-8">}</span><span class="p">,</span><span class="p" data-group-id="3565352662-9">{</span><span class="ss">key3</span><span class="p">,</span><span class="p" data-group-id="3565352662-10">{</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="3565352662-10">}</span><span class="p" data-group-id="3565352662-9">}</span><span class="p" data-group-id="3565352662-6">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="get/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#get/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12695,19 +12695,19 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> get(Key) -> Val | undefined when Key :: <a href="#t:term/0">term</a>(), Val :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the value <code class="inline">Val</code> associated with <code class="inline">Key</code> in the process dictionary, or
│ │ │  <code class="inline">undefined</code> if <code class="inline">Key</code> does not exist.</p><p>The expected time complexity for the current implementation of this function is
│ │ │  O(<code class="inline">1</code>) and the worst case time complexity is O(<code class="inline">N</code>), where <code class="inline">N</code> is the number of
│ │ │ -items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="3293454626-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="ss">merry</span><span class="p" data-group-id="3293454626-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="3293454626-2">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p" data-group-id="3293454626-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="3293454626-3">(</span><span class="p" data-group-id="3293454626-4">{</span><span class="ss">any</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3293454626-5">[</span><span class="ss">valid</span><span class="p">,</span><span class="w"> </span><span class="ss">term</span><span class="p" data-group-id="3293454626-5">]</span><span class="p" data-group-id="3293454626-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3293454626-6">{</span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="3293454626-6">}</span><span class="p" data-group-id="3293454626-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">get</span><span class="p" data-group-id="3293454626-7">(</span><span class="p" data-group-id="3293454626-8">{</span><span class="ss">any</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3293454626-9">[</span><span class="ss">valid</span><span class="p">,</span><span class="w"> </span><span class="ss">term</span><span class="p" data-group-id="3293454626-9">]</span><span class="p" data-group-id="3293454626-8">}</span><span class="p" data-group-id="3293454626-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="3293454626-10">{</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="3293454626-10">}</span></code></pre>
│ │ │ +items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="9093035456-1">(</span><span class="ss">key1</span><span class="p">,</span><span class="w"> </span><span class="ss">merry</span><span class="p" data-group-id="9093035456-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="9093035456-2">(</span><span class="ss">key2</span><span class="p">,</span><span class="w"> </span><span class="ss">lambs</span><span class="p" data-group-id="9093035456-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="9093035456-3">(</span><span class="p" data-group-id="9093035456-4">{</span><span class="ss">any</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9093035456-5">[</span><span class="ss">valid</span><span class="p">,</span><span class="w"> </span><span class="ss">term</span><span class="p" data-group-id="9093035456-5">]</span><span class="p" data-group-id="9093035456-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9093035456-6">{</span><span class="ss">are</span><span class="p">,</span><span class="w"> </span><span class="ss">playing</span><span class="p" data-group-id="9093035456-6">}</span><span class="p" data-group-id="9093035456-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">get</span><span class="p" data-group-id="9093035456-7">(</span><span class="p" data-group-id="9093035456-8">{</span><span class="ss">any</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9093035456-9">[</span><span class="ss">valid</span><span class="p">,</span><span class="w"> </span><span class="ss">term</span><span class="p" data-group-id="9093035456-9">]</span><span class="p" data-group-id="9093035456-8">}</span><span class="p" data-group-id="9093035456-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="9093035456-10">{</span><span class="ss">are</span><span class="p">,</span><span class="ss">playing</span><span class="p" data-group-id="9093035456-10">}</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="get_keys/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#get_keys/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12730,19 +12730,19 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> get_keys() -> [Key] when Key :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a list of all keys present in the process dictionary. The items in the
│ │ │ -returned list can be in any order.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="6157783687-1">(</span><span class="ss">dog</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6157783687-2">{</span><span class="ss">animal</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="6157783687-2">}</span><span class="p" data-group-id="6157783687-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="6157783687-3">(</span><span class="ss">cow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6157783687-4">{</span><span class="ss">animal</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="6157783687-4">}</span><span class="p" data-group-id="6157783687-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="6157783687-5">(</span><span class="ss">lamb</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="6157783687-6">{</span><span class="ss">animal</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="6157783687-6">}</span><span class="p" data-group-id="6157783687-5">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">get_keys</span><span class="p" data-group-id="6157783687-7">(</span><span class="p" data-group-id="6157783687-7">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6157783687-8">[</span><span class="ss">dog</span><span class="p">,</span><span class="ss">cow</span><span class="p">,</span><span class="ss">lamb</span><span class="p" data-group-id="6157783687-8">]</span></code></pre>
│ │ │ +returned list can be in any order.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="1952290377-1">(</span><span class="ss">dog</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1952290377-2">{</span><span class="ss">animal</span><span class="p">,</span><span class="mi">1</span><span class="p" data-group-id="1952290377-2">}</span><span class="p" data-group-id="1952290377-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1952290377-3">(</span><span class="ss">cow</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1952290377-4">{</span><span class="ss">animal</span><span class="p">,</span><span class="mi">2</span><span class="p" data-group-id="1952290377-4">}</span><span class="p" data-group-id="1952290377-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1952290377-5">(</span><span class="ss">lamb</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1952290377-6">{</span><span class="ss">animal</span><span class="p">,</span><span class="mi">3</span><span class="p" data-group-id="1952290377-6">}</span><span class="p" data-group-id="1952290377-5">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">get_keys</span><span class="p" data-group-id="1952290377-7">(</span><span class="p" data-group-id="1952290377-7">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1952290377-8">[</span><span class="ss">dog</span><span class="p">,</span><span class="ss">cow</span><span class="p">,</span><span class="ss">lamb</span><span class="p" data-group-id="1952290377-8">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="get_keys/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#get_keys/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12763,22 +12763,22 @@
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> get_keys(Val) -> [Key] when Val :: <a href="#t:term/0">term</a>(), Key :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a list of keys that are associated with the value <code class="inline">Val</code> in the process
│ │ │ -dictionary. The items in the returned list can be in any order.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="1895191370-1">(</span><span class="ss">mary</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1895191370-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1895191370-2">}</span><span class="p" data-group-id="1895191370-1">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="1895191370-3">(</span><span class="ss">had</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1895191370-4">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1895191370-4">}</span><span class="p" data-group-id="1895191370-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="1895191370-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1895191370-6">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1895191370-6">}</span><span class="p" data-group-id="1895191370-5">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="1895191370-7">(</span><span class="ss">little</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1895191370-8">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1895191370-8">}</span><span class="p" data-group-id="1895191370-7">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="1895191370-9">(</span><span class="ss">dog</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1895191370-10">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1895191370-10">}</span><span class="p" data-group-id="1895191370-9">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">put</span><span class="p" data-group-id="1895191370-11">(</span><span class="ss">lamb</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1895191370-12">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1895191370-12">}</span><span class="p" data-group-id="1895191370-11">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="nf">get_keys</span><span class="p" data-group-id="1895191370-13">(</span><span class="p" data-group-id="1895191370-14">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1895191370-14">}</span><span class="p" data-group-id="1895191370-13">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1895191370-15">[</span><span class="ss">mary</span><span class="p">,</span><span class="ss">had</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">little</span><span class="p">,</span><span class="ss">lamb</span><span class="p" data-group-id="1895191370-15">]</span></code></pre>
│ │ │ +dictionary. The items in the returned list can be in any order.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">put</span><span class="p" data-group-id="1197197473-1">(</span><span class="ss">mary</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197197473-2">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1197197473-2">}</span><span class="p" data-group-id="1197197473-1">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1197197473-3">(</span><span class="ss">had</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197197473-4">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1197197473-4">}</span><span class="p" data-group-id="1197197473-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1197197473-5">(</span><span class="ss">a</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197197473-6">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1197197473-6">}</span><span class="p" data-group-id="1197197473-5">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1197197473-7">(</span><span class="ss">little</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197197473-8">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1197197473-8">}</span><span class="p" data-group-id="1197197473-7">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1197197473-9">(</span><span class="ss">dog</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197197473-10">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p" data-group-id="1197197473-10">}</span><span class="p" data-group-id="1197197473-9">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">put</span><span class="p" data-group-id="1197197473-11">(</span><span class="ss">lamb</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1197197473-12">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1197197473-12">}</span><span class="p" data-group-id="1197197473-11">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">get_keys</span><span class="p" data-group-id="1197197473-13">(</span><span class="p" data-group-id="1197197473-14">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p" data-group-id="1197197473-14">}</span><span class="p" data-group-id="1197197473-13">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="1197197473-15">[</span><span class="ss">mary</span><span class="p">,</span><span class="ss">had</span><span class="p">,</span><span class="ss">a</span><span class="p">,</span><span class="ss">little</span><span class="p">,</span><span class="ss">lamb</span><span class="p" data-group-id="1197197473-15">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="group_leader/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#group_leader/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -12925,17 +12925,17 @@
│ │ │  <p><code class="inline">Pid</code> must refer to a process at the local node.</p><p>Returns <code class="inline">true</code> if the process exists and is alive, that is, is not exiting and
│ │ │  has not exited. Otherwise returns <code class="inline">false</code>.</p><p>If process <code class="inline">P1</code> calls <a href="#is_process_alive/1"><code class="inline">is_process_alive(P2Pid)</code></a> it is
│ │ │  guaranteed that all signals, sent from <code class="inline">P1</code> to <code class="inline">P2</code> (<code class="inline">P2</code> is the process with
│ │ │  identifier <code class="inline">P2Pid</code>) before the call, will be delivered to <code class="inline">P2</code> before the
│ │ │  aliveness of <code class="inline">P2</code> is checked. This guarantee means that one can use
│ │ │  <a href="#is_process_alive/1"><code class="inline">is_process_alive/1</code></a> to let a process <code class="inline">P1</code> wait until a
│ │ │  process <code class="inline">P2</code>, which has got an exit signal with reason <code class="inline">kill</code> from P1, is
│ │ │ -killed.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">exit</span><span class="p" data-group-id="6552101223-1">(</span><span class="n">P2Pid</span><span class="p">,</span><span class="w"> </span><span class="ss">kill</span><span class="p" data-group-id="6552101223-1">)</span><span class="p">,</span><span class="w">
│ │ │ +killed.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">exit</span><span class="p" data-group-id="6440692579-1">(</span><span class="n">P2Pid</span><span class="p">,</span><span class="w"> </span><span class="ss">kill</span><span class="p" data-group-id="6440692579-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="c1">% P2 might not be killed</span><span class="w">
│ │ │ -</span><span class="nf">is_process_alive</span><span class="p" data-group-id="6552101223-2">(</span><span class="n">P2Pid</span><span class="p" data-group-id="6552101223-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">is_process_alive</span><span class="p" data-group-id="6440692579-2">(</span><span class="n">P2Pid</span><span class="p" data-group-id="6440692579-2">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="c1">% P2 is not alive (the call above always return false)</span></code></pre><p>See the documentation about <a href="../../../doc/system/ref_man_processes.html#signals">signals</a>
│ │ │  and <a href="#exit/2">erlang:exit/2</a> for more information about signals and exit
│ │ │  signals.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="link/1">
│ │ │  
│ │ │ @@ -13016,24 +13016,24 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> monitor(process, <a href="#t:monitor_process_identifier/0">monitor_process_identifier</a>()) -> MonitorRef when MonitorRef :: <a href="#t:reference/0">reference</a>();
│ │ │               (port, <a href="#t:monitor_port_identifier/0">monitor_port_identifier</a>()) -> MonitorRef when MonitorRef :: <a href="#t:reference/0">reference</a>();
│ │ │               (time_offset, clock_service) -> MonitorRef when MonitorRef :: <a href="#t:reference/0">reference</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Sends a monitor request of type <code class="inline">Type</code> to the entity identified by <code class="inline">Item</code>.</p><p id="monitor_message">If the monitored entity does not exist or it changes monitored state, the caller
│ │ │ -of <a href="#monitor/2"><code class="inline">monitor/2</code></a> is notified by a message on the following format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0290716277-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="0290716277-1">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The monitor request is an asynchronous signal. That is, it takes time before
│ │ │ +of <a href="#monitor/2"><code class="inline">monitor/2</code></a> is notified by a message on the following format:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="5515043404-1">{</span><span class="n">Tag</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="5515043404-1">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The monitor request is an asynchronous signal. That is, it takes time before
│ │ │  the signal reaches its destination.</p></section><p><code class="inline">Type</code> can be one of the following atoms: <code class="inline">process</code>, <code class="inline">port</code> or <code class="inline">time_offset</code>.</p><p>A <code class="inline">process</code> or <code class="inline">port</code> monitor is triggered only once, after that it is removed
│ │ │  from both monitoring process and the monitored entity. Monitors are fired when
│ │ │  the monitored process or port terminates, does not exist at the moment of
│ │ │  creation, or if the connection to it is lost. If the connection to it is lost,
│ │ │  we do not know if it still exists. The monitoring is also turned off when
│ │ │  <a href="#demonitor/1"><code class="inline">demonitor/1</code></a> is called.</p><p>A <code class="inline">process</code> or <code class="inline">port</code> monitor by name resolves the <code class="inline">RegisteredName</code> to <a href="#t:pid/0"><code class="inline">pid/0</code></a>
│ │ │  or <a href="#t:port/0"><code class="inline">port/0</code></a> only once at the moment of monitor instantiation, later changes to
│ │ │  the name registration will not affect the existing monitor.</p><p>When a <code class="inline">process</code> or <code class="inline">port</code> monitor is triggered, a <code class="inline">'DOWN'</code> message is sent that
│ │ │ -has the following pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="0011629126-1">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="0011629126-1">}</span></code></pre><p>In the monitor message <code class="inline">MonitorRef</code> and <code class="inline">Type</code> are the same as described
│ │ │ +has the following pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="8574030896-1">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Object</span><span class="p">,</span><span class="w"> </span><span class="n">Info</span><span class="p" data-group-id="8574030896-1">}</span></code></pre><p>In the monitor message <code class="inline">MonitorRef</code> and <code class="inline">Type</code> are the same as described
│ │ │  earlier, and:</p><ul><li><p><strong><code class="inline">Object</code></strong> - The monitored entity, which triggered the event. When
│ │ │  monitoring a process or a local port, <code class="inline">Object</code> will be equal to the <a href="#t:pid/0"><code class="inline">pid/0</code></a>
│ │ │  or <a href="#t:port/0"><code class="inline">port/0</code></a> that was being monitored. When monitoring process or port by
│ │ │  name, <code class="inline">Object</code> will have format <code class="inline">{RegisteredName, Node}</code> where
│ │ │  <code class="inline">RegisteredName</code> is the name which has been used with
│ │ │  <a href="#monitor/2"><code class="inline">monitor/2</code></a> call and <code class="inline">Node</code> is local or remote node name (for
│ │ │  ports monitored by name, <code class="inline">Node</code> is always local node name).</p></li><li><p><strong><code class="inline">Info</code></strong> - Either the exit reason of the process, <code class="inline">noproc</code> (process or port
│ │ │ @@ -13069,15 +13069,15 @@
│ │ │  offset is changed when the runtime system detects that the
│ │ │  <a href="time_correction.html#os-system-time">OS system time</a> has changed. The runtime
│ │ │  system does, however, not detect this immediately when it occurs. A task
│ │ │  checking the time offset is scheduled to execute at least once a minute, so
│ │ │  under normal operation this is to be detected within a minute, but during
│ │ │  heavy load it can take longer time.</p><p>The monitor is <em>not</em> automatically removed after it has been triggered. That
│ │ │  is, repeated changes of the time offset trigger the monitor repeatedly.</p><p>When the monitor is triggered a <code class="inline">'CHANGE'</code> message is sent to the monitoring
│ │ │ -process. A <code class="inline">'CHANGE'</code> message has the following pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="4709649361-1">{</span><span class="ss">&#39;CHANGE&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Item</span><span class="p">,</span><span class="w"> </span><span class="n">NewTimeOffset</span><span class="p" data-group-id="4709649361-1">}</span></code></pre><p>where <code class="inline">MonitorRef</code>, <code class="inline">Type</code>, and <code class="inline">Item</code> are the same as described above, and
│ │ │ +process. A <code class="inline">'CHANGE'</code> message has the following pattern:</p><pre><code class="makeup erlang" translate="no"><span class="p" data-group-id="7554751003-1">{</span><span class="ss">&#39;CHANGE&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">MonitorRef</span><span class="p">,</span><span class="w"> </span><span class="n">Type</span><span class="p">,</span><span class="w"> </span><span class="n">Item</span><span class="p">,</span><span class="w"> </span><span class="n">NewTimeOffset</span><span class="p" data-group-id="7554751003-1">}</span></code></pre><p>where <code class="inline">MonitorRef</code>, <code class="inline">Type</code>, and <code class="inline">Item</code> are the same as described above, and
│ │ │  <code class="inline">NewTimeOffset</code> is the new time offset.</p><p>When the <code class="inline">'CHANGE'</code> message has been received you are guaranteed not to
│ │ │  retrieve the old time offset when calling
│ │ │  <a href="#time_offset/0"><code class="inline">erlang:time_offset/0</code></a>. Notice that you can observe the
│ │ │  change of the time offset when calling <a href="#time_offset/0"><code class="inline">erlang:time_offset/0</code></a> before you get
│ │ │  the <code class="inline">'CHANGE'</code> message.</p><p>Available since OTP 18.0.</p></li></ul><p>Making several calls to <a href="#monitor/2"><code class="inline">monitor/2</code></a> for the same <code class="inline">Item</code> and/or
│ │ │  <code class="inline">Type</code> is not an error; it results in as many independent monitoring instances.</p><p>The monitor functionality is expected to be extended. That is, other <code class="inline">Type</code>s and
│ │ │  <code class="inline">Item</code>s are expected to be supported in a future release.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>If or when <a href="#monitor/2"><code class="inline">monitor/2</code></a> is extended, other possible values for
│ │ │ @@ -13133,78 +13133,78 @@
│ │ │  via the alias is received. When a reply message is received via the alias
│ │ │  the monitor will also be automatically removed. This is useful in
│ │ │  client/server scenarios when a client monitors the server and will get the
│ │ │  reply via the alias. Once the response is received both the alias and the
│ │ │  monitor will be automatically removed regardless of whether the response is
│ │ │  a reply or a <code class="inline">'DOWN'</code> message. The alias can also still be deactivated via a
│ │ │  call to <a href="#unalias/1"><code class="inline">unalias/1</code></a>. Note that if the alias is removed using
│ │ │ -the <a href="#unalias/1"><code class="inline">unalias/1</code></a> BIF, the monitor will still be left active.</p></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="2022574271-1">(</span><span class="p" data-group-id="2022574271-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +the <a href="#unalias/1"><code class="inline">unalias/1</code></a> BIF, the monitor will still be left active.</p></li></ul><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="0593377368-1">(</span><span class="p" data-group-id="0593377368-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2022574271-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="2022574271-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="2022574271-3">(</span><span class="n">Request</span><span class="p" data-group-id="2022574271-3">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2022574271-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2022574271-4">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0593377368-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0593377368-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="0593377368-3">(</span><span class="n">Request</span><span class="p" data-group-id="0593377368-3">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">AliasReqId</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0593377368-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0593377368-4">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="2022574271-5">(</span><span class="p" data-group-id="2022574271-5">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="0593377368-5">(</span><span class="p" data-group-id="0593377368-5">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="2022574271-6">(</span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="2022574271-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">AliasMonReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="2022574271-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2022574271-8">[</span><span class="p" data-group-id="2022574271-9">{</span><span class="ss">alias</span><span class="p">,</span><span class="w"> </span><span class="ss">reply_demonitor</span><span class="p" data-group-id="2022574271-9">}</span><span class="p" data-group-id="2022574271-8">]</span><span class="p" data-group-id="2022574271-7">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="2022574271-10">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasMonReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="2022574271-10">}</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="0593377368-6">(</span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0593377368-6">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">AliasMonReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="0593377368-7">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="0593377368-8">[</span><span class="p" data-group-id="0593377368-9">{</span><span class="ss">alias</span><span class="p">,</span><span class="w"> </span><span class="ss">reply_demonitor</span><span class="p" data-group-id="0593377368-9">}</span><span class="p" data-group-id="0593377368-8">]</span><span class="p" data-group-id="0593377368-7">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="0593377368-10">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">AliasMonReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="0593377368-10">}</span><span class="p">,</span><span class="w">
│ │ │      </span><span class="c1">%% Alias as well as monitor will be automatically deactivated if we</span><span class="w">
│ │ │      </span><span class="c1">%% receive a reply or a &#39;DOWN&#39; message since we used &#39;reply_demonitor&#39;</span><span class="w">
│ │ │      </span><span class="c1">%% as unalias option...</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2022574271-11">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasMonReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="2022574271-11">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0593377368-11">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">AliasMonReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="0593377368-11">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │              </span><span class="n">Result</span><span class="p">;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="2022574271-12">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">AliasMonReqId</span><span class="p">,</span><span class="w"> </span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ExitReason</span><span class="p" data-group-id="2022574271-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="nf">error</span><span class="p" data-group-id="2022574271-13">(</span><span class="n">ExitReason</span><span class="p" data-group-id="2022574271-13">)</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="0593377368-12">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">AliasMonReqId</span><span class="p">,</span><span class="w"> </span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ExitReason</span><span class="p" data-group-id="0593377368-12">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="nf">error</span><span class="p" data-group-id="0593377368-13">(</span><span class="n">ExitReason</span><span class="p" data-group-id="0593377368-13">)</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">.</span></code></pre><p>Note that both the server and the client in this example must be executing on
│ │ │  at least OTP 24 systems in order for this to work.</p><p>For more information on process aliases see the
│ │ │  <a href="../../../doc/system/ref_man_processes.html#process-aliases"><em>Process Aliases</em></a> section
│ │ │  of the <em>Erlang Reference Manual</em>.</p></li><li><p><strong><code class="inline">{tag, UserDefinedTag}</code></strong> - Replace the default <code class="inline">Tag</code> with <code class="inline">UserDefinedTag</code>
│ │ │  in the <a href="#monitor_message">monitor message</a> delivered when the
│ │ │  monitor is triggered. For example, when monitoring a process, the <code class="inline">'DOWN'</code> tag
│ │ │  in the down message will be replaced by <code class="inline">UserDefinedTag</code>.</p><p>An example of how the <code class="inline">{tag, UserDefinedTag}</code> option can be used in order to
│ │ │  enable the new
│ │ │  <a href="../../../doc/system/eff_guide_processes.html#receiving-messages">selective receive optimization</a>,
│ │ │ -introduced in OTP 24, when making multiple requests to different servers:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="5004986314-1">(</span><span class="p" data-group-id="5004986314-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +introduced in OTP 24, when making multiple requests to different servers:</p><pre><code class="makeup erlang" translate="no"><span class="nf">server</span><span class="p" data-group-id="1652833360-1">(</span><span class="p" data-group-id="1652833360-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="k">receive</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="5004986314-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="5004986314-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="5004986314-3">(</span><span class="n">Request</span><span class="p" data-group-id="5004986314-3">)</span><span class="p">,</span><span class="w">
│ │ │ -            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5004986314-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5004986314-5">(</span><span class="p" data-group-id="5004986314-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5004986314-4">}</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1652833360-2">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="n">From</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1652833360-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +            </span><span class="n">Result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">perform_request</span><span class="p" data-group-id="1652833360-3">(</span><span class="n">Request</span><span class="p" data-group-id="1652833360-3">)</span><span class="p">,</span><span class="w">
│ │ │ +            </span><span class="n">From</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1652833360-4">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1652833360-5">(</span><span class="p" data-group-id="1652833360-5">)</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1652833360-4">}</span><span class="w">
│ │ │      </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">server</span><span class="p" data-group-id="5004986314-6">(</span><span class="p" data-group-id="5004986314-6">)</span><span class="p">.</span><span class="w">
│ │ │ +    </span><span class="nf">server</span><span class="p" data-group-id="1652833360-6">(</span><span class="p" data-group-id="1652833360-6">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">client</span><span class="p" data-group-id="5004986314-7">(</span><span class="n">ServerPids</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="5004986314-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_list</span><span class="p" data-group-id="5004986314-8">(</span><span class="n">ServerPids</span><span class="p" data-group-id="5004986314-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -    </span><span class="n">ReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="5004986314-9">(</span><span class="p" data-group-id="5004986314-9">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="5004986314-10">(</span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="5004986314-11">(</span><span class="n">ServerPid</span><span class="p" data-group-id="5004986314-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                          </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="5004986314-12">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w">
│ │ │ -                                      </span><span class="p" data-group-id="5004986314-13">[</span><span class="p" data-group-id="5004986314-14">{</span><span class="ss">tag</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5004986314-15">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p" data-group-id="5004986314-15">}</span><span class="p" data-group-id="5004986314-14">}</span><span class="p" data-group-id="5004986314-13">]</span><span class="p" data-group-id="5004986314-12">)</span><span class="p">,</span><span class="w">
│ │ │ -                          </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="5004986314-16">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="5004986314-17">(</span><span class="p" data-group-id="5004986314-17">)</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="5004986314-16">}</span><span class="w">
│ │ │ +</span><span class="nf">client</span><span class="p" data-group-id="1652833360-7">(</span><span class="n">ServerPids</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1652833360-7">)</span><span class="w"> </span><span class="k">when</span><span class="w"> </span><span class="nf">is_list</span><span class="p" data-group-id="1652833360-8">(</span><span class="n">ServerPids</span><span class="p" data-group-id="1652833360-8">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="n">ReqId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">make_ref</span><span class="p" data-group-id="1652833360-9">(</span><span class="p" data-group-id="1652833360-9">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foreach</span><span class="p" data-group-id="1652833360-10">(</span><span class="nf">fun</span><span class="w"> </span><span class="p" data-group-id="1652833360-11">(</span><span class="n">ServerPid</span><span class="p" data-group-id="1652833360-11">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                          </span><span class="p">_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">monitor</span><span class="p" data-group-id="1652833360-12">(</span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w">
│ │ │ +                                      </span><span class="p" data-group-id="1652833360-13">[</span><span class="p" data-group-id="1652833360-14">{</span><span class="ss">tag</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1652833360-15">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p" data-group-id="1652833360-15">}</span><span class="p" data-group-id="1652833360-14">}</span><span class="p" data-group-id="1652833360-13">]</span><span class="p" data-group-id="1652833360-12">)</span><span class="p">,</span><span class="w">
│ │ │ +                          </span><span class="n">ServerPid</span><span class="w"> </span><span class="o">!</span><span class="w"> </span><span class="p" data-group-id="1652833360-16">{</span><span class="ss">request</span><span class="p">,</span><span class="w"> </span><span class="nf">self</span><span class="p" data-group-id="1652833360-17">(</span><span class="p" data-group-id="1652833360-17">)</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Request</span><span class="p" data-group-id="1652833360-16">}</span><span class="w">
│ │ │                    </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -                  </span><span class="n">ServerPids</span><span class="p" data-group-id="5004986314-10">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">receive_replies</span><span class="p" data-group-id="5004986314-18">(</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="5004986314-19">(</span><span class="n">ServerPids</span><span class="p" data-group-id="5004986314-19">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5004986314-20">[</span><span class="p" data-group-id="5004986314-20">]</span><span class="p" data-group-id="5004986314-18">)</span><span class="p">.</span><span class="w">
│ │ │ +                  </span><span class="n">ServerPids</span><span class="p" data-group-id="1652833360-10">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="nf">receive_replies</span><span class="p" data-group-id="1652833360-18">(</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="nf">length</span><span class="p" data-group-id="1652833360-19">(</span><span class="n">ServerPids</span><span class="p" data-group-id="1652833360-19">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1652833360-20">[</span><span class="p" data-group-id="1652833360-20">]</span><span class="p" data-group-id="1652833360-18">)</span><span class="p">.</span><span class="w">
│ │ │  
│ │ │ -</span><span class="nf">receive_replies</span><span class="p" data-group-id="5004986314-21">(</span><span class="p">_</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5004986314-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">receive_replies</span><span class="p" data-group-id="1652833360-21">(</span><span class="p">_</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1652833360-21">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="n">Acc</span><span class="p">;</span><span class="w">
│ │ │ -</span><span class="nf">receive_replies</span><span class="p" data-group-id="5004986314-22">(</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5004986314-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +</span><span class="nf">receive_replies</span><span class="p" data-group-id="1652833360-22">(</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="p">,</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1652833360-22">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │      </span><span class="c1">%% The compiler will detect that we match on the &#39;ReqId&#39;</span><span class="w">
│ │ │      </span><span class="c1">%% reference in all clauses, and will enable the selective</span><span class="w">
│ │ │      </span><span class="c1">%% receive optimization which makes the receive able to</span><span class="w">
│ │ │      </span><span class="c1">%% skip past all messages present in the message queue at</span><span class="w">
│ │ │      </span><span class="c1">%% the time when the &#39;ReqId&#39; reference was created...</span><span class="w">
│ │ │      </span><span class="n">Res</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">receive</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="5004986314-23">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5004986314-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="1652833360-23">{</span><span class="ss">reply</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1652833360-23">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │                    </span><span class="c1">%% Here we typically would have deactivated the</span><span class="w">
│ │ │                    </span><span class="c1">%% monitor by a call to demonitor(Mon, [flush]) but</span><span class="w">
│ │ │                    </span><span class="c1">%% we ignore this in this example for simplicity...</span><span class="w">
│ │ │ -                  </span><span class="p" data-group-id="5004986314-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="5004986314-24">}</span><span class="p">;</span><span class="w">
│ │ │ -              </span><span class="p" data-group-id="5004986314-25">{</span><span class="p" data-group-id="5004986314-26">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p" data-group-id="5004986314-26">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Mon</span><span class="p">,</span><span class="w"> </span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ExitReason</span><span class="p" data-group-id="5004986314-25">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                  </span><span class="p" data-group-id="5004986314-27">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ExitReason</span><span class="p" data-group-id="5004986314-27">}</span><span class="w">
│ │ │ +                  </span><span class="p" data-group-id="1652833360-24">{</span><span class="ss">ok</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">Result</span><span class="p" data-group-id="1652833360-24">}</span><span class="p">;</span><span class="w">
│ │ │ +              </span><span class="p" data-group-id="1652833360-25">{</span><span class="p" data-group-id="1652833360-26">{</span><span class="ss">&#39;DOWN&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">ReqId</span><span class="p" data-group-id="1652833360-26">}</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="n">Mon</span><span class="p">,</span><span class="w"> </span><span class="ss">process</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ExitReason</span><span class="p" data-group-id="1652833360-25">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                  </span><span class="p" data-group-id="1652833360-27">{</span><span class="ss">error</span><span class="p">,</span><span class="w"> </span><span class="n">ServerPid</span><span class="p">,</span><span class="w"> </span><span class="n">ExitReason</span><span class="p" data-group-id="1652833360-27">}</span><span class="w">
│ │ │            </span><span class="k">end</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="nf">receive_replies</span><span class="p" data-group-id="5004986314-28">(</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5004986314-29">[</span><span class="n">Res</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="5004986314-29">]</span><span class="p" data-group-id="5004986314-28">)</span><span class="p">.</span></code></pre><p>In order for this example to work as intended, the client must be executing on
│ │ │ +    </span><span class="nf">receive_replies</span><span class="p" data-group-id="1652833360-28">(</span><span class="n">ReqId</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1652833360-29">[</span><span class="n">Res</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Acc</span><span class="p" data-group-id="1652833360-29">]</span><span class="p" data-group-id="1652833360-28">)</span><span class="p">.</span></code></pre><p>In order for this example to work as intended, the client must be executing on
│ │ │  at least an OTP 24 system, but the servers may execute on older systems.</p></li></ul>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="nif_error/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#nif_error/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -13910,15 +13910,15 @@
│ │ │                    (sensitive, Boolean) -> OldBoolean when Boolean :: <a href="#t:boolean/0">boolean</a>(), OldBoolean :: <a href="#t:boolean/0">boolean</a>();
│ │ │                    ({monitor_nodes, <a href="#t:term/0">term</a>()}, <a href="#t:term/0">term</a>()) -> <a href="#t:term/0">term</a>();
│ │ │                    (monitor_nodes, <a href="#t:term/0">term</a>()) -> <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Sets the process flag indicated to the specified value. Returns the previous value
│ │ │ -of the flag.</p><p><code class="inline">Flag</code> is one of the following:</p><ul><li><pre id="process_flag_async_dist"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="0926705856-1">(</span><span class="ss">async_dist</span><span class="p">,</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="0926705856-2">(</span><span class="p" data-group-id="0926705856-2">)</span><span class="p" data-group-id="0926705856-1">)</span></code></pre><p>Enable or disable <em>fully asynchronous distributed signaling</em> for the calling
│ │ │ +of the flag.</p><p><code class="inline">Flag</code> is one of the following:</p><ul><li><pre id="process_flag_async_dist"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8356066635-1">(</span><span class="ss">async_dist</span><span class="p">,</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="8356066635-2">(</span><span class="p" data-group-id="8356066635-2">)</span><span class="p" data-group-id="8356066635-1">)</span></code></pre><p>Enable or disable <em>fully asynchronous distributed signaling</em> for the calling
│ │ │  process. When disabled, which is the default, the process sending a distributed
│ │ │  signal will block in the send operation if the buffer for the distribution
│ │ │  channel reach the <a href="erl_cmd.html#%2Bzdbbl">distribution buffer busy limit</a>. The
│ │ │  process will remain blocked until the buffer shrinks enough. This might in some
│ │ │  cases take a substantial amount of time. When <code class="inline">async_dist</code> is enabled, send
│ │ │  operations of distributed signals will always buffer the signal on the outgoing
│ │ │  distribution channel and then immediately return. That is, these send operations
│ │ │ @@ -13935,22 +13935,22 @@
│ │ │  caller.</p><p>The <code class="inline">async_dist</code> flag can also be set on a new process when spawning it using
│ │ │  the <a href="#spawn_opt/4"><code class="inline">spawn_opt()</code></a> BIF with the option
│ │ │  <a href="#spawn_opt_async_dist"><code class="inline">{async_dist, Enable}</code></a>. The default
│ │ │  <code class="inline">async_dist</code> flag to use on newly spawned processes can be set by passing the
│ │ │  command line argument <a href="erl_cmd.html#%2Bpad"><code class="inline">+pad &lt;boolean&gt;</code></a> when starting the
│ │ │  runtime system. If the <code class="inline">+pad &lt;boolean&gt;</code> command line argument is not passed, the
│ │ │  default value of the <code class="inline">async_dist</code> flag will be <code class="inline">false</code>.</p><p>You can inspect the state of the <code class="inline">async_dist</code> process flag of a process by
│ │ │ -calling <a href="#process_info_async_dist"><code class="inline">process_info(Pid, async_dist)</code></a>.</p></li><li><pre id="process_flag_trap_exit"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="6712067216-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="6712067216-2">(</span><span class="p" data-group-id="6712067216-2">)</span><span class="p" data-group-id="6712067216-1">)</span></code></pre><p>When <code class="inline">trap_exit</code> is set to <code class="inline">true</code>, exit signals arriving to a process are
│ │ │ +calling <a href="#process_info_async_dist"><code class="inline">process_info(Pid, async_dist)</code></a>.</p></li><li><pre id="process_flag_trap_exit"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="7943989323-1">(</span><span class="ss">trap_exit</span><span class="p">,</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="7943989323-2">(</span><span class="p" data-group-id="7943989323-2">)</span><span class="p" data-group-id="7943989323-1">)</span></code></pre><p>When <code class="inline">trap_exit</code> is set to <code class="inline">true</code>, exit signals arriving to a process are
│ │ │  converted to <code class="inline">{'EXIT', From, Reason}</code> messages, which can be received as
│ │ │  ordinary messages. If <code class="inline">trap_exit</code> is set to <code class="inline">false</code>, the process exits if it
│ │ │  receives an exit signal other than <code class="inline">normal</code> and the exit signal is propagated to
│ │ │ -its linked processes. Application processes are normally not to trap exits.</p><p>See also <a href="#exit/2"><code class="inline">exit/2</code></a>.</p></li><li><pre id="process_flag_error_handler"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="5583601926-1">(</span><span class="ss">error_handler</span><span class="p">,</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="5583601926-2">(</span><span class="p" data-group-id="5583601926-2">)</span><span class="p" data-group-id="5583601926-1">)</span></code></pre><p>Used by a process to redefine the <a href="../../../lib/kernel-10.2.7.2/doc/html/error_handler.html"><code class="inline">error_handler</code></a> for undefined function calls and
│ │ │ +its linked processes. Application processes are normally not to trap exits.</p><p>See also <a href="#exit/2"><code class="inline">exit/2</code></a>.</p></li><li><pre id="process_flag_error_handler"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8346440736-1">(</span><span class="ss">error_handler</span><span class="p">,</span><span class="w"> </span><span class="nf">module</span><span class="p" data-group-id="8346440736-2">(</span><span class="p" data-group-id="8346440736-2">)</span><span class="p" data-group-id="8346440736-1">)</span></code></pre><p>Used by a process to redefine the <a href="../../../lib/kernel-10.2.7.2/doc/html/error_handler.html"><code class="inline">error_handler</code></a> for undefined function calls and
│ │ │  undefined registered processes. Use this flag with substantial caution, as code
│ │ │ -auto-loading depends on the correct operation of the error handling module.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="0145594828-1">(</span><span class="ss">fullsweep_after</span><span class="p">,</span><span class="w">  </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0145594828-2">(</span><span class="p" data-group-id="0145594828-2">)</span><span class="p" data-group-id="0145594828-1">)</span></code></pre><p>Changes the maximum number of generational collections before forcing a
│ │ │ -fullsweep for the calling process.</p></li><li><pre id="process_flag_min_heap_size"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8576186220-1">(</span><span class="ss">min_heap_size</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8576186220-2">(</span><span class="p" data-group-id="8576186220-2">)</span><span class="p" data-group-id="8576186220-1">)</span></code></pre><p>Changes the minimum heap size for the calling process.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="2299062739-1">(</span><span class="ss">min_bin_vheap_size</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2299062739-2">(</span><span class="p" data-group-id="2299062739-2">)</span><span class="p" data-group-id="2299062739-1">)</span></code></pre><p>Changes the minimum binary virtual heap size for the calling process.</p></li><li><pre id="process_flag_max_heap_size"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="3579834014-1">(</span><span class="ss">max_heap_size</span><span class="p">,</span><span class="w"> </span><span class="nf">max_heap_size</span><span class="p" data-group-id="3579834014-2">(</span><span class="p" data-group-id="3579834014-2">)</span><span class="p" data-group-id="3579834014-1">)</span></code></pre><p>This flag sets the maximum heap size for the calling process. If <code class="inline">MaxHeapSize</code>
│ │ │ +auto-loading depends on the correct operation of the error handling module.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="7176730452-1">(</span><span class="ss">fullsweep_after</span><span class="p">,</span><span class="w">  </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="7176730452-2">(</span><span class="p" data-group-id="7176730452-2">)</span><span class="p" data-group-id="7176730452-1">)</span></code></pre><p>Changes the maximum number of generational collections before forcing a
│ │ │ +fullsweep for the calling process.</p></li><li><pre id="process_flag_min_heap_size"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="1343190269-1">(</span><span class="ss">min_heap_size</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1343190269-2">(</span><span class="p" data-group-id="1343190269-2">)</span><span class="p" data-group-id="1343190269-1">)</span></code></pre><p>Changes the minimum heap size for the calling process.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8501584493-1">(</span><span class="ss">min_bin_vheap_size</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8501584493-2">(</span><span class="p" data-group-id="8501584493-2">)</span><span class="p" data-group-id="8501584493-1">)</span></code></pre><p>Changes the minimum binary virtual heap size for the calling process.</p></li><li><pre id="process_flag_max_heap_size"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="2936087059-1">(</span><span class="ss">max_heap_size</span><span class="p">,</span><span class="w"> </span><span class="nf">max_heap_size</span><span class="p" data-group-id="2936087059-2">(</span><span class="p" data-group-id="2936087059-2">)</span><span class="p" data-group-id="2936087059-1">)</span></code></pre><p>This flag sets the maximum heap size for the calling process. If <code class="inline">MaxHeapSize</code>
│ │ │  is an integer, the system default values for <code class="inline">kill</code> and <code class="inline">error_logger</code> are used.</p><p>For details on how the heap grows, see
│ │ │  <a href="garbagecollection.html#sizing-the-heap">Sizing the heap</a> in the ERTS internal
│ │ │  documentation.</p><ul><li><p><strong><code class="inline">size</code></strong> - The maximum size in words of the process. If set to zero, the
│ │ │  heap size limit is disabled. <code class="inline">badarg</code> is be thrown if the value is smaller
│ │ │  than <a href="#process_flag_min_heap_size"><code class="inline">min_heap_size</code></a>. The size check
│ │ │  is only done when a garbage collection is triggered.</p><p><code class="inline">size</code> is the entire heap of the process when garbage collection is triggered.
│ │ │  This includes all generational heaps, the process stack, any
│ │ │ @@ -13978,27 +13978,27 @@
│ │ │  of it is referred by the process.</p><p>If <code class="inline">include_shared_binaries</code> is not defined in the map, the system default is
│ │ │  used. The default system default is <code class="inline">false</code>. It can be changed by either the
│ │ │  option <a href="erl_cmd.html#%2Bhmaxib">+hmaxib</a> in <a href="erl_cmd.html">erl</a>, or
│ │ │  <a href="#system_flag_max_heap_size"><code class="inline">erlang:system_flag(max_heap_size, MaxHeapSize)</code></a>.</p></li></ul><p>The heap size of a process is quite hard to predict, especially the amount of
│ │ │  memory that is used during the garbage collection. When contemplating using this
│ │ │  option, it is recommended to first run it in production with <code class="inline">kill</code> set to
│ │ │  <code class="inline">false</code> and inspect the log events to see what the normal peak sizes of the
│ │ │ -processes in the system is and then tune the value accordingly.</p></li><li><pre id="process_flag_message_queue_data"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="9831533386-1">(</span><span class="ss">message_queue_data</span><span class="p">,</span><span class="w"> </span><span class="nf">message_queue_data</span><span class="p" data-group-id="9831533386-2">(</span><span class="p" data-group-id="9831533386-2">)</span><span class="p" data-group-id="9831533386-1">)</span></code></pre><p>Determines how messages in the message queue are stored, as follows:</p><ul><li><p><strong><code class="inline">off_heap</code></strong> - <em>All</em> messages in the message queue will be stored outside
│ │ │ +processes in the system is and then tune the value accordingly.</p></li><li><pre id="process_flag_message_queue_data"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8052750359-1">(</span><span class="ss">message_queue_data</span><span class="p">,</span><span class="w"> </span><span class="nf">message_queue_data</span><span class="p" data-group-id="8052750359-2">(</span><span class="p" data-group-id="8052750359-2">)</span><span class="p" data-group-id="8052750359-1">)</span></code></pre><p>Determines how messages in the message queue are stored, as follows:</p><ul><li><p><strong><code class="inline">off_heap</code></strong> - <em>All</em> messages in the message queue will be stored outside
│ │ │  the process heap. This implies that <em>no</em> messages in the message queue will be
│ │ │  part of a garbage collection of the process.</p></li><li><p><strong><code class="inline">on_heap</code></strong> - All messages in the message queue will eventually be placed on
│ │ │  the process heap. They can, however, be temporarily stored off the heap. This
│ │ │  is how messages have always been stored up until ERTS 8.0.</p></li></ul><p>The default value of the <code class="inline">message_queue_data</code> process flag is determined by the
│ │ │  command-line argument <a href="erl_cmd.html#%2Bhmqd"><code class="inline">+hmqd</code></a> in <a href="erl_cmd.html">erl</a>.</p><p>If the process may potentially accumulate a large number of messages in its
│ │ │  queue it is recommended to set the flag value to <code class="inline">off_heap</code>. This is due to the
│ │ │  fact that the garbage collection of a process that has a large number of
│ │ │  messages stored on the heap can become extremely expensive and the process can
│ │ │  consume large amounts of memory. The performance of the actual message passing
│ │ │  is, however, generally better when the flag value is <code class="inline">on_heap</code>.</p><p>Changing the flag value causes any existing messages to be moved. The move
│ │ │  operation is initiated, but not necessarily completed, by the time the function
│ │ │ -returns.</p></li><li><pre id="process_flag_priority"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="4266501795-1">(</span><span class="ss">priority</span><span class="p">,</span><span class="w"> </span><span class="nf">priority_level</span><span class="p" data-group-id="4266501795-2">(</span><span class="p" data-group-id="4266501795-2">)</span><span class="p" data-group-id="4266501795-1">)</span></code></pre><p>Sets the process priority. <code class="inline">Level</code> is an atom. Four priority levels exist:
│ │ │ +returns.</p></li><li><pre id="process_flag_priority"><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8070362691-1">(</span><span class="ss">priority</span><span class="p">,</span><span class="w"> </span><span class="nf">priority_level</span><span class="p" data-group-id="8070362691-2">(</span><span class="p" data-group-id="8070362691-2">)</span><span class="p" data-group-id="8070362691-1">)</span></code></pre><p>Sets the process priority. <code class="inline">Level</code> is an atom. Four priority levels exist:
│ │ │  <code class="inline">low</code>, <code class="inline">normal</code>, <code class="inline">high</code>, and <code class="inline">max</code>. Default is <code class="inline">normal</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Priority level <code class="inline">max</code> is reserved for internal use in the Erlang runtime
│ │ │  system, and is <em>not</em> to be used by others.</p></section><p>Internally in each priority level, processes are scheduled in a round robin
│ │ │  fashion.</p><p>Execution of processes on priority <code class="inline">normal</code> and <code class="inline">low</code> are interleaved. Processes
│ │ │  on priority <code class="inline">low</code> are selected for execution less frequently than processes on
│ │ │  priority <code class="inline">normal</code>.</p><p>When runnable processes on priority <code class="inline">high</code> exist, no processes on priority <code class="inline">low</code>
│ │ │  or <code class="inline">normal</code> are selected for execution. Notice however that this does <em>not</em> mean
│ │ │  that no processes on priority <code class="inline">low</code> or <code class="inline">normal</code> can run when processes are
│ │ │ @@ -14019,24 +14019,24 @@
│ │ │  process during the call. Even if this is not the case with one version of the
│ │ │  code that you have no control over, it can be the case in a future version of
│ │ │  it. This can, for example, occur if a <code class="inline">high</code> priority process triggers code
│ │ │  loading, as the code server runs on priority <code class="inline">normal</code>.</p><p>Other priorities than <code class="inline">normal</code> are normally not needed. When other priorities
│ │ │  are used, use them with care, <em>especially</em> priority <code class="inline">high</code>. A process on
│ │ │  priority <code class="inline">high</code> is only to perform work for short periods. Busy looping for long
│ │ │  periods in a <code class="inline">high</code> priority process causes most likely problems, as important
│ │ │ -OTP servers run on priority <code class="inline">normal</code>.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="9847098344-1">(</span><span class="ss">save_calls</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span><span class="p">.</span><span class="mi">10000</span><span class="p" data-group-id="9847098344-1">)</span></code></pre><p><code class="inline">N</code> must be an integer in the interval 0..10000. If <code class="inline">N</code> &gt; 0, call saving is made
│ │ │ +OTP servers run on priority <code class="inline">normal</code>.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="9874734921-1">(</span><span class="ss">save_calls</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">.</span><span class="p">.</span><span class="mi">10000</span><span class="p" data-group-id="9874734921-1">)</span></code></pre><p><code class="inline">N</code> must be an integer in the interval 0..10000. If <code class="inline">N</code> &gt; 0, call saving is made
│ │ │  active for the process. This means that information about the <code class="inline">N</code> most recent
│ │ │  global function calls, BIF calls, sends, and receives made by the process are
│ │ │  saved in a list, which can be retrieved with
│ │ │  <a href="#process_info/2"><code class="inline">process_info(Pid, last_calls)</code></a>. A global function call is
│ │ │  one in which the module of the function is explicitly mentioned. Only a fixed
│ │ │  amount of information is saved, as follows:</p><ul><li>A tuple <code class="inline">{Module, Function, Arity}</code> for function calls</li><li>The atoms <code class="inline">send</code>, <code class="inline">'receive'</code>, and <code class="inline">timeout</code> for sends and receives
│ │ │  (<code class="inline">'receive'</code> when a message is received and <code class="inline">timeout</code> when a receive times
│ │ │  out)</li></ul><p>If <code class="inline">N</code> = 0, call saving is disabled for the process, which is the default.
│ │ │ -Whenever the size of the call saving list is set, its contents are reset.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="8458994672-1">(</span><span class="ss">sensitive</span><span class="p">,</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="8458994672-2">(</span><span class="p" data-group-id="8458994672-2">)</span><span class="p" data-group-id="8458994672-1">)</span></code></pre><p>Sets or clears flag <code class="inline">sensitive</code> for the current process. When a process has been
│ │ │ +Whenever the size of the call saving list is set, its contents are reset.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">process_flag</span><span class="p" data-group-id="5876708764-1">(</span><span class="ss">sensitive</span><span class="p">,</span><span class="w"> </span><span class="nf">boolean</span><span class="p" data-group-id="5876708764-2">(</span><span class="p" data-group-id="5876708764-2">)</span><span class="p" data-group-id="5876708764-1">)</span></code></pre><p>Sets or clears flag <code class="inline">sensitive</code> for the current process. When a process has been
│ │ │  marked as sensitive by calling
│ │ │  <a href="#process_flag/2"><code class="inline">process_flag(sensitive, true)</code></a>, features in the runtime
│ │ │  system that can be used for examining the data or inner working of the process
│ │ │  are silently disabled.</p><p>Features that are disabled include (but are not limited to) the following:</p><ul><li>Tracing. Trace flags can still be set for the process, but no trace messages
│ │ │  of any kind are generated. (If flag <code class="inline">sensitive</code> is turned off, trace messages
│ │ │  are again generated if any trace flags are set.)</li><li>Sequential tracing. The sequential trace token is propagated as usual, but no
│ │ │  sequential trace messages are generated.</li></ul><p><code class="inline">process_info/1,2</code> cannot be used to read out the message queue or the process
│ │ │ @@ -14280,16 +14280,16 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns a list of process identifiers corresponding to all the processes
│ │ │  currently existing on the local node.</p><p>Notice that an exiting process exists, but is not alive. That is,
│ │ │  <a href="#is_process_alive/1"><code class="inline">is_process_alive/1</code></a> returns <code class="inline">false</code> for an exiting
│ │ │  process, but its process identifier is part of the result returned from
│ │ │ -<a href="#processes/0"><code class="inline">processes/0</code></a>.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">processes</span><span class="p" data-group-id="6211617024-1">(</span><span class="p" data-group-id="6211617024-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6211617024-2">[</span><span class="o">&lt;</span><span class="mf">0.0</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.2</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.5</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.7</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.8</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="6211617024-2">]</span></code></pre>
│ │ │ +<a href="#processes/0"><code class="inline">processes/0</code></a>.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">processes</span><span class="p" data-group-id="5187680982-1">(</span><span class="p" data-group-id="5187680982-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="5187680982-2">[</span><span class="o">&lt;</span><span class="mf">0.0</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.2</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.4</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.5</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.7</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p">,</span><span class="o">&lt;</span><span class="mf">0.8</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span><span class="p" data-group-id="5187680982-2">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="put/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#put/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -14313,18 +14313,18 @@
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Adds a new <code class="inline">Key</code> to the process dictionary, associated with the value <code class="inline">Val</code>, and
│ │ │  returns <code class="inline">undefined</code>. If <code class="inline">Key</code> exists, the old value is deleted and replaced by
│ │ │  <code class="inline">Val</code>, and the function returns the old value.</p><p>The average time complexity for the current implementation of this function is
│ │ │  O(<code class="inline">1</code>) and the worst case time complexity is O(<code class="inline">N</code>), where <code class="inline">N</code> is the number of
│ │ │ -items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">put</span><span class="p" data-group-id="8138378536-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">walrus</span><span class="p" data-group-id="8138378536-1">)</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">put</span><span class="p" data-group-id="8138378536-2">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">carpenter</span><span class="p" data-group-id="8138378536-2">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">get</span><span class="p" data-group-id="8138378536-3">(</span><span class="ss">name</span><span class="p" data-group-id="8138378536-3">)</span><span class="p">,</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8138378536-4">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="8138378536-4">}</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="8138378536-5">{</span><span class="ss">undefined</span><span class="p">,</span><span class="ss">walrus</span><span class="p">,</span><span class="ss">carpenter</span><span class="p" data-group-id="8138378536-5">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The values stored when <code class="inline">put</code> is evaluated within the scope of a <code class="inline">catch</code> are
│ │ │ +items in the process dictionary.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">X</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">put</span><span class="p" data-group-id="7479271963-1">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">walrus</span><span class="p" data-group-id="7479271963-1">)</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">put</span><span class="p" data-group-id="7479271963-2">(</span><span class="ss">name</span><span class="p">,</span><span class="w"> </span><span class="ss">carpenter</span><span class="p" data-group-id="7479271963-2">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="n">Z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nf">get</span><span class="p" data-group-id="7479271963-3">(</span><span class="ss">name</span><span class="p" data-group-id="7479271963-3">)</span><span class="p">,</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7479271963-4">{</span><span class="n">X</span><span class="p">,</span><span class="w"> </span><span class="n">Y</span><span class="p">,</span><span class="w"> </span><span class="n">Z</span><span class="p" data-group-id="7479271963-4">}</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7479271963-5">{</span><span class="ss">undefined</span><span class="p">,</span><span class="ss">walrus</span><span class="p">,</span><span class="ss">carpenter</span><span class="p" data-group-id="7479271963-5">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The values stored when <code class="inline">put</code> is evaluated within the scope of a <code class="inline">catch</code> are
│ │ │  not retracted if a <code class="inline">throw</code> is evaluated, or if an error occurs.</p></section>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="raise/3">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#raise/3" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -14395,15 +14395,15 @@
│ │ │        </div>
│ │ │  
│ │ │  <p>Registers the name <code class="inline">RegName</code> with a process identifier (pid) or a port
│ │ │  identifier in the
│ │ │  <a href="../../../doc/system/ref_man_processes.html#runtime-service"><code class="inline">name registry</code></a>.
│ │ │  <code class="inline">RegName</code>, which must be an atom, can be used instead of the pid or port
│ │ │  identifier in send operator (<code class="inline">RegName ! Message</code>) and most other BIFs that take
│ │ │ -a pid or port identifies as an argument.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">register</span><span class="p" data-group-id="3515305835-1">(</span><span class="ss">db</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="3515305835-1">)</span><span class="p">.</span><span class="w">
│ │ │ +a pid or port identifies as an argument.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">register</span><span class="p" data-group-id="2186492463-1">(</span><span class="ss">db</span><span class="p">,</span><span class="w"> </span><span class="n">Pid</span><span class="p" data-group-id="2186492463-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><p>The registered name is considered a
│ │ │  <a href="../../../doc/system/ref_man_processes.html#visible-resources">Directly Visible Erlang Resource</a>
│ │ │  and is automatically unregistered when the process terminates.</p><p>Failures:</p><ul><li><p><strong><code class="inline">badarg</code></strong> - If <code class="inline">PidOrPort</code> is not an existing local process or port.</p></li><li><p><strong><code class="inline">badarg</code></strong> - If <code class="inline">RegName</code> is already in use.</p></li><li><p><strong><code class="inline">badarg</code></strong> - If the process or port is already registered (already has a
│ │ │  name).</p></li><li><p><strong><code class="inline">badarg</code></strong> - If <code class="inline">RegName</code> is the atom <code class="inline">undefined</code>.</p></li></ul>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="registered/0">
│ │ │ @@ -14427,16 +14427,16 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> registered() -> [RegName] when RegName :: <a href="#t:atom/0">atom</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns a list of names that have been registered using <a href="#register/2"><code class="inline">register/2</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">registered</span><span class="p" data-group-id="2974295793-1">(</span><span class="p" data-group-id="2974295793-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="2974295793-2">[</span><span class="ss">code_server</span><span class="p">,</span><span class="w"> </span><span class="ss">file_server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">user</span><span class="p">,</span><span class="w"> </span><span class="ss">my_db</span><span class="p" data-group-id="2974295793-2">]</span></code></pre>
│ │ │ +<p>Returns a list of names that have been registered using <a href="#register/2"><code class="inline">register/2</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">registered</span><span class="p" data-group-id="8608529850-1">(</span><span class="p" data-group-id="8608529850-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="8608529850-2">[</span><span class="ss">code_server</span><span class="p">,</span><span class="w"> </span><span class="ss">file_server</span><span class="p">,</span><span class="w"> </span><span class="ss">init</span><span class="p">,</span><span class="w"> </span><span class="ss">user</span><span class="p">,</span><span class="w"> </span><span class="ss">my_db</span><span class="p" data-group-id="8608529850-2">]</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="resume_process/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#resume_process/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │        <i class="ri-link-m" aria-hidden="true"></i>
│ │ │ @@ -14491,15 +14491,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> self() -> <a href="#t:pid/0">pid</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns the process identifier of the calling process.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">self</span><span class="p" data-group-id="8945449543-1">(</span><span class="p" data-group-id="8945449543-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Returns the process identifier of the calling process.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">self</span><span class="p" data-group-id="8659878316-1">(</span><span class="p" data-group-id="8659878316-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.26</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="send/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#send/2" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -14741,15 +14741,15 @@
│ │ │  <p>Returns the process identifier of a new process started by the application of
│ │ │  <code class="inline">Module:Function</code> to <code class="inline">Args</code>.</p><p><a href="../../../lib/kernel-10.2.7.2/doc/html/error_handler.html"><code class="inline">error_handler:undefined_function(Module, Function, Args)</code></a> is
│ │ │   evaluated by the new process if <code class="inline">Module:Function/Arity</code> does not exist
│ │ │  (where <code class="inline">Arity</code> is the length of <code class="inline">Args</code>). The error handler can be redefined
│ │ │  (see <a href="#process_flag/2"><code class="inline">process_flag/2</code></a>). If
│ │ │  <code class="inline">error_handler</code> is undefined, or the user has redefined the default
│ │ │  <code class="inline">error_handler</code> and its replacement is undefined, a failure with reason <code class="inline">undef</code>
│ │ │ -occurs.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">spawn</span><span class="p" data-group-id="2894994330-1">(</span><span class="ss">speed</span><span class="p">,</span><span class="w"> </span><span class="ss">regulator</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="2894994330-2">[</span><span class="ss">high_speed</span><span class="p">,</span><span class="w"> </span><span class="ss">thin_cut</span><span class="p" data-group-id="2894994330-2">]</span><span class="p" data-group-id="2894994330-1">)</span><span class="p">.</span><span class="w">
│ │ │ +occurs.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">spawn</span><span class="p" data-group-id="5658299314-1">(</span><span class="ss">speed</span><span class="p">,</span><span class="w"> </span><span class="ss">regulator</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="5658299314-2">[</span><span class="ss">high_speed</span><span class="p">,</span><span class="w"> </span><span class="ss">thin_cut</span><span class="p" data-group-id="5658299314-2">]</span><span class="p" data-group-id="5658299314-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.13</span><span class="p">.</span><span class="mi">1</span><span class="o">&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="spawn/4">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#spawn/4" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -15689,22 +15689,22 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> throw(Any) -> <a href="#t:no_return/0">no_return</a>() when Any :: <a href="#t:term/0">term</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Raises an exception of class <code class="inline">throw</code>. Intended to be used to do non-local
│ │ │  returns from functions.</p><p>If evaluated within a <a href="../../../doc/system/expressions.html#catch-and-throw">catch expression</a>, the
│ │ │ -catch expression returns value <code class="inline">Any</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="3354981193-1">(</span><span class="p" data-group-id="3354981193-2">{</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">there</span><span class="p" data-group-id="3354981193-2">}</span><span class="p" data-group-id="3354981193-1">)</span><span class="p">.</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="3354981193-3">{</span><span class="ss">hello</span><span class="p">,</span><span class="ss">there</span><span class="p" data-group-id="3354981193-3">}</span></code></pre><p>If evaluated within a <code class="inline">try</code>-block of a
│ │ │ +catch expression returns value <code class="inline">Any</code>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="k">catch</span><span class="w"> </span><span class="nf">throw</span><span class="p" data-group-id="1346294944-1">(</span><span class="p" data-group-id="1346294944-2">{</span><span class="ss">hello</span><span class="p">,</span><span class="w"> </span><span class="ss">there</span><span class="p" data-group-id="1346294944-2">}</span><span class="p" data-group-id="1346294944-1">)</span><span class="p">.</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="1346294944-3">{</span><span class="ss">hello</span><span class="p">,</span><span class="ss">there</span><span class="p" data-group-id="1346294944-3">}</span></code></pre><p>If evaluated within a <code class="inline">try</code>-block of a
│ │ │  <a href="../../../doc/system/expressions.html#try">try expression</a>, the value <code class="inline">Any</code> can be caught
│ │ │  within the catch block.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="k">try</span><span class="w">
│ │ │ -    </span><span class="nf">throw</span><span class="p" data-group-id="4603705099-1">(</span><span class="p" data-group-id="4603705099-2">{</span><span class="ss">my_exception</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Something happened&quot;</span><span class="p" data-group-id="4603705099-2">}</span><span class="p" data-group-id="4603705099-1">)</span><span class="w">
│ │ │ +    </span><span class="nf">throw</span><span class="p" data-group-id="7250734471-1">(</span><span class="p" data-group-id="7250734471-2">{</span><span class="ss">my_exception</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Something happened&quot;</span><span class="p" data-group-id="7250734471-2">}</span><span class="p" data-group-id="7250734471-1">)</span><span class="w">
│ │ │  </span><span class="k">catch</span><span class="w">
│ │ │ -    </span><span class="nc">throw</span><span class="p">:</span><span class="p" data-group-id="4603705099-3">{</span><span class="ss">my_exception</span><span class="p">,</span><span class="w"> </span><span class="n">Desc</span><span class="p" data-group-id="4603705099-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="4603705099-4">(</span><span class="ss">standard_error</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Error: </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4603705099-5">[</span><span class="n">Desc</span><span class="p" data-group-id="4603705099-5">]</span><span class="p" data-group-id="4603705099-4">)</span><span class="w">
│ │ │ +    </span><span class="nc">throw</span><span class="p">:</span><span class="p" data-group-id="7250734471-3">{</span><span class="ss">my_exception</span><span class="p">,</span><span class="w"> </span><span class="n">Desc</span><span class="p" data-group-id="7250734471-3">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="nc">io</span><span class="p">:</span><span class="nf">format</span><span class="p" data-group-id="7250734471-4">(</span><span class="ss">standard_error</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;Error: </span><span class="si">~s</span><span class="si">~n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7250734471-5">[</span><span class="n">Desc</span><span class="p" data-group-id="7250734471-5">]</span><span class="p" data-group-id="7250734471-4">)</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>Failure: <code class="inline">nocatch</code> if not caught by an exception handler.</p><p>See the guide about <a href="../../../doc/system/errors.html">errors and error handling</a> for
│ │ │  additional information.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="unalias/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -15774,17 +15774,17 @@
│ │ │  <a href="#process_flag_trap_exit">trapping exits</a>, an
│ │ │  <code class="inline">{'EXIT', Id, ExitReason}</code> message due to the link may have been placed in the
│ │ │  message queue of the caller before the <a href="#unlink/1"><code class="inline">unlink(Id)</code></a> call
│ │ │  completed. Also note that the <code class="inline">{'EXIT', Id, ExitReason}</code> message may be the
│ │ │  result of the link, but may also be the result of the unlikee sending the caller
│ │ │  an exit signal by calling the <a href="#exit/2"><code class="inline">exit/2</code></a> BIF. Therefore, it may or may not be
│ │ │  appropriate to clean up the message queue after a call to
│ │ │ -<a href="#unlink/1"><code class="inline">unlink(Id)</code></a> as follows, when trapping exits:</p><pre><code class="makeup erlang" translate="no"><span class="nf">unlink</span><span class="p" data-group-id="2152267351-1">(</span><span class="n">Id</span><span class="p" data-group-id="2152267351-1">)</span><span class="p">,</span><span class="w">
│ │ │ +<a href="#unlink/1"><code class="inline">unlink(Id)</code></a> as follows, when trapping exits:</p><pre><code class="makeup erlang" translate="no"><span class="nf">unlink</span><span class="p" data-group-id="5268493673-1">(</span><span class="n">Id</span><span class="p" data-group-id="5268493673-1">)</span><span class="p">,</span><span class="w">
│ │ │  </span><span class="k">receive</span><span class="w">
│ │ │ -    </span><span class="p" data-group-id="2152267351-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="2152267351-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +    </span><span class="p" data-group-id="5268493673-2">{</span><span class="ss">&#39;EXIT&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">Id</span><span class="p">,</span><span class="w"> </span><span class="p">_</span><span class="p" data-group-id="5268493673-2">}</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="k">after</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │          </span><span class="ss">true</span><span class="w">
│ │ │  </span><span class="k">end</span></code></pre><p>The link removal is performed asynchronously. If such a link does not exist,
│ │ │  nothing is done. A detailed description of the
│ │ │  <a href="erl_dist_protocol.html#link_protocol">link protocol</a> can be found in the
│ │ │  <em>Distribution Protocol</em> chapter of the <em>ERTS User's Guide</em>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>For some important information about distributed signals, see the
│ │ │ @@ -15815,15 +15815,15 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> unregister(RegName) -> true when RegName :: <a href="#t:atom/0">atom</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Removes the <a href="#register/2"><code class="inline">registered name</code></a> <code class="inline">RegName</code> associated with a
│ │ │  process identifier or a port identifier from the
│ │ │ -<a href="../../../doc/system/ref_man_processes.html#runtime-service"><code class="inline">name registry</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">unregister</span><span class="p" data-group-id="9461324400-1">(</span><span class="ss">db</span><span class="p" data-group-id="9461324400-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<a href="../../../doc/system/ref_man_processes.html#runtime-service"><code class="inline">name registry</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">unregister</span><span class="p" data-group-id="3304041405-1">(</span><span class="ss">db</span><span class="p" data-group-id="3304041405-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">true</span></code></pre><p>Keep in mind that you can still receive signals associated with the registered
│ │ │  name after it has been unregistered as the sender may have looked up the name
│ │ │  before sending to it.</p><p>Users are advised not to unregister system processes.</p><p>Failure: <code class="inline">badarg</code> if <code class="inline">RegName</code> is not a registered name.</p>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="whereis/1">
│ │ │  
│ │ │ @@ -15849,15 +15849,15 @@
│ │ │            <pre translate="no"><span class="attribute">-spec</span> whereis(RegName) -> <a href="#t:pid/0">pid</a>() | <a href="#t:port/0">port</a>() | undefined when RegName :: <a href="#t:atom/0">atom</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │  <p>Returns the process identifier or port identifier with the
│ │ │  <a href="#register/2"><code class="inline">registered name</code></a> <code class="inline">RegName</code> from the
│ │ │  <a href="../../../doc/system/ref_man_processes.html#runtime-service"><code class="inline">name registry</code></a>. Returns
│ │ │ -<code class="inline">undefined</code> if the name is not registered.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">whereis</span><span class="p" data-group-id="9180393837-1">(</span><span class="ss">db</span><span class="p" data-group-id="9180393837-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">undefined</code> if the name is not registered.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">whereis</span><span class="p" data-group-id="8837705516-1">(</span><span class="ss">db</span><span class="p" data-group-id="8837705516-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="o">&lt;</span><span class="mf">0.43</span><span class="p">.</span><span class="mi">0</span><span class="o">&gt;</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="yield/0">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#yield/0" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -15924,15 +15924,15 @@
│ │ │  
│ │ │        <div class="specs">
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> halt() -> <a href="#t:no_return/0">no_return</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Equivalent to calling <a href="#halt/2"><code class="inline">halt(0, [])</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">halt</span><span class="p" data-group-id="2416002050-1">(</span><span class="p" data-group-id="2416002050-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Equivalent to calling <a href="#halt/2"><code class="inline">halt(0, [])</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">halt</span><span class="p" data-group-id="7386463919-1">(</span><span class="p" data-group-id="7386463919-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">os_prompt</span><span class="c1">%</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="halt/1">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │      <a href="#halt/1" class="detail-link" data-no-tooltip aria-label="Link to this function">
│ │ │ @@ -15955,15 +15955,15 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> halt(Status :: <a href="#t:non_neg_integer/0">non_neg_integer</a>()) -> <a href="#t:no_return/0">no_return</a>();
│ │ │            (Abort :: abort) -> <a href="#t:no_return/0">no_return</a>();
│ │ │            (CrashDumpSlogan :: <a href="#t:string/0">string</a>()) -> <a href="#t:no_return/0">no_return</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Equivalent to calling <a href="#halt/2"><code class="inline">halt(HaltType, [])</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">halt</span><span class="p" data-group-id="1926003684-1">(</span><span class="mi">17</span><span class="p" data-group-id="1926003684-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<p>Equivalent to calling <a href="#halt/2"><code class="inline">halt(HaltType, [])</code></a>.</p><p>For example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">halt</span><span class="p" data-group-id="5467323700-1">(</span><span class="mi">17</span><span class="p" data-group-id="5467323700-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">os_prompt</span><span class="c1">% echo $?</span><span class="w">
│ │ │  </span><span class="mi">17</span><span class="w">
│ │ │  </span><span class="ss">os_prompt</span><span class="c1">%</span></code></pre>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="halt/2">
│ │ │  
│ │ │ @@ -15990,15 +15990,15 @@
│ │ │  
│ │ │            <pre translate="no"><span class="attribute">-spec</span> halt(Status :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(), Options :: <a href="#t:halt_options/0">halt_options</a>()) -> <a href="#t:no_return/0">no_return</a>();
│ │ │            (Abort :: abort, Options :: <a href="#t:halt_options/0">halt_options</a>()) -> <a href="#t:no_return/0">no_return</a>();
│ │ │            (CrashDumpSlogan :: <a href="#t:string/0">string</a>(), Options :: <a href="#t:halt_options/0">halt_options</a>()) -> <a href="#t:no_return/0">no_return</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Halt the runtime system.</p><ul><li><pre id="halt_status_2"><code class="makeup erlang" translate="no"><span class="nf">halt</span><span class="p" data-group-id="9737230555-1">(</span><span class="n">Status</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="9737230555-2">(</span><span class="p" data-group-id="9737230555-2">)</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">halt_options</span><span class="p" data-group-id="9737230555-3">(</span><span class="p" data-group-id="9737230555-3">)</span><span class="p" data-group-id="9737230555-1">)</span></code></pre><p>Halt the runtime system with status code <code class="inline">Status</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>On many platforms, the OS supports only status codes 0-255. A too large
│ │ │ +<p>Halt the runtime system.</p><ul><li><pre id="halt_status_2"><code class="makeup erlang" translate="no"><span class="nf">halt</span><span class="p" data-group-id="3971455739-1">(</span><span class="n">Status</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3971455739-2">(</span><span class="p" data-group-id="3971455739-2">)</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">halt_options</span><span class="p" data-group-id="3971455739-3">(</span><span class="p" data-group-id="3971455739-3">)</span><span class="p" data-group-id="3971455739-1">)</span></code></pre><p>Halt the runtime system with status code <code class="inline">Status</code>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>On many platforms, the OS supports only status codes 0-255. A too large
│ │ │  status code is truncated by clearing the high bits.</p></section><p>Currently the following options are valid:</p><ul><li><p><strong><code class="inline" id="halt_flush">{flush, EnableFlushing}</code></strong> - If <code class="inline">EnableFlushing</code> equals
│ │ │  <code class="inline">true</code>, which also is the default behavior, the runtime system will perform
│ │ │  the following operations before terminating:</p><ul><li>Flush all outstanding output.</li><li>Send all Erlang ports exit signals and wait for them to exit.</li><li>Wait for all async threads to complete all outstanding async jobs.</li><li>Call all installed <a href="erl_nif.html#on_halt">NIF <em>on halt</em> callbacks</a>.</li><li>Wait for all ongoing
│ │ │  <a href="erl_nif.html#delay_halt">NIF calls with the <em>delay halt</em> setting</a> enabled
│ │ │  to return.</li><li>Call all installed <code class="inline">atexit</code>/<code class="inline">on_exit</code> callbacks.</li></ul><p>If <code class="inline">EnableFlushing</code> equals <code class="inline">false</code>, the runtime system will terminate
│ │ │  immediately without performing any of the above listed operations.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Runtime systems prior to OTP 26.0 called all installed <code class="inline">atexit</code>/<code class="inline">on_exit</code>
│ │ │  callbacks also when <code class="inline">flush</code> was disabled, but as of OTP 26.0 this is no
│ │ │ @@ -16007,18 +16007,18 @@
│ │ │  termination of the runtime system. <code class="inline">Timeout</code> is in milliseconds. The default
│ │ │  value is determined by the the <code class="inline">erl</code> <a href="erl_cmd.html#+zhft"><code class="inline">+zhft &lt;Timeout&gt;</code></a>
│ │ │  command line flag.</p><p>If flushing has been ongoing for <code class="inline">Timeout</code> milliseconds, flushing operations
│ │ │  will be interrupted and the runtime system will immediately be terminated
│ │ │  with the exit code <code class="inline">255</code>. If flushing is not enabled, the timeout will have
│ │ │  no effect on the system.</p><p>See also the <code class="inline">erl</code> <a href="erl_cmd.html#+zhft"><code class="inline">+zhft &lt;Timeout&gt;</code></a> command line flag.
│ │ │  Note that the shortest timeout set by the command line flag and the
│ │ │ -<code class="inline">flush_timeout</code> option will be the actual timeout value in effect.</p><p>Since: OTP 27.0</p></li></ul></li><li><pre id="halt_abort_2"><code class="makeup erlang" translate="no"><span class="nf">halt</span><span class="p" data-group-id="0563644861-1">(</span><span class="n">Abort</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">halt_options</span><span class="p" data-group-id="0563644861-2">(</span><span class="p" data-group-id="0563644861-2">)</span><span class="p" data-group-id="0563644861-1">)</span></code></pre><p>Halt the Erlang runtime system by aborting and produce a core dump if core
│ │ │ +<code class="inline">flush_timeout</code> option will be the actual timeout value in effect.</p><p>Since: OTP 27.0</p></li></ul></li><li><pre id="halt_abort_2"><code class="makeup erlang" translate="no"><span class="nf">halt</span><span class="p" data-group-id="9981259225-1">(</span><span class="n">Abort</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">abort</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">halt_options</span><span class="p" data-group-id="9981259225-2">(</span><span class="p" data-group-id="9981259225-2">)</span><span class="p" data-group-id="9981259225-1">)</span></code></pre><p>Halt the Erlang runtime system by aborting and produce a core dump if core
│ │ │  dumping has been enabled in the environment that the runtime system is
│ │ │  executing in.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The <a href="#halt_flush"><code class="inline">{flush, boolean()}</code></a> option will be ignored, and
│ │ │ -flushing will be disabled.</p></section></li><li><pre id="halt_crash_dump_2"><code class="makeup erlang" translate="no"><span class="nf">halt</span><span class="p" data-group-id="1685037934-1">(</span><span class="n">CrashDumpSlogan</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="1685037934-2">(</span><span class="p" data-group-id="1685037934-2">)</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">halt_options</span><span class="p" data-group-id="1685037934-3">(</span><span class="p" data-group-id="1685037934-3">)</span><span class="p" data-group-id="1685037934-1">)</span></code></pre><p>Halt the Erlang runtime system and generate an
│ │ │ +flushing will be disabled.</p></section></li><li><pre id="halt_crash_dump_2"><code class="makeup erlang" translate="no"><span class="nf">halt</span><span class="p" data-group-id="0337108656-1">(</span><span class="n">CrashDumpSlogan</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">string</span><span class="p" data-group-id="0337108656-2">(</span><span class="p" data-group-id="0337108656-2">)</span><span class="p">,</span><span class="w"> </span><span class="n">Options</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">halt_options</span><span class="p" data-group-id="0337108656-3">(</span><span class="p" data-group-id="0337108656-3">)</span><span class="p" data-group-id="0337108656-1">)</span></code></pre><p>Halt the Erlang runtime system and generate an
│ │ │  <a href="crash_dump.html">Erlang crash dump</a>. The string <code class="inline">CrashDumpSlogan</code> will be used
│ │ │  as slogan in the Erlang crash dump created. The slogan will be trunkated if
│ │ │  <code class="inline">CrashDumpSlogan</code> is longer than 1023 characters.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The <a href="#halt_flush"><code class="inline">{flush, boolean()}</code></a> option will be ignored, and
│ │ │  flushing will be disabled.</p></section><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>Behavior changes compared to earlier versions:</p><ul><li>Before OTP 24.2, the slogan was truncated if <code class="inline">CrashDumpSlogan</code> was longer
│ │ │  than 200 characters. Now it will be truncated if longer than 1023
│ │ │  characters.</li><li>Before OTP 20.1, only code points in the range 0-255 were accepted in the
│ │ │  slogan. Now any Unicode string is valid.</li></ul></section></li></ul>
│ │ │ @@ -16195,19 +16195,19 @@
│ │ │                  (wall_clock) -> {Total_Wallclock_Time, Wallclock_Time_Since_Last_Call}
│ │ │                      when
│ │ │                          Total_Wallclock_Time :: <a href="#t:non_neg_integer/0">non_neg_integer</a>(),
│ │ │                          Wallclock_Time_Since_Last_Call :: <a href="#t:non_neg_integer/0">non_neg_integer</a>().</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Returns statistics about the current system.</p><p>The possible flags are:</p><ul><li><pre id="statistics_active_tasks"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="7775841603-1">(</span><span class="ss">active_tasks</span><span class="p" data-group-id="7775841603-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7775841603-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="7775841603-3">(</span><span class="p" data-group-id="7775841603-3">)</span><span class="p" data-group-id="7775841603-2">]</span></code></pre><p>Returns the same as
│ │ │ +<p>Returns statistics about the current system.</p><p>The possible flags are:</p><ul><li><pre id="statistics_active_tasks"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="4730428289-1">(</span><span class="ss">active_tasks</span><span class="p" data-group-id="4730428289-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4730428289-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="4730428289-3">(</span><span class="p" data-group-id="4730428289-3">)</span><span class="p" data-group-id="4730428289-2">]</span></code></pre><p>Returns the same as
│ │ │  <a href="#statistics_active_tasks_all"><code class="inline">statistics(active_tasks_all)</code></a> with
│ │ │  the exception that no information about the dirty IO run queue and its
│ │ │  associated schedulers is part of the result. That is, only tasks that are
│ │ │ -expected to be CPU bound are part of the result.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_active_tasks_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="5445026074-1">(</span><span class="ss">active_tasks_all</span><span class="p" data-group-id="5445026074-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5445026074-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="5445026074-3">(</span><span class="p" data-group-id="5445026074-3">)</span><span class="p" data-group-id="5445026074-2">]</span></code></pre><p>Returns a list where each element represents the amount of active processes and
│ │ │ +expected to be CPU bound are part of the result.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_active_tasks_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="9959421048-1">(</span><span class="ss">active_tasks_all</span><span class="p" data-group-id="9959421048-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="9959421048-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="9959421048-3">(</span><span class="p" data-group-id="9959421048-3">)</span><span class="p" data-group-id="9959421048-2">]</span></code></pre><p>Returns a list where each element represents the amount of active processes and
│ │ │  ports on each run queue and its associated schedulers. That is, the number of
│ │ │  processes and ports that are ready to run, or are currently running. Values for
│ │ │  normal run queues and their associated schedulers are located first in the
│ │ │  resulting list. The first element corresponds to scheduler number 1 and so on.
│ │ │  If support for dirty schedulers exist, an element with the value for the dirty
│ │ │  CPU run queue and its associated dirty CPU schedulers follow and then as last
│ │ │  element the value for the dirty IO run queue and its associated dirty IO
│ │ │ @@ -16221,44 +16221,44 @@
│ │ │  migrate to other normal run queues. This has to be taken into account when
│ │ │  evaluating the result.</p></section><p>See also
│ │ │  <a href="#statistics_total_active_tasks"><code class="inline">statistics(total_active_tasks)</code></a>,
│ │ │  <a href="#statistics_run_queue_lengths"><code class="inline">statistics(run_queue_lengths)</code></a>,
│ │ │  <a href="#statistics_run_queue_lengths_all"><code class="inline">statistics(run_queue_lengths_all)</code></a>,
│ │ │  <a href="#statistics_total_run_queue_lengths"><code class="inline">statistics(total_run_queue_lengths)</code></a>,
│ │ │  and
│ │ │ -<a href="#statistics_total_run_queue_lengths_all"><code class="inline">statistics(total_run_queue_lengths_all)</code></a>.</p><p>Available since OTP 20.0</p></li><li><pre id="statistics_context_switches"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="5642036237-1">(</span><span class="ss">context_switches</span><span class="p" data-group-id="5642036237-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5642036237-2">{</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="5642036237-3">(</span><span class="p" data-group-id="5642036237-3">)</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5642036237-2">}</span></code></pre><p>Returns the total number of context switches since the system started.</p></li><li><pre id="statistics_exact_reductions"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="0603886908-1">(</span><span class="ss">exact_reductions</span><span class="p" data-group-id="0603886908-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0603886908-2">{</span><span class="n">Total</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0603886908-3">(</span><span class="p" data-group-id="0603886908-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0603886908-4">(</span><span class="p" data-group-id="0603886908-4">)</span><span class="p" data-group-id="0603886908-2">}</span></code></pre><p>Returns the number of exact reductions.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p><a href="#statistics/1"><code class="inline">statistics(exact_reductions)</code></a> is a more expensive operation
│ │ │ -than <a href="#statistics_reductions">statistics(reductions)</a>.</p></section></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="8011438639-1">(</span><span class="ss">garbage_collection</span><span class="p" data-group-id="8011438639-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8011438639-2">{</span><span class="w"> </span><span class="n">NumerOfGCs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8011438639-3">(</span><span class="p" data-group-id="8011438639-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">WordsReclaimed</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8011438639-4">(</span><span class="p" data-group-id="8011438639-4">)</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8011438639-2">}</span></code></pre><p>Returns information about garbage collection, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">statistics</span><span class="p" data-group-id="6413927270-1">(</span><span class="ss">garbage_collection</span><span class="p" data-group-id="6413927270-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="6413927270-2">{</span><span class="mi">85</span><span class="p">,</span><span class="mi">23961</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="6413927270-2">}</span></code></pre><p>This information can be invalid for some implementations.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3322785621-1">(</span><span class="ss">io</span><span class="p" data-group-id="3322785621-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3322785621-2">{</span><span class="p" data-group-id="3322785621-3">{</span><span class="ss">input</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3322785621-4">(</span><span class="p" data-group-id="3322785621-4">)</span><span class="p" data-group-id="3322785621-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3322785621-5">{</span><span class="ss">output</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3322785621-6">(</span><span class="p" data-group-id="3322785621-6">)</span><span class="p" data-group-id="3322785621-5">}</span><span class="p" data-group-id="3322785621-2">}</span></code></pre><p>Returns <code class="inline">Input</code>, which is the total number of bytes received through ports, and
│ │ │ -<code class="inline">Output</code>, which is the total number of bytes output to ports.</p></li><li><pre id="statistics_microstate_accounting"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="5406256153-1">(</span><span class="ss">microstate_accounting</span><span class="p" data-group-id="5406256153-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5406256153-2">[</span><span class="n">MSAcc_Thread</span><span class="p" data-group-id="5406256153-2">]</span></code></pre><p>Microstate accounting can be used to measure how much time the Erlang runtime
│ │ │ +<a href="#statistics_total_run_queue_lengths_all"><code class="inline">statistics(total_run_queue_lengths_all)</code></a>.</p><p>Available since OTP 20.0</p></li><li><pre id="statistics_context_switches"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="5242166434-1">(</span><span class="ss">context_switches</span><span class="p" data-group-id="5242166434-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="5242166434-2">{</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="5242166434-3">(</span><span class="p" data-group-id="5242166434-3">)</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="5242166434-2">}</span></code></pre><p>Returns the total number of context switches since the system started.</p></li><li><pre id="statistics_exact_reductions"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3905689530-1">(</span><span class="ss">exact_reductions</span><span class="p" data-group-id="3905689530-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3905689530-2">{</span><span class="n">Total</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3905689530-3">(</span><span class="p" data-group-id="3905689530-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3905689530-4">(</span><span class="p" data-group-id="3905689530-4">)</span><span class="p" data-group-id="3905689530-2">}</span></code></pre><p>Returns the number of exact reductions.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p><a href="#statistics/1"><code class="inline">statistics(exact_reductions)</code></a> is a more expensive operation
│ │ │ +than <a href="#statistics_reductions">statistics(reductions)</a>.</p></section></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3945900387-1">(</span><span class="ss">garbage_collection</span><span class="p" data-group-id="3945900387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="3945900387-2">{</span><span class="w"> </span><span class="n">NumerOfGCs</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3945900387-3">(</span><span class="p" data-group-id="3945900387-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">WordsReclaimed</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3945900387-4">(</span><span class="p" data-group-id="3945900387-4">)</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="3945900387-2">}</span></code></pre><p>Returns information about garbage collection, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">statistics</span><span class="p" data-group-id="2718439539-1">(</span><span class="ss">garbage_collection</span><span class="p" data-group-id="2718439539-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="2718439539-2">{</span><span class="mi">85</span><span class="p">,</span><span class="mi">23961</span><span class="p">,</span><span class="mi">0</span><span class="p" data-group-id="2718439539-2">}</span></code></pre><p>This information can be invalid for some implementations.</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="4826900713-1">(</span><span class="ss">io</span><span class="p" data-group-id="4826900713-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="4826900713-2">{</span><span class="p" data-group-id="4826900713-3">{</span><span class="ss">input</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="4826900713-4">(</span><span class="p" data-group-id="4826900713-4">)</span><span class="p" data-group-id="4826900713-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="4826900713-5">{</span><span class="ss">output</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="4826900713-6">(</span><span class="p" data-group-id="4826900713-6">)</span><span class="p" data-group-id="4826900713-5">}</span><span class="p" data-group-id="4826900713-2">}</span></code></pre><p>Returns <code class="inline">Input</code>, which is the total number of bytes received through ports, and
│ │ │ +<code class="inline">Output</code>, which is the total number of bytes output to ports.</p></li><li><pre id="statistics_microstate_accounting"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3347099804-1">(</span><span class="ss">microstate_accounting</span><span class="p" data-group-id="3347099804-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3347099804-2">[</span><span class="n">MSAcc_Thread</span><span class="p" data-group-id="3347099804-2">]</span></code></pre><p>Microstate accounting can be used to measure how much time the Erlang runtime
│ │ │  system spends doing various tasks. It is designed to be as lightweight as
│ │ │  possible, but some overhead exists when this is enabled. Microstate accounting
│ │ │  is meant to be a profiling tool to help finding performance bottlenecks. To
│ │ │  <code class="inline">start</code>/<code class="inline">stop</code>/<code class="inline">reset</code> microstate accounting, use system flag
│ │ │  <a href="#system_flag_microstate_accounting"><code class="inline">microstate_accounting</code></a>.</p><p><a href="#statistics/1"><code class="inline">statistics(microstate_accounting)</code></a> returns a list of maps
│ │ │  representing some of the OS threads within ERTS. Each map contains <code class="inline">type</code> and
│ │ │  <code class="inline">id</code> fields that can be used to identify what thread it is, and also a counters
│ │ │  field that contains data about how much time has been spent in the various
│ │ │ -states.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4290781409-1">(</span><span class="ss">microstate_accounting</span><span class="p" data-group-id="4290781409-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4290781409-2">[</span><span class="p" data-group-id="4290781409-3">#{</span><span class="ss">counters</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="4290781409-4">#{</span><span class="ss">aux</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1899182914</span><span class="p">,</span><span class="w">
│ │ │ +states.</p><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="6560462081-1">(</span><span class="ss">microstate_accounting</span><span class="p" data-group-id="6560462081-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="6560462081-2">[</span><span class="p" data-group-id="6560462081-3">#{</span><span class="ss">counters</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="p" data-group-id="6560462081-4">#{</span><span class="ss">aux</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1899182914</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">check_io</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">2605863602</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">emulator</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">45731880463</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">gc</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1512206910</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">other</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5421338456</span><span class="p">,</span><span class="w">
│ │ │                   </span><span class="ss">port</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">221631</span><span class="p">,</span><span class="w">
│ │ │ -                 </span><span class="ss">sleep</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5150294100</span><span class="p" data-group-id="4290781409-4">}</span><span class="p">,</span><span class="w">
│ │ │ +                 </span><span class="ss">sleep</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">5150294100</span><span class="p" data-group-id="6560462081-4">}</span><span class="p">,</span><span class="w">
│ │ │     </span><span class="ss">id</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w">
│ │ │ -   </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">scheduler</span><span class="p" data-group-id="4290781409-3">}</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="4290781409-2">]</span></code></pre><p>The time unit is the same as returned by <a href="../../../lib/kernel-10.2.7.2/doc/html/os.html#perf_counter/0"><code class="inline">os:perf_counter/0</code></a>. So, to convert it
│ │ │ -to milliseconds, you can do something like this:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3843196325-1">(</span><span class="w">
│ │ │ -  </span><span class="nf">fun</span><span class="p" data-group-id="3843196325-2">(</span><span class="p" data-group-id="3843196325-3">#{</span><span class="w"> </span><span class="ss">counters</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Cnt</span><span class="w"> </span><span class="p" data-group-id="3843196325-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="3843196325-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -         </span><span class="n">MsCnt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="3843196325-4">(</span><span class="nf">fun</span><span class="p" data-group-id="3843196325-5">(</span><span class="p">_</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">PerfCount</span><span class="p" data-group-id="3843196325-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -                                    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">convert_time_unit</span><span class="p" data-group-id="3843196325-6">(</span><span class="n">PerfCount</span><span class="p">,</span><span class="w"> </span><span class="ss">perf_counter</span><span class="p">,</span><span class="w"> </span><span class="mi">1000</span><span class="p" data-group-id="3843196325-6">)</span><span class="w">
│ │ │ -                           </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Cnt</span><span class="p" data-group-id="3843196325-4">)</span><span class="p">,</span><span class="w">
│ │ │ -         </span><span class="n">M</span><span class="p" data-group-id="3843196325-7">#{</span><span class="w"> </span><span class="ss">counters</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">MsCnt</span><span class="w"> </span><span class="p" data-group-id="3843196325-7">}</span><span class="w">
│ │ │ -  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3843196325-8">(</span><span class="ss">microstate_accounting</span><span class="p" data-group-id="3843196325-8">)</span><span class="p" data-group-id="3843196325-1">)</span><span class="p">.</span></code></pre><p>Notice that these values are not guaranteed to be the exact time spent in each
│ │ │ +   </span><span class="ss">type</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"> </span><span class="ss">scheduler</span><span class="p" data-group-id="6560462081-3">}</span><span class="p">|</span><span class="p">.</span><span class="p">.</span><span class="p">.</span><span class="p" data-group-id="6560462081-2">]</span></code></pre><p>The time unit is the same as returned by <a href="../../../lib/kernel-10.2.7.2/doc/html/os.html#perf_counter/0"><code class="inline">os:perf_counter/0</code></a>. So, to convert it
│ │ │ +to milliseconds, you can do something like this:</p><pre><code class="makeup erlang" translate="no"><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9899684627-1">(</span><span class="w">
│ │ │ +  </span><span class="nf">fun</span><span class="p" data-group-id="9899684627-2">(</span><span class="p" data-group-id="9899684627-3">#{</span><span class="w"> </span><span class="ss">counters</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">Cnt</span><span class="w"> </span><span class="p" data-group-id="9899684627-3">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">M</span><span class="p" data-group-id="9899684627-2">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +         </span><span class="n">MsCnt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">maps</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="9899684627-4">(</span><span class="nf">fun</span><span class="p" data-group-id="9899684627-5">(</span><span class="p">_</span><span class="n">K</span><span class="p">,</span><span class="w"> </span><span class="n">PerfCount</span><span class="p" data-group-id="9899684627-5">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +                                    </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">convert_time_unit</span><span class="p" data-group-id="9899684627-6">(</span><span class="n">PerfCount</span><span class="p">,</span><span class="w"> </span><span class="ss">perf_counter</span><span class="p">,</span><span class="w"> </span><span class="mi">1000</span><span class="p" data-group-id="9899684627-6">)</span><span class="w">
│ │ │ +                           </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="n">Cnt</span><span class="p" data-group-id="9899684627-4">)</span><span class="p">,</span><span class="w">
│ │ │ +         </span><span class="n">M</span><span class="p" data-group-id="9899684627-7">#{</span><span class="w"> </span><span class="ss">counters</span><span class="w"> </span><span class="p">:=</span><span class="w"> </span><span class="n">MsCnt</span><span class="w"> </span><span class="p" data-group-id="9899684627-7">}</span><span class="w">
│ │ │ +  </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="9899684627-8">(</span><span class="ss">microstate_accounting</span><span class="p" data-group-id="9899684627-8">)</span><span class="p" data-group-id="9899684627-1">)</span><span class="p">.</span></code></pre><p>Notice that these values are not guaranteed to be the exact time spent in each
│ │ │  state. This is because of various optimisation done to keep the overhead as
│ │ │  small as possible.</p><p><code class="inline">MSAcc_Thread_Type</code>s:</p><ul><li><p><strong><code class="inline">scheduler</code></strong> - The main execution threads that do most of the work. See
│ │ │  <a href="erl_cmd.html#%2BS">erl +S</a> for more details.</p></li><li><p><strong><code class="inline">dirty_cpu_scheduler</code></strong> - The threads for long running cpu intensive work.
│ │ │  See <a href="erl_cmd.html#%2BSDcpu">erl +SDcpu</a> for more details.</p></li><li><p><strong><code class="inline">dirty_io_scheduler</code></strong> - The threads for long running I/O work. See
│ │ │  <a href="erl_cmd.html#%2BSDio">erl +SDio</a> for more details.</p></li><li><p><strong><code class="inline">async</code></strong> - Async threads are used by various linked-in drivers (mainly the
│ │ │  file drivers) do offload non-CPU intensive work. See
│ │ │  <a href="erl_cmd.html#async_thread_pool_size">erl +A</a> for more details.</p></li><li><p><strong><code class="inline">aux</code></strong> - Takes care of any work that is not specifically assigned to a
│ │ │ @@ -16282,28 +16282,28 @@
│ │ │  states this time is part of the <code class="inline">gc</code> state.</p></li><li><p><strong><code class="inline">nif</code></strong> - Time spent in NIFs. Without extra states this time is part of the
│ │ │  <code class="inline">emulator</code> state.</p></li><li><p><strong><code class="inline">send</code></strong> - Time spent sending messages (processes only). Without extra
│ │ │  states this time is part of the <code class="inline">emulator</code> state.</p></li><li><p><strong><code class="inline">timers</code></strong> - Time spent managing timers. Without extra states this time is
│ │ │  part of the <code class="inline">other</code> state.</p></li></ul><p>The utility module <a href="../../../lib/runtime_tools-2.1.1/doc/html/msacc.html"><code class="inline">msacc</code></a> can be used to more easily analyse these
│ │ │  statistics.</p><p>Returns <code class="inline">undefined</code> if system flag
│ │ │  <a href="#system_flag_microstate_accounting"><code class="inline">microstate_accounting</code></a> is
│ │ │  turned off.</p><p>The list of thread information is unsorted and can appear in different order
│ │ │ -between calls.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The threads and states are subject to change without any prior notice.</p></section><p>Available since OTP 19.0</p></li><li><pre id="statistics_reductions"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="1341611941-1">(</span><span class="ss">reductions</span><span class="p" data-group-id="1341611941-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1341611941-2">{</span><span class="n">Reductions</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1341611941-3">(</span><span class="p" data-group-id="1341611941-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1341611941-4">(</span><span class="p" data-group-id="1341611941-4">)</span><span class="p" data-group-id="1341611941-2">}</span></code></pre><p>Returns information about reductions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">statistics</span><span class="p" data-group-id="9575861781-1">(</span><span class="ss">reductions</span><span class="p" data-group-id="9575861781-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="9575861781-2">{</span><span class="mi">2046</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="9575861781-2">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>As from ERTS 5.5 (Erlang/OTP R11B), this value does not include reductions
│ │ │ +between calls.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The threads and states are subject to change without any prior notice.</p></section><p>Available since OTP 19.0</p></li><li><pre id="statistics_reductions"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="0762055837-1">(</span><span class="ss">reductions</span><span class="p" data-group-id="0762055837-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0762055837-2">{</span><span class="n">Reductions</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0762055837-3">(</span><span class="p" data-group-id="0762055837-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0762055837-4">(</span><span class="p" data-group-id="0762055837-4">)</span><span class="p" data-group-id="0762055837-2">}</span></code></pre><p>Returns information about reductions, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">statistics</span><span class="p" data-group-id="0196619602-1">(</span><span class="ss">reductions</span><span class="p" data-group-id="0196619602-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0196619602-2">{</span><span class="mi">2046</span><span class="p">,</span><span class="mi">11</span><span class="p" data-group-id="0196619602-2">}</span></code></pre><section role="note" class="admonition info"><h4 class="admonition-title info">Change</h4><p>As from ERTS 5.5 (Erlang/OTP R11B), this value does not include reductions
│ │ │  performed in current time slices of currently scheduled processes. If an exact
│ │ │  value is wanted, use
│ │ │ -<a href="#statistics_exact_reductions"><code class="inline">statistics(exact_reductions)</code></a>.</p></section></li><li><pre id="statistics_run_queue"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="1917924888-1">(</span><span class="ss">run_queue</span><span class="p" data-group-id="1917924888-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1917924888-2">(</span><span class="p" data-group-id="1917924888-2">)</span></code></pre><p>Returns the total length of all normal and dirty CPU run queues. That is, queued
│ │ │ +<a href="#statistics_exact_reductions"><code class="inline">statistics(exact_reductions)</code></a>.</p></section></li><li><pre id="statistics_run_queue"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="0589310075-1">(</span><span class="ss">run_queue</span><span class="p" data-group-id="0589310075-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0589310075-2">(</span><span class="p" data-group-id="0589310075-2">)</span></code></pre><p>Returns the total length of all normal and dirty CPU run queues. That is, queued
│ │ │  work that is expected to be CPU bound. The information is gathered atomically.
│ │ │  That is, the result is a consistent snapshot of the state, but this operation is
│ │ │  much more expensive compared to
│ │ │  <a href="#statistics_total_run_queue_lengths"><code class="inline">statistics(total_run_queue_lengths)</code></a>,
│ │ │ -especially when a large amount of schedulers is used.</p></li><li><pre id="statistics_run_queue_lengths"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="7565228611-1">(</span><span class="ss">run_queue_lengths</span><span class="p" data-group-id="7565228611-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="7565228611-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="7565228611-3">(</span><span class="p" data-group-id="7565228611-3">)</span><span class="p" data-group-id="7565228611-2">]</span></code></pre><p>Returns the same as
│ │ │ +especially when a large amount of schedulers is used.</p></li><li><pre id="statistics_run_queue_lengths"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="8084085611-1">(</span><span class="ss">run_queue_lengths</span><span class="p" data-group-id="8084085611-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="8084085611-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8084085611-3">(</span><span class="p" data-group-id="8084085611-3">)</span><span class="p" data-group-id="8084085611-2">]</span></code></pre><p>Returns the same as
│ │ │  <a href="#statistics_run_queue_lengths_all"><code class="inline">statistics(run_queue_lengths_all)</code></a>
│ │ │  with the exception that no information about the dirty IO run queue is part of
│ │ │  the result. That is, only run queues with work that is expected to be CPU bound
│ │ │ -is part of the result.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_run_queue_lengths_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="0080200283-1">(</span><span class="ss">run_queue_lengths_all</span><span class="p" data-group-id="0080200283-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="0080200283-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0080200283-3">(</span><span class="p" data-group-id="0080200283-3">)</span><span class="p" data-group-id="0080200283-2">]</span></code></pre><p>Returns a list where each element represents the amount of processes and ports
│ │ │ +is part of the result.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_run_queue_lengths_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="2285868942-1">(</span><span class="ss">run_queue_lengths_all</span><span class="p" data-group-id="2285868942-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2285868942-2">[</span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2285868942-3">(</span><span class="p" data-group-id="2285868942-3">)</span><span class="p" data-group-id="2285868942-2">]</span></code></pre><p>Returns a list where each element represents the amount of processes and ports
│ │ │  ready to run for each run queue. Values for normal run queues are located first
│ │ │  in the resulting list. The first element corresponds to the normal run queue of
│ │ │  scheduler number 1 and so on. If support for dirty schedulers exist, values for
│ │ │  the dirty CPU run queue and the dirty IO run queue follow (in that order) at the
│ │ │  end. The information is <em>not</em> gathered atomically. That is, the result is not
│ │ │  necessarily a consistent snapshot of the state, but instead quite efficiently
│ │ │  gathered.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Each normal scheduler has one run queue that it manages. If dirty schedulers
│ │ │ @@ -16315,21 +16315,21 @@
│ │ │  evaluating the result.</p></section><p>See also
│ │ │  <a href="#statistics_run_queue_lengths"><code class="inline">statistics(run_queue_lengths)</code></a>,
│ │ │  <a href="#statistics_total_run_queue_lengths_all"><code class="inline">statistics(total_run_queue_lengths_all)</code></a>,
│ │ │  <a href="#statistics_total_run_queue_lengths"><code class="inline">statistics(total_run_queue_lengths)</code></a>,
│ │ │  <a href="#statistics_active_tasks"><code class="inline">statistics(active_tasks)</code></a>,
│ │ │  <a href="#statistics_active_tasks_all"><code class="inline">statistics(active_tasks_all)</code></a>, and
│ │ │  <a href="#statistics_total_active_tasks"><code class="inline">statistics(total_active_tasks)</code></a>,
│ │ │ -<a href="#statistics_total_active_tasks_all"><code class="inline">statistics(total_active_tasks_all)</code></a>.</p><p>Available since OTP 20.0</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3054574686-1">(</span><span class="ss">runtime</span><span class="p" data-group-id="3054574686-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="3054574686-2">{</span><span class="n">Total</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3054574686-3">(</span><span class="p" data-group-id="3054574686-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3054574686-4">(</span><span class="p" data-group-id="3054574686-4">)</span><span class="p" data-group-id="3054574686-2">}</span></code></pre><p>Returns information about runtime, in milliseconds.</p><p>This is the sum of the runtime for all threads in the Erlang runtime system and
│ │ │ +<a href="#statistics_total_active_tasks_all"><code class="inline">statistics(total_active_tasks_all)</code></a>.</p><p>Available since OTP 20.0</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="2728818989-1">(</span><span class="ss">runtime</span><span class="p" data-group-id="2728818989-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2728818989-2">{</span><span class="n">Total</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2728818989-3">(</span><span class="p" data-group-id="2728818989-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2728818989-4">(</span><span class="p" data-group-id="2728818989-4">)</span><span class="p" data-group-id="2728818989-2">}</span></code></pre><p>Returns information about runtime, in milliseconds.</p><p>This is the sum of the runtime for all threads in the Erlang runtime system and
│ │ │  can therefore be greater than the wall clock time.</p><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p>This value might wrap due to limitations in the underlying functionality
│ │ │ -provided by the operating system that is used.</p></section><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">statistics</span><span class="p" data-group-id="4832099749-1">(</span><span class="ss">runtime</span><span class="p" data-group-id="4832099749-1">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="4832099749-2">{</span><span class="mi">1690</span><span class="p">,</span><span class="mi">1620</span><span class="p" data-group-id="4832099749-2">}</span></code></pre></li><li><pre id="statistics_scheduler_wall_time"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="0800773154-1">(</span><span class="ss">scheduler_wall_time</span><span class="p" data-group-id="0800773154-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="0800773154-2">[</span><span class="p" data-group-id="0800773154-3">{</span><span class="n">Id</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">pos_integer</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ActiveTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0800773154-4">(</span><span class="p" data-group-id="0800773154-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">TotalTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0800773154-5">(</span><span class="p" data-group-id="0800773154-5">)</span><span class="p" data-group-id="0800773154-3">}</span><span class="p" data-group-id="0800773154-2">]</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ +provided by the operating system that is used.</p></section><p>Example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nf">statistics</span><span class="p" data-group-id="0250150665-1">(</span><span class="ss">runtime</span><span class="p" data-group-id="0250150665-1">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="0250150665-2">{</span><span class="mi">1690</span><span class="p">,</span><span class="mi">1620</span><span class="p" data-group-id="0250150665-2">}</span></code></pre></li><li><pre id="statistics_scheduler_wall_time"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="6093471343-1">(</span><span class="ss">scheduler_wall_time</span><span class="p" data-group-id="6093471343-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="6093471343-2">[</span><span class="p" data-group-id="6093471343-3">{</span><span class="n">Id</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">pos_integer</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ActiveTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="6093471343-4">(</span><span class="p" data-group-id="6093471343-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">TotalTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="6093471343-5">(</span><span class="p" data-group-id="6093471343-5">)</span><span class="p" data-group-id="6093471343-3">}</span><span class="p" data-group-id="6093471343-2">]</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │    </span><span class="ss">undefined</span></code></pre><p>Returns information describing how much time
│ │ │  <a href="#system_info_schedulers">normal</a> and
│ │ │  <a href="#system_info_dirty_cpu_schedulers">dirty CPU</a> schedulers in the
│ │ │  system have been busy. This value is normally a better indicator of how much
│ │ │  load an Erlang node is under instead of looking at the CPU utilization provided
│ │ │  by tools such as <code class="inline">top</code> or <code class="inline">sysstat</code>. This is because <code class="inline">scheduler_wall_time</code> also
│ │ │  includes time where the scheduler is waiting for some other reasource (such as
│ │ │ @@ -16361,60 +16361,60 @@
│ │ │  Dirty CPU schedulers will have scheduler identifiers in the range
│ │ │  <code class="inline">erlang:system_info(schedulers) &lt; SchedulerId =&lt; erlang:system_info(schedulers) +</code><a href="#system_info_dirty_cpu_schedulers"><code class="inline">erlang:system_info(dirty_cpu_schedulers)</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>The different types of schedulers handle specific types of jobs. Every job is
│ │ │  assigned to a specific scheduler type. Jobs can migrate between different
│ │ │  schedulers of the same type, but never between schedulers of different types.
│ │ │  This fact has to be taken under consideration when evaluating the result
│ │ │  returned.</p></section><p>You can use <code class="inline">scheduler_wall_time</code> to calculate scheduler utilization. First you
│ │ │  take a sample of the values returned by
│ │ │ -<code class="inline">erlang:statistics(scheduler_wall_time)</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_flag</span><span class="p" data-group-id="4700993806-1">(</span><span class="ss">scheduler_wall_time</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="4700993806-1">)</span><span class="p">.</span><span class="w">
│ │ │ +<code class="inline">erlang:statistics(scheduler_wall_time)</code>.</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_flag</span><span class="p" data-group-id="3735523848-1">(</span><span class="ss">scheduler_wall_time</span><span class="p">,</span><span class="w"> </span><span class="ss">true</span><span class="p" data-group-id="3735523848-1">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">false</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="n">Ts0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="4700993806-2">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="4700993806-3">(</span><span class="ss">scheduler_wall_time</span><span class="p" data-group-id="4700993806-3">)</span><span class="p" data-group-id="4700993806-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ +&gt; </span><span class="n">Ts0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="3735523848-2">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="3735523848-3">(</span><span class="ss">scheduler_wall_time</span><span class="p" data-group-id="3735523848-3">)</span><span class="p" data-group-id="3735523848-2">)</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span></code></pre><p>Some time later the user takes another snapshot and calculates scheduler
│ │ │ -utilization per scheduler, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Ts1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="1687089838-1">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="1687089838-2">(</span><span class="ss">scheduler_wall_time</span><span class="p" data-group-id="1687089838-2">)</span><span class="p" data-group-id="1687089838-1">)</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │ +utilization per scheduler, for example:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">Ts1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">sort</span><span class="p" data-group-id="7644456563-1">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">statistics</span><span class="p" data-group-id="7644456563-2">(</span><span class="ss">scheduler_wall_time</span><span class="p" data-group-id="7644456563-2">)</span><span class="p" data-group-id="7644456563-1">)</span><span class="p">,</span><span class="w"> </span><span class="ss">ok</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="ss">ok</span><span class="gp unselectable">
│ │ │ -&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="1687089838-3">(</span><span class="nf">fun</span><span class="p" data-group-id="1687089838-4">(</span><span class="p" data-group-id="1687089838-5">{</span><span class="p" data-group-id="1687089838-6">{</span><span class="n">I</span><span class="p">,</span><span class="w"> </span><span class="n">A0</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="1687089838-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1687089838-7">{</span><span class="n">I</span><span class="p">,</span><span class="w"> </span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="1687089838-7">}</span><span class="p" data-group-id="1687089838-5">}</span><span class="p" data-group-id="1687089838-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="1687089838-8">{</span><span class="n">I</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="1687089838-9">(</span><span class="n">A1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">A0</span><span class="p" data-group-id="1687089838-9">)</span><span class="o">/</span><span class="p" data-group-id="1687089838-10">(</span><span class="n">T1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="1687089838-10">)</span><span class="p" data-group-id="1687089838-8">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">zip</span><span class="p" data-group-id="1687089838-11">(</span><span class="n">Ts0</span><span class="p">,</span><span class="n">Ts1</span><span class="p" data-group-id="1687089838-11">)</span><span class="p" data-group-id="1687089838-3">)</span><span class="p">.</span><span class="w">
│ │ │ -</span><span class="p" data-group-id="1687089838-12">[</span><span class="p" data-group-id="1687089838-13">{</span><span class="mi">1</span><span class="p">,</span><span class="mf">0.9743474730177548</span><span class="p" data-group-id="1687089838-13">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-14">{</span><span class="mi">2</span><span class="p">,</span><span class="mf">0.9744843782751444</span><span class="p" data-group-id="1687089838-14">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-15">{</span><span class="mi">3</span><span class="p">,</span><span class="mf">0.9995902361669045</span><span class="p" data-group-id="1687089838-15">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-16">{</span><span class="mi">4</span><span class="p">,</span><span class="mf">0.9738012596572161</span><span class="p" data-group-id="1687089838-16">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-17">{</span><span class="mi">5</span><span class="p">,</span><span class="mf">0.9717956667018103</span><span class="p" data-group-id="1687089838-17">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-18">{</span><span class="mi">6</span><span class="p">,</span><span class="mf">0.9739235846420741</span><span class="p" data-group-id="1687089838-18">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-19">{</span><span class="mi">7</span><span class="p">,</span><span class="mf">0.973237033077876</span><span class="p" data-group-id="1687089838-19">}</span><span class="p">,</span><span class="w">
│ │ │ - </span><span class="p" data-group-id="1687089838-20">{</span><span class="mi">8</span><span class="p">,</span><span class="mf">0.9741297293248656</span><span class="p" data-group-id="1687089838-20">}</span><span class="p" data-group-id="1687089838-12">]</span></code></pre><p>Using the same snapshots to calculate a total scheduler utilization:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="8592331660-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="8592331660-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="8592331660-2">(</span><span class="nf">fun</span><span class="p" data-group-id="8592331660-3">(</span><span class="p" data-group-id="8592331660-4">{</span><span class="p" data-group-id="8592331660-5">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A0</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="8592331660-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8592331660-6">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="8592331660-6">}</span><span class="p" data-group-id="8592331660-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8592331660-7">{</span><span class="n">Ai</span><span class="p">,</span><span class="n">Ti</span><span class="p" data-group-id="8592331660-7">}</span><span class="p" data-group-id="8592331660-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -        </span><span class="p" data-group-id="8592331660-8">{</span><span class="n">Ai</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="8592331660-9">(</span><span class="n">A1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">A0</span><span class="p" data-group-id="8592331660-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Ti</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="8592331660-10">(</span><span class="n">T1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="8592331660-10">)</span><span class="p" data-group-id="8592331660-8">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="8592331660-11">{</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="8592331660-11">}</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">zip</span><span class="p" data-group-id="8592331660-12">(</span><span class="n">Ts0</span><span class="p">,</span><span class="n">Ts1</span><span class="p" data-group-id="8592331660-12">)</span><span class="p" data-group-id="8592331660-2">)</span><span class="p">,</span><span class="w">
│ │ │ +&gt; </span><span class="nc">lists</span><span class="p">:</span><span class="nf">map</span><span class="p" data-group-id="7644456563-3">(</span><span class="nf">fun</span><span class="p" data-group-id="7644456563-4">(</span><span class="p" data-group-id="7644456563-5">{</span><span class="p" data-group-id="7644456563-6">{</span><span class="n">I</span><span class="p">,</span><span class="w"> </span><span class="n">A0</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="7644456563-6">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7644456563-7">{</span><span class="n">I</span><span class="p">,</span><span class="w"> </span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7644456563-7">}</span><span class="p" data-group-id="7644456563-5">}</span><span class="p" data-group-id="7644456563-4">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7644456563-8">{</span><span class="n">I</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7644456563-9">(</span><span class="n">A1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">A0</span><span class="p" data-group-id="7644456563-9">)</span><span class="o">/</span><span class="p" data-group-id="7644456563-10">(</span><span class="n">T1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="7644456563-10">)</span><span class="p" data-group-id="7644456563-8">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">zip</span><span class="p" data-group-id="7644456563-11">(</span><span class="n">Ts0</span><span class="p">,</span><span class="n">Ts1</span><span class="p" data-group-id="7644456563-11">)</span><span class="p" data-group-id="7644456563-3">)</span><span class="p">.</span><span class="w">
│ │ │ +</span><span class="p" data-group-id="7644456563-12">[</span><span class="p" data-group-id="7644456563-13">{</span><span class="mi">1</span><span class="p">,</span><span class="mf">0.9743474730177548</span><span class="p" data-group-id="7644456563-13">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-14">{</span><span class="mi">2</span><span class="p">,</span><span class="mf">0.9744843782751444</span><span class="p" data-group-id="7644456563-14">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-15">{</span><span class="mi">3</span><span class="p">,</span><span class="mf">0.9995902361669045</span><span class="p" data-group-id="7644456563-15">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-16">{</span><span class="mi">4</span><span class="p">,</span><span class="mf">0.9738012596572161</span><span class="p" data-group-id="7644456563-16">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-17">{</span><span class="mi">5</span><span class="p">,</span><span class="mf">0.9717956667018103</span><span class="p" data-group-id="7644456563-17">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-18">{</span><span class="mi">6</span><span class="p">,</span><span class="mf">0.9739235846420741</span><span class="p" data-group-id="7644456563-18">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-19">{</span><span class="mi">7</span><span class="p">,</span><span class="mf">0.973237033077876</span><span class="p" data-group-id="7644456563-19">}</span><span class="p">,</span><span class="w">
│ │ │ + </span><span class="p" data-group-id="7644456563-20">{</span><span class="mi">8</span><span class="p">,</span><span class="mf">0.9741297293248656</span><span class="p" data-group-id="7644456563-20">}</span><span class="p" data-group-id="7644456563-12">]</span></code></pre><p>Using the same snapshots to calculate a total scheduler utilization:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="p" data-group-id="7342178962-1">{</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p" data-group-id="7342178962-1">}</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">foldl</span><span class="p" data-group-id="7342178962-2">(</span><span class="nf">fun</span><span class="p" data-group-id="7342178962-3">(</span><span class="p" data-group-id="7342178962-4">{</span><span class="p" data-group-id="7342178962-5">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A0</span><span class="p">,</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="7342178962-5">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7342178962-6">{</span><span class="p">_</span><span class="p">,</span><span class="w"> </span><span class="n">A1</span><span class="p">,</span><span class="w"> </span><span class="n">T1</span><span class="p" data-group-id="7342178962-6">}</span><span class="p" data-group-id="7342178962-4">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7342178962-7">{</span><span class="n">Ai</span><span class="p">,</span><span class="n">Ti</span><span class="p" data-group-id="7342178962-7">}</span><span class="p" data-group-id="7342178962-3">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +        </span><span class="p" data-group-id="7342178962-8">{</span><span class="n">Ai</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="7342178962-9">(</span><span class="n">A1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">A0</span><span class="p" data-group-id="7342178962-9">)</span><span class="p">,</span><span class="w"> </span><span class="n">Ti</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p" data-group-id="7342178962-10">(</span><span class="n">T1</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">T0</span><span class="p" data-group-id="7342178962-10">)</span><span class="p" data-group-id="7342178962-8">}</span><span class="w"> </span><span class="k">end</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="7342178962-11">{</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p" data-group-id="7342178962-11">}</span><span class="p">,</span><span class="w"> </span><span class="nc">lists</span><span class="p">:</span><span class="nf">zip</span><span class="p" data-group-id="7342178962-12">(</span><span class="n">Ts0</span><span class="p">,</span><span class="n">Ts1</span><span class="p" data-group-id="7342178962-12">)</span><span class="p" data-group-id="7342178962-2">)</span><span class="p">,</span><span class="w">
│ │ │    </span><span class="n">TotalSchedulerUtilization</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">A</span><span class="o">/</span><span class="n">T</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">0.9769136803764825</span></code></pre><p>Total scheduler utilization will equal <code class="inline">1.0</code> when all schedulers have been
│ │ │  active all the time between the two measurements.</p><p>Another (probably more) useful value is to calculate total scheduler utilization
│ │ │ -weighted against maximum amount of available CPU time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">WeightedSchedulerUtilization</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="5183818536-1">(</span><span class="n">TotalSchedulerUtilization</span><span class="w">
│ │ │ -                                  </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="5183818536-2">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="5183818536-3">(</span><span class="ss">schedulers</span><span class="p" data-group-id="5183818536-3">)</span><span class="w">
│ │ │ -                                     </span><span class="o">+</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="5183818536-4">(</span><span class="ss">dirty_cpu_schedulers</span><span class="p" data-group-id="5183818536-4">)</span><span class="p" data-group-id="5183818536-2">)</span><span class="p" data-group-id="5183818536-1">)</span><span class="w">
│ │ │ -                                 </span><span class="o">/</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="5183818536-5">(</span><span class="ss">logical_processors_available</span><span class="p" data-group-id="5183818536-5">)</span><span class="p">.</span><span class="w">
│ │ │ +weighted against maximum amount of available CPU time:</p><pre><code class="makeup erlang" translate="no"><span class="gp unselectable">&gt; </span><span class="n">WeightedSchedulerUtilization</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="1965986322-1">(</span><span class="n">TotalSchedulerUtilization</span><span class="w">
│ │ │ +                                  </span><span class="o">*</span><span class="w"> </span><span class="p" data-group-id="1965986322-2">(</span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="1965986322-3">(</span><span class="ss">schedulers</span><span class="p" data-group-id="1965986322-3">)</span><span class="w">
│ │ │ +                                     </span><span class="o">+</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="1965986322-4">(</span><span class="ss">dirty_cpu_schedulers</span><span class="p" data-group-id="1965986322-4">)</span><span class="p" data-group-id="1965986322-2">)</span><span class="p" data-group-id="1965986322-1">)</span><span class="w">
│ │ │ +                                 </span><span class="o">/</span><span class="w"> </span><span class="nc">erlang</span><span class="p">:</span><span class="nf">system_info</span><span class="p" data-group-id="1965986322-5">(</span><span class="ss">logical_processors_available</span><span class="p" data-group-id="1965986322-5">)</span><span class="p">.</span><span class="w">
│ │ │  </span><span class="mf">0.9769136803764825</span></code></pre><p>This weighted scheduler utilization will reach <code class="inline">1.0</code> when schedulers are active
│ │ │  the same amount of time as maximum available CPU time. If more schedulers exist
│ │ │  than available logical processors, this value may be greater than <code class="inline">1.0</code>.</p><p>As of ERTS version 9.0, the Erlang runtime system will as default have more
│ │ │  schedulers than logical processors. This due to the dirty schedulers.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p><code class="inline">scheduler_wall_time</code> is by default disabled. To enable it, use
│ │ │ -<a href="#system_flag_scheduler_wall_time"><code class="inline">erlang:system_flag(scheduler_wall_time, true)</code></a>.</p></section><p>Available since OTP R15B01</p></li><li><pre id="statistics_scheduler_wall_time_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="8356518020-1">(</span><span class="ss">scheduler_wall_time_all</span><span class="p" data-group-id="8356518020-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ -  </span><span class="p" data-group-id="8356518020-2">[</span><span class="p" data-group-id="8356518020-3">{</span><span class="n">Id</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">pos_integer</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">ActiveTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8356518020-4">(</span><span class="p" data-group-id="8356518020-4">)</span><span class="p">,</span><span class="w">
│ │ │ -    </span><span class="n">TotalTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8356518020-5">(</span><span class="p" data-group-id="8356518020-5">)</span><span class="p" data-group-id="8356518020-3">}</span><span class="p" data-group-id="8356518020-2">]</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │ +<a href="#system_flag_scheduler_wall_time"><code class="inline">erlang:system_flag(scheduler_wall_time, true)</code></a>.</p></section><p>Available since OTP R15B01</p></li><li><pre id="statistics_scheduler_wall_time_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="8011791596-1">(</span><span class="ss">scheduler_wall_time_all</span><span class="p" data-group-id="8011791596-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w">
│ │ │ +  </span><span class="p" data-group-id="8011791596-2">[</span><span class="p" data-group-id="8011791596-3">{</span><span class="n">Id</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="ss">pos_integer</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">ActiveTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8011791596-4">(</span><span class="p" data-group-id="8011791596-4">)</span><span class="p">,</span><span class="w">
│ │ │ +    </span><span class="n">TotalTime</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8011791596-5">(</span><span class="p" data-group-id="8011791596-5">)</span><span class="p" data-group-id="8011791596-3">}</span><span class="p" data-group-id="8011791596-2">]</span><span class="w"> </span><span class="p">|</span><span class="w">
│ │ │    </span><span class="ss">undefined</span></code></pre><p>Equivalent to
│ │ │  <a href="#statistics_scheduler_wall_time"><code class="inline">statistics(scheduler_wall_time)</code></a>,
│ │ │  except that it also include information about all dirty I/O schedulers.</p><p>Dirty IO schedulers will have scheduler identifiers in the range
│ │ │  <a href="#system_info_schedulers"><code class="inline">erlang:system_info(schedulers)</code></a><code class="inline">+</code><a href="#system_info_dirty_cpu_schedulers"><code class="inline">erlang:system_info(dirty_cpu_schedulers)</code></a><code class="inline">&lt; SchedulerId =&lt; erlang:system_info(schedulers) + erlang:system_info(dirty_cpu_schedulers) +</code><a href="#system_info_dirty_io_schedulers"><code class="inline">erlang:system_info(dirty_io_schedulers)</code></a>.</p><section role="note" class="admonition info"><h4 class="admonition-title info">Note</h4><p>Note that work executing on dirty I/O schedulers are expected to mainly wait
│ │ │  for I/O. That is, when you get high scheduler utilization on dirty I/O
│ │ │ -schedulers, CPU utilization is <em>not</em> expected to be high due to this work.</p></section><p>Available since OTP 20.0</p></li><li><pre id="statistics_total_active_tasks"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="0793647996-1">(</span><span class="ss">total_active_tasks</span><span class="p" data-group-id="0793647996-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="0793647996-2">(</span><span class="p" data-group-id="0793647996-2">)</span></code></pre><p>Equivalent to calling
│ │ │ +schedulers, CPU utilization is <em>not</em> expected to be high due to this work.</p></section><p>Available since OTP 20.0</p></li><li><pre id="statistics_total_active_tasks"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3743892619-1">(</span><span class="ss">total_active_tasks</span><span class="p" data-group-id="3743892619-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3743892619-2">(</span><span class="p" data-group-id="3743892619-2">)</span></code></pre><p>Equivalent to calling
│ │ │  <code class="inline">lists:sum(</code><a href="#statistics_active_tasks"><code class="inline">statistics(active_tasks)</code></a><code class="inline">)</code>,
│ │ │ -but more efficient.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_total_active_tasks_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="8618373731-1">(</span><span class="ss">total_active_tasks_all</span><span class="p" data-group-id="8618373731-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="8618373731-2">(</span><span class="p" data-group-id="8618373731-2">)</span></code></pre><p>Equivalent to calling
│ │ │ +but more efficient.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_total_active_tasks_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="7306168869-1">(</span><span class="ss">total_active_tasks_all</span><span class="p" data-group-id="7306168869-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="7306168869-2">(</span><span class="p" data-group-id="7306168869-2">)</span></code></pre><p>Equivalent to calling
│ │ │  <code class="inline">lists:sum(</code><a href="#statistics_active_tasks_all"><code class="inline">statistics(active_tasks_all)</code></a><code class="inline">)</code>,
│ │ │ -but more efficient.</p><p>Available since OTP 20.0</p></li><li><pre id="statistics_total_run_queue_lengths"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="2249223067-1">(</span><span class="ss">total_run_queue_lengths</span><span class="p" data-group-id="2249223067-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2249223067-2">(</span><span class="p" data-group-id="2249223067-2">)</span></code></pre><p>Equivalent to calling
│ │ │ +but more efficient.</p><p>Available since OTP 20.0</p></li><li><pre id="statistics_total_run_queue_lengths"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="3029879499-1">(</span><span class="ss">total_run_queue_lengths</span><span class="p" data-group-id="3029879499-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3029879499-2">(</span><span class="p" data-group-id="3029879499-2">)</span></code></pre><p>Equivalent to calling
│ │ │  <code class="inline">lists:sum(</code><a href="#statistics_run_queue_lengths"><code class="inline">statistics(run_queue_lengths)</code></a><code class="inline">)</code>,
│ │ │ -but more efficient.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_total_run_queue_lengths_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="2953252798-1">(</span><span class="ss">total_run_queue_lengths_all</span><span class="p" data-group-id="2953252798-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2953252798-2">(</span><span class="p" data-group-id="2953252798-2">)</span></code></pre><p>Equivalent to calling
│ │ │ +but more efficient.</p><p>Available since OTP 18.3</p></li><li><pre id="statistics_total_run_queue_lengths_all"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="7063003459-1">(</span><span class="ss">total_run_queue_lengths_all</span><span class="p" data-group-id="7063003459-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="7063003459-2">(</span><span class="p" data-group-id="7063003459-2">)</span></code></pre><p>Equivalent to calling
│ │ │  <code class="inline">lists:sum(</code><a href="#statistics_run_queue_lengths_all"><code class="inline">statistics(run_queue_lengths_all)</code></a><code class="inline">)</code>,
│ │ │ -but more efficient.</p><p>Available since OTP 20.0</p></li><li><pre id="statistics_wall_clock"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="2189686196-1">(</span><span class="ss">wall_clock</span><span class="p" data-group-id="2189686196-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="2189686196-2">{</span><span class="n">Total</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2189686196-3">(</span><span class="p" data-group-id="2189686196-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="2189686196-4">(</span><span class="p" data-group-id="2189686196-4">)</span><span class="p" data-group-id="2189686196-2">}</span></code></pre><p>Returns information about wall clock. <code class="inline">wall_clock</code> can be used in the same
│ │ │ +but more efficient.</p><p>Available since OTP 20.0</p></li><li><pre id="statistics_wall_clock"><code class="makeup erlang" translate="no"><span class="nf">statistics</span><span class="p" data-group-id="1142154890-1">(</span><span class="ss">wall_clock</span><span class="p" data-group-id="1142154890-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="p" data-group-id="1142154890-2">{</span><span class="n">Total</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1142154890-3">(</span><span class="p" data-group-id="1142154890-3">)</span><span class="p">,</span><span class="w"> </span><span class="n">SinceLastCall</span><span class="w"> </span><span class="p">:</span><span class="p">:</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="1142154890-4">(</span><span class="p" data-group-id="1142154890-4">)</span><span class="p" data-group-id="1142154890-2">}</span></code></pre><p>Returns information about wall clock. <code class="inline">wall_clock</code> can be used in the same
│ │ │  manner as <code class="inline">runtime</code>, except that real time is measured as opposed to runtime or
│ │ │  CPU time.</p></li></ul>
│ │ │    </section>
│ │ │  </section>
│ │ │  <section class="detail" id="system_flag/2">
│ │ │  
│ │ │    <div class="detail-header">
│ │ │ @@ -16478,65 +16478,65 @@
│ │ │                       when
│ │ │                           Tracer :: <a href="#t:pid/0">pid</a>() | <a href="#t:port/0">port</a>() | {<a href="#t:module/0">module</a>(), <a href="#t:term/0">term</a>()} | false,
│ │ │                           PrevTracer :: <a href="#t:pid/0">pid</a>() | <a href="#t:port/0">port</a>() | {<a href="#t:module/0">module</a>(), <a href="#t:term/0">term</a>()} | false;
│ │ │                   (reset_seq_trace, true) -> true.</pre>
│ │ │  
│ │ │        </div>
│ │ │  
│ │ │ -<p>Sets a system flag to the given value.</p><p>The possible flags to set are:</p><ul><li><pre><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-id="4473759666-1">(</span><span class="ss">backtrace_depths</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="4473759666-2">(</span><span class="p" data-group-id="4473759666-2">)</span><span class="p" data-group-id="4473759666-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="4473759666-3">(</span><span class="p" data-group-id="4473759666-3">)</span></code></pre><p> Sets the maximum depth of call stack back-traces in the exit reason element of
│ │ │ +<p>Sets a system flag to the given value.</p><p>The possible flags to set are:</p><ul><li><pre><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-id="3576178982-1">(</span><span class="ss">backtrace_depths</span><span class="p">,</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3576178982-2">(</span><span class="p" data-group-id="3576178982-2">)</span><span class="p" data-group-id="3576178982-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">non_neg_integer</span><span class="p" data-group-id="3576178982-3">(</span><span class="p" data-group-id="3576178982-3">)</span></code></pre><p> Sets the maximum depth of call stack back-traces in the exit reason element of
│ │ │  <code class="inline">'EXIT'</code> tuples. The flag also limits the stacktrace depth returned by
│ │ │ -<a href="#process_info/2"><code class="inline">process_info/2</code></a> item <a href="#process_info_current_stacktrace"><code class="inline">current_stacktrace</code></a>.</p><p>Returns the old value of the flag.</p></li><li><pre id="system_flag_cpu_topology"><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-id="6358570336-1">(</span><span class="ss">cpu_topology</span><span class="p">,</span><span class="w"> </span><span class="nf">cpu_topology</span><span class="p" data-group-id="6358570336-2">(</span><span class="p" data-group-id="6358570336-2">)</span><span class="p" data-group-id="6358570336-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">cpu_topology</span><span class="p" data-group-id="6358570336-3">(</span><span class="p" data-group-id="6358570336-3">)</span></code></pre><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p><em>This argument is deprecated.</em> Instead of using this argument, use
│ │ │ +<a href="#process_info/2"><code class="inline">process_info/2</code></a> item <a href="#process_info_current_stacktrace"><code class="inline">current_stacktrace</code></a>.</p><p>Returns the old value of the flag.</p></li><li><pre id="system_flag_cpu_topology"><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-id="5586692740-1">(</span><span class="ss">cpu_topology</span><span class="p">,</span><span class="w"> </span><span class="nf">cpu_topology</span><span class="p" data-group-id="5586692740-2">(</span><span class="p" data-group-id="5586692740-2">)</span><span class="p" data-group-id="5586692740-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">cpu_topology</span><span class="p" data-group-id="5586692740-3">(</span><span class="p" data-group-id="5586692740-3">)</span></code></pre><section role="note" class="admonition warning"><h4 class="admonition-title warning">Warning</h4><p><em>This argument is deprecated.</em> Instead of using this argument, use
│ │ │  command-line argument <a href="erl_cmd.html#%2Bsct"><code class="inline">+sct</code></a> in <a href="erl_cmd.html">erl</a>.</p><p>When this argument is removed, a final CPU topology to use is determined at
│ │ │  emulator boot time.</p></section><p>Sets the user-defined <code class="inline">CpuTopology</code>. The user-defined CPU topology overrides any
│ │ │  automatically detected CPU topology. By passing <code class="inline">undefined</code> as <code class="inline">CpuTopology</code>,
│ │ │  the system reverts to the CPU topology automatically detected. The returned
│ │ │  value equals the value returned from <code class="inline">erlang:system_info(cpu_topology)</code> before
│ │ │  the change was made.</p><p>Returns the old value of the flag.</p><p>The CPU topology is used when binding schedulers to logical processors. If
│ │ │  schedulers are already bound when the CPU topology is changed, the schedulers
│ │ │  are sent a request to rebind according to the new CPU topology.</p><p>The user-defined CPU topology can also be set by passing command-line argument
│ │ │  <a href="erl_cmd.html#%2Bsct"><code class="inline">+sct</code></a> to <a href="erl_cmd.html">erl</a>.</p><p>For information on type <code class="inline">CpuTopology</code> and more, see
│ │ │  <a href="#system_info_cpu_topology"><code class="inline">erlang:system_info(cpu_topology)</code></a> as
│ │ │  well as command-line flags <a href="erl_cmd.html#%2Bsct"><code class="inline">+sct</code></a> and
│ │ │ -<a href="erl_cmd.html#%2Bsbt"><code class="inline">+sbt</code></a> in <a href="erl_cmd.html">erl</a>.</p></li><li><pre id="system_flag_dirty_cpu_schedulers_online"><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-id="1243940387-1">(</span><span class="ss">dirty_cpu_schedulers_online</span><span class="p">,</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="1243940387-2">(</span><span class="p" data-group-id="1243940387-2">)</span><span class="p" data-group-id="1243940387-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="1243940387-3">(</span><span class="p" data-group-id="1243940387-3">)</span></code></pre><p>Sets the number of dirty CPU schedulers online. Range is
│ │ │ +<a href="erl_cmd.html#%2Bsbt"><code class="inline">+sbt</code></a> in <a href="erl_cmd.html">erl</a>.</p></li><li><pre id="system_flag_dirty_cpu_schedulers_online"><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-id="7279175228-1">(</span><span class="ss">dirty_cpu_schedulers_online</span><span class="p">,</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="7279175228-2">(</span><span class="p" data-group-id="7279175228-2">)</span><span class="p" data-group-id="7279175228-1">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nf">pos_integer</span><span class="p" data-group-id="7279175228-3">(</span><span class="p" data-group-id="7279175228-3">)</span></code></pre><p>Sets the number of dirty CPU schedulers online. Range is
│ │ │  <code class="inline">1 &lt;= DirtyCPUSchedulersOnline &lt;= N</code>, where <code class="inline">N</code> is the smallest of the return
│ │ │  values of <code class="inline">erlang:system_info(dirty_cpu_schedulers)</code> and
│ │ │  <code class="inline">erlang:system_info(schedulers_online)</code>.</p><p>Returns the old value of the flag.</p><p>The number of dirty CPU schedulers online can change if the number of schedulers
│ │ │  online changes. For example, if 12 schedulers and 6 dirty CPU schedulers are
│ │ │  online, and <a href="#system_flag/2"><code class="inline">system_flag/2</code></a> is used to set the number of
│ │ │  schedulers online to 6, then the number of dirty CPU schedulers online is
│ │ │  automatically decreased by half as well, down to 3. Similarly, the number of
│ │ │  dirty CPU schedulers online increases proportionally to increases in the number
│ │ │  of schedulers online.</p><p>For more information, see
│ │ │  <a href="#system_info_dirty_cpu_schedulers"><code class="inline">erlang:system_info(dirty_cpu_schedulers)</code></a>
│ │ │  and
│ │ │ -<a href="#system_info_dirty_cpu_schedulers_online"><code class="inline">erlang:system_info(dirty_cpu_schedulers_online)</code></a>.</p><p>Available since OTP 17.0</p></li><li><pre><code class="makeup erlang" translate="no"><span class="nf">system_flag</span><span class="p" data-group-

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